Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix Xamarin.Android.sln build with xbuild #4

Merged
merged 3 commits into from
Apr 23, 2016
Merged

Fix Xamarin.Android.sln build with xbuild #4

merged 3 commits into from
Apr 23, 2016

Conversation

radical
Copy link
Member

@radical radical commented Apr 22, 2016

No description provided.

Ankit Jain added 3 commits April 22, 2016 18:03
This is required because of a bug in xbuild. It tries to look for the
Java.Interop projects which are referenced from the other projects, in
the sln itself, because it needs to figure out a build order for *all*
the projects. It should probably allow projects not being present in sln
and build them via the reference.
- Build _GenerateJavaCallableWrappers *after* CoreBuild instead of
  CoreCompile. This is because it depends on Mono.Android.dll being in
  the OutputDir, but the *copy* to that directory happens *after*
  CoreCompile.

  This was hit when Mono.Android.dll would get compiled to
  obj/Debug/Mono.Android.dll , but before it can be copied, jcw-gen is
  run which expects Mono.Android.dll in the bin/Debug, thus breaking the
  build.

- Paths passed to jcw-gen.exe as arguments should be relative to the
  directory containing jcw-gen.exe or should be absolute.
@jonpryor jonpryor merged commit 707dd1b into dotnet:master Apr 23, 2016
radical pushed a commit that referenced this pull request May 8, 2018
When `JniRuntime.CreationOptions.DestroyRuntimeOnDispose` is true,
`JavaVM::DestroyJavaVM()` will be invoked when the `JniRuntime`
instance is disposed *or* finalized.

`JreRuntime.CreateJreVM()` would *always* set
`DestroyRuntimeOnDispose` to true, because it called
`JNI_CreateJavaVM()`, so *of course* you'd want to destroy the
Java VM, right?

Which brings us to unit tests. I don't know of any "before all test
fixtures run" and "after all test fixtures run" extension points,
which means:

1. The JVM needs to be created implicitly, "on demand."
2. There's no good way to destroy the JVM created in (1) after all
    tests have finished executing.

Which *really* means that the `JreRuntime` instance is *finalized*,
which sets us up for the unholy trifecta of AppDomain unloads,
finalizers, and JVM shutdown:

For unknown reasons, ~randomly, when running the unit tests (e.g.
`make run-tests`), the test runner will *hang*, indefinitely.

Attaching `lldb` and triggering a backtrace shows the unholy trifecta:

Finalization:

	thread #4: tid = 0x403831, 0x00007fff9656bdb6 libsystem_kernel.dylib`__psynch_cvwait + 10, name = 'tid_1403'
	  ...
	  frame #10: 0x00000001001ccb4a mono64`mono_gc_run_finalize(obj=<unavailable>, data=<unavailable>) + 938 at gc.c:256 [opt]
	  frame #11: 0x00000001001cdd4a mono64`finalizer_thread [inlined] finalize_domain_objects + 51 at gc.c:681 [opt]
	  frame #12: 0x00000001001cdd17 mono64`finalizer_thread(unused=<unavailable>) + 295 at gc.c:730 [opt]

JVM destruction:

	thread #4: tid = 0x403831, 0x00007fff9656bdb6 libsystem_kernel.dylib`__psynch_cvwait + 10, name = 'tid_1403'
	  frame #0: 0x00007fff9656bdb6 libsystem_kernel.dylib`__psynch_cvwait + 10
	  frame #1: 0x00007fffa04d4728 libsystem_pthread.dylib`_pthread_cond_wait + 767
	  frame #2: 0x000000010ba5bc76 libjvm.dylib`os::PlatformEvent::park() + 192
	  frame #3: 0x000000010ba38e32 libjvm.dylib`ParkCommon(ParkEvent*, long) + 42
	  frame #4: 0x000000010ba39708 libjvm.dylib`Monitor::IWait(Thread*, long) + 168
	  frame #5: 0x000000010ba398f0 libjvm.dylib`Monitor::wait(bool, long, bool) + 246
	  frame #6: 0x000000010bb3dca2 libjvm.dylib`Threads::destroy_vm() + 80
	  frame #7: 0x000000010b8fd665 libjvm.dylib`jni_DestroyJavaVM + 254

AppDomain unload:

	thread #37: tid = 0x4038fb, 0x00007fff9656bdb6 libsystem_kernel.dylib`__psynch_cvwait + 10
	  frame #0: 0x00007fff9656bdb6 libsystem_kernel.dylib`__psynch_cvwait + 10
	  frame #1: 0x00007fffa04d4728 libsystem_pthread.dylib`_pthread_cond_wait + 767
	  frame #2: 0x0000000100234a7f mono64`mono_os_cond_timedwait [inlined] mono_os_cond_wait(cond=0x0000000102016e50, mutex=0x0000000102016e10) + 11 at mono-os-mutex.h:105 [opt]
	  frame #3: 0x0000000100234a74 mono64`mono_os_cond_timedwait(cond=0x0000000102016e50, mutex=0x0000000102016e10, timeout_ms=<unavailable>) + 164 at mono-os-mutex.h:120 [opt]
	  frame #4: 0x0000000100234828 mono64`_wapi_handle_timedwait_signal_handle(handle=0x0000000000000440, timeout=4294967295, alertable=1, poll=<unavailable>, alerted=0x0000700000a286f4) + 536 at handles.c:1554 [opt]
	  frame #5: 0x0000000100246370 mono64`wapi_WaitForSingleObjectEx(handle=<unavailable>, timeout=<unavailable>, alertable=<unavailable>) + 592 at wait.c:189 [opt]
	  frame #6: 0x00000001001c832e mono64`mono_domain_try_unload [inlined] guarded_wait(timeout=4294967295, alertable=1) + 30 at appdomain.c:2390 [opt]
	  frame #7: 0x00000001001c8310 mono64`mono_domain_try_unload(domain=0x000000010127ccb0, exc=0x0000700000a287a0) + 416 at appdomain.c:2482 [opt]
	  frame #8: 0x00000001001c7db2 mono64`ves_icall_System_AppDomain_InternalUnload [inlined] mono_domain_unload(domain=<unavailable>) + 20 at appdomain.c:2379 [opt]
	  frame #9: 0x00000001001c7d9e mono64`ves_icall_System_AppDomain_InternalUnload(domain_id=<unavailable>) + 46 at appdomain.c:2039 [opt]

This randomly results in deadlock, and hung Jenkins bots.

Fix this behavior by altering `JreRuntime.CreateJreVM()` to *not*
override the value of
`JniRuntime.CreationOptions.DestroyRuntimeOnDispose`. This allows the
constructor of the `JreRuntime` instance to decide whether or not the
JVM is destroyed.

In the case of TestJVM, we *don't* want to destroy the JVM.

This prevents the JVM from being destroyed, which in turn prevents the
hang during process shutdown.
grendello added a commit to grendello/xamarin-android that referenced this pull request Jul 18, 2018
Xamarin.Android uses the ILRepack
task (https://www.nuget.org/packages/ILRepack.Lib.MSBuild.Task/) to repack/merge
the `Xamarin.Android.Build.Tasks` assembly, a step that is performed after the
`Xamarin.Android.Build.Tasks` project build completes. The step takes the
project's output assembly and several other dependencies and merges them into
one, replacing the original output assembly. For the majority of time it works
flawlessly, however the scenario described below causes a Mono runtime
crash (similar to this one mono/mono#9613, although
not identical).

The crash causes aren't yet know in every detail, but the high level overview of
the issue is as follows. Mono runtime uses the `mmap(2)` system call on Unix to
map the on-disk image of the assembly into memory. The mmapped area is used
whenever the same assembly is loaded (e.g. via `Assembly.LoadFrom`) into the
application to save time and memory. The memory is mapped as private which means
that anything written to the mapped area by the Mono process is effectively
discarded, that is not reflected in the file on disk. The protection, however,
doesn't work in the other direction - when an external process (or even the same
Mono process) writes to the file that was mmapped. Unfortunately, the OS kernel
behavior in such instance is left undefined by the POSIX standard - the kernel
can choose to reflect the on-disk change in the mapping or ignore it. On macOS
the write is ignored, on Linux, however, the write leads either to the SIGBUS
signal being sent to the process or corruption to the mmapped memory
area (details of how this happens are, as of yet, unknown - it's just a theory
at this point). The problem occurs in our case when the `ILRepacker` task
overwrites the `Xamarin.Android.Build.Tasks.dll` assembly with its
merged/repackaged form and that, somehow, corrupts Mono runtime's memory mapping
of that assembly, eventually leading to a segfault:

  #0  0x00007f974fd1b23a in __waitpid (pid=pid@entry=120561, stat_loc=stat_loc@entry=0x7f9712162b9c, options=options@entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:30
  #1  0x000055b471f36c96 in dump_native_stacktrace (ctx=0x7f97121637c0, signal=0x55b472147cd3 "SIGSEGV") at mini-posix.c:719
  #2  0x000055b471f36df2 in mono_dump_native_crash_info (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-posix.c:742
  #3  0x000055b471ecc620 in mono_handle_native_crash (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-exceptions.c:2938
  dotnet#4  0x000055b471e4c82c in mono_sigsegv_signal_handler (_dummy=7, _info=0x7f97121638f0, context=0x7f97121637c0) at mini-runtime.c:3441
  dotnet#5  <signal handler called>
  dotnet#6  __strcasecmp_l_avx () at ../sysdeps/x86_64/multiarch/strcmp-sse42.S:199
  dotnet#7  0x000055b471fb2105 in mono_assembly_names_equal_flags (l=l@entry=0x7f96e0004370, r=r@entry=0x7f97307edb60, flags=flags@entry=MONO_ANAME_EQ_IGNORE_CASE) at assembly.c:663
  dotnet#8  0x000055b471fa7baf in mono_domain_assembly_search (aname=0x7f96e0004370, user_data=0x0) at appdomain.c:2242
  dotnet#9  0x000055b471fb10f7 in mono_assembly_invoke_search_hook_internal (aname=aname@entry=0x7f96e0004370, requesting=requesting@entry=0x0, refonly=0, postload=postload@entry=0) at assembly.c:1755
  dotnet#10 0x000055b471fb4526 in mono_assembly_load_from_predicate (image=image@entry=0x7f96e001aae0, fname=fname@entry=0x7f96e000bc50 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=asmctx@entry=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2638
  dotnet#11 0x000055b471fb635c in mono_assembly_open_predicate (filename=<optimized out>, filename@entry=0x7f96e000ae40 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2206
  dotnet#12 0x000055b471fabd42 in ves_icall_System_Reflection_Assembly_LoadFrom (fname=..., refOnly=<optimized out>, error=0x7f9712164050) at appdomain.c:2272
  dotnet#13 0x00000000412f4007 in ?? ()
  dotnet#14 0x00007f97440e1918 in ?? ()
  dotnet#15 0x00007f9749bd1800 in ?? ()
  dotnet#16 0x00000000e36e75af in ?? ()
  dotnet#17 0x00007f974434fda8 in ?? ()
  dotnet#18 0x00007f9749bd18e0 in ?? ()
  dotnet#19 0x00007f96e0002820 in ?? ()
  dotnet#20 0x00007f9712164160 in ?? ()
  dotnet#21 0x00007f9712164010 in ?? ()
  dotnet#22 0x0000000000000000 in ?? ()

The crash occurs in frame 7, because the `r` parameter (an instance of the
`MonoAssembly` structure) contains pointers that used to point to valid places
in the `Xamarin.Android.Build.Tasks` assembbly's mmaped area, but now point to
garbage data. One of those corrupted pointers is the ASCII assembly name - which
is used by the function in frame 7.

The situation can be detected by the runtime by using advisory locks and
reporting the attempt to overwrite the mmapped area, however a fix would require
creating a copy of all the assembly's in-memory data before the write is allowed
and that might be too expensive. None of those measures are currently
implemented by Mono (and it isn't sure if any of them will ever be implemented).

The crash this commit fixes occurs in a very specific scenario - when building
the `OpenTK.csproj` project *directly* (that is passing it as parameter to
`msbuild`), which causes a the `Xamarin.Android.Build.Tasks` assembly to be
loaded for use in the `<UsingTask/>` msbuild statement, but at the same time
`OpenTK.csproj` references the `Xamarin.Android.Build.Tasks` *project* which
causes the ILRepacker task to run unconditionally, attempting to repack the
assemblies again and leading to the crash described above.

The fix, courtesy of @jonpryor, is to make the ILRepacker target not run every
time but only whenver the assembly has to be re-packed because it has just been
rebuilt.
grendello added a commit to grendello/xamarin-android that referenced this pull request Jul 19, 2018
Xamarin.Android uses the ILRepack
task (https://www.nuget.org/packages/ILRepack.Lib.MSBuild.Task/) to repack/merge
the `Xamarin.Android.Build.Tasks` assembly, a step that is performed after the
`Xamarin.Android.Build.Tasks` project build completes. The step takes the
project's output assembly and several other dependencies and merges them into
one, replacing the original output assembly. For the majority of time it works
flawlessly, however the scenario described below causes a Mono runtime
crash (similar to this one mono/mono#9613, although
not identical).

The crash causes aren't yet know in every detail, but the high level overview of
the issue is as follows. Mono runtime uses the `mmap(2)` system call on Unix to
map the on-disk image of the assembly into memory. The mmapped area is used
whenever the same assembly is loaded (e.g. via `Assembly.LoadFrom`) into the
application to save time and memory. The memory is mapped as private which means
that anything written to the mapped area by the Mono process is effectively
discarded, that is not reflected in the file on disk. The protection, however,
doesn't work in the other direction - when an external process (or even the same
Mono process) writes to the file that was mmapped. Unfortunately, the OS kernel
behavior in such instance is left undefined by the POSIX standard - the kernel
can choose to reflect the on-disk change in the mapping or ignore it. On macOS
the write is ignored, on Linux, however, the write leads either to the SIGBUS
signal being sent to the process or corruption to the mmapped memory
area (details of how this happens are, as of yet, unknown - it's just a theory
at this point). The problem occurs in our case when the `ILRepacker` task
overwrites the `Xamarin.Android.Build.Tasks.dll` assembly with its
merged/repackaged form and that, somehow, corrupts Mono runtime's memory mapping
of that assembly, eventually leading to a segfault:

  #0  0x00007f974fd1b23a in __waitpid (pid=pid@entry=120561, stat_loc=stat_loc@entry=0x7f9712162b9c, options=options@entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:30
  #1  0x000055b471f36c96 in dump_native_stacktrace (ctx=0x7f97121637c0, signal=0x55b472147cd3 "SIGSEGV") at mini-posix.c:719
  #2  0x000055b471f36df2 in mono_dump_native_crash_info (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-posix.c:742
  #3  0x000055b471ecc620 in mono_handle_native_crash (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-exceptions.c:2938
  dotnet#4  0x000055b471e4c82c in mono_sigsegv_signal_handler (_dummy=7, _info=0x7f97121638f0, context=0x7f97121637c0) at mini-runtime.c:3441
  dotnet#5  <signal handler called>
  dotnet#6  __strcasecmp_l_avx () at ../sysdeps/x86_64/multiarch/strcmp-sse42.S:199
  dotnet#7  0x000055b471fb2105 in mono_assembly_names_equal_flags (l=l@entry=0x7f96e0004370, r=r@entry=0x7f97307edb60, flags=flags@entry=MONO_ANAME_EQ_IGNORE_CASE) at assembly.c:663
  dotnet#8  0x000055b471fa7baf in mono_domain_assembly_search (aname=0x7f96e0004370, user_data=0x0) at appdomain.c:2242
  dotnet#9  0x000055b471fb10f7 in mono_assembly_invoke_search_hook_internal (aname=aname@entry=0x7f96e0004370, requesting=requesting@entry=0x0, refonly=0, postload=postload@entry=0) at assembly.c:1755
  dotnet#10 0x000055b471fb4526 in mono_assembly_load_from_predicate (image=image@entry=0x7f96e001aae0, fname=fname@entry=0x7f96e000bc50 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=asmctx@entry=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2638
  dotnet#11 0x000055b471fb635c in mono_assembly_open_predicate (filename=<optimized out>, filename@entry=0x7f96e000ae40 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2206
  dotnet#12 0x000055b471fabd42 in ves_icall_System_Reflection_Assembly_LoadFrom (fname=..., refOnly=<optimized out>, error=0x7f9712164050) at appdomain.c:2272
  dotnet#13 0x00000000412f4007 in ?? ()
  dotnet#14 0x00007f97440e1918 in ?? ()
  dotnet#15 0x00007f9749bd1800 in ?? ()
  dotnet#16 0x00000000e36e75af in ?? ()
  dotnet#17 0x00007f974434fda8 in ?? ()
  dotnet#18 0x00007f9749bd18e0 in ?? ()
  dotnet#19 0x00007f96e0002820 in ?? ()
  dotnet#20 0x00007f9712164160 in ?? ()
  dotnet#21 0x00007f9712164010 in ?? ()
  dotnet#22 0x0000000000000000 in ?? ()

The accompanying managed stacktrace looks as follows:

  Stacktrace:

  at <unknown> <0xffffffff>
  at (wrapper managed-to-native) System.Reflection.Assembly.LoadFrom (string,bool) [0x0001b] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Reflection.Assembly.LoadFrom (string) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/corlib/System.Reflection/Assembly.cs:539
  at System.Reflection.Assembly.UnsafeLoadFrom (string) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/corlib/System.Reflection/Assembly.cs:571
  at Microsoft.Build.Shared.TypeLoader.LoadAssembly (Microsoft.Build.Shared.AssemblyLoadInfo) [0x0001e] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Shared.TypeLoader/AssemblyInfoToLoadedTypes.ScanAssemblyForPublicTypes () [0x00007] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Shared.TypeLoader/AssemblyInfoToLoadedTypes/<>c__DisplayClass8_0.<GetLoadedTypeByTypeName>b__0 (string) [0x000b4] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Collections.Concurrent.ConcurrentDictionary`2<TKey_REF, TValue_REF>.GetOrAdd (TKey_REF,System.Func`2<TKey_REF, TValue_REF>) [0x00034] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.Shared.TypeLoader/AssemblyInfoToLoadedTypes.GetLoadedTypeByTypeName (string) [0x0003c] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Shared.TypeLoader.GetLoadedType (System.Collections.Concurrent.ConcurrentDictionary`2<System.Func`3<System.Type, object, bool>, System.Collections.Concurrent.ConcurrentDictionary`2<Microsoft.Build.Shared.AssemblyLoadInfo, Microsoft.Build.Shared.TypeLoader/AssemblyInfoToLoadedTypes>>,string,Microsoft.Build.Shared.AssemblyLoadInfo) [0x00042] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Shared.TypeLoader.Load (string,Microsoft.Build.Shared.AssemblyLoadInfo) [0x00008] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.AssemblyTaskFactory.InitializeFactory (Microsoft.Build.Shared.AssemblyLoadInfo,string,System.Collections.Generic.IDictionary`2<string, Microsoft.Build.Framework.TaskPropertyInfo>,string,System.Collections.Generic.IDictionary`2<string, string>,bool,Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.Construction.ElementLocation,string) [0x00058] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Execution.TaskRegistry/RegisteredTaskRecord.GetTaskFactory (Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.Construction.ElementLocation,string) [0x000b8] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Execution.TaskRegistry/RegisteredTaskRecord.CanTaskBeCreatedByFactory (string,string,System.Collections.Generic.IDictionary`2<string, string>,Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.Construction.ElementLocation) [0x0003b] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Execution.TaskRegistry.GetMatchingRegistration (string,System.Collections.Generic.List`1<Microsoft.Build.Execution.TaskRegistry/RegisteredTaskRecord>,string,System.Collections.Generic.IDictionary`2<string, string>,Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.Construction.ElementLocation) [0x0001a] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Execution.TaskRegistry.GetTaskRegistrationRecord (string,string,System.Collections.Generic.IDictionary`2<string, string>,bool,Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.Construction.ElementLocation,bool&) [0x00169] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.Execution.TaskRegistry.GetRegisteredTask (string,string,System.Collections.Generic.IDictionary`2<string, string>,bool,Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.Construction.ElementLocation) [0x00010] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TaskExecutionHost.FindTaskInRegistry (System.Collections.Generic.IDictionary`2<string, string>) [0x00038] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.FindTask (System.Collections.Generic.IDictionary`2<string, string>) [0x0000b] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<ExecuteBucket>d__19.MoveNext () [0x0011e] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<Microsoft.Build.BackEnd.WorkUnitResult>.Start<Microsoft.Build.BackEnd.TaskBuilder/<ExecuteBucket>d__19> (Microsoft.Build.BackEnd.TaskBuilder/<ExecuteBucket>d__19&) [0x0002c] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:471
  at Microsoft.Build.BackEnd.TaskBuilder.ExecuteBucket (Microsoft.Build.BackEnd.TaskHost,Microsoft.Build.BackEnd.ItemBucket,Microsoft.Build.BackEnd.TaskExecutionMode,System.Collections.Generic.Dictionary`2<string, string>) [0x00048] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__18.MoveNext () [0x0016a] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<Microsoft.Build.BackEnd.WorkUnitResult>.Start<Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__18> (Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__18&) [0x0002c] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:471
  at Microsoft.Build.BackEnd.TaskBuilder.ExecuteTask (Microsoft.Build.BackEnd.TaskExecutionMode,Microsoft.Build.BackEnd.Lookup) [0x00037] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__13.MoveNext () [0x00193] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<Microsoft.Build.BackEnd.WorkUnitResult>.Start<Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__13> (Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__13&) [0x0002c] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:471
  at Microsoft.Build.BackEnd.TaskBuilder.ExecuteTask (Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.BackEnd.BuildRequestEntry,Microsoft.Build.BackEnd.ITargetBuilderCallback,Microsoft.Build.Execution.ProjectTargetInstanceChild,Microsoft.Build.BackEnd.TaskExecutionMode,Microsoft.Build.BackEnd.Lookup,Microsoft.Build.BackEnd.Lookup,System.Threading.CancellationToken) [0x0006c] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TargetEntry/<ProcessBucket>d__52.MoveNext () [0x00091] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<Microsoft.Build.BackEnd.WorkUnitResult>.Start<Microsoft.Build.BackEnd.TargetEntry/<ProcessBucket>d__52> (Microsoft.Build.BackEnd.TargetEntry/<ProcessBucket>d__52&) [0x0002c] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:471
  at Microsoft.Build.BackEnd.TargetEntry.ProcessBucket (Microsoft.Build.BackEnd.ITaskBuilder,Microsoft.Build.BackEnd.Logging.TargetLoggingContext,Microsoft.Build.BackEnd.TaskExecutionMode,Microsoft.Build.BackEnd.Lookup,Microsoft.Build.BackEnd.Lookup) [0x00051] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TargetEntry/<ExecuteTarget>d__45.MoveNext () [0x002bb] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start<Microsoft.Build.BackEnd.TargetEntry/<ExecuteTarget>d__45> (Microsoft.Build.BackEnd.TargetEntry/<ExecuteTarget>d__45&) [0x0002c] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:316
  at Microsoft.Build.BackEnd.TargetEntry.ExecuteTarget (Microsoft.Build.BackEnd.ITaskBuilder,Microsoft.Build.BackEnd.BuildRequestEntry,Microsoft.Build.BackEnd.Logging.ProjectLoggingContext,System.Threading.CancellationToken) [0x00048] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at Microsoft.Build.BackEnd.TargetBuilder/<ProcessTargetStack>d__21.MoveNext () [0x003a5] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<System.Threading.Tasks.VoidTaskResult>.TrySetResult (System.Threading.Tasks.VoidTaskResult) [0x0004f] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:433
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<System.Threading.Tasks.VoidTaskResult>.SetResult (System.Threading.Tasks.VoidTaskResult) [0x0003d] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:608
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<System.Threading.Tasks.VoidTaskResult>.SetResult (System.Threading.Tasks.Task`1<System.Threading.Tasks.VoidTaskResult>) [0x00010] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:636
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult () [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:378
  at Microsoft.Build.BackEnd.TargetEntry/<ExecuteTarget>d__45.MoveNext () [0x00720] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.TargetEntry/<ProcessBucket>d__52.MoveNext () [0x001d5] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__13.MoveNext () [0x0021e] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<ExecuteTask>d__18.MoveNext () [0x002be] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<ExecuteBucket>d__19.MoveNext () [0x003e5] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<InitializeAndExecuteTask>d__24.MoveNext () [0x0012d] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.TaskBuilder/<ExecuteInstantiatedTask>d__26.MoveNext () [0x0065e] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<bool>.TrySetResult (bool) [0x0004f] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:433
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<bool>.SetResult (bool) [0x0003d] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:608
  at Microsoft.Build.BackEnd.MSBuild/<ExecuteInternal>d__76.MoveNext () [0x004dd] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<bool>.TrySetResult (bool) [0x0004f] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:433
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<bool>.SetResult (bool) [0x0003d] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:608
  at Microsoft.Build.BackEnd.MSBuild/<BuildProjectsInParallel>d__77.MoveNext () [0x0014a] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<bool>.TrySetResult (bool) [0x0004f] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:433
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<bool>.SetResult (bool) [0x0003d] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:608
  at Microsoft.Build.BackEnd.MSBuild/<ExecuteTargets>d__80.MoveNext () [0x00713] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<Microsoft.Build.Framework.BuildEngineResult>.TrySetResult (Microsoft.Build.Framework.BuildEngineResult) [0x0004f] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:433
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<Microsoft.Build.Framework.BuildEngineResult>.SetResult (Microsoft.Build.Framework.BuildEngineResult) [0x0003d] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:608
  at Microsoft.Build.BackEnd.TaskHost/<InternalBuildProjects>d__49.MoveNext () [0x0025c] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<Microsoft.Build.Framework.BuildEngineResult>.TrySetResult (Microsoft.Build.Framework.BuildEngineResult) [0x0004f] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:433
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<Microsoft.Build.Framework.BuildEngineResult>.SetResult (Microsoft.Build.Framework.BuildEngineResult) [0x0003d] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:608
  at Microsoft.Build.BackEnd.TaskHost/<BuildProjectFilesInParallelAsync>d__53.MoveNext () [0x004fb] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.RequestBuilder/<BuildProjects>d__33.MoveNext () [0x00263] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<TResult_REF>.TrySetResult (TResult_REF) [0x0004f] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<TResult_REF>.SetResult (TResult_REF) [0x0003d] in <79002cfb0e6e431d8465d6dcea08995e>:0
  at Microsoft.Build.BackEnd.RequestBuilder/<StartNewBuildRequests>d__51.MoveNext () [0x0020e] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.InvokeMoveNext (object) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1094
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore/MoveNextRunner.Run () [0x00024] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1075
  at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction (System.Action,bool,System.Threading.Tasks.Task&) [0x0001a] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs:680
  at System.Threading.Tasks.Task.FinishContinuations () [0x00052] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:3198
  at System.Threading.Tasks.Task.FinishStageThree () [0x0003c] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2247
  at System.Threading.Tasks.Task`1<int>.TrySetResult (int) [0x0004f] in /home/grendel/vc/mono/mono/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:433
  at System.Threading.Tasks.TaskCompletionSource`1<int>.TrySetResult (int) [0x00000] in /home/grendel/vc/mono/mono/external/corefx/src/Common/src/CoreLib/System/Threading/Tasks/TaskCompletionSource.cs:274
  at Microsoft.Build.Shared.AwaitExtensions/<>c__DisplayClass7_2.<ToTask>b__0 (object,bool) [0x00038] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
  at System.Threading.RegisteredWaitHandle.DoCallBack (object) [0x00008] in /home/grendel/vc/mono/mono/mcs/class/corlib/System.Threading/RegisteredWaitHandle.cs:103
  at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context (object) [0x0000d] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/threadpool.cs:1308
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:961
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:908
  at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem () [0x00021] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/threadpool.cs:1285
  at System.Threading.ThreadPoolWorkQueue.Dispatch () [0x00074] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/threadpool.cs:858
  at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback () [0x00000] in /home/grendel/vc/mono/mono/mcs/class/referencesource/mscorlib/system/threading/threadpool.cs:1213
  at (wrapper runtime-invoke) <Module>.runtime_invoke_bool (object,intptr,intptr,intptr) [0x0001f] in <79002cfb0e6e431d8465d6dcea08995e>:0

The crash occurs in frame 7, because the `r` parameter (an instance of the
`MonoAssembly` structure) contains pointers that used to point to valid places
in the `Xamarin.Android.Build.Tasks` assembbly's mmaped area, but now point to
garbage data. One of those corrupted pointers is the ASCII assembly name - which
is used by the function in frame 7.

The situation can be detected by the runtime by using advisory locks and
reporting the attempt to overwrite the mmapped area, however a fix would require
creating a copy of all the assembly's in-memory data before the write is allowed
and that might be too expensive. None of those measures are currently
implemented by Mono (and it isn't sure if any of them will ever be implemented).

The crash this commit fixes occurs in a very specific scenario - when building
the `OpenTK.csproj` project *directly* (that is passing it as parameter to
`msbuild`), which causes a the `Xamarin.Android.Build.Tasks` assembly to be
loaded for use in the `<UsingTask/>` msbuild statement, but at the same time
`OpenTK.csproj` references the `Xamarin.Android.Build.Tasks` *project* which
causes the ILRepacker task to run unconditionally, attempting to repack the
assemblies again and leading to the crash described above.

The fix, courtesy of @jonpryor, is to make the ILRepacker target not run every
time but only whenver the assembly has to be re-packed because it has just been
rebuilt.
jonpryor pushed a commit that referenced this pull request Jul 19, 2018
Xamarin.Android uses the [ILRepack task][0] to repack/merge the
`Xamarin.Android.Build.Tasks.dll` assembly (610ade7), a step that is
performed after the `Xamarin.Android.Build.Tasks.csproj` project's
`Build` target completes.  The step takes the project's output
assembly -- `Xamarin.Android.Build.Tasks.dll` -- and several other
dependencies, then merges them into one, *replacing* the original
output assembly.

The majority of time it works flawlessly, however when building the
`monodroid` repo we observe a Mono runtime crash, similar-but-not-
identical to [mono issue 9613][m9613].  Not all details are
understood, but the high level overview of the issue is as follows:
Mono runtime uses the **mmap**(2) system call on Unix to map the
on-disk image of the assembly into memory.  The `mmapp`ed area is
used whenever the same assembly is loaded (e.g.
`Assembly.LoadFrom()`) into the application to save time and memory.
The memory is mapped as private which means that anything written to
the mapped area by the Mono process is effectively discarded, that is
not reflected in the file on disk.  The protection, however, doesn't
work in the other direction: when an external process (or even the
same Mono process!) writes to the file that was `mmapp`ed.
Unfortunately, the OS kernel behavior in such instance is left
undefined by the POSIX standard: the kernel can choose to reflect the
on-disk change in the mapping or ignore it.  On macOS the write is
ignored; on Linux, the write leads either to the `SIGBUS` signal
being sent to the process or corruption to the `mmap`ped memory area
(details of how this happens are, as of yet, unknown; it's just a
theory at this point).  The problem occurs in our case when the
`<ILRepacker/>` task overwrites the `Xamarin.Android.Build.Tasks.dll`
assembly with its merged/repackaged form and that, somehow, corrupts
Mono runtime's memory mapping of that assembly, eventually crashing:

        ## native crash
        #0  0x00007f974fd1b23a in __waitpid (pid=pid@entry=120561, stat_loc=stat_loc@entry=0x7f9712162b9c, options=options@entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:30
        #1  0x000055b471f36c96 in dump_native_stacktrace (ctx=0x7f97121637c0, signal=0x55b472147cd3 "SIGSEGV") at mini-posix.c:719
        #2  0x000055b471f36df2 in mono_dump_native_crash_info (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-posix.c:742
        #3  0x000055b471ecc620 in mono_handle_native_crash (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-exceptions.c:2938
        #4  0x000055b471e4c82c in mono_sigsegv_signal_handler (_dummy=7, _info=0x7f97121638f0, context=0x7f97121637c0) at mini-runtime.c:3441
        #5  <signal handler called>
        #6  __strcasecmp_l_avx () at ../sysdeps/x86_64/multiarch/strcmp-sse42.S:199
        #7  0x000055b471fb2105 in mono_assembly_names_equal_flags (l=l@entry=0x7f96e0004370, r=r@entry=0x7f97307edb60, flags=flags@entry=MONO_ANAME_EQ_IGNORE_CASE) at assembly.c:663
        #8  0x000055b471fa7baf in mono_domain_assembly_search (aname=0x7f96e0004370, user_data=0x0) at appdomain.c:2242
        #9  0x000055b471fb10f7 in mono_assembly_invoke_search_hook_internal (aname=aname@entry=0x7f96e0004370, requesting=requesting@entry=0x0, refonly=0, postload=postload@entry=0) at assembly.c:1755
        #10 0x000055b471fb4526 in mono_assembly_load_from_predicate (image=image@entry=0x7f96e001aae0, fname=fname@entry=0x7f96e000bc50 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=asmctx@entry=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2638
        #11 0x000055b471fb635c in mono_assembly_open_predicate (filename=<optimized out>, filename@entry=0x7f96e000ae40 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2206
        #12 0x000055b471fabd42 in ves_icall_System_Reflection_Assembly_LoadFrom (fname=..., refOnly=<optimized out>, error=0x7f9712164050) at appdomain.c:2272
        ...

        ## managed stacktrace
        at <unknown> <0xffffffff>
        at (wrapper managed-to-native) System.Reflection.Assembly.LoadFrom (string,bool) [0x0001b] in <79002cfb0e6e431d8465d6dcea08995e>:0
        at System.Reflection.Assembly.LoadFrom (string) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/corlib/System.Reflection/Assembly.cs:539
        at System.Reflection.Assembly.UnsafeLoadFrom (string) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/corlib/System.Reflection/Assembly.cs:571
        at Microsoft.Build.Shared.TypeLoader.LoadAssembly (Microsoft.Build.Shared.AssemblyLoadInfo) [0x0001e] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
        ...

The crash occurs in frame 7, because the `r` parameter (an instance
of the `MonoAssembly` structure) contains pointers that used to point
to valid places in the `Xamarin.Android.Build.Tasks.dll`s `mmap`ed
area, but now point to garbage data.  One of those corrupted pointers
is the ASCII assembly name - which is used by the function in frame 7.

The crash this commit fixes occurs in a very specific scenario: when
building the `OpenTK.csproj` project *directly*
(e.g. `msbuild OpenTK.csproj`), which causes the
`Xamarin.Android.Build.Tasks.dll` assembly to be loaded for use in
the `<UsingTask/>` MSBuild statement, but at the same time 
`OpenTK.csproj` has a `@(ProjectReference)` to
`Xamarin.Android.Build.Tasks.csproj`, which caused the
`<ILRepacker/>` task to run unconditionally, attempting to repack the
assemblies again and leading to the crash described above.

The fix, courtesy of @jonpryor, is to make the `ILRepacker` target
not run every time but only whenever the assembly has to be re-packed
because it has just been rebuilt.

This also improves rebuild times.

[0]: https://www.nuget.org/packages/ILRepack.Lib.MSBuild.Task
[m9613]: mono/mono#9613
jonpryor pushed a commit that referenced this pull request Aug 3, 2018
Xamarin.Android uses the [ILRepack task][0] to repack/merge the
`Xamarin.Android.Build.Tasks.dll` assembly (610ade7), a step that is
performed after the `Xamarin.Android.Build.Tasks.csproj` project's
`Build` target completes.  The step takes the project's output
assembly -- `Xamarin.Android.Build.Tasks.dll` -- and several other
dependencies, then merges them into one, *replacing* the original
output assembly.

The majority of time it works flawlessly, however when building the
`monodroid` repo we observe a Mono runtime crash, similar-but-not-
identical to [mono issue 9613][m9613].  Not all details are
understood, but the high level overview of the issue is as follows:
Mono runtime uses the **mmap**(2) system call on Unix to map the
on-disk image of the assembly into memory.  The `mmapp`ed area is
used whenever the same assembly is loaded (e.g.
`Assembly.LoadFrom()`) into the application to save time and memory.
The memory is mapped as private which means that anything written to
the mapped area by the Mono process is effectively discarded, that is
not reflected in the file on disk.  The protection, however, doesn't
work in the other direction: when an external process (or even the
same Mono process!) writes to the file that was `mmapp`ed.
Unfortunately, the OS kernel behavior in such instance is left
undefined by the POSIX standard: the kernel can choose to reflect the
on-disk change in the mapping or ignore it.  On macOS the write is
ignored; on Linux, the write leads either to the `SIGBUS` signal
being sent to the process or corruption to the `mmap`ped memory area
(details of how this happens are, as of yet, unknown; it's just a
theory at this point).  The problem occurs in our case when the
`<ILRepacker/>` task overwrites the `Xamarin.Android.Build.Tasks.dll`
assembly with its merged/repackaged form and that, somehow, corrupts
Mono runtime's memory mapping of that assembly, eventually crashing:

        ## native crash
        #0  0x00007f974fd1b23a in __waitpid (pid=pid@entry=120561, stat_loc=stat_loc@entry=0x7f9712162b9c, options=options@entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:30
        #1  0x000055b471f36c96 in dump_native_stacktrace (ctx=0x7f97121637c0, signal=0x55b472147cd3 "SIGSEGV") at mini-posix.c:719
        #2  0x000055b471f36df2 in mono_dump_native_crash_info (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-posix.c:742
        #3  0x000055b471ecc620 in mono_handle_native_crash (signal=signal@entry=0x55b472147cd3 "SIGSEGV", ctx=ctx@entry=0x7f97121637c0, info=info@entry=0x7f97121638f0) at mini-exceptions.c:2938
        #4  0x000055b471e4c82c in mono_sigsegv_signal_handler (_dummy=7, _info=0x7f97121638f0, context=0x7f97121637c0) at mini-runtime.c:3441
        #5  <signal handler called>
        #6  __strcasecmp_l_avx () at ../sysdeps/x86_64/multiarch/strcmp-sse42.S:199
        #7  0x000055b471fb2105 in mono_assembly_names_equal_flags (l=l@entry=0x7f96e0004370, r=r@entry=0x7f97307edb60, flags=flags@entry=MONO_ANAME_EQ_IGNORE_CASE) at assembly.c:663
        #8  0x000055b471fa7baf in mono_domain_assembly_search (aname=0x7f96e0004370, user_data=0x0) at appdomain.c:2242
        #9  0x000055b471fb10f7 in mono_assembly_invoke_search_hook_internal (aname=aname@entry=0x7f96e0004370, requesting=requesting@entry=0x0, refonly=0, postload=postload@entry=0) at assembly.c:1755
        #10 0x000055b471fb4526 in mono_assembly_load_from_predicate (image=image@entry=0x7f96e001aae0, fname=fname@entry=0x7f96e000bc50 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=asmctx@entry=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2638
        #11 0x000055b471fb635c in mono_assembly_open_predicate (filename=<optimized out>, filename@entry=0x7f96e000ae40 "/home/grendel/vc/xamarin/monodroid/monodroid/external/xamarin-android/src/Xamarin.Android.Build.Tasks/../../packages/ILRepack.Lib.MSBuild.Task.2.0.15.4/build/ILRepack.Lib.MSBuild.Task.dll", asmctx=MONO_ASMCTX_LOADFROM, predicate=predicate@entry=0x0, user_data=user_data@entry=0x0, status=status@entry=0x7f9712163fd4) at assembly.c:2206
        #12 0x000055b471fabd42 in ves_icall_System_Reflection_Assembly_LoadFrom (fname=..., refOnly=<optimized out>, error=0x7f9712164050) at appdomain.c:2272
        ...

        ## managed stacktrace
        at <unknown> <0xffffffff>
        at (wrapper managed-to-native) System.Reflection.Assembly.LoadFrom (string,bool) [0x0001b] in <79002cfb0e6e431d8465d6dcea08995e>:0
        at System.Reflection.Assembly.LoadFrom (string) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/corlib/System.Reflection/Assembly.cs:539
        at System.Reflection.Assembly.UnsafeLoadFrom (string) [0x00000] in /home/grendel/vc/mono/mono/mcs/class/corlib/System.Reflection/Assembly.cs:571
        at Microsoft.Build.Shared.TypeLoader.LoadAssembly (Microsoft.Build.Shared.AssemblyLoadInfo) [0x0001e] in <bdc5207a22bb42ae9fe3f3d07e82871e>:0
        ...

The crash occurs in frame 7, because the `r` parameter (an instance
of the `MonoAssembly` structure) contains pointers that used to point
to valid places in the `Xamarin.Android.Build.Tasks.dll`s `mmap`ed
area, but now point to garbage data.  One of those corrupted pointers
is the ASCII assembly name - which is used by the function in frame 7.

The crash this commit fixes occurs in a very specific scenario: when
building the `OpenTK.csproj` project *directly*
(e.g. `msbuild OpenTK.csproj`), which causes the
`Xamarin.Android.Build.Tasks.dll` assembly to be loaded for use in
the `<UsingTask/>` MSBuild statement, but at the same time 
`OpenTK.csproj` has a `@(ProjectReference)` to
`Xamarin.Android.Build.Tasks.csproj`, which caused the
`<ILRepacker/>` task to run unconditionally, attempting to repack the
assemblies again and leading to the crash described above.

The fix, courtesy of @jonpryor, is to make the `ILRepacker` target
not run every time but only whenever the assembly has to be re-packed
because it has just been rebuilt.

This also improves rebuild times.

[0]: https://www.nuget.org/packages/ILRepack.Lib.MSBuild.Task
[m9613]: mono/mono#9613
lewurm added a commit to lewurm/xamarin-android that referenced this pull request Nov 20, 2018
dellis1972 referenced this pull request in dellis1972/xamarin-android Feb 5, 2019
When using fastdev typemaps we get the following error

```
01-31 10:57:34.336  5802  5802 F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0 in tid 5802 (haredandroidios), pid 5802 (haredandroidios)
01-31 10:57:34.358  5829  5829 I crash_dump32: obtaining output fd from tombstoned, type: kDebuggerdTombstone
01-31 10:57:34.358  1685  1685 I /system/bin/tombstoned: received crash request for pid 5802
01-31 10:57:34.359  5829  5829 I crash_dump32: performing dump of process 5802 (target tid = 5802)
01-31 10:57:34.363  5829  5829 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
01-31 10:57:34.363  5829  5829 F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86/generic_x86:9/PSR1.180720.012/4923214:userdebug/test-keys'
01-31 10:57:34.363  5829  5829 F DEBUG   : Revision: '0'
01-31 10:57:34.363  5829  5829 F DEBUG   : ABI: 'x86'
01-31 10:57:34.363  5829  5829 F DEBUG   : pid: 5802, tid: 5802, name: haredandroidios  >>> com.xamarin.blankformssharedandroidios <<<
01-31 10:57:34.363  5829  5829 F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
01-31 10:57:34.363  5829  5829 F DEBUG   : Cause: null pointer dereference
01-31 10:57:34.363  5829  5829 F DEBUG   :     eax 00000000  ebx e6b2e754  ecx 00000000  edx 00000000
01-31 10:57:34.363  5829  5829 F DEBUG   :     edi e0cc58f0  esi 00000000
01-31 10:57:34.363  5829  5829 F DEBUG   :     ebp ffd85ff8  esp ffd85fcc  eip e6a60532
01-31 10:57:34.459  5829  5829 F DEBUG   :
01-31 10:57:34.459  5829  5829 F DEBUG   : backtrace:
01-31 10:57:34.459  5829  5829 F DEBUG   :     #00 pc 0001e532  /system/lib/libc.so (strlen+18)
01-31 10:57:34.459  5829  5829 F DEBUG   :     #1 pc 00075952  /system/lib/libc.so (strdup+34)
01-31 10:57:34.459  5829  5829 F DEBUG   :     #2 pc 0000f6ab  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::add_type_mapping(xamarin::android::internal::TypeMappingInfo**, char const*, char const*, char const*)+667)
01-31 10:57:34.459  5829  5829 F DEBUG   :     #3 pc 00010ed7  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::try_load_typemaps_from_directory(char const*)+871)
01-31 10:57:34.459  5829  5829 F DEBUG   :     #4 pc 000233b8  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (gather_bundled_assemblies(_JNIEnv*, xamarin::android::jstring_array_wrapper&, bool, int*)+248)
01-31 10:57:34.459  5829  5829 F DEBUG   :     #5 pc 000229c6  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (create_domain(_JNIEnv*, _jclass*, xamarin::android::jstring_array_wrapper&, _jstring*, _jobject*, bool)+166)
01-31 10:57:34.459  5829  5829 F DEBUG   :     #6 pc 0001f20c  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (create_and_initialize_domain(_JNIEnv*, _jclass*, xamarin::android::jstring_array_wrapper&, _jobjectArray*, _jobject*, bool)+204)
01-31 10:57:34.460  5829  5829 F DEBUG   :     #7 pc 0001c7af  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (Java_mono_android_Runtime_init+4255)
```

The was down to the `try_load_typemaps_from_directory` passing a
`nullptr` to the `add_type_mapping` method. This method was
calling `strdup`, which does NOT like `nullptr`.

Since the `source_entry` argument is only used for logging we
migth as well create a constant string with a value of
`.__override__` so that if there is a problem we can see
from the logs this was a fastdev issue.
jonpryor pushed a commit that referenced this pull request Feb 5, 2019
When using fastdev typemaps files we get the following error:

	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0 in tid 5802 (haredandroidios), pid 5802 (haredandroidios)
	I crash_dump32: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	I /system/bin/tombstoned: received crash request for pid 5802
	I crash_dump32: performing dump of process 5802 (target tid = 5802)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86/generic_x86:9/PSR1.180720.012/4923214:userdebug/test-keys'
	F DEBUG   : Revision: '0'
	F DEBUG   : ABI: 'x86'
	F DEBUG   : pid: 5802, tid: 5802, name: haredandroidios  >>> com.xamarin.blankformssharedandroidios <<<
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
	F DEBUG   : Cause: null pointer dereference
	F DEBUG   :     eax 00000000  ebx e6b2e754  ecx 00000000  edx 00000000
	F DEBUG   :     edi e0cc58f0  esi 00000000
	F DEBUG   :     ebp ffd85ff8  esp ffd85fcc  eip e6a60532
	F DEBUG   :
	F DEBUG   : backtrace:
	F DEBUG   :     #00 pc 0001e532  /system/lib/libc.so (strlen+18)
	F DEBUG   :     #1 pc 00075952  /system/lib/libc.so (strdup+34)
	F DEBUG   :     #2 pc 0000f6ab  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::add_type_mapping(xamarin::android::internal::TypeMappingInfo**, char const*, char const*, char const*)+667)
	F DEBUG   :     #3 pc 00010ed7  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::try_load_typemaps_from_directory(char const*)+871)
	F DEBUG   :     #4 pc 000233b8  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (gather_bundled_assemblies(_JNIEnv*, xamarin::android::jstring_array_wrapper&, bool, int*)+248)
	F DEBUG   :     #5 pc 000229c6  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (create_domain(_JNIEnv*, _jclass*, xamarin::android::jstring_array_wrapper&, _jstring*, _jobject*, bool)+166)
	F DEBUG   :     #6 pc 0001f20c  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (create_and_initialize_domain(_JNIEnv*, _jclass*, xamarin::android::jstring_array_wrapper&, _jobjectArray*, _jobject*, bool)+204)
	F DEBUG   :     #7 pc 0001c7af  /data/app/com.xamarin.blankformssharedandroidios-nCq7hL5Bz-TYILJl3W97zw==/lib/x86/libmonodroid.so (Java_mono_android_Runtime_init+4255)


The was down to the `try_load_typemaps_from_directory()` passing a
`nullptr` to the `add_type_mapping()` method.  This method was
calling **strdup**(3), which does NOT like `nullptr`.

Since the `source_entry` argument is only used for logging we might
as well create a constant string with a value of `.__override__` so
that if there is a problem we can see from the logs this was a
fastdev issue.
grendello added a commit to grendello/xamarin-android that referenced this pull request Apr 8, 2020
Context: 7117414

7117414 introduced native code which queries
the Mono runtime to obtain an instance of `MonoClass` for a given
`MonoReflectionType` as well as the `MonoImage` associated with the
class.  However, it appears that in certain cases the class pointer
stored `MonoReflectionType` doesn't lead us to getting a valid
`MonoImage` instance, causing a segfault similar to:

    04-08 15:52:55.015 19030 19030 F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021 in tid 19030 (s.swipeviewdemo), pid 19030 (s.swipeviewdemo)
    04-08 15:52:55.037 19061 19061 I crash_dump32: obtaining output fd from tombstoned, type: kDebuggerdTombstone
    04-08 15:52:55.037  1834  1834 I /system/bin/tombstoned: received crash request for pid 19030
    04-08 15:52:55.038 19061 19061 I crash_dump32: performing dump of process 19030 (target tid = 19030)
    04-08 15:52:55.042 19061 19061 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    04-08 15:52:55.042 19061 19061 F DEBUG   : Build fingerprint: 'google/sdk_gphone_x86/generic_x86:10/QSR1.191030.002/5978551:userdebug/dev-keys'
    04-08 15:52:55.043 19061 19061 F DEBUG   : Revision: '0'
    04-08 15:52:55.043 19061 19061 F DEBUG   : ABI: 'x86'
    04-08 15:52:55.043 19061 19061 F DEBUG   : Timestamp: 2020-04-08 15:52:55+0200
    04-08 15:52:55.043 19061 19061 F DEBUG   : pid: 19030, tid: 19030, name: s.swipeviewdemo  >>> nl.versluis.swipeviewdemo <<<
    04-08 15:52:55.043 19061 19061 F DEBUG   : uid: 10135
    04-08 15:52:55.043 19061 19061 F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021
    04-08 15:52:55.043 19061 19061 F DEBUG   :     eax 03000005  ebx cb9f4d24  ecx 7191c13b  edx 00000004
    04-08 15:52:55.043 19061 19061 F DEBUG   :     edi 03000005  esi ffb22080
    04-08 15:52:55.043 19061 19061 F DEBUG   :     ebp ffb22108  esp ffb2206c  eip cbcfc1e4
    04-08 15:52:55.077 19061 19061 F DEBUG   :
    04-08 15:52:55.077 19061 19061 F DEBUG   : backtrace:
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #00 pc 001b41e4  /data/app/Mono.Android.DebugRuntime-umHhDz421s4-tshrHwha0w==/lib/x86/libmonosgen-32bit-2.0.so (mono_image_get_name+4)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #1 pc 0000cac7  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoType*, _MonoClass*, unsigned char const*)+263) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #2 pc 0000c8cc  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+124) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #3 pc 0001621a  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::MonodroidRuntime::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+42) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       dotnet#4 pc 000325af  <anonymous:c7858000>

Investigating the issue I discovered that one of two things happened:

  1. the returned `MonoImage` instance was invalid, or
	2. the instance was valid but image name stored in `MonoImage` was
     `null`

In case of 1. I would see something similar to this in the crash log:

    04-08 15:52:55.015 19030 19030 I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
    04-08 15:52:55.015 19030 19030 I monodroid:   type == 0xc6e60d3c, klass == 0xc6e60cb8, mvid == 0xc8c02d90
    04-08 15:52:55.015 19030 19030 I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
    04-08 15:52:55.015 19030 19030 I monodroid:   calling mono_class_get_image (0xc6e60cb8)
    04-08 15:52:55.015 19030 19030 I monodroid:     image == 0x3000005

It would happen in 32-bit builds only, the 64-bit builds would lead to a
different issue, the 2. above:

    04-08 16:05:13.446 28985 28985 I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
    04-08 16:05:13.447 28985 28985 I monodroid:   type == 0x7ce3fecc78, klass == 0x7ce3fecb98, mvid == 0x7ce9404520
    04-08 16:05:13.447 28985 28985 I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
    04-08 16:05:13.447 28985 28985 I monodroid:   calling mono_class_get_image (0x7ce3fecb98)
    04-08 16:05:13.447 28985 28985 I monodroid:     image == 0x7ce3fecbc8
    04-08 16:05:13.447 28985 28985 I monodroid:     image_name == <null>

Case 1. would result in a segfault inside the `mono_image_get_name`
call, because the pointer value was clearly invalid, while case 2. would
result in a crash inside `strlen` which was passed a `null` pointer.

I found out that the root cause was in the `mono_type_get_class` call
which is supposed to be used with great caution as it eventually calls
the `mono_type_get_class_internal` function which is supposed to be
called only for object types `MONO_TYPE_CLASS` and `MONO_TYPE_VALUETYPE`
but not `MONO_TYPE_GENERICINST` type which is precisely the type that
caused the crash.  The fix is to call the `mono_class_from_mono_type`
function instead which, albeit slower, is safer and works correctly in
all cases.

Fixing this led to the next issue, a managed exception thrown after the
runtime failed to map managed type name to Java type name:

    04-08 18:08:58.886 30726 30726 W monodroid-assembly: typemap: unable to find mapping to a Java type from managed type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android'
    04-08 18:08:58.886 30726 30726 I monodroid-timing: Typemap.managed_to_java: end, total time; elapsed: 0s:0::33177
    04-08 18:08:58.888 30726 30726 D Mono    : DllImport attempting to load: '/system/lib64/liblog.so'.
    04-08 18:08:58.889 30726 30726 D Mono    : DllImport loaded library '/system/lib64/liblog.so'.
    04-08 18:08:58.889 30726 30726 D Mono    : DllImport searching in: '/system/lib64/liblog.so' ('/system/lib64/liblog.so').
    04-08 18:08:58.889 30726 30726 D Mono    : Searching for '__android_log_print'.
    04-08 18:08:58.889 30726 30726 D Mono    : Probing '__android_log_print'.
    04-08 18:08:58.889 30726 30726 D Mono    : Found as '__android_log_print'.
    04-08 18:08:58.891 30726 30726 I MonoDroid: UNHANDLED EXCEPTION:
    04-08 18:08:58.899 30726 30726 I MonoDroid: System.NotSupportedException: Cannot create instance of type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[[Xamarin.Forms.Page, Xamarin.Forms.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null]]': no Java peer type found.
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods..ctor (System.Type declaringType) [0x0004b] in <514e1249792e47a180b3f1293306b972>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.GetConstructorsForType (System.Type declaringType) [0x00031] in <514e1249792e47a180b3f1293306b972>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance (System.String constructorSignature, System.Type declaringType, Java.Interop.JniArgumentValue* parameters) [0x00038] in <514e1249792e47a180b3f1293306b972>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Android.Support.V4.App.FragmentPagerAdapter..ctor (Android.Support.V4.App.FragmentManager fm) [0x0005b] in <fefee6c2c695459088a9df092723e052>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T]..ctor (Xamarin.Forms.MultiPage`1[T] page, Android.Support.V4.App.FragmentManager fragmentManager) [0x00000] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.CreateFormsViewPager (Android.Content.Context context, Xamarin.Forms.TabbedPage tabbedPage) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1[TElement] e) [0x001cd] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000c0] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0001f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.AddChild (Xamarin.Forms.Page page, System.Boolean layout) [0x0000d] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPageInternal (Xamarin.Forms.Page newRoot) [0x00061] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPage (Xamarin.Forms.Page newRoot) [0x000e6] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.InternalSetPage (Xamarin.Forms.Page page) [0x0003f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.SetMainPage () [0x0000c] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.LoadApplication (Xamarin.Forms.Application application) [0x00140] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at SwipeViewDemo.Droid.MainActivity.OnCreate (Android.OS.Bundle savedInstanceState) [0x00035] in <15e30af50bb64ff6b6d20ac6fd546763>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x0000f] in <515e813169e54876823978ab785f569a>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.7(intptr,intptr,intptr)

Note that the type name as seen by the native code (via
`mono_get_type_name_full`) is
`Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T],
Xamarin.Forms.Platform.Android` while we should be looking for
`Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1`
instead.  The discrepancy was caused by calling
`mono_get_type_name_full` with its format parameter set to
`MONO_TYPE_NAME_FORMAT_REFLECTION`, while what we needed to do is to
pass it the format value of `MONO_TYPE_NAME_FORMAT_FULL_NAME` which this
commit implements.
grendello added a commit to grendello/xamarin-android that referenced this pull request Apr 8, 2020
Context: 7117414

7117414 introduced native code which queries
the Mono runtime to obtain an instance of `MonoClass` for a given
`MonoReflectionType` as well as the `MonoImage` associated with the
class.  However, it appears that in certain cases the class pointer
stored `MonoReflectionType` doesn't lead us to getting a valid
`MonoImage` instance, causing a segfault similar to:

    04-08 15:52:55.015 19030 19030 F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021 in tid 19030 (s.swipeviewdemo), pid 19030 (s.swipeviewdemo)
    04-08 15:52:55.037 19061 19061 I crash_dump32: obtaining output fd from tombstoned, type: kDebuggerdTombstone
    04-08 15:52:55.037  1834  1834 I /system/bin/tombstoned: received crash request for pid 19030
    04-08 15:52:55.038 19061 19061 I crash_dump32: performing dump of process 19030 (target tid = 19030)
    04-08 15:52:55.042 19061 19061 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    04-08 15:52:55.042 19061 19061 F DEBUG   : Build fingerprint: 'google/sdk_gphone_x86/generic_x86:10/QSR1.191030.002/5978551:userdebug/dev-keys'
    04-08 15:52:55.043 19061 19061 F DEBUG   : Revision: '0'
    04-08 15:52:55.043 19061 19061 F DEBUG   : ABI: 'x86'
    04-08 15:52:55.043 19061 19061 F DEBUG   : Timestamp: 2020-04-08 15:52:55+0200
    04-08 15:52:55.043 19061 19061 F DEBUG   : pid: 19030, tid: 19030, name: s.swipeviewdemo  >>> nl.versluis.swipeviewdemo <<<
    04-08 15:52:55.043 19061 19061 F DEBUG   : uid: 10135
    04-08 15:52:55.043 19061 19061 F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021
    04-08 15:52:55.043 19061 19061 F DEBUG   :     eax 03000005  ebx cb9f4d24  ecx 7191c13b  edx 00000004
    04-08 15:52:55.043 19061 19061 F DEBUG   :     edi 03000005  esi ffb22080
    04-08 15:52:55.043 19061 19061 F DEBUG   :     ebp ffb22108  esp ffb2206c  eip cbcfc1e4
    04-08 15:52:55.077 19061 19061 F DEBUG   :
    04-08 15:52:55.077 19061 19061 F DEBUG   : backtrace:
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #00 pc 001b41e4  /data/app/Mono.Android.DebugRuntime-umHhDz421s4-tshrHwha0w==/lib/x86/libmonosgen-32bit-2.0.so (mono_image_get_name+4)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #1 pc 0000cac7  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoType*, _MonoClass*, unsigned char const*)+263) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #2 pc 0000c8cc  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+124) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       #3 pc 0001621a  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::MonodroidRuntime::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+42) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
    04-08 15:52:55.077 19061 19061 F DEBUG   :       dotnet#4 pc 000325af  <anonymous:c7858000>

Investigating the issue I discovered that one of two things happened:

  1. the returned `MonoImage` instance was invalid, or
  2. the instance was valid but image name stored in `MonoImage` was
     `null`

In case of 1. I would see something similar to this in the crash log:

    04-08 15:52:55.015 19030 19030 I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
    04-08 15:52:55.015 19030 19030 I monodroid:   type == 0xc6e60d3c, klass == 0xc6e60cb8, mvid == 0xc8c02d90
    04-08 15:52:55.015 19030 19030 I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
    04-08 15:52:55.015 19030 19030 I monodroid:   calling mono_class_get_image (0xc6e60cb8)
    04-08 15:52:55.015 19030 19030 I monodroid:     image == 0x3000005

It would happen in 32-bit builds only, the 64-bit builds would lead to a
different issue, the 2. above:

    04-08 16:05:13.446 28985 28985 I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
    04-08 16:05:13.447 28985 28985 I monodroid:   type == 0x7ce3fecc78, klass == 0x7ce3fecb98, mvid == 0x7ce9404520
    04-08 16:05:13.447 28985 28985 I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
    04-08 16:05:13.447 28985 28985 I monodroid:   calling mono_class_get_image (0x7ce3fecb98)
    04-08 16:05:13.447 28985 28985 I monodroid:     image == 0x7ce3fecbc8
    04-08 16:05:13.447 28985 28985 I monodroid:     image_name == <null>

Case 1. would result in a segfault inside the `mono_image_get_name`
call, because the pointer value was clearly invalid, while case 2. would
result in a crash inside `strlen` which was passed a `null` pointer.

I found out that the root cause was in the `mono_type_get_class` call
which is supposed to be used with great caution as it eventually calls
the `mono_type_get_class_internal` function which is supposed to be
called only for object types `MONO_TYPE_CLASS` and `MONO_TYPE_VALUETYPE`
but not `MONO_TYPE_GENERICINST` type which is precisely the type that
caused the crash.  The fix is to call the `mono_class_from_mono_type`
function instead which, albeit slower, is safer and works correctly in
all cases.

Fixing this led to the next issue, a managed exception thrown after the
runtime failed to map managed type name to Java type name:

    04-08 18:08:58.886 30726 30726 W monodroid-assembly: typemap: unable to find mapping to a Java type from managed type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android'
    04-08 18:08:58.886 30726 30726 I monodroid-timing: Typemap.managed_to_java: end, total time; elapsed: 0s:0::33177
    04-08 18:08:58.888 30726 30726 D Mono    : DllImport attempting to load: '/system/lib64/liblog.so'.
    04-08 18:08:58.889 30726 30726 D Mono    : DllImport loaded library '/system/lib64/liblog.so'.
    04-08 18:08:58.889 30726 30726 D Mono    : DllImport searching in: '/system/lib64/liblog.so' ('/system/lib64/liblog.so').
    04-08 18:08:58.889 30726 30726 D Mono    : Searching for '__android_log_print'.
    04-08 18:08:58.889 30726 30726 D Mono    : Probing '__android_log_print'.
    04-08 18:08:58.889 30726 30726 D Mono    : Found as '__android_log_print'.
    04-08 18:08:58.891 30726 30726 I MonoDroid: UNHANDLED EXCEPTION:
    04-08 18:08:58.899 30726 30726 I MonoDroid: System.NotSupportedException: Cannot create instance of type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[[Xamarin.Forms.Page, Xamarin.Forms.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null]]': no Java peer type found.
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods..ctor (System.Type declaringType) [0x0004b] in <514e1249792e47a180b3f1293306b972>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.GetConstructorsForType (System.Type declaringType) [0x00031] in <514e1249792e47a180b3f1293306b972>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance (System.String constructorSignature, System.Type declaringType, Java.Interop.JniArgumentValue* parameters) [0x00038] in <514e1249792e47a180b3f1293306b972>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Android.Support.V4.App.FragmentPagerAdapter..ctor (Android.Support.V4.App.FragmentManager fm) [0x0005b] in <fefee6c2c695459088a9df092723e052>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T]..ctor (Xamarin.Forms.MultiPage`1[T] page, Android.Support.V4.App.FragmentManager fragmentManager) [0x00000] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.CreateFormsViewPager (Android.Content.Context context, Xamarin.Forms.TabbedPage tabbedPage) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1[TElement] e) [0x001cd] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000c0] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0001f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.AddChild (Xamarin.Forms.Page page, System.Boolean layout) [0x0000d] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPageInternal (Xamarin.Forms.Page newRoot) [0x00061] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPage (Xamarin.Forms.Page newRoot) [0x000e6] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.InternalSetPage (Xamarin.Forms.Page page) [0x0003f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.SetMainPage () [0x0000c] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.LoadApplication (Xamarin.Forms.Application application) [0x00140] in <9d12bb15abb54c508c4bee636d1b3a42>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at SwipeViewDemo.Droid.MainActivity.OnCreate (Android.OS.Bundle savedInstanceState) [0x00035] in <15e30af50bb64ff6b6d20ac6fd546763>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x0000f] in <515e813169e54876823978ab785f569a>:0
    04-08 18:08:58.899 30726 30726 I MonoDroid:   at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.7(intptr,intptr,intptr)

Note that the type name as seen by the native code (via
`mono_get_type_name_full`) is
`Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T],
Xamarin.Forms.Platform.Android` while we should be looking for
`Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1`
instead.  The discrepancy was caused by calling
`mono_get_type_name_full` with its format parameter set to
`MONO_TYPE_NAME_FORMAT_REFLECTION`, while what we needed to do is to
pass it the format value of `MONO_TYPE_NAME_FORMAT_FULL_NAME` which this
commit implements.
jonpryor pushed a commit that referenced this pull request Apr 9, 2020
Context: https://github.com/jfversluis/SwipeViewDemo
Context: https://github.com/xamarin/Xamarin.Forms/blob/fa33ca3b3ac5c7c875023db785b56c67015e13b1/Xamarin.Forms.Platform.Android/AppCompat/TabbedPageRenderer.cs#L512

Commit 7117414 introduced native code which queries the Mono runtime
to obtain an instance of a `MonoClass` for a given `MonoReflectionType`
as well as the `MonoImage` associated with the `MonoClass`:

	// EmbeddedAssemblies::typemap_managed_to_java(MonoReflectionType *reflection_type, const uint8_t *mvid)
	MonoReflectionType     *reflection_type = …
	MonoType               *type            = mono_reflection_type_get_type (reflection_type);
	MonoClass              *klass           = mono_type_get_class (type);   // PROBLEMATIC
	// EmbeddedAssemblies::typemap_managed_to_java(MonoType *type, MonoClass *klass, const uint8_t *mvid)
	MonoImage              *image           = mono_class_get_image (klass);

However, it appears that when dealing with closed generic types -- such
as with `new GenericHolder<int>()` -- the above call chain results in a
SIGSEGV instead of a valid `MonoImage*`:

	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021 in tid 19030 (s.swipeviewdemo), pid 19030 (s.swipeviewdemo)
	I crash_dump32: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	I /system/bin/tombstoned: received crash request for pid 19030
	I crash_dump32: performing dump of process 19030 (target tid = 19030)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'google/sdk_gphone_x86/generic_x86:10/QSR1.191030.002/5978551:userdebug/dev-keys'
	F DEBUG   : Revision: '0'
	F DEBUG   : ABI: 'x86'
	F DEBUG   : Timestamp: 2020-04-08 15:52:55+0200
	F DEBUG   : pid: 19030, tid: 19030, name: s.swipeviewdemo  >>> nl.versluis.swipeviewdemo <<<
	F DEBUG   : uid: 10135
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021
	F DEBUG   :     eax 03000005  ebx cb9f4d24  ecx 7191c13b  edx 00000004
	F DEBUG   :     edi 03000005  esi ffb22080
	F DEBUG   :     ebp ffb22108  esp ffb2206c  eip cbcfc1e4
	F DEBUG   :
	F DEBUG   : backtrace:
	F DEBUG   :       #00 pc 001b41e4  /data/app/Mono.Android.DebugRuntime-umHhDz421s4-tshrHwha0w==/lib/x86/libmonosgen-32bit-2.0.so (mono_image_get_name+4)
	F DEBUG   :       #1 pc 0000cac7  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoType*, _MonoClass*, unsigned char const*)+263) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #2 pc 0000c8cc  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+124) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #3 pc 0001621a  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::MonodroidRuntime::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+42) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #4 pc 000325af  <anonymous:c7858000>

Investigating the issue I discovered that one of two things happened:

 1. the returned `MonoImage` instance was invalid, *or*
 2. the instance was valid but image name stored in `MonoImage`
    was `null`

(1) would only happen in 32-bit builds, resulting in a SIGSEGV within
`mono_image_get_name()`, because the `image` pointer value of 0x3000005
was invalid:

	I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
	I monodroid:   type == 0xc6e60d3c, klass == 0xc6e60cb8, mvid == 0xc8c02d90
	I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
	I monodroid:   calling mono_class_get_image (0xc6e60cb8)
	I monodroid:     image == 0x3000005

(2) only happened in 64-bit builds, resulting in a SIGSEGV as
`strlen()` was passed a `null` pointer:

	I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
	I monodroid:   type == 0x7ce3fecc78, klass == 0x7ce3fecb98, mvid == 0x7ce9404520
	I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
	I monodroid:   calling mono_class_get_image (0x7ce3fecb98)
	I monodroid:     image == 0x7ce3fecbc8
	I monodroid:     image_name == <null>

I found out that the root cause was in the `mono_type_get_class()` call
which is supposed to be used with great caution as it eventually calls
the `mono_type_get_class_internal()` function which is supposed to be
called only for object types `MONO_TYPE_CLASS` and `MONO_TYPE_VALUETYPE`
but not `MONO_TYPE_GENERICINST`, and `MONO_TYPE_GENERICINST` is used
for closed generic types.

The fix is to call the `mono_class_from_mono_type()` function instead
which, albeit slower, is safer and works correctly in all cases:

	// EmbeddedAssemblies::typemap_managed_to_java(MonoReflectionType *reflection_type, const uint8_t *mvid)
	MonoReflectionType     *reflection_type = …
	MonoType               *type            = mono_reflection_type_get_type (reflection_type);
	MonoClass              *klass           = mono_class_from_mono_type (type);     // PART OF THE FIX
	// EmbeddedAssemblies::typemap_managed_to_java(MonoType *type, MonoClass *klass, const uint8_t *mvid)
	MonoImage              *image           = mono_class_get_image (klass)

Fixing this led to the next issue, a managed exception thrown after the
runtime failed to map a managed type name to Java type name:

	W monodroid-assembly: typemap: unable to find mapping to a Java type from managed type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android'
	I monodroid-timing: Typemap.managed_to_java: end, total time; elapsed: 0s:0::33177
	D Mono    : DllImport attempting to load: '/system/lib64/liblog.so'.
	D Mono    : DllImport loaded library '/system/lib64/liblog.so'.
	D Mono    : DllImport searching in: '/system/lib64/liblog.so' ('/system/lib64/liblog.so').
	D Mono    : Searching for '__android_log_print'.
	D Mono    : Probing '__android_log_print'.
	D Mono    : Found as '__android_log_print'.
	I MonoDroid: UNHANDLED EXCEPTION:
	I MonoDroid: System.NotSupportedException: Cannot create instance of type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[[Xamarin.Forms.Page, Xamarin.Forms.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null]]': no Java peer type found.
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods..ctor (System.Type declaringType) [0x0004b] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.GetConstructorsForType (System.Type declaringType) [0x00031] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance (System.String constructorSignature, System.Type declaringType, Java.Interop.JniArgumentValue* parameters) [0x00038] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Android.Support.V4.App.FragmentPagerAdapter..ctor (Android.Support.V4.App.FragmentManager fm) [0x0005b] in <fefee6c2c695459088a9df092723e052>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T]..ctor (Xamarin.Forms.MultiPage`1[T] page, Android.Support.V4.App.FragmentManager fragmentManager) [0x00000] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.CreateFormsViewPager (Android.Content.Context context, Xamarin.Forms.TabbedPage tabbedPage) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1[TElement] e) [0x001cd] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000c0] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0001f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.AddChild (Xamarin.Forms.Page page, System.Boolean layout) [0x0000d] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPageInternal (Xamarin.Forms.Page newRoot) [0x00061] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPage (Xamarin.Forms.Page newRoot) [0x000e6] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.InternalSetPage (Xamarin.Forms.Page page) [0x0003f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.SetMainPage () [0x0000c] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.LoadApplication (Xamarin.Forms.Application application) [0x00140] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at SwipeViewDemo.Droid.MainActivity.OnCreate (Android.OS.Bundle savedInstanceState) [0x00035] in <15e30af50bb64ff6b6d20ac6fd546763>:0
	I MonoDroid:   at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x0000f] in <515e813169e54876823978ab785f569a>:0
	I MonoDroid:   at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.7(intptr,intptr,intptr)

Note that the type name as seen by the native code via
`mono_get_type_name_full()` is:

	Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android

while `Mono.Android.dll` expects to be looking for:

	Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1, Xamarin.Forms.Platform.Android

This discrepancy was caused by calling `mono_get_type_name_full()`
with its format parameter set to `MONO_TYPE_NAME_FORMAT_REFLECTION`,
while we needed the format value of `MONO_TYPE_NAME_FORMAT_FULL_NAME`.
jonpryor pushed a commit that referenced this pull request Apr 9, 2020
Context: https://github.com/jfversluis/SwipeViewDemo
Context: https://github.com/xamarin/Xamarin.Forms/blob/fa33ca3b3ac5c7c875023db785b56c67015e13b1/Xamarin.Forms.Platform.Android/AppCompat/TabbedPageRenderer.cs#L512

Commit 7117414 introduced native code which queries the Mono runtime
to obtain an instance of a `MonoClass` for a given `MonoReflectionType`
as well as the `MonoImage` associated with the `MonoClass`:

	// EmbeddedAssemblies::typemap_managed_to_java(MonoReflectionType *reflection_type, const uint8_t *mvid)
	MonoReflectionType     *reflection_type = …
	MonoType               *type            = mono_reflection_type_get_type (reflection_type);
	MonoClass              *klass           = mono_type_get_class (type);   // PROBLEMATIC
	// EmbeddedAssemblies::typemap_managed_to_java(MonoType *type, MonoClass *klass, const uint8_t *mvid)
	MonoImage              *image           = mono_class_get_image (klass);

However, it appears that when dealing with closed generic types -- such
as with `new GenericHolder<int>()` -- the above call chain results in a
SIGSEGV instead of a valid `MonoImage*`:

	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021 in tid 19030 (s.swipeviewdemo), pid 19030 (s.swipeviewdemo)
	I crash_dump32: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	I /system/bin/tombstoned: received crash request for pid 19030
	I crash_dump32: performing dump of process 19030 (target tid = 19030)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'google/sdk_gphone_x86/generic_x86:10/QSR1.191030.002/5978551:userdebug/dev-keys'
	F DEBUG   : Revision: '0'
	F DEBUG   : ABI: 'x86'
	F DEBUG   : Timestamp: 2020-04-08 15:52:55+0200
	F DEBUG   : pid: 19030, tid: 19030, name: s.swipeviewdemo  >>> nl.versluis.swipeviewdemo <<<
	F DEBUG   : uid: 10135
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021
	F DEBUG   :     eax 03000005  ebx cb9f4d24  ecx 7191c13b  edx 00000004
	F DEBUG   :     edi 03000005  esi ffb22080
	F DEBUG   :     ebp ffb22108  esp ffb2206c  eip cbcfc1e4
	F DEBUG   :
	F DEBUG   : backtrace:
	F DEBUG   :       #00 pc 001b41e4  /data/app/Mono.Android.DebugRuntime-umHhDz421s4-tshrHwha0w==/lib/x86/libmonosgen-32bit-2.0.so (mono_image_get_name+4)
	F DEBUG   :       #1 pc 0000cac7  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoType*, _MonoClass*, unsigned char const*)+263) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #2 pc 0000c8cc  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+124) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #3 pc 0001621a  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::MonodroidRuntime::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+42) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #4 pc 000325af  <anonymous:c7858000>

Investigating the issue I discovered that one of two things happened:

 1. the returned `MonoImage` instance was invalid, *or*
 2. the instance was valid but image name stored in `MonoImage`
    was `null`

(1) would only happen in 32-bit builds, resulting in a SIGSEGV within
`mono_image_get_name()`, because the `image` pointer value of 0x3000005
was invalid:

	I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
	I monodroid:   type == 0xc6e60d3c, klass == 0xc6e60cb8, mvid == 0xc8c02d90
	I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
	I monodroid:   calling mono_class_get_image (0xc6e60cb8)
	I monodroid:     image == 0x3000005

(2) only happened in 64-bit builds, resulting in a SIGSEGV as
`strlen()` was passed a `null` pointer:

	I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
	I monodroid:   type == 0x7ce3fecc78, klass == 0x7ce3fecb98, mvid == 0x7ce9404520
	I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
	I monodroid:   calling mono_class_get_image (0x7ce3fecb98)
	I monodroid:     image == 0x7ce3fecbc8
	I monodroid:     image_name == <null>

I found out that the root cause was in the `mono_type_get_class()` call
which is supposed to be used with great caution as it eventually calls
the `mono_type_get_class_internal()` function which is supposed to be
called only for object types `MONO_TYPE_CLASS` and `MONO_TYPE_VALUETYPE`
but not `MONO_TYPE_GENERICINST`, and `MONO_TYPE_GENERICINST` is used
for closed generic types.

The fix is to call the `mono_class_from_mono_type()` function instead
which, albeit slower, is safer and works correctly in all cases:

	// EmbeddedAssemblies::typemap_managed_to_java(MonoReflectionType *reflection_type, const uint8_t *mvid)
	MonoReflectionType     *reflection_type = …
	MonoType               *type            = mono_reflection_type_get_type (reflection_type);
	MonoClass              *klass           = mono_class_from_mono_type (type);     // PART OF THE FIX
	// EmbeddedAssemblies::typemap_managed_to_java(MonoType *type, MonoClass *klass, const uint8_t *mvid)
	MonoImage              *image           = mono_class_get_image (klass)

Fixing this led to the next issue, a managed exception thrown after the
runtime failed to map a managed type name to Java type name:

	W monodroid-assembly: typemap: unable to find mapping to a Java type from managed type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android'
	I monodroid-timing: Typemap.managed_to_java: end, total time; elapsed: 0s:0::33177
	D Mono    : DllImport attempting to load: '/system/lib64/liblog.so'.
	D Mono    : DllImport loaded library '/system/lib64/liblog.so'.
	D Mono    : DllImport searching in: '/system/lib64/liblog.so' ('/system/lib64/liblog.so').
	D Mono    : Searching for '__android_log_print'.
	D Mono    : Probing '__android_log_print'.
	D Mono    : Found as '__android_log_print'.
	I MonoDroid: UNHANDLED EXCEPTION:
	I MonoDroid: System.NotSupportedException: Cannot create instance of type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[[Xamarin.Forms.Page, Xamarin.Forms.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null]]': no Java peer type found.
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods..ctor (System.Type declaringType) [0x0004b] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.GetConstructorsForType (System.Type declaringType) [0x00031] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance (System.String constructorSignature, System.Type declaringType, Java.Interop.JniArgumentValue* parameters) [0x00038] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Android.Support.V4.App.FragmentPagerAdapter..ctor (Android.Support.V4.App.FragmentManager fm) [0x0005b] in <fefee6c2c695459088a9df092723e052>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T]..ctor (Xamarin.Forms.MultiPage`1[T] page, Android.Support.V4.App.FragmentManager fragmentManager) [0x00000] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.CreateFormsViewPager (Android.Content.Context context, Xamarin.Forms.TabbedPage tabbedPage) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1[TElement] e) [0x001cd] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000c0] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0001f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.AddChild (Xamarin.Forms.Page page, System.Boolean layout) [0x0000d] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPageInternal (Xamarin.Forms.Page newRoot) [0x00061] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPage (Xamarin.Forms.Page newRoot) [0x000e6] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.InternalSetPage (Xamarin.Forms.Page page) [0x0003f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.SetMainPage () [0x0000c] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.LoadApplication (Xamarin.Forms.Application application) [0x00140] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at SwipeViewDemo.Droid.MainActivity.OnCreate (Android.OS.Bundle savedInstanceState) [0x00035] in <15e30af50bb64ff6b6d20ac6fd546763>:0
	I MonoDroid:   at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x0000f] in <515e813169e54876823978ab785f569a>:0
	I MonoDroid:   at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.7(intptr,intptr,intptr)

Note that the type name as seen by the native code via
`mono_get_type_name_full()` is:

	Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android

while `Mono.Android.dll` expects to be looking for:

	Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1, Xamarin.Forms.Platform.Android

This discrepancy was caused by calling `mono_get_type_name_full()`
with its format parameter set to `MONO_TYPE_NAME_FORMAT_REFLECTION`,
while we needed the format value of `MONO_TYPE_NAME_FORMAT_FULL_NAME`.
jonpryor pushed a commit that referenced this pull request Apr 9, 2020
Context: https://github.com/jfversluis/SwipeViewDemo
Context: https://github.com/xamarin/Xamarin.Forms/blob/fa33ca3b3ac5c7c875023db785b56c67015e13b1/Xamarin.Forms.Platform.Android/AppCompat/TabbedPageRenderer.cs#L512

Commit 7117414 introduced native code which queries the Mono runtime
to obtain an instance of a `MonoClass` for a given `MonoReflectionType`
as well as the `MonoImage` associated with the `MonoClass`:

	// EmbeddedAssemblies::typemap_managed_to_java(MonoReflectionType *reflection_type, const uint8_t *mvid)
	MonoReflectionType     *reflection_type = …
	MonoType               *type            = mono_reflection_type_get_type (reflection_type);
	MonoClass              *klass           = mono_type_get_class (type);   // PROBLEMATIC
	// EmbeddedAssemblies::typemap_managed_to_java(MonoType *type, MonoClass *klass, const uint8_t *mvid)
	MonoImage              *image           = mono_class_get_image (klass);

However, it appears that when dealing with closed generic types -- such
as with `new GenericHolder<int>()` -- the above call chain results in a
SIGSEGV instead of a valid `MonoImage*`:

	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021 in tid 19030 (s.swipeviewdemo), pid 19030 (s.swipeviewdemo)
	I crash_dump32: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	I /system/bin/tombstoned: received crash request for pid 19030
	I crash_dump32: performing dump of process 19030 (target tid = 19030)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'google/sdk_gphone_x86/generic_x86:10/QSR1.191030.002/5978551:userdebug/dev-keys'
	F DEBUG   : Revision: '0'
	F DEBUG   : ABI: 'x86'
	F DEBUG   : Timestamp: 2020-04-08 15:52:55+0200
	F DEBUG   : pid: 19030, tid: 19030, name: s.swipeviewdemo  >>> nl.versluis.swipeviewdemo <<<
	F DEBUG   : uid: 10135
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3000021
	F DEBUG   :     eax 03000005  ebx cb9f4d24  ecx 7191c13b  edx 00000004
	F DEBUG   :     edi 03000005  esi ffb22080
	F DEBUG   :     ebp ffb22108  esp ffb2206c  eip cbcfc1e4
	F DEBUG   :
	F DEBUG   : backtrace:
	F DEBUG   :       #00 pc 001b41e4  /data/app/Mono.Android.DebugRuntime-umHhDz421s4-tshrHwha0w==/lib/x86/libmonosgen-32bit-2.0.so (mono_image_get_name+4)
	F DEBUG   :       #1 pc 0000cac7  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoType*, _MonoClass*, unsigned char const*)+263) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #2 pc 0000c8cc  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+124) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #3 pc 0001621a  /data/app/nl.versluis.swipeviewdemo-jCFH_bcCNuFx1tLUhaJ4nw==/lib/x86/libmonodroid.so (xamarin::android::internal::MonodroidRuntime::typemap_managed_to_java(_MonoReflectionType*, unsigned char const*)+42) (BuildId: a2585ad379f788049e463af58c8686e9cdc1e778)
	F DEBUG   :       #4 pc 000325af  <anonymous:c7858000>

Investigating the issue I discovered that one of two things happened:

 1. the returned `MonoImage` instance was invalid, *or*
 2. the instance was valid but image name stored in `MonoImage`
    was `null`

(1) would only happen in 32-bit builds, resulting in a SIGSEGV within
`mono_image_get_name()`, because the `image` pointer value of 0x3000005
was invalid:

	I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
	I monodroid:   type == 0xc6e60d3c, klass == 0xc6e60cb8, mvid == 0xc8c02d90
	I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
	I monodroid:   calling mono_class_get_image (0xc6e60cb8)
	I monodroid:     image == 0x3000005

(2) only happened in 64-bit builds, resulting in a SIGSEGV as
`strlen()` was passed a `null` pointer:

	I monodroid: const char *xamarin::android::internal::EmbeddedAssemblies::typemap_managed_to_java(MonoType *, MonoClass *, const uint8_t *)
	I monodroid:   type == 0x7ce3fecc78, klass == 0x7ce3fecb98, mvid == 0x7ce9404520
	I monodroid:   type name == Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[Xamarin.Forms.Page]
	I monodroid:   calling mono_class_get_image (0x7ce3fecb98)
	I monodroid:     image == 0x7ce3fecbc8
	I monodroid:     image_name == <null>

I found out that the root cause was in the `mono_type_get_class()` call
which is supposed to be used with great caution as it eventually calls
the `mono_type_get_class_internal()` function which is supposed to be
called only for object types `MONO_TYPE_CLASS` and `MONO_TYPE_VALUETYPE`
but not `MONO_TYPE_GENERICINST`, and `MONO_TYPE_GENERICINST` is used
for closed generic types.

The fix is to call the `mono_class_from_mono_type()` function instead
which, albeit slower, is safer and works correctly in all cases:

	// EmbeddedAssemblies::typemap_managed_to_java(MonoReflectionType *reflection_type, const uint8_t *mvid)
	MonoReflectionType     *reflection_type = …
	MonoType               *type            = mono_reflection_type_get_type (reflection_type);
	MonoClass              *klass           = mono_class_from_mono_type (type);     // PART OF THE FIX
	// EmbeddedAssemblies::typemap_managed_to_java(MonoType *type, MonoClass *klass, const uint8_t *mvid)
	MonoImage              *image           = mono_class_get_image (klass)

Fixing this led to the next issue, a managed exception thrown after the
runtime failed to map a managed type name to Java type name:

	W monodroid-assembly: typemap: unable to find mapping to a Java type from managed type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android'
	I monodroid-timing: Typemap.managed_to_java: end, total time; elapsed: 0s:0::33177
	D Mono    : DllImport attempting to load: '/system/lib64/liblog.so'.
	D Mono    : DllImport loaded library '/system/lib64/liblog.so'.
	D Mono    : DllImport searching in: '/system/lib64/liblog.so' ('/system/lib64/liblog.so').
	D Mono    : Searching for '__android_log_print'.
	D Mono    : Probing '__android_log_print'.
	D Mono    : Found as '__android_log_print'.
	I MonoDroid: UNHANDLED EXCEPTION:
	I MonoDroid: System.NotSupportedException: Cannot create instance of type 'Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[[Xamarin.Forms.Page, Xamarin.Forms.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null]]': no Java peer type found.
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods..ctor (System.Type declaringType) [0x0004b] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.GetConstructorsForType (System.Type declaringType) [0x00031] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance (System.String constructorSignature, System.Type declaringType, Java.Interop.JniArgumentValue* parameters) [0x00038] in <514e1249792e47a180b3f1293306b972>:0
	I MonoDroid:   at Android.Support.V4.App.FragmentPagerAdapter..ctor (Android.Support.V4.App.FragmentManager fm) [0x0005b] in <fefee6c2c695459088a9df092723e052>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T]..ctor (Xamarin.Forms.MultiPage`1[T] page, Android.Support.V4.App.FragmentManager fragmentManager) [0x00000] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.CreateFormsViewPager (Android.Content.Context context, Xamarin.Forms.TabbedPage tabbedPage) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.TabbedPageRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1[TElement] e) [0x001cd] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000c0] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0001f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.AddChild (Xamarin.Forms.Page page, System.Boolean layout) [0x0000d] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPageInternal (Xamarin.Forms.Page newRoot) [0x00061] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPage (Xamarin.Forms.Page newRoot) [0x000e6] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.InternalSetPage (Xamarin.Forms.Page page) [0x0003f] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.SetMainPage () [0x0000c] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.LoadApplication (Xamarin.Forms.Application application) [0x00140] in <9d12bb15abb54c508c4bee636d1b3a42>:0
	I MonoDroid:   at SwipeViewDemo.Droid.MainActivity.OnCreate (Android.OS.Bundle savedInstanceState) [0x00035] in <15e30af50bb64ff6b6d20ac6fd546763>:0
	I MonoDroid:   at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x0000f] in <515e813169e54876823978ab785f569a>:0
	I MonoDroid:   at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.7(intptr,intptr,intptr)

Note that the type name as seen by the native code via
`mono_get_type_name_full()` is:

	Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1[T], Xamarin.Forms.Platform.Android

while `Mono.Android.dll` expects to be looking for:

	Xamarin.Forms.Platform.Android.AppCompat.FormsFragmentPagerAdapter`1, Xamarin.Forms.Platform.Android

This discrepancy was caused by calling `mono_get_type_name_full()`
with its format parameter set to `MONO_TYPE_NAME_FORMAT_REFLECTION`,
while we needed the format value of `MONO_TYPE_NAME_FORMAT_FULL_NAME`.
grendello added a commit to grendello/xamarin-android that referenced this pull request May 11, 2020
Fixes: dotnet#4596
Context: a017561
Context: https://gist.github.com/pjcollins/87762e81f1f3c7e8b821356e4612eecf

A missing parameter in a call to `log_debug` added in a017561 may lead
to a segfault when `assembly` log category and `debug` log level are
enabled:

		F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3 in tid 922 (DrawableTinting), pid 922 (DrawableTinting)
		I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
		I /system/bin/tombstoned: received crash request for pid 922
		I crash_dump64: performing dump of process 922 (target tid = 922)
		F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
		F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:9/PSR1.180720.012/4923214:userdebug/test-keys'
		F DEBUG   : Revision: '0'
		F DEBUG   : ABI: 'x86_64'
		F DEBUG   : pid: 922, tid: 922, name: DrawableTinting  >>> com.xamarin.DrawableTinting <<<
		F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3
		F DEBUG   : Cause: null pointer dereference
		F DEBUG   :     rax 0000000000000000  rbx 00007ffed3c283c0  rcx 0000000000000003  rdx 0000000000000002
		F DEBUG   :     r8  00007ffed3c283c0  r9  00000000ffffffff  r10 00007ffed3c283d0  r11 00007ffed3c28824
		F DEBUG   :     r12 00007c88774a2f17  r13 00000000ffffffff  r14 0000000000000000  r15 00007ffed3c283d0
		F DEBUG   :     rdi 0000000000000003  rsi 00007ffed3c283bb
		F DEBUG   :     rbp 00007ffed3c28f18  rsp 00007ffed3c28288  rip 00007c890f860761
		F DEBUG   :
		F DEBUG   : backtrace:
		F DEBUG   :     #00 pc 0000000000020761  /system/lib64/libc.so (strlen+17)
		F DEBUG   :     #1 pc 000000000006e761  /system/lib64/libc.so (__vfprintf+5953)
		F DEBUG   :     #2 pc 000000000008df5d  /system/lib64/libc.so (vsnprintf+189)
		F DEBUG   :     #3 pc 0000000000007b60  /system/lib64/liblog.so (__android_log_vprint+64)
		F DEBUG   :     dotnet#4 pc 000000000001350c  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (log_debug_nocheck(_LogCategories, char const*, ...)+204)
		F DEBUG   :     dotnet#5 pc 000000000000de6a  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+538)
		F DEBUG   :     dotnet#6 pc 000000000000df13  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99)
		F DEBUG   :     dotnet#7 pc 00000000000d57f8  <anonymous:0000000042d04000>

Add the missing parameter to prevent the `SIGSEGV` from happening.
jonpryor pushed a commit that referenced this pull request May 11, 2020
…4673)

Fixes: #4596
Context: a017561
Context: https://gist.github.com/pjcollins/87762e81f1f3c7e8b821356e4612eecf

A missing parameter in a call to `log_debug` added iFixes: #4596
Context: a017561
Context: https://gist.github.com/pjcollins/87762e81f1f3c7e8b821356e4612eecf

A missing parameter in a call to `log_debug()` added in a017561 may
lead to a segfault when `assembly` log category and `debug` log level
are enabled:

	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3 in tid 922 (DrawableTinting), pid 922 (DrawableTinting)
	I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	I /system/bin/tombstoned: received crash request for pid 922
	I crash_dump64: performing dump of process 922 (target tid = 922)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:9/PSR1.180720.012/4923214:userdebug/test-keys'
	F DEBUG   : Revision: '0'
	F DEBUG   : ABI: 'x86_64'
	F DEBUG   : pid: 922, tid: 922, name: DrawableTinting  >>> com.xamarin.DrawableTinting <<<
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3
	F DEBUG   : Cause: null pointer dereference
	F DEBUG   :     rax 0000000000000000  rbx 00007ffed3c283c0  rcx 0000000000000003  rdx 0000000000000002
	F DEBUG   :     r8  00007ffed3c283c0  r9  00000000ffffffff  r10 00007ffed3c283d0  r11 00007ffed3c28824
	F DEBUG   :     r12 00007c88774a2f17  r13 00000000ffffffff  r14 0000000000000000  r15 00007ffed3c283d0
	F DEBUG   :     rdi 0000000000000003  rsi 00007ffed3c283bb
	F DEBUG   :     rbp 00007ffed3c28f18  rsp 00007ffed3c28288  rip 00007c890f860761
	F DEBUG   :
	F DEBUG   : backtrace:
	F DEBUG   :     #00 pc 0000000000020761  /system/lib64/libc.so (strlen+17)
	F DEBUG   :     #1 pc 000000000006e761  /system/lib64/libc.so (__vfprintf+5953)
	F DEBUG   :     #2 pc 000000000008df5d  /system/lib64/libc.so (vsnprintf+189)
	F DEBUG   :     #3 pc 0000000000007b60  /system/lib64/liblog.so (__android_log_vprint+64)
	F DEBUG   :     #4 pc 000000000001350c  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (log_debug_nocheck(_LogCategories, char const*, ...)+204)
	F DEBUG   :     #5 pc 000000000000de6a  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+538)
	F DEBUG   :     #6 pc 000000000000df13  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99)
	F DEBUG   :     #7 pc 00000000000d57f8  <anonymous:0000000042d04000>

Add the missing parameter to prevent the `SIGSEGV` from happening.n a017561 may lead
to a segfault when `assembly` log category and `debug` log level are
enabled:

		F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3 in tid 922 (DrawableTinting), pid 922 (DrawableTinting)
		I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
		I /system/bin/tombstoned: received crash request for pid 922
		I crash_dump64: performing dump of process 922 (target tid = 922)
		F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
		F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:9/PSR1.180720.012/4923214:userdebug/test-keys'
		F DEBUG   : Revision: '0'
		F DEBUG   : ABI: 'x86_64'
		F DEBUG   : pid: 922, tid: 922, name: DrawableTinting  >>> com.xamarin.DrawableTinting <<<
		F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3
		F DEBUG   : Cause: null pointer dereference
		F DEBUG   :     rax 0000000000000000  rbx 00007ffed3c283c0  rcx 0000000000000003  rdx 0000000000000002
		F DEBUG   :     r8  00007ffed3c283c0  r9  00000000ffffffff  r10 00007ffed3c283d0  r11 00007ffed3c28824
		F DEBUG   :     r12 00007c88774a2f17  r13 00000000ffffffff  r14 0000000000000000  r15 00007ffed3c283d0
		F DEBUG   :     rdi 0000000000000003  rsi 00007ffed3c283bb
		F DEBUG   :     rbp 00007ffed3c28f18  rsp 00007ffed3c28288  rip 00007c890f860761
		F DEBUG   :
		F DEBUG   : backtrace:
		F DEBUG   :     #00 pc 0000000000020761  /system/lib64/libc.so (strlen+17)
		F DEBUG   :     #1 pc 000000000006e761  /system/lib64/libc.so (__vfprintf+5953)
		F DEBUG   :     #2 pc 000000000008df5d  /system/lib64/libc.so (vsnprintf+189)
		F DEBUG   :     #3 pc 0000000000007b60  /system/lib64/liblog.so (__android_log_vprint+64)
		F DEBUG   :     #4 pc 000000000001350c  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (log_debug_nocheck(_LogCategories, char const*, ...)+204)
		F DEBUG   :     #5 pc 000000000000de6a  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+538)
		F DEBUG   :     #6 pc 000000000000df13  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99)
		F DEBUG   :     #7 pc 00000000000d57f8  <anonymous:0000000042d04000>

Add the missing parameter to prevent the `SIGSEGV` from happening.
jonpryor pushed a commit that referenced this pull request May 12, 2020
…4673)

Fixes: #4596
Context: a017561
Context: https://gist.github.com/pjcollins/87762e81f1f3c7e8b821356e4612eecf

A missing parameter in a call to `log_debug` added iFixes: #4596
Context: a017561
Context: https://gist.github.com/pjcollins/87762e81f1f3c7e8b821356e4612eecf

A missing parameter in a call to `log_debug()` added in a017561 may
lead to a segfault when `assembly` log category and `debug` log level
are enabled:

	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3 in tid 922 (DrawableTinting), pid 922 (DrawableTinting)
	I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	I /system/bin/tombstoned: received crash request for pid 922
	I crash_dump64: performing dump of process 922 (target tid = 922)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:9/PSR1.180720.012/4923214:userdebug/test-keys'
	F DEBUG   : Revision: '0'
	F DEBUG   : ABI: 'x86_64'
	F DEBUG   : pid: 922, tid: 922, name: DrawableTinting  >>> com.xamarin.DrawableTinting <<<
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3
	F DEBUG   : Cause: null pointer dereference
	F DEBUG   :     rax 0000000000000000  rbx 00007ffed3c283c0  rcx 0000000000000003  rdx 0000000000000002
	F DEBUG   :     r8  00007ffed3c283c0  r9  00000000ffffffff  r10 00007ffed3c283d0  r11 00007ffed3c28824
	F DEBUG   :     r12 00007c88774a2f17  r13 00000000ffffffff  r14 0000000000000000  r15 00007ffed3c283d0
	F DEBUG   :     rdi 0000000000000003  rsi 00007ffed3c283bb
	F DEBUG   :     rbp 00007ffed3c28f18  rsp 00007ffed3c28288  rip 00007c890f860761
	F DEBUG   :
	F DEBUG   : backtrace:
	F DEBUG   :     #00 pc 0000000000020761  /system/lib64/libc.so (strlen+17)
	F DEBUG   :     #1 pc 000000000006e761  /system/lib64/libc.so (__vfprintf+5953)
	F DEBUG   :     #2 pc 000000000008df5d  /system/lib64/libc.so (vsnprintf+189)
	F DEBUG   :     #3 pc 0000000000007b60  /system/lib64/liblog.so (__android_log_vprint+64)
	F DEBUG   :     #4 pc 000000000001350c  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (log_debug_nocheck(_LogCategories, char const*, ...)+204)
	F DEBUG   :     #5 pc 000000000000de6a  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+538)
	F DEBUG   :     #6 pc 000000000000df13  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99)
	F DEBUG   :     #7 pc 00000000000d57f8  <anonymous:0000000042d04000>

Add the missing parameter to prevent the `SIGSEGV` from happening.n a017561 may lead
to a segfault when `assembly` log category and `debug` log level are
enabled:

		F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3 in tid 922 (DrawableTinting), pid 922 (DrawableTinting)
		I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
		I /system/bin/tombstoned: received crash request for pid 922
		I crash_dump64: performing dump of process 922 (target tid = 922)
		F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
		F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:9/PSR1.180720.012/4923214:userdebug/test-keys'
		F DEBUG   : Revision: '0'
		F DEBUG   : ABI: 'x86_64'
		F DEBUG   : pid: 922, tid: 922, name: DrawableTinting  >>> com.xamarin.DrawableTinting <<<
		F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3
		F DEBUG   : Cause: null pointer dereference
		F DEBUG   :     rax 0000000000000000  rbx 00007ffed3c283c0  rcx 0000000000000003  rdx 0000000000000002
		F DEBUG   :     r8  00007ffed3c283c0  r9  00000000ffffffff  r10 00007ffed3c283d0  r11 00007ffed3c28824
		F DEBUG   :     r12 00007c88774a2f17  r13 00000000ffffffff  r14 0000000000000000  r15 00007ffed3c283d0
		F DEBUG   :     rdi 0000000000000003  rsi 00007ffed3c283bb
		F DEBUG   :     rbp 00007ffed3c28f18  rsp 00007ffed3c28288  rip 00007c890f860761
		F DEBUG   :
		F DEBUG   : backtrace:
		F DEBUG   :     #00 pc 0000000000020761  /system/lib64/libc.so (strlen+17)
		F DEBUG   :     #1 pc 000000000006e761  /system/lib64/libc.so (__vfprintf+5953)
		F DEBUG   :     #2 pc 000000000008df5d  /system/lib64/libc.so (vsnprintf+189)
		F DEBUG   :     #3 pc 0000000000007b60  /system/lib64/liblog.so (__android_log_vprint+64)
		F DEBUG   :     #4 pc 000000000001350c  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (log_debug_nocheck(_LogCategories, char const*, ...)+204)
		F DEBUG   :     #5 pc 000000000000de6a  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+538)
		F DEBUG   :     #6 pc 000000000000df13  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99)
		F DEBUG   :     #7 pc 00000000000d57f8  <anonymous:0000000042d04000>

Add the missing parameter to prevent the `SIGSEGV` from happening.
jonpryor pushed a commit that referenced this pull request May 12, 2020
…4673)

Fixes: #4596
Context: a017561
Context: https://gist.github.com/pjcollins/87762e81f1f3c7e8b821356e4612eecf

A missing parameter in a call to `log_debug` added iFixes: #4596
Context: a017561
Context: https://gist.github.com/pjcollins/87762e81f1f3c7e8b821356e4612eecf

A missing parameter in a call to `log_debug()` added in a017561 may
lead to a segfault when `assembly` log category and `debug` log level
are enabled:

	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3 in tid 922 (DrawableTinting), pid 922 (DrawableTinting)
	I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	I /system/bin/tombstoned: received crash request for pid 922
	I crash_dump64: performing dump of process 922 (target tid = 922)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:9/PSR1.180720.012/4923214:userdebug/test-keys'
	F DEBUG   : Revision: '0'
	F DEBUG   : ABI: 'x86_64'
	F DEBUG   : pid: 922, tid: 922, name: DrawableTinting  >>> com.xamarin.DrawableTinting <<<
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3
	F DEBUG   : Cause: null pointer dereference
	F DEBUG   :     rax 0000000000000000  rbx 00007ffed3c283c0  rcx 0000000000000003  rdx 0000000000000002
	F DEBUG   :     r8  00007ffed3c283c0  r9  00000000ffffffff  r10 00007ffed3c283d0  r11 00007ffed3c28824
	F DEBUG   :     r12 00007c88774a2f17  r13 00000000ffffffff  r14 0000000000000000  r15 00007ffed3c283d0
	F DEBUG   :     rdi 0000000000000003  rsi 00007ffed3c283bb
	F DEBUG   :     rbp 00007ffed3c28f18  rsp 00007ffed3c28288  rip 00007c890f860761
	F DEBUG   :
	F DEBUG   : backtrace:
	F DEBUG   :     #00 pc 0000000000020761  /system/lib64/libc.so (strlen+17)
	F DEBUG   :     #1 pc 000000000006e761  /system/lib64/libc.so (__vfprintf+5953)
	F DEBUG   :     #2 pc 000000000008df5d  /system/lib64/libc.so (vsnprintf+189)
	F DEBUG   :     #3 pc 0000000000007b60  /system/lib64/liblog.so (__android_log_vprint+64)
	F DEBUG   :     #4 pc 000000000001350c  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (log_debug_nocheck(_LogCategories, char const*, ...)+204)
	F DEBUG   :     #5 pc 000000000000de6a  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+538)
	F DEBUG   :     #6 pc 000000000000df13  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99)
	F DEBUG   :     #7 pc 00000000000d57f8  <anonymous:0000000042d04000>

Add the missing parameter to prevent the `SIGSEGV` from happening.n a017561 may lead
to a segfault when `assembly` log category and `debug` log level are
enabled:

		F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3 in tid 922 (DrawableTinting), pid 922 (DrawableTinting)
		I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
		I /system/bin/tombstoned: received crash request for pid 922
		I crash_dump64: performing dump of process 922 (target tid = 922)
		F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
		F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:9/PSR1.180720.012/4923214:userdebug/test-keys'
		F DEBUG   : Revision: '0'
		F DEBUG   : ABI: 'x86_64'
		F DEBUG   : pid: 922, tid: 922, name: DrawableTinting  >>> com.xamarin.DrawableTinting <<<
		F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x3
		F DEBUG   : Cause: null pointer dereference
		F DEBUG   :     rax 0000000000000000  rbx 00007ffed3c283c0  rcx 0000000000000003  rdx 0000000000000002
		F DEBUG   :     r8  00007ffed3c283c0  r9  00000000ffffffff  r10 00007ffed3c283d0  r11 00007ffed3c28824
		F DEBUG   :     r12 00007c88774a2f17  r13 00000000ffffffff  r14 0000000000000000  r15 00007ffed3c283d0
		F DEBUG   :     rdi 0000000000000003  rsi 00007ffed3c283bb
		F DEBUG   :     rbp 00007ffed3c28f18  rsp 00007ffed3c28288  rip 00007c890f860761
		F DEBUG   :
		F DEBUG   : backtrace:
		F DEBUG   :     #00 pc 0000000000020761  /system/lib64/libc.so (strlen+17)
		F DEBUG   :     #1 pc 000000000006e761  /system/lib64/libc.so (__vfprintf+5953)
		F DEBUG   :     #2 pc 000000000008df5d  /system/lib64/libc.so (vsnprintf+189)
		F DEBUG   :     #3 pc 0000000000007b60  /system/lib64/liblog.so (__android_log_vprint+64)
		F DEBUG   :     #4 pc 000000000001350c  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (log_debug_nocheck(_LogCategories, char const*, ...)+204)
		F DEBUG   :     #5 pc 000000000000de6a  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+538)
		F DEBUG   :     #6 pc 000000000000df13  /data/app/com.xamarin.DrawableTinting-zvchh4ya_DW11GfpEPFICw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99)
		F DEBUG   :     #7 pc 00000000000d57f8  <anonymous:0000000042d04000>

Add the missing parameter to prevent the `SIGSEGV` from happening.
grendello added a commit to grendello/xamarin-android that referenced this pull request May 26, 2020
Fixes: dotnet#4713
Context: mono/mono@10795da1c065c
Context: mono/mono@8c085a99b32e9

Whenever Xamarin.Android runtime needs to instantiate a managed type, it
first looks it up by calling the following function:

    MonoType *type = mono_reflection_type_from_name ("MyType, Assembly", nullptr);

The `nullptr` pointer refers to an instance of the Mono `MonoImage`
structure and if `null`, it should cause Mono to find the correct image
containing the type and load it, if not already loaded.

The pointer is propagated down the call chain inside Mono and due to one
of the functions called not properly validating its arguments, the
`null` pointer was dereferenced, leading to a crash similar to:

    libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0 in tid 11029 (ompanyname.app3), pid 11029 (ompanyname.app3)
    crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
    /system/bin/tombstoned: received crash request for pid 11029
    crash_dump64: performing dump of process 11029 (target tid = 11029)
    DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    DEBUG   : Build fingerprint: 'google/sdk_gphone_x86_64/generic_x86_64:10/QSR1.190920.001/5891938:user/release-keys'
    DEBUG   : Revision: '0'
    DEBUG   : ABI: 'x86_64'
    DEBUG   : Timestamp: 2020-05-25 14:45:29+0200
    DEBUG   : pid: 11029, tid: 11029, name: ompanyname.app3  >>> com.companyname.app3 <<<
    DEBUG   : uid: 10134
    DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0
    DEBUG   : Cause: null pointer dereference
    DEBUG   :     rax 000000000000002f  rbx 0000000000000001  rcx 0000000000000000  rdx 0000000000000030
    DEBUG   :     r8  0000000000000003  r9  000000000013e2e2  r10 0173eed800000000  r11 0000000000000206
    DEBUG   :     r12 0000000000000000  r13 00007478530343c0  r14 00007478075eda33  r15 000074780763efb0
    DEBUG   :     rdi 0000000000000000  rsi 00007478e2cb14d0
    DEBUG   :     rbp 00007ffef3a35680  rsp 00007ffef3a355d0  rip 0000747807a4066a
    DEBUG   :
    DEBUG   : backtrace:
    DEBUG   :       #00 pc 00000000003ba66a  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (_mono_reflection_get_type_from_info+474)
    DEBUG   :       #1 pc 00000000003ba3d1  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name_checked+321)
    DEBUG   :       #2 pc 00000000003ba26d  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name+125)
    DEBUG   :       #3 pc 000000000000ddb5  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+389) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
    DEBUG   :       dotnet#4 pc 000000000000def3  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
    DEBUG   :       dotnet#5 pc 0000000000069532  <anonymous:5ad25000>

Mono commit mono/mono@10795da1c06 fixes this issue.

Other changes:

 * mono/mono@89d772a3abb Always include Unicode charinfo, so tar made in csc mode works in mcs mode (#19813)
 * mono/mono@e9d3af508e4 Bump bockbuild to get mono/bockbuild#159
 * mono/mono@d6f0c25d34d [2020-02] Bump msbuild to track mono-2019-12 (#19661)
grendello added a commit to grendello/xamarin-android that referenced this pull request May 27, 2020
Fixes: dotnet#4713
Context: mono/mono@10795da1c065c
Context: mono/mono@8c085a99b32e9

Whenever Xamarin.Android runtime needs to instantiate a managed type, it
first looks it up by calling the following function:

    MonoType *type = mono_reflection_type_from_name ("MyType, Assembly", nullptr);

The `nullptr` pointer refers to an instance of the Mono `MonoImage`
structure and if `null`, it should cause Mono to find the correct image
containing the type and load it, if not already loaded.

The pointer is propagated down the call chain inside Mono and due to one
of the functions called not properly validating its arguments, the
`null` pointer was dereferenced, leading to a crash similar to:

    libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0 in tid 11029 (ompanyname.app3), pid 11029 (ompanyname.app3)
    crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
    /system/bin/tombstoned: received crash request for pid 11029
    crash_dump64: performing dump of process 11029 (target tid = 11029)
    DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    DEBUG   : Build fingerprint: 'google/sdk_gphone_x86_64/generic_x86_64:10/QSR1.190920.001/5891938:user/release-keys'
    DEBUG   : Revision: '0'
    DEBUG   : ABI: 'x86_64'
    DEBUG   : Timestamp: 2020-05-25 14:45:29+0200
    DEBUG   : pid: 11029, tid: 11029, name: ompanyname.app3  >>> com.companyname.app3 <<<
    DEBUG   : uid: 10134
    DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0
    DEBUG   : Cause: null pointer dereference
    DEBUG   :     rax 000000000000002f  rbx 0000000000000001  rcx 0000000000000000  rdx 0000000000000030
    DEBUG   :     r8  0000000000000003  r9  000000000013e2e2  r10 0173eed800000000  r11 0000000000000206
    DEBUG   :     r12 0000000000000000  r13 00007478530343c0  r14 00007478075eda33  r15 000074780763efb0
    DEBUG   :     rdi 0000000000000000  rsi 00007478e2cb14d0
    DEBUG   :     rbp 00007ffef3a35680  rsp 00007ffef3a355d0  rip 0000747807a4066a
    DEBUG   :
    DEBUG   : backtrace:
    DEBUG   :       #00 pc 00000000003ba66a  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (_mono_reflection_get_type_from_info+474)
    DEBUG   :       #1 pc 00000000003ba3d1  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name_checked+321)
    DEBUG   :       #2 pc 00000000003ba26d  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name+125)
    DEBUG   :       #3 pc 000000000000ddb5  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+389) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
    DEBUG   :       dotnet#4 pc 000000000000def3  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
    DEBUG   :       dotnet#5 pc 0000000000069532  <anonymous:5ad25000>

Mono commit mono/mono@10795da1c06 fixes this issue.

Other changes:

 * mono/mono@89d772a3abb Always include Unicode charinfo, so tar made in csc mode works in mcs mode (#19813)
 * mono/mono@e9d3af508e4 Bump bockbuild to get mono/bockbuild#159
 * mono/mono@d6f0c25d34d [2020-02] Bump msbuild to track mono-2019-12 (#19661)
jonpryor pushed a commit that referenced this pull request May 27, 2020
Fixes: #4713

Context: mono/mono@10795da1c065c
Context: mono/mono@8c085a99b32e9

Changes: mono/mono@075c3f0...8c085a9

  * mono/mono@8c085a99b32: [reflection] Check whether a pointer is valid before dereferencing (#19842)
  * mono/mono@89d772a3abb: Always include Unicode charinfo, so tar made in csc mode works in mcs mode (#19813)
  * mono/mono@e9d3af508e4: Bump bockbuild to get mono/bockbuild#159
  * mono/mono@d6f0c25d34d: [2020-02] Bump msbuild to track mono-2019-12 (#19661)

Whenever Xamarin.Android runtime needs to instantiate a managed type,
it first looks it up by calling:

	MonoType *type = mono_reflection_type_from_name ("MyType, Assembly", nullptr);

The `nullptr` pointer refers to an instance of the Mono `MonoImage`
structure and if `nullptr`, it should cause Mono to find the correct
image containing the type and load it, if not already loaded.

The pointer is propagated down the call chain inside Mono and due to
one of the functions called not properly validating its arguments, the
`nullptr` pointer was dereferenced, leading to a crash similar to:

	libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0 in tid 11029 (ompanyname.app3), pid 11029 (ompanyname.app3)
	crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	/system/bin/tombstoned: received crash request for pid 11029
	crash_dump64: performing dump of process 11029 (target tid = 11029)
	DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	DEBUG   : Build fingerprint: 'google/sdk_gphone_x86_64/generic_x86_64:10/QSR1.190920.001/5891938:user/release-keys'
	DEBUG   : Revision: '0'
	DEBUG   : ABI: 'x86_64'
	DEBUG   : Timestamp: 2020-05-25 14:45:29+0200
	DEBUG   : pid: 11029, tid: 11029, name: ompanyname.app3  >>> com.companyname.app3 <<<
	DEBUG   : uid: 10134
	DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0
	DEBUG   : Cause: null pointer dereference
	DEBUG   :     rax 000000000000002f  rbx 0000000000000001  rcx 0000000000000000  rdx 0000000000000030
	DEBUG   :     r8  0000000000000003  r9  000000000013e2e2  r10 0173eed800000000  r11 0000000000000206
	DEBUG   :     r12 0000000000000000  r13 00007478530343c0  r14 00007478075eda33  r15 000074780763efb0
	DEBUG   :     rdi 0000000000000000  rsi 00007478e2cb14d0
	DEBUG   :     rbp 00007ffef3a35680  rsp 00007ffef3a355d0  rip 0000747807a4066a
	DEBUG   :
	DEBUG   : backtrace:
	DEBUG   :       #00 pc 00000000003ba66a  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (_mono_reflection_get_type_from_info+474)
	DEBUG   :       #1 pc 00000000003ba3d1  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name_checked+321)
	DEBUG   :       #2 pc 00000000003ba26d  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name+125)
	DEBUG   :       #3 pc 000000000000ddb5  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+389) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
	DEBUG   :       #4 pc 000000000000def3  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
	DEBUG   :       #5 pc 0000000000069532  <anonymous:5ad25000>

Mono commit mono/mono@10795da1c06 fixes this issue.
jonpryor pushed a commit that referenced this pull request May 28, 2020
Fixes: #4713

Context: mono/mono@10795da1c065c
Context: mono/mono@8c085a99b32e9

Changes: mono/mono@075c3f0...8c085a9

  * mono/mono@8c085a99b32: [reflection] Check whether a pointer is valid before dereferencing (#19842)
  * mono/mono@89d772a3abb: Always include Unicode charinfo, so tar made in csc mode works in mcs mode (#19813)
  * mono/mono@e9d3af508e4: Bump bockbuild to get mono/bockbuild#159
  * mono/mono@d6f0c25d34d: [2020-02] Bump msbuild to track mono-2019-12 (#19661)

Whenever Xamarin.Android runtime needs to instantiate a managed type,
it first looks it up by calling:

	MonoType *type = mono_reflection_type_from_name ("MyType, Assembly", nullptr);

The `nullptr` pointer refers to an instance of the Mono `MonoImage`
structure and if `nullptr`, it should cause Mono to find the correct
image containing the type and load it, if not already loaded.

The pointer is propagated down the call chain inside Mono and due to
one of the functions called not properly validating its arguments, the
`nullptr` pointer was dereferenced, leading to a crash similar to:

	libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0 in tid 11029 (ompanyname.app3), pid 11029 (ompanyname.app3)
	crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
	/system/bin/tombstoned: received crash request for pid 11029
	crash_dump64: performing dump of process 11029 (target tid = 11029)
	DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	DEBUG   : Build fingerprint: 'google/sdk_gphone_x86_64/generic_x86_64:10/QSR1.190920.001/5891938:user/release-keys'
	DEBUG   : Revision: '0'
	DEBUG   : ABI: 'x86_64'
	DEBUG   : Timestamp: 2020-05-25 14:45:29+0200
	DEBUG   : pid: 11029, tid: 11029, name: ompanyname.app3  >>> com.companyname.app3 <<<
	DEBUG   : uid: 10134
	DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x4c0
	DEBUG   : Cause: null pointer dereference
	DEBUG   :     rax 000000000000002f  rbx 0000000000000001  rcx 0000000000000000  rdx 0000000000000030
	DEBUG   :     r8  0000000000000003  r9  000000000013e2e2  r10 0173eed800000000  r11 0000000000000206
	DEBUG   :     r12 0000000000000000  r13 00007478530343c0  r14 00007478075eda33  r15 000074780763efb0
	DEBUG   :     rdi 0000000000000000  rsi 00007478e2cb14d0
	DEBUG   :     rbp 00007ffef3a35680  rsp 00007ffef3a355d0  rip 0000747807a4066a
	DEBUG   :
	DEBUG   : backtrace:
	DEBUG   :       #00 pc 00000000003ba66a  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (_mono_reflection_get_type_from_info+474)
	DEBUG   :       #1 pc 00000000003ba3d1  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name_checked+321)
	DEBUG   :       #2 pc 00000000003ba26d  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonosgen-2.0.so (mono_reflection_type_from_name+125)
	DEBUG   :       #3 pc 000000000000ddb5  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(char const*)+389) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
	DEBUG   :       #4 pc 000000000000def3  /data/app/com.companyname.app3-aQUF6Ge6_v-WaLb5i8Q7vw==/lib/x86_64/libmonodroid.so (xamarin::android::internal::EmbeddedAssemblies::typemap_java_to_managed(_MonoString*)+99) (BuildId: 9952f1cfe0d910ae631abc73479f88eef34fd71d)
	DEBUG   :       #5 pc 0000000000069532  <anonymous:5ad25000>

Mono commit mono/mono@10795da1c06 fixes this issue.
grendello added a commit to grendello/xamarin-android that referenced this pull request Oct 26, 2021
Context: dotnet#6420 (comment)

Clang's AddressSanitizer detected the following:

    10-26 15:55:25.393  2488  2488 I Mono.Android_Tests: ==2488==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x8a600774 at pc 0xaeee9982 bp 0xbf98dc68 sp 0xbf98dc60
    10-26 15:55:25.394  2488  2488 I Mono.Android_Tests: WRITE of size 4 at 0x8a600774 thread T0
    10-26 15:55:25.398  2488  2488 I Mono.Android_Tests:     #0 0xaeee9981  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38981)
    10-26 15:55:25.398  2488  2488 I Mono.Android_Tests:     #1 0xaeef92d9  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x482d9)
    10-26 15:55:25.398  2488  2488 I Mono.Android_Tests:     #2 0xaef009ae  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x4f9ae)
    10-26 15:55:25.398  2488  2488 I Mono.Android_Tests:     #3 0xaef06d14  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x55d14)
    10-26 15:55:25.399  2488  2488 I Mono.Android_Tests: 0x8a600774 is located 0 bytes to the right of 4-byte region [0x8a600770,0x8a600774)
    10-26 15:55:25.399  2488  2488 I Mono.Android_Tests: allocated by thread T0 here:
    10-26 15:55:25.399  2488  2488 I Mono.Android_Tests:     #0 0xaedbe925  (/data/app/Mono.Android_Tests-1/lib/x86/libclang_rt.asan-i686-android.so+0xb6925)
    10-26 15:55:25.399  2488  2488 I Mono.Android_Tests:     #1 0xaeee9ae1  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38ae1)
    10-26 15:55:25.399  2488  2488 I Mono.Android_Tests:     #2 0xaeee9751  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38751)
    10-26 15:55:25.399  2488  2488 I Mono.Android_Tests:     #3 0xaeef92d9  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x482d9)
    10-26 15:55:25.399  2488  2488 I Mono.Android_Tests:     dotnet#4 0xaef009ae  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x4f9ae)
    10-26 15:55:25.400  2488  2488 I Mono.Android_Tests:     dotnet#5 0xaef06d14  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x55d14)
    10-26 15:55:25.400  2488  2488 I Mono.Android_Tests:     dotnet#6 0xb30cb970  (/data/dalvik-cache/x86/data@app@Mono.Android_Tests-1@base.apk@classes.dex+0x5c970)
    10-26 15:55:25.400  2488  2488 I Mono.Android_Tests: SUMMARY: AddressSanitizer: heap-buffer-overflow (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38981)

Address of the offending region points to
`BasicUtilities::monodroid_strsplit` and is likely the line modified in
this commit.  Append terminating `nullptr` to vector instead of
overwriting the last element.
jonpryor pushed a commit that referenced this pull request Oct 29, 2021
Context: #6420 (comment)

Clang's AddressSanitizer detected the following:

	Mono.Android_Tests: ==2488==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x8a600774 at pc 0xaeee9982 bp 0xbf98dc68 sp 0xbf98dc60
	Mono.Android_Tests: WRITE of size 4 at 0x8a600774 thread T0
	Mono.Android_Tests:     #0 0xaeee9981  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38981)
	Mono.Android_Tests:     #1 0xaeef92d9  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x482d9)
	Mono.Android_Tests:     #2 0xaef009ae  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x4f9ae)
	Mono.Android_Tests:     #3 0xaef06d14  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x55d14)
	Mono.Android_Tests: 0x8a600774 is located 0 bytes to the right of 4-byte region [0x8a600770,0x8a600774)
	Mono.Android_Tests: allocated by thread T0 here:
	Mono.Android_Tests:     #0 0xaedbe925  (/data/app/Mono.Android_Tests-1/lib/x86/libclang_rt.asan-i686-android.so+0xb6925)
	Mono.Android_Tests:     #1 0xaeee9ae1  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38ae1)
	Mono.Android_Tests:     #2 0xaeee9751  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38751)
	Mono.Android_Tests:     #3 0xaeef92d9  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x482d9)
	Mono.Android_Tests:     #4 0xaef009ae  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x4f9ae)
	Mono.Android_Tests:     #5 0xaef06d14  (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x55d14)
	Mono.Android_Tests:     #6 0xb30cb970  (/data/dalvik-cache/x86/data@app@Mono.Android_Tests-1@base.apk@classes.dex+0x5c970)
	Mono.Android_Tests: SUMMARY: AddressSanitizer: heap-buffer-overflow (/data/app/Mono.Android_Tests-1/lib/x86/libmonodroid.so+0x38981)

Address of the offending region points to
`BasicUtilities::monodroid_strsplit()` and is likely the line
modified in this commit.  Append terminating `nullptr` to `vector`
instead of overwriting the last element.
jonathanpeppers referenced this pull request in jonathanpeppers/xamarin-android Jan 26, 2022
Context: dotnet/maui#4262

`dotnet new maui-blazor` crashes at runtime, if you do:

    dotnet build -t:Run -c Release

You can turn *off* the linker to solve this issue:

    dotnet build -t:Run -c Release -p:AndroidLinkMode=None

(or `PublishTrimmed=false`)

The app crashes in way that you get a native crash:

    backtrace:
    #00 pc 000000000065d8fc  /apex/com.android.art/lib64/libart.so (void art::StackVisitor::WalkStack<(art::StackVisitor::CountTransitions)0>(bool)+156) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
    #1 pc 000000000069b25d  /apex/com.android.art/lib64/libart.so (art::Thread::GetCurrentMethod(unsigned int*, bool, bool) const+157) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
    #2 pc 0000000000430fed  /apex/com.android.art/lib64/libart.so (art::JNI<false>::FindClass(_JNIEnv*, char const*)+765) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
    #3 pc 0000000000047e5a  /data/app/~~0Qm6D1S0sO3f1lwfakN0PA==/com.companyname.mauiapp2-08UokVCH5k_PlbZEH_hhkA==/split_config.x86_64.apk!libmono-android.release.so (offset 0x11e000) (java_interop_jnienv_find_class+26) (BuildId: 3d04f8b946590175e97b89aee2e3b19ceed4b524)
    #4 pc 00000000000128ac  <anonymous:41640000>

After much investigation... We found that
`Java.IO.InputStreamHandler.GetReadHandler()` was linked away.

This is because:

1. `Mono.Android.dll` has it's Java stubs precompiled into
   `mono.android.jar` and `mono.android.dex`.

2. Since `Mono.Android.dll` doesn't go through `GenerateJavaStubs`,
   the linker has no way to know if the missing method is used -- it
   is only called from Java in the crashing app.

To make the crash better, we need to `try-catch` *all* exceptions in
`RegisterNativeMembers()` and pass them to
`AndroidRuntime.RaisePendingException()`. This is because
`RegisterNativeMembers()` is called directly from Java.

Now the crash shows:

    01-26 12:20:20.290 29264 29264 I MonoDroid: Android.Runtime.JavaProxyThrowable: Exception_WasThrown, Android.Runtime.JavaProxyThrowable
    01-26 12:20:20.290 29264 29264 I MonoDroid:
    01-26 12:20:20.290 29264 29264 I MonoDroid:   --- End of managed Android.Runtime.JavaProxyThrowable stack trace ---
    01-26 12:20:20.290 29264 29264 I MonoDroid: android.runtime.JavaProxyThrowable: System.ArgumentException: Arg_DlgtTargMeth
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String , Boolean , Boolean )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.AndroidTypeManager.RegisterNativeMembers(JniType , Type , String )
    01-26 12:20:20.290 29264 29264 I MonoDroid: --- End of stack trace from previous location ---
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference , JniMethodInfo , JniArgumentValue* )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue* )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue[] )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.FindClass(String )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.AllocObject(String )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue* )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue[] )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.InputStreamAdapter..ctor(Stream )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.InputStreamAdapter.ToLocalJniHandle(Stream )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Webkit.WebResourceResponse..ctor(String , String , Int32 , String , IDictionary`2 , Stream )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Microsoft.AspNetCore.Components.WebView.Maui.WebKitWebViewClient.ShouldInterceptRequest(WebView view, IWebResourceRequest request)
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Webkit.WebViewClient.n_ShouldInterceptRequest_Landroid_webkit_WebView_Landroid_webkit_WebResourceRequest_(IntPtr , IntPtr , IntPtr , IntPtr )
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.n_shouldInterceptRequest(Native Method)
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.shouldInterceptRequest(WebKitWebViewClient.java:39)
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at Rr.a(chromium-TrichromeWebViewGoogle.apk-stable-410410686:16)
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at org.chromium.android_webview.AwContentsBackgroundThreadClient.shouldInterceptRequestFromNative(chromium-TrichromeWebViewGoogle.apk-stable-410410686:2)
    01-26 12:20:20.290 29264 29264 I MonoDroid:
    01-26 12:20:20.290 29264 29264 I MonoDroid:   --- End of managed Android.Runtime.JavaProxyThrowable stack trace ---
    01-26 12:20:20.290 29264 29264 I MonoDroid: android.runtime.JavaProxyThrowable: System.ArgumentException: Arg_DlgtTargMeth
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String , Boolean , Boolean )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.AndroidTypeManager.RegisterNativeMembers(JniType , Type , String )
    01-26 12:20:20.290 29264 29264 I MonoDroid: --- End of stack trace from previous location ---
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference , JniMethodInfo , JniArgumentValue* )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue* )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue[] )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.FindClass(String )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.AllocObject(String )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue* )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue[] )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.InputStreamAdapter..ctor(Stream )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Runtime.InputStreamAdapter.ToLocalJniHandle(Stream )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Webkit.WebResourceResponse..ctor(String , String , Int32 , String , IDictionary`2 , Stream )
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Microsoft.AspNetCore.Components.WebView.Maui.WebKitWebViewClient.ShouldInterceptRequest(WebView view, IWebResourceRequest request)
    01-26 12:20:20.290 29264 29264 I MonoDroid:    at Android.Webkit.WebViewClient.n_ShouldInterceptRequest_Landroid_webkit_WebView_Landroid_webkit_WebResourceRequest_(IntPtr , IntPtr , IntPtr , IntPtr )
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.n_shouldInterceptRequest(Native Method)
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.shouldInterceptRequest(WebKitWebViewClient.java:39)
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at Rr.a(chromium-TrichromeWebViewGoogle.apk-stable-410410686:16)
    01-26 12:20:20.290 29264 29264 I MonoDroid: 	at org.chromium.android_webview.AwContentsBackgroundThreadClient.shouldInterceptRequestFromNative(chromium-TrichromeWebViewGoogle.apk-stable-410410686:2)

This is much easier to reason about, and will save us time in the future.

A fix to the actual linker problem will be coming in another PR.
jonpryor pushed a commit that referenced this pull request Jan 27, 2022
Context: dotnet/maui#4262
Context: #6675

If you run the `maui-blazor` template in a Release build:

	dotnet build -t:Run -c Release

it crashes at runtime:

	D monodroid-assembly: typemap: type with token 33555274 (0x200034a) in module {C7B4CC8F-7A03-4A3F-A34A-DC66EDC548B9} (Mono.Android) corresponds to Java type 'android/runtime/JavaProxyThrowable'
	…
	F DEBUG   : backtrace:
	F DEBUG   : #00 pc 000000000065d8fc  /apex/com.android.art/lib64/libart.so (void art::StackVisitor::WalkStack<(art::StackVisitor::CountTransitions)0>(bool)+156) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
	F DEBUG   : #1 pc 000000000069b25d  /apex/com.android.art/lib64/libart.so (art::Thread::GetCurrentMethod(unsigned int*, bool, bool) const+157) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
	F DEBUG   : #2 pc 0000000000430fed  /apex/com.android.art/lib64/libart.so (art::JNI<false>::FindClass(_JNIEnv*, char const*)+765) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
	F DEBUG   : #3 pc 0000000000047e5a  /data/app/~~0Qm6D1S0sO3f1lwfakN0PA==/com.companyname.mauiapp2-08UokVCH5k_PlbZEH_hhkA==/split_config.x86_64.apk!libmono-android.release.so (offset 0x11e000) (java_interop_jnienv_find_class+26) (BuildId: 3d04f8b946590175e97b89aee2e3b19ceed4b524)
	F DEBUG   : #4 pc 00000000000128ac  <anonymous:41640000>

The crash can be avoided by disabling the linker:

	dotnet build -t:Run -c Release -p:AndroidLinkMode=None
	# -or-
	dotnet build -t:Run -c Release -p:PublishTrimmed=false

However, let us return to the crash: *why* is it crashing?
This isn't a "good debugging experience"; we have no useful context.

Lots of investigation later -- all hail printf debugging -- and we
found that the cause of the crash was an unhandled exception:

 1. `Mono.Android.dll` has it's Java Callable Wrappers generated
    from the *unlinked* assembly, into `mono.android.jar` and
    `mono.android.dex` files.  The Java Callable Wrapper for
    `Android.Runtime.InputStreamAdapter` thus includes *all*
    `Read()` method overloads.

 2. When the app is built in Release configuration, linking is
    enabled, and *some* of the `InputStreamAdapter.Read()` methods
    are removed by the linker, along with the
    `Java.IO.InputStream.Read()` methods that were overridden.

 3. At runtime, we perform [Java Type Registration][0] for the
    `Android.Runtime.InputStreamAdapter` type, which eventually calls
    `AndroidTypeManager.RegisterNativeMembers()`, which eventually
    attempts to *effectively* do:

        Delegate.CreateDelegate (
	        typeof(Func<Delegate>),
	        typeof(InputStreamAdapter),
	        "GetReadHandler");

 4. Because of (2), `Java.IO.InputStream.GetReadHandler()`
    *does not exist*, and thus `Delegate.CreateDelegate()` throws an
    `ArgumentException`.

So far, so reasonable, but…

 5. `AndroidTypeManager.RegisterNativeMembers()` didn't catch any
    exceptions, nor did any other method between the original Java
    `Runtime.register()` invocation and
    `AndroidTypeManager.RegisterNativeMembers()`.  The result is that
    a C# exception was "in flight", and Mono then proceeded to
    *tear down the stack frame* as it unwound the callstack looking
    for `catch` handlers.

At this point, the process is toast: the runtime stack is FUBAR.

This is also why the `backtrace:` is "rooted" in
`JNIEnv::FindClass()`: `JNIEnv::FindClass()` invokes Java static
constructors before returning, which is how the static constructor in
the Java Callable Wrapper for `InputStreamAdapter` called
`Runtime.register()` in the first place.

All of this makes for a miserable debugging experience.

Fixing the "original" linker issue will be done in
#6675.

This hasn't been an issue in "Classic" Xamarin.Android, presumably
because the classic linker isn't as good as the net6 linker.

What we want to do *here* is improve this debugging experience, by
"wrapping" `AndroidTypeManager.RegisterNativeMembers()` in a
`try`/`catch` block, which can then *marshal the thrown exception*
back to Java.  This *prevents* Mono from unwinding the callstack past
a JNI boundary, and avoids the annoying-to-debug app crash.

After this change, we get a much friendlier unhandled exception crash:

	I MonoDroid: Android.Runtime.JavaProxyThrowable: Exception_WasThrown, Android.Runtime.JavaProxyThrowable
	I MonoDroid:
	I MonoDroid:   --- End of managed Android.Runtime.JavaProxyThrowable stack trace ---
	I MonoDroid: android.runtime.JavaProxyThrowable: System.ArgumentException: Arg_DlgtTargMeth
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String , Boolean , Boolean )
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String )
	I MonoDroid:    at Android.Runtime.AndroidTypeManager.RegisterNativeMembers(JniType , Type , String )
	I MonoDroid: --- End of stack trace from previous location ---
	I MonoDroid:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference , JniMethodInfo , JniArgumentValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue[] )
	I MonoDroid:    at Android.Runtime.JNIEnv.FindClass(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.AllocObject(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue[] )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter..ctor(Stream )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter.ToLocalJniHandle(Stream )
	I MonoDroid:    at Android.Webkit.WebResourceResponse..ctor(String , String , Int32 , String , IDictionary`2 , Stream )
	I MonoDroid:    at Microsoft.AspNetCore.Components.WebView.Maui.WebKitWebViewClient.ShouldInterceptRequest(WebView view, IWebResourceRequest request)
	I MonoDroid:    at Android.Webkit.WebViewClient.n_ShouldInterceptRequest_Landroid_webkit_WebView_Landroid_webkit_WebResourceRequest_(IntPtr , IntPtr , IntPtr , IntPtr )
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.n_shouldInterceptRequest(Native Method)
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.shouldInterceptRequest(WebKitWebViewClient.java:39)
	I MonoDroid: 	at Rr.a(chromium-TrichromeWebViewGoogle.apk-stable-410410686:16)
	I MonoDroid: 	at org.chromium.android_webview.AwContentsBackgroundThreadClient.shouldInterceptRequestFromNative(chromium-TrichromeWebViewGoogle.apk-stable-410410686:2)
	I MonoDroid:
	I MonoDroid:   --- End of managed Android.Runtime.JavaProxyThrowable stack trace ---
	I MonoDroid: android.runtime.JavaProxyThrowable: System.ArgumentException: Arg_DlgtTargMeth
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String , Boolean , Boolean )
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String )
	I MonoDroid:    at Android.Runtime.AndroidTypeManager.RegisterNativeMembers(JniType , Type , String )
	I MonoDroid: --- End of stack trace from previous location ---
	I MonoDroid:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference , JniMethodInfo , JniArgumentValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue[] )
	I MonoDroid:    at Android.Runtime.JNIEnv.FindClass(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.AllocObject(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue[] )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter..ctor(Stream )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter.ToLocalJniHandle(Stream )
	I MonoDroid:    at Android.Webkit.WebResourceResponse..ctor(String , String , Int32 , String , IDictionary`2 , Stream )
	I MonoDroid:    at Microsoft.AspNetCore.Components.WebView.Maui.WebKitWebViewClient.ShouldInterceptRequest(WebView view, IWebResourceRequest request)
	I MonoDroid:    at Android.Webkit.WebViewClient.n_ShouldInterceptRequest_Landroid_webkit_WebView_Landroid_webkit_WebResourceRequest_(IntPtr , IntPtr , IntPtr , IntPtr )
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.n_shouldInterceptRequest(Native Method)
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.shouldInterceptRequest(WebKitWebViewClient.java:39)
	I MonoDroid: 	at Rr.a(chromium-TrichromeWebViewGoogle.apk-stable-410410686:16)
	I MonoDroid: 	at org.chromium.android_webview.AwContentsBackgroundThreadClient.shouldInterceptRequestFromNative(chromium-TrichromeWebViewGoogle.apk-stable-410410686:2)

This is much easier to reason about, and will save us time in
the future.

[0]: https://github.com/xamarin/xamarin-android/wiki/Blueprint#java-type-registration
jonathanpeppers added a commit that referenced this pull request Jan 27, 2022
Context: dotnet/maui#4262
Context: #6675

If you run the `maui-blazor` template in a Release build:

	dotnet build -t:Run -c Release

it crashes at runtime:

	D monodroid-assembly: typemap: type with token 33555274 (0x200034a) in module {C7B4CC8F-7A03-4A3F-A34A-DC66EDC548B9} (Mono.Android) corresponds to Java type 'android/runtime/JavaProxyThrowable'
	…
	F DEBUG   : backtrace:
	F DEBUG   : #00 pc 000000000065d8fc  /apex/com.android.art/lib64/libart.so (void art::StackVisitor::WalkStack<(art::StackVisitor::CountTransitions)0>(bool)+156) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
	F DEBUG   : #1 pc 000000000069b25d  /apex/com.android.art/lib64/libart.so (art::Thread::GetCurrentMethod(unsigned int*, bool, bool) const+157) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
	F DEBUG   : #2 pc 0000000000430fed  /apex/com.android.art/lib64/libart.so (art::JNI<false>::FindClass(_JNIEnv*, char const*)+765) (BuildId: 7fbaf2a1a3317bd634b00eb90e32291e)
	F DEBUG   : #3 pc 0000000000047e5a  /data/app/~~0Qm6D1S0sO3f1lwfakN0PA==/com.companyname.mauiapp2-08UokVCH5k_PlbZEH_hhkA==/split_config.x86_64.apk!libmono-android.release.so (offset 0x11e000) (java_interop_jnienv_find_class+26) (BuildId: 3d04f8b946590175e97b89aee2e3b19ceed4b524)
	F DEBUG   : #4 pc 00000000000128ac  <anonymous:41640000>

The crash can be avoided by disabling the linker:

	dotnet build -t:Run -c Release -p:AndroidLinkMode=None
	# -or-
	dotnet build -t:Run -c Release -p:PublishTrimmed=false

However, let us return to the crash: *why* is it crashing?
This isn't a "good debugging experience"; we have no useful context.

Lots of investigation later -- all hail printf debugging -- and we
found that the cause of the crash was an unhandled exception:

 1. `Mono.Android.dll` has it's Java Callable Wrappers generated
    from the *unlinked* assembly, into `mono.android.jar` and
    `mono.android.dex` files.  The Java Callable Wrapper for
    `Android.Runtime.InputStreamAdapter` thus includes *all*
    `Read()` method overloads.

 2. When the app is built in Release configuration, linking is
    enabled, and *some* of the `InputStreamAdapter.Read()` methods
    are removed by the linker, along with the
    `Java.IO.InputStream.Read()` methods that were overridden.

 3. At runtime, we perform [Java Type Registration][0] for the
    `Android.Runtime.InputStreamAdapter` type, which eventually calls
    `AndroidTypeManager.RegisterNativeMembers()`, which eventually
    attempts to *effectively* do:

        Delegate.CreateDelegate (
	        typeof(Func<Delegate>),
	        typeof(InputStreamAdapter),
	        "GetReadHandler");

 4. Because of (2), `Java.IO.InputStream.GetReadHandler()`
    *does not exist*, and thus `Delegate.CreateDelegate()` throws an
    `ArgumentException`.

So far, so reasonable, but…

 5. `AndroidTypeManager.RegisterNativeMembers()` didn't catch any
    exceptions, nor did any other method between the original Java
    `Runtime.register()` invocation and
    `AndroidTypeManager.RegisterNativeMembers()`.  The result is that
    a C# exception was "in flight", and Mono then proceeded to
    *tear down the stack frame* as it unwound the callstack looking
    for `catch` handlers.

At this point, the process is toast: the runtime stack is FUBAR.

This is also why the `backtrace:` is "rooted" in
`JNIEnv::FindClass()`: `JNIEnv::FindClass()` invokes Java static
constructors before returning, which is how the static constructor in
the Java Callable Wrapper for `InputStreamAdapter` called
`Runtime.register()` in the first place.

All of this makes for a miserable debugging experience.

Fixing the "original" linker issue will be done in
#6675.

This hasn't been an issue in "Classic" Xamarin.Android, presumably
because the classic linker isn't as good as the net6 linker.

What we want to do *here* is improve this debugging experience, by
"wrapping" `AndroidTypeManager.RegisterNativeMembers()` in a
`try`/`catch` block, which can then *marshal the thrown exception*
back to Java.  This *prevents* Mono from unwinding the callstack past
a JNI boundary, and avoids the annoying-to-debug app crash.

After this change, we get a much friendlier unhandled exception crash:

	I MonoDroid: Android.Runtime.JavaProxyThrowable: Exception_WasThrown, Android.Runtime.JavaProxyThrowable
	I MonoDroid:
	I MonoDroid:   --- End of managed Android.Runtime.JavaProxyThrowable stack trace ---
	I MonoDroid: android.runtime.JavaProxyThrowable: System.ArgumentException: Arg_DlgtTargMeth
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String , Boolean , Boolean )
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String )
	I MonoDroid:    at Android.Runtime.AndroidTypeManager.RegisterNativeMembers(JniType , Type , String )
	I MonoDroid: --- End of stack trace from previous location ---
	I MonoDroid:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference , JniMethodInfo , JniArgumentValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue[] )
	I MonoDroid:    at Android.Runtime.JNIEnv.FindClass(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.AllocObject(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue[] )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter..ctor(Stream )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter.ToLocalJniHandle(Stream )
	I MonoDroid:    at Android.Webkit.WebResourceResponse..ctor(String , String , Int32 , String , IDictionary`2 , Stream )
	I MonoDroid:    at Microsoft.AspNetCore.Components.WebView.Maui.WebKitWebViewClient.ShouldInterceptRequest(WebView view, IWebResourceRequest request)
	I MonoDroid:    at Android.Webkit.WebViewClient.n_ShouldInterceptRequest_Landroid_webkit_WebView_Landroid_webkit_WebResourceRequest_(IntPtr , IntPtr , IntPtr , IntPtr )
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.n_shouldInterceptRequest(Native Method)
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.shouldInterceptRequest(WebKitWebViewClient.java:39)
	I MonoDroid: 	at Rr.a(chromium-TrichromeWebViewGoogle.apk-stable-410410686:16)
	I MonoDroid: 	at org.chromium.android_webview.AwContentsBackgroundThreadClient.shouldInterceptRequestFromNative(chromium-TrichromeWebViewGoogle.apk-stable-410410686:2)
	I MonoDroid:
	I MonoDroid:   --- End of managed Android.Runtime.JavaProxyThrowable stack trace ---
	I MonoDroid: android.runtime.JavaProxyThrowable: System.ArgumentException: Arg_DlgtTargMeth
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String , Boolean , Boolean )
	I MonoDroid:    at System.Delegate.CreateDelegate(Type , Type , String )
	I MonoDroid:    at Android.Runtime.AndroidTypeManager.RegisterNativeMembers(JniType , Type , String )
	I MonoDroid: --- End of stack trace from previous location ---
	I MonoDroid:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference , JniMethodInfo , JniArgumentValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.CallStaticObjectMethod(IntPtr , IntPtr , JValue[] )
	I MonoDroid:    at Android.Runtime.JNIEnv.FindClass(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.AllocObject(String )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue* )
	I MonoDroid:    at Android.Runtime.JNIEnv.StartCreateInstance(String , String , JValue[] )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter..ctor(Stream )
	I MonoDroid:    at Android.Runtime.InputStreamAdapter.ToLocalJniHandle(Stream )
	I MonoDroid:    at Android.Webkit.WebResourceResponse..ctor(String , String , Int32 , String , IDictionary`2 , Stream )
	I MonoDroid:    at Microsoft.AspNetCore.Components.WebView.Maui.WebKitWebViewClient.ShouldInterceptRequest(WebView view, IWebResourceRequest request)
	I MonoDroid:    at Android.Webkit.WebViewClient.n_ShouldInterceptRequest_Landroid_webkit_WebView_Landroid_webkit_WebResourceRequest_(IntPtr , IntPtr , IntPtr , IntPtr )
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.n_shouldInterceptRequest(Native Method)
	I MonoDroid: 	at crc64d693e2d9159537db.WebKitWebViewClient.shouldInterceptRequest(WebKitWebViewClient.java:39)
	I MonoDroid: 	at Rr.a(chromium-TrichromeWebViewGoogle.apk-stable-410410686:16)
	I MonoDroid: 	at org.chromium.android_webview.AwContentsBackgroundThreadClient.shouldInterceptRequestFromNative(chromium-TrichromeWebViewGoogle.apk-stable-410410686:2)

This is much easier to reason about, and will save us time in
the future.

[0]: https://github.com/xamarin/xamarin-android/wiki/Blueprint#java-type-registration
jonpryor added a commit that referenced this pull request Jul 21, 2022
Changes: xamarin/NRefactory@495405a...f324292

  * xamarin/NRefactory@f3242923: Add .NET 6.0 target framework
  * xamarin/NRefactory@074fabe9: Merge pull request #3 from xamarin/net6
  * xamarin/NRefactory@fb5f1535: Merge pull request #4 from xamarin/dev/sandy/obsolete
  * xamarin/NRefactory@9233d6a8: Merge pull request #5 from xamarin/dev/sandy/mergemain
  * xamarin/NRefactory@b2991f92: Merge remote-tracking branch 'origin/master' into dev/sandy/mergemain
  * xamarin/NRefactory@e9c0609e: Fix use of obsolete member
  * xamarin/NRefactory@a6885a74: Allow building with .NET 6
grendello added a commit to grendello/xamarin-android that referenced this pull request Sep 15, 2022
    9-15 22:56:28.431 15070 15090 W monodroid: jclass java_interop_jnienv_find_class(JNIEnv *, jthrowable *, const char *) looking for 'android/content/Intent$ShortcutIconResource'
    --------- beginning of crash
    09-15 22:56:28.432 15070 15090 F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0xbb60ca20 in tid 15090 (Instrumentation), pid 15070 (droid.NET_Tests)
    09-15 22:56:28.757 15103 15103 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    09-15 22:56:28.757 15103 15103 F DEBUG   : Build fingerprint: 'google/raven/raven:13/TP1A.220624.021/8877034:user/release-keys'
    09-15 22:56:28.757 15103 15103 F DEBUG   : Revision: 'MP1.0'
    09-15 22:56:28.757 15103 15103 F DEBUG   : ABI: 'arm64'
    09-15 22:56:28.757 15103 15103 F DEBUG   : Timestamp: 2022-09-15 22:56:28.545823727+0200
    09-15 22:56:28.757 15103 15103 F DEBUG   : Process uptime: 3s
    09-15 22:56:28.757 15103 15103 F DEBUG   : Cmdline: Mono.Android.NET_Tests
    09-15 22:56:28.757 15103 15103 F DEBUG   : pid: 15070, tid: 15090, name: Instrumentation  >>> Mono.Android.NET_Tests <<<
    09-15 22:56:28.757 15103 15103 F DEBUG   : uid: 10638
    09-15 22:56:28.757 15103 15103 F DEBUG   : tagged_addr_ctrl: 0000000000000001 (PR_TAGGED_ADDR_ENABLE)
    09-15 22:56:28.757 15103 15103 F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x00000000bb60ca20
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x0  b400006e8ea08350  x1  0000000000000001  x2  0000000000000001  x3  0000000000000010
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x4  0000006dbaea7233  x5  0000006deea682be  x6  0000000000000020  x7  0000000000000020
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x8  0000000000000008  x9  00000000bb60c9e0  x10 0000006deea682a7  x11 0000006deea682a7
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x12 3d2120746e696f70  x13 7274706c6c756e20  x14 0000006d3d90b998  x15 000000a74ab3008e
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x16 0000006dbb60f6b8  x17 0000007074e7b9ac  x18 0000006d394cc000  x19 0000006d3d90b6d8
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x20 b400006e8ea08350  x21 0000000000000001  x22 0000006d3d90e000  x23 0000006d3d90b6d8
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x24 0000006d3d90b830  x25 0000006d3d90bb80  x26 0000006e7ea14cf0  x27 b400006e8ea08350
    09-15 22:56:28.757 15103 15103 F DEBUG   :     x28 0000000000000000  x29 0000006d3d90b5d0
    09-15 22:56:28.757 15103 15103 F DEBUG   :     lr  0000006dbb16f3dc  sp  0000006d3d90b5b0  pc  0000006dbb171d44  pst 0000000080001000
    09-15 22:56:28.757 15103 15103 F DEBUG   : backtrace:
    09-15 22:56:28.757 15103 15103 F DEBUG   :       #00 pc 0000000000371d44  /apex/com.android.art/lib64/libart.so (art::ArtMethod::PrettyMethod(bool)+76) (BuildId: 56e704c544e6c624201be2ab4933e853)
    09-15 22:56:28.757 15103 15103 F DEBUG   :       #1 pc 000000000036f3d8  /apex/com.android.art/lib64/libart.so (void art::StackVisitor::WalkStack<(art::StackVisitor::CountTransitions)0>(bool)+5464) (BuildId: 56e704c544e6c624201be2ab4933e853)
    09-15 22:56:28.757 15103 15103 F DEBUG   :       #2 pc 00000000005a0370  /apex/com.android.art/lib64/libart.so (art::JNI<true>::FindClass(_JNIEnv*, char const*)+480) (BuildId: 56e704c544e6c624201be2ab4933e853)
    09-15 22:56:28.757 15103 15103 F DEBUG   :       #3 pc 00000000005c8948  /apex/com.android.art/lib64/libart.so (art::(anonymous namespace)::CheckJNI::FindClass(_JNIEnv*, char const*) (.__uniq.99033978352804627313491551960229047428.llvm.5591279935177935698)+228) (BuildId: 56e704c544e6c624201be2ab4933e853)
    09-15 22:56:28.757 15103 15103 F DEBUG   :       dotnet#4 pc 000000000004de28  /data/app/~~aJedheWQLPfk1ulUOfKVyg==/Mono.Android.NET_Tests-XvAL5W7BvZDwkEbYfmLTIQ==/lib/arm64/libmonodroid.so (java_interop_jnienv_find_class+84) (BuildId: a92c56b31adcb233a4674b5eb523c0aaa67a811d)
    09-15 22:56:28.757 15103 15103 F DEBUG   :       dotnet#5 pc 000000000000b220  <anonymous:705fcb1000>
grendello added a commit to grendello/xamarin-android that referenced this pull request Nov 22, 2022
It won't fix the failure, but extra logging might be useful at some
point. The current failure is:

    droid.NET_Test: java_vm_ext.cc:570] JNI DETECTED ERROR IN APPLICATION: use of invalid jobject 0x7100941bb830
    backtrace:
           #00 pc 00000000000943f8  /apex/com.android.runtime/lib64/bionic/libc.so (syscall+24) (BuildId: a08a19770d6696739c847e29c3f5f650)
           #1 pc 0000000000097146  /apex/com.android.runtime/lib64/bionic/libc.so (abort+182) (BuildId: a08a19770d6696739c847e29c3f5f650)
           #2 pc 000000000055321f  /apex/com.android.runtime/lib64/libart.so (art::Runtime::Abort(char const*)+2399) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           #3 pc 000000000000c873  /system/lib64/libbase.so (android::base::LogMessage::~LogMessage()+611) (BuildId: 40d2b536dbf0730fdc31abd2b469f94f)
           dotnet#4 pc 00000000003ede64  /apex/com.android.runtime/lib64/libart.so (art::JavaVMExt::JniAbort(char const*, char const*)+1604) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#5 pc 00000000003ee16a  /apex/com.android.runtime/lib64/libart.so (art::JavaVMExt::JniAbortF(char const*, char const*, ...)+234) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#6 pc 00000000005adf7b  /apex/com.android.runtime/lib64/libart.so (art::Thread::DecodeJObject(_jobject*) const+875) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#7 pc 00000000003def7b  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::ScopedCheck::CheckInstance(art::ScopedObjectAccess&, art::(anonymous namespace)::ScopedCheck::InstanceKind, _jobject*, bool)+91) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#8 pc 00000000003de1e5  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::ScopedCheck::CheckPossibleHeapValue(art::ScopedObjectAccess&, char, art::(anonymous namespace)::JniValueType)+485) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#9 pc 00000000003de2d4  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::ScopedCheck::CheckPossibleHeapValue(art::ScopedObjectAccess&, char, art::(anonymous namespace)::JniValueType)+724) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#10 pc 00000000003dd712  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::ScopedCheck::Check(art::ScopedObjectAccess&, bool, char const*, art::(anonymous namespace)::JniValueType*)+690) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#11 pc 00000000003e28c0  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::CheckJNI::CheckCallArgs(art::ScopedObjectAccess&, art::(anonymous namespace)::ScopedCheck&, _JNIEnv*, _jobject*, _jclass*, _jmethodID*, art::InvokeType, art::(anonymous namespace)::VarArgs const*)+160) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#12 pc 00000000003e1a9e  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::CheckJNI::CallMethodV(char const*, _JNIEnv*, _jobject*, _jclass*, _jmethodID*, __va_list_tag*, art::Primitive::Type, art::InvokeType)+910) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#13 pc 00000000003cf551  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::CheckJNI::CallObjectMethod(_JNIEnv*, _jobject*, _jmethodID*, ...)+177) (BuildId: 8bb3225e7c408f2ca23abac3db0417f2)
           dotnet#14 pc 00000000000013ec  /data/app/Mono.Android.NET_Tests--O9vgexkYeCx3nX-AuvLTQ==/split_config.x86_64.apk!libreuse-threads.so (offset 0xa8d000) (BuildId: 562d86d81ebdd3bb6b7528e2a9235ff84827294e)
           dotnet#15 pc 0000000000100fce  /apex/com.android.runtime/lib64/bionic/libc.so (__pthread_start(void*)+30) (BuildId: a08a19770d6696739c847e29c3f5f650)
           dotnet#16 pc 0000000000098fe7  /apex/com.android.runtime/lib64/bionic/libc.so (__start_thread+55) (BuildId: a08a19770d6696739c847e29c3f5f650)
jonpryor pushed a commit that referenced this pull request Jan 26, 2023
…7732)

Fixes: #7335

Context: d236af5

Commit d236af5 introduced embedded assembly compression, using LZ4,
which speeds up startup and reduces final package size.

Assemblies are compressed at build time and, at the same time, pre-
allocated buffers for the **decompressed** data are allocated in
`libxamarin-app.so`.  The buffers are then passed to the LZ4 APIs,
all threads using the same output buffer.  The assumption was that we
can do fine without locking as even if overlapped decompression
happens, the output data will be the same and so even if two threads
do the same thing at the same time, the data will be valid at all
times, so long as at least one thread completes the decompression.

This assumption proved to be **largely** true, but it appears that in
high concurrency cases it is possible that the data in the
decompression buffer differs.  This can result in app crashes:

	A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 3092 (.NET ThreadPool), pid 2727 (myapp.name)
	A/DEBUG: pid: 2727, tid: 3092, name: .NET ThreadPool  >>> myapp.name <<<
	A/DEBUG:       #1 pc 0000000000029b1c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmono-android.release.so (offset 0x103d000) (xamarin::android::internal::MonodroidRuntime::mono_log_handler(char const*, char const*, char const*, int, void*)+144) (BuildId: 29c5a3805a0bedee1eede9b6668d7c676aa63371)
	A/DEBUG:       #2 pc 00000000002680bc  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       #3 pc 00000000002681e8  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       #4 pc 000000000008555c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (mono_metadata_string_heap+188) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	…

My guess is that LZ4 either uses the output buffer as a scratchpad
area when decompressing or that it initializes/modifies the buffer
before writing actual data in it.  With overlapped decompression, it
may lead to one thread overwriting valid data previously written by
another thread, so that when the latter returns the buffer it thought
to have had valid data may contain certain bytes temporarily
overwritten by the decompression session in the other, still running,
thread.  It may happen that MonoVM reads the corrupted data just when
it is still invalid (before the still running decompression session
actually writes the valid data), a classic race condition.

To fix this, the decompression block is now protected with a startup-
aware mutex.  Mutex will be held only after the initial startup phase
is completed, so there should not be much loss of startup performance.
jonpryor pushed a commit to jonpryor/xamarin-android that referenced this pull request Jan 26, 2023
…otnet#7732)

Fixes: dotnet#7335

Context: d236af5

Commit d236af5 introduced embedded assembly compression, using LZ4,
which speeds up startup and reduces final package size.

Assemblies are compressed at build time and, at the same time, pre-
allocated buffers for the **decompressed** data are allocated in
`libxamarin-app.so`.  The buffers are then passed to the LZ4 APIs,
all threads using the same output buffer.  The assumption was that we
can do fine without locking as even if overlapped decompression
happens, the output data will be the same and so even if two threads
do the same thing at the same time, the data will be valid at all
times, so long as at least one thread completes the decompression.

This assumption proved to be **largely** true, but it appears that in
high concurrency cases it is possible that the data in the
decompression buffer differs.  This can result in app crashes:

	A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 3092 (.NET ThreadPool), pid 2727 (myapp.name)
	A/DEBUG: pid: 2727, tid: 3092, name: .NET ThreadPool  >>> myapp.name <<<
	A/DEBUG:       #1 pc 0000000000029b1c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmono-android.release.so (offset 0x103d000) (xamarin::android::internal::MonodroidRuntime::mono_log_handler(char const*, char const*, char const*, int, void*)+144) (BuildId: 29c5a3805a0bedee1eede9b6668d7c676aa63371)
	A/DEBUG:       #2 pc 00000000002680bc  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       dotnet#3 pc 00000000002681e8  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       dotnet#4 pc 000000000008555c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (mono_metadata_string_heap+188) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	…

My guess is that LZ4 either uses the output buffer as a scratchpad
area when decompressing or that it initializes/modifies the buffer
before writing actual data in it.  With overlapped decompression, it
may lead to one thread overwriting valid data previously written by
another thread, so that when the latter returns the buffer it thought
to have had valid data may contain certain bytes temporarily
overwritten by the decompression session in the other, still running,
thread.  It may happen that MonoVM reads the corrupted data just when
it is still invalid (before the still running decompression session
actually writes the valid data), a classic race condition.

To fix this, the decompression block is now protected with a startup-
aware mutex.  Mutex will be held only after the initial startup phase
is completed, so there should not be much loss of startup performance.
jonpryor pushed a commit to jonpryor/xamarin-android that referenced this pull request Jan 27, 2023
…otnet#7732)

Fixes: dotnet#7335

Context: d236af5

Commit d236af5 introduced embedded assembly compression, using LZ4,
which speeds up startup and reduces final package size.

Assemblies are compressed at build time and, at the same time, pre-
allocated buffers for the **decompressed** data are allocated in
`libxamarin-app.so`.  The buffers are then passed to the LZ4 APIs,
all threads using the same output buffer.  The assumption was that we
can do fine without locking as even if overlapped decompression
happens, the output data will be the same and so even if two threads
do the same thing at the same time, the data will be valid at all
times, so long as at least one thread completes the decompression.

This assumption proved to be **largely** true, but it appears that in
high concurrency cases it is possible that the data in the
decompression buffer differs.  This can result in app crashes:

	A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 3092 (.NET ThreadPool), pid 2727 (myapp.name)
	A/DEBUG: pid: 2727, tid: 3092, name: .NET ThreadPool  >>> myapp.name <<<
	A/DEBUG:       #1 pc 0000000000029b1c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmono-android.release.so (offset 0x103d000) (xamarin::android::internal::MonodroidRuntime::mono_log_handler(char const*, char const*, char const*, int, void*)+144) (BuildId: 29c5a3805a0bedee1eede9b6668d7c676aa63371)
	A/DEBUG:       #2 pc 00000000002680bc  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       dotnet#3 pc 00000000002681e8  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       dotnet#4 pc 000000000008555c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (mono_metadata_string_heap+188) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	…

My guess is that LZ4 either uses the output buffer as a scratchpad
area when decompressing or that it initializes/modifies the buffer
before writing actual data in it.  With overlapped decompression, it
may lead to one thread overwriting valid data previously written by
another thread, so that when the latter returns the buffer it thought
to have had valid data may contain certain bytes temporarily
overwritten by the decompression session in the other, still running,
thread.  It may happen that MonoVM reads the corrupted data just when
it is still invalid (before the still running decompression session
actually writes the valid data), a classic race condition.

To fix this, the decompression block is now protected with a startup-
aware mutex.  Mutex will be held only after the initial startup phase
is completed, so there should not be much loss of startup performance.
jonpryor pushed a commit to jonpryor/xamarin-android that referenced this pull request Jan 27, 2023
…otnet#7732)

Fixes: dotnet#7335

Context: d236af5

Commit d236af5 introduced embedded assembly compression, using LZ4,
which speeds up startup and reduces final package size.

Assemblies are compressed at build time and, at the same time, pre-
allocated buffers for the **decompressed** data are allocated in
`libxamarin-app.so`.  The buffers are then passed to the LZ4 APIs,
all threads using the same output buffer.  The assumption was that we
can do fine without locking as even if overlapped decompression
happens, the output data will be the same and so even if two threads
do the same thing at the same time, the data will be valid at all
times, so long as at least one thread completes the decompression.

This assumption proved to be **largely** true, but it appears that in
high concurrency cases it is possible that the data in the
decompression buffer differs.  This can result in app crashes:

	A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 3092 (.NET ThreadPool), pid 2727 (myapp.name)
	A/DEBUG: pid: 2727, tid: 3092, name: .NET ThreadPool  >>> myapp.name <<<
	A/DEBUG:       #1 pc 0000000000029b1c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmono-android.release.so (offset 0x103d000) (xamarin::android::internal::MonodroidRuntime::mono_log_handler(char const*, char const*, char const*, int, void*)+144) (BuildId: 29c5a3805a0bedee1eede9b6668d7c676aa63371)
	A/DEBUG:       #2 pc 00000000002680bc  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       dotnet#3 pc 00000000002681e8  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       dotnet#4 pc 000000000008555c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (mono_metadata_string_heap+188) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	…

My guess is that LZ4 either uses the output buffer as a scratchpad
area when decompressing or that it initializes/modifies the buffer
before writing actual data in it.  With overlapped decompression, it
may lead to one thread overwriting valid data previously written by
another thread, so that when the latter returns the buffer it thought
to have had valid data may contain certain bytes temporarily
overwritten by the decompression session in the other, still running,
thread.  It may happen that MonoVM reads the corrupted data just when
it is still invalid (before the still running decompression session
actually writes the valid data), a classic race condition.

To fix this, the decompression block is now protected with a startup-
aware mutex.  Mutex will be held only after the initial startup phase
is completed, so there should not be much loss of startup performance.
jonpryor pushed a commit that referenced this pull request Jan 28, 2023
…7732)

Fixes: #7335

Context: d236af5

Commit d236af5 introduced embedded assembly compression, using LZ4,
which speeds up startup and reduces final package size.

Assemblies are compressed at build time and, at the same time, pre-
allocated buffers for the **decompressed** data are allocated in
`libxamarin-app.so`.  The buffers are then passed to the LZ4 APIs,
all threads using the same output buffer.  The assumption was that we
can do fine without locking as even if overlapped decompression
happens, the output data will be the same and so even if two threads
do the same thing at the same time, the data will be valid at all
times, so long as at least one thread completes the decompression.

This assumption proved to be **largely** true, but it appears that in
high concurrency cases it is possible that the data in the
decompression buffer differs.  This can result in app crashes:

	A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 3092 (.NET ThreadPool), pid 2727 (myapp.name)
	A/DEBUG: pid: 2727, tid: 3092, name: .NET ThreadPool  >>> myapp.name <<<
	A/DEBUG:       #1 pc 0000000000029b1c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmono-android.release.so (offset 0x103d000) (xamarin::android::internal::MonodroidRuntime::mono_log_handler(char const*, char const*, char const*, int, void*)+144) (BuildId: 29c5a3805a0bedee1eede9b6668d7c676aa63371)
	A/DEBUG:       #2 pc 00000000002680bc  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       #3 pc 00000000002681e8  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       #4 pc 000000000008555c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (mono_metadata_string_heap+188) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	…

My guess is that LZ4 either uses the output buffer as a scratchpad
area when decompressing or that it initializes/modifies the buffer
before writing actual data in it.  With overlapped decompression, it
may lead to one thread overwriting valid data previously written by
another thread, so that when the latter returns the buffer it thought
to have had valid data may contain certain bytes temporarily
overwritten by the decompression session in the other, still running,
thread.  It may happen that MonoVM reads the corrupted data just when
it is still invalid (before the still running decompression session
actually writes the valid data), a classic race condition.

To fix this, the decompression block is now protected with a startup-
aware mutex.  Mutex will be held only after the initial startup phase
is completed, so there should not be much loss of startup performance.
grendello added a commit to grendello/xamarin-android that referenced this pull request Feb 21, 2023
…otnet#7732)

Fixes: dotnet#7335

Context: d236af5

Commit d236af5 introduced embedded assembly compression, using LZ4,
which speeds up startup and reduces final package size.

Assemblies are compressed at build time and, at the same time, pre-
allocated buffers for the **decompressed** data are allocated in
`libxamarin-app.so`.  The buffers are then passed to the LZ4 APIs,
all threads using the same output buffer.  The assumption was that we
can do fine without locking as even if overlapped decompression
happens, the output data will be the same and so even if two threads
do the same thing at the same time, the data will be valid at all
times, so long as at least one thread completes the decompression.

This assumption proved to be **largely** true, but it appears that in
high concurrency cases it is possible that the data in the
decompression buffer differs.  This can result in app crashes:

	A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 3092 (.NET ThreadPool), pid 2727 (myapp.name)
	A/DEBUG: pid: 2727, tid: 3092, name: .NET ThreadPool  >>> myapp.name <<<
	A/DEBUG:       #1 pc 0000000000029b1c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmono-android.release.so (offset 0x103d000) (xamarin::android::internal::MonodroidRuntime::mono_log_handler(char const*, char const*, char const*, int, void*)+144) (BuildId: 29c5a3805a0bedee1eede9b6668d7c676aa63371)
	A/DEBUG:       #2 pc 00000000002680bc  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       #3 pc 00000000002681e8  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       dotnet#4 pc 000000000008555c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (mono_metadata_string_heap+188) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	…

My guess is that LZ4 either uses the output buffer as a scratchpad
area when decompressing or that it initializes/modifies the buffer
before writing actual data in it.  With overlapped decompression, it
may lead to one thread overwriting valid data previously written by
another thread, so that when the latter returns the buffer it thought
to have had valid data may contain certain bytes temporarily
overwritten by the decompression session in the other, still running,
thread.  It may happen that MonoVM reads the corrupted data just when
it is still invalid (before the still running decompression session
actually writes the valid data), a classic race condition.

To fix this, the decompression block is now protected with a startup-
aware mutex.  Mutex will be held only after the initial startup phase
is completed, so there should not be much loss of startup performance.
jonpryor pushed a commit that referenced this pull request Feb 27, 2023
…7817)

Fixes: #7335

Context: d236af5

Commit d236af5 introduced embedded assembly compression, using LZ4,
which speeds up startup and reduces final package size.

Assemblies are compressed at build time and, at the same time, pre-
allocated buffers for the **decompressed** data are allocated in
`libxamarin-app.so`.  The buffers are then passed to the LZ4 APIs,
all threads using the same output buffer.  The assumption was that we
can do fine without locking as even if overlapped decompression
happens, the output data will be the same and so even if two threads
do the same thing at the same time, the data will be valid at all
times, so long as at least one thread completes the decompression.

This assumption proved to be **largely** true, but it appears that in
high concurrency cases it is possible that the data in the
decompression buffer differs.  This can result in app crashes:

	A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 3092 (.NET ThreadPool), pid 2727 (myapp.name)
	A/DEBUG: pid: 2727, tid: 3092, name: .NET ThreadPool  >>> myapp.name <<<
	A/DEBUG:       #1 pc 0000000000029b1c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmono-android.release.so (offset 0x103d000) (xamarin::android::internal::MonodroidRuntime::mono_log_handler(char const*, char const*, char const*, int, void*)+144) (BuildId: 29c5a3805a0bedee1eede9b6668d7c676aa63371)
	A/DEBUG:       #2 pc 00000000002680bc  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       #3 pc 00000000002681e8  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	A/DEBUG:       #4 pc 000000000008555c  /data/app/myapp.name-B9t_3dF9i8mDxJEKodZw5w==/split_config.arm64_v8a.apk!libmonosgen-2.0.so (offset 0x109b000) (mono_metadata_string_heap+188) (BuildId: 4a5dd4396e8816b7f69881838bd549285213d53b)
	…

My guess is that LZ4 either uses the output buffer as a scratchpad
area when decompressing or that it initializes/modifies the buffer
before writing actual data in it.  With overlapped decompression, it
may lead to one thread overwriting valid data previously written by
another thread, so that when the latter returns the buffer it thought
to have had valid data may contain certain bytes temporarily
overwritten by the decompression session in the other, still running,
thread.  It may happen that MonoVM reads the corrupted data just when
it is still invalid (before the still running decompression session
actually writes the valid data), a classic race condition.

To fix this, the decompression block is now protected with a startup-
aware mutex.  Mutex will be held only after the initial startup phase
is completed, so there should not be much loss of startup performance.
jonpryor pushed a commit that referenced this pull request Jul 13, 2023
Context: 929e701
Context: ce2bc68
Context: #7473
Context: #8155

The managed linker can produce assemblies optimized for the target
`$(RuntimeIdentifier)` (RID), which means that they will differ
between different RIDs.  Our "favorite" example of this is
`IntPtr.Size`, which is inlined by the linker into `4` or `8` when
targeting 32-bit or 64-bit platforms.  (See also #7473 and 929e701.)

Another platform difference may come in the shape of CPU intrinsics
which will change the JIT-generated native code in ways that will
crash the application if the assembler instructions generated for the
intrinsics aren't supported by the underlying processor.

In addition, the per-RID assemblies will have different [MVID][0]s
and **may** have different type and method metadata token IDs, which
is important because typemaps *use* type and metadata token IDs; see
also ce2bc68.

All of this taken together invalidates our previous assumption that
all the managed assemblies are identical.  "Simply" using
`IntPtr.Size` in an assembly that contains `Java.Lang.Object`
subclasses will break things.

This in turn could cause "mysterious" behavior or crashes in Release
applications; see also Issue #8155.

Prevent the potential problems by processing each per-RID assembly
separately and output correct per-RID LLVM IR assembly using the
appropriate per-RID information.

Additionally, during testing I found that for our use of Cecil within
`<GenerateJavaStubs/>` doesn't consistently remove the fields,
delegates, and methods we remove in `MarshalMethodsAssemblyRewriter`
when marshal methods are enabled, or it generates subtly broken
assemblies which cause **some** applications to segfault at run time
like so:

	I monodroid-gc: 1 outstanding GREFs. Performing a full GC!
	F libc    : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x8 in tid 12379 (t6.helloandroid), pid 12379 (t6.helloandroid)
	F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
	F DEBUG   : Build fingerprint: 'google/raven_beta/raven:14/UPB3.230519.014/10284690:user/release-keys'
	F DEBUG   : Revision: 'MP1.0'
	F DEBUG   : ABI: 'arm64'
	F DEBUG   : Timestamp: 2023-07-04 22:09:58.762982002+0200
	F DEBUG   : Process uptime: 1s
	F DEBUG   : Cmdline: com.microsoft.net6.helloandroid
	F DEBUG   : pid: 12379, tid: 12379, name: t6.helloandroid  >>> com.microsoft.net6.helloandroid <<<
	F DEBUG   : uid: 10288
	F DEBUG   : tagged_addr_ctrl: 0000000000000001 (PR_TAGGED_ADDR_ENABLE)
	F DEBUG   : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0000000000000008
	F DEBUG   : Cause: null pointer dereference
	F DEBUG   :     x0  0000000000000000  x1  0000007ba1401af0  x2  00000000000000fa  x3  0000000000000001
	F DEBUG   :     x4  0000007ba1401b38  x5  0000007b9f2a8360  x6  0000000000000000  x7  0000000000000000
	F DEBUG   :     x8  ffffffffffc00000  x9  0000007b9f800000  x10 0000000000000000  x11 0000007ba1400000
	F DEBUG   :     x12 0000000000000000  x13 0000007ba374ad58  x14 0000000000000000  x15 00000013ead77d66
	F DEBUG   :     x16 0000007ba372f210  x17 0000007ebdaa4a80  x18 0000007edf612000  x19 000000000000001f
	F DEBUG   :     x20 0000000000000000  x21 0000007b9f2a8320  x22 0000007b9fb02000  x23 0000000000000018
	F DEBUG   :     x24 0000007ba374ad08  x25 0000000000000004  x26 0000007b9f2a4618  x27 0000000000000000
	F DEBUG   :     x28 ffffffffffffffff  x29 0000007fc592a780
	F DEBUG   :     lr  0000007ba3701f44  sp  0000007fc592a730  pc  0000007ba3701e0c  pst 0000000080001000
	F DEBUG   : 8 total frames
	F DEBUG   : backtrace:
	F DEBUG   :       #00 pc 00000000002d4e0c  /data/app/~~Av24J15xbf20XdrY3X2_wA==/com.microsoft.net6.helloandroid-4DusuNWIAkz1Ssi7fWVF-g==/lib/arm64/libmonosgen-2.0.so (BuildId: 761134f2369377582cc3a8e25ecccb43a2e0a877)
	F DEBUG   :       #1 pc 00000000002c29e8  /data/app/~~Av24J15xbf20XdrY3X2_wA==/com.microsoft.net6.helloandroid-4DusuNWIAkz1Ssi7fWVF-g==/lib/arm64/libmonosgen-2.0.so (BuildId: 761134f2369377582cc3a8e25ecccb43a2e0a877)
	F DEBUG   :       #2 pc 00000000002c34bc  /data/app/~~Av24J15xbf20XdrY3X2_wA==/com.microsoft.net6.helloandroid-4DusuNWIAkz1Ssi7fWVF-g==/lib/arm64/libmonosgen-2.0.so (BuildId: 761134f2369377582cc3a8e25ecccb43a2e0a877)
	F DEBUG   :       #3 pc 00000000002c2254  /data/app/~~Av24J15xbf20XdrY3X2_wA==/com.microsoft.net6.helloandroid-4DusuNWIAkz1Ssi7fWVF-g==/lib/arm64/libmonosgen-2.0.so (BuildId: 761134f2369377582cc3a8e25ecccb43a2e0a877)
	F DEBUG   :       #4 pc 00000000002be0bc  /data/app/~~Av24J15xbf20XdrY3X2_wA==/com.microsoft.net6.helloandroid-4DusuNWIAkz1Ssi7fWVF-g==/lib/arm64/libmonosgen-2.0.so (BuildId: 761134f2369377582cc3a8e25ecccb43a2e0a877)
	F DEBUG   :       #5 pc 00000000002bf050  /data/app/~~Av24J15xbf20XdrY3X2_wA==/com.microsoft.net6.helloandroid-4DusuNWIAkz1Ssi7fWVF-g==/lib/arm64/libmonosgen-2.0.so (BuildId: 761134f2369377582cc3a8e25ecccb43a2e0a877)
	F DEBUG   :       #6 pc 00000000002a53a4  /data/app/~~Av24J15xbf20XdrY3X2_wA==/com.microsoft.net6.helloandroid-4DusuNWIAkz1Ssi7fWVF-g==/lib/arm64/libmonosgen-2.0.so (mono_gc_collect+44) (BuildId: 761134f2369377582cc3a8e25ecccb43a2e0a877)
	F DEBUG   :       #7 pc 000000000000513c  <anonymous:7ec716b000>

This is because we generate Java Callable Wrappers over a set of
original (linked or not) assemblies, then we scan them for classes
derived from `Java.Lang.Object` and use that set as input to the
marshal methods rewriter, which makes the changes (generates wrapper
methods, decorates wrapped methods with `[UnmanagedCallersOnly]`,
removes the old delegate methods as well as delegate backing fields)
to all the `Java.Lang.Object` subclasses, then writes the modified
assembly to a `new/<assembly.dll>` location (efa14e2), followed by
copying the newly written assemblies back to the original location.
At this point, we have the results returned by the subclass scanner
in memory and **new** versions of those types on disk, but they are
out of sync, since the types in memory refer to the **old** assemblies,
but AOT is ran on the **new** assemblies which have a different layout,
changed MVIDs and, potentially, different type and method token IDs
(because we added some methods, removed others etc) and thus it causes
the crashes at the run time.  The now invalid set of "old" types is
passed to the typemap generator.  This only worked by accident, because
we (incorrectly) used only the first linked assembly which happened
to be the same one passed to the JLO scanner and AOT - so everything
was fine at the execution time.

Address this by *disabling* LLVM Marshal Methods (8bc7a3e) for .NET 8,
setting `$(AndroidEnableMarshalMethods)`=False by default.
We'll attempt to fix these issues for .NET 9.

[0]: https://learn.microsoft.com/dotnet/api/system.reflection.module.moduleversionid?view=net-7.0
jonpryor added a commit that referenced this pull request Jan 26, 2024
Context: dotnet/java-interop@6b3637d

The story so far is that some of our unit tests are crashing, and
have been in one form or another since 4332ea0
(the bump to dotnet/java-interop@def5bc0).

The current crash, from the PR build for 7b46391:

	D monodroid-assembly: typemap: assembly 'Java.Interop-Tests' hasn't been loaded yet, attempting a full load
	W monodroid-assembly: typemap: failed to load managed assembly 'Java.Interop-Tests.dll'. No such file or directory
	E monodroid-assembly: typemap: unable to load assembly 'Java.Interop-Tests' when looking up managed type corresponding to Java type 'java/lang/Object'
	I monodroid-timing: [1/5] Typemap.java_to_managed: end, total time; elapsed: 0:0::260000
	W monodroid-assembly: typemap: called from
	W monodroid-assembly: at Java.Interop.TypeManager.GetJavaToManagedType(String )
	W monodroid-assembly:    at Java.Interop.TypeManager.CreateInstance(IntPtr , JniHandleOwnership , Type )
	W monodroid-assembly:    at Java.Lang.Object.GetObject(IntPtr , JniHandleOwnership , Type )
	W monodroid-assembly:    at Java.Lang.Object._GetObject[IIterator](IntPtr , JniHandleOwnership )
	W monodroid-assembly:    at Java.Lang.Object.GetObject[IIterator](IntPtr handle, JniHandleOwnership transfer)
	W monodroid-assembly:    at Android.Runtime.JavaSet.Iterator()
	W monodroid-assembly:    at Android.Runtime.JavaSet`1[[System.String, System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetEnumerator()
	W monodroid-assembly:    at Xamarin.Android.UnitTests.TestInstrumentation`1[[Xamarin.Android.UnitTests.NUnit.NUnitTestRunner, TestRunner.NUnit.NET, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ProcessArguments()
	W monodroid-assembly:    at Xamarin.Android.UnitTests.TestInstrumentation`1[[Xamarin.Android.UnitTests.NUnit.NUnitTestRunner, TestRunner.NUnit.NET, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].OnCreate(Bundle arguments)
	W monodroid-assembly:    at Android.App.Instrumentation.n_OnCreate_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_arguments)
	W monodroid-assembly:    at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V(_JniMarshal_PPL_V callback, IntPtr jnienv, IntPtr klazz, IntPtr p0)
	E droid.NET_Test: JNI ERROR (app bug): accessed stale Local 0x75  (index 7 in a table of size 7)
	F droid.NET_Test: java_vm_ext.cc:570] JNI DETECTED ERROR IN APPLICATION: use of deleted local reference 0x75

There are *three* "concerning" items here:

 1. typemaps are trying to load `Java.Interop-Tests`, and failing:

        typemap: failed to load managed assembly 'Java.Interop-Tests.dll'. No such file or directory

    @grendello is looking into this.

 2. The binding for `java/lang/Object` is coming from
    Java.Interop-Tests, not Mono.Android (?!)

        typemap: unable to load assembly 'Java.Interop-Tests' when looking up managed type corresponding to Java type 'java/lang/Object'

    dotnet/java-interop#1181 has a fix for this, and we're not
    applying the fix yet because we believe that it will hide (1).

 3. The JNI error, which crashes the process:

        F droid.NET_Test: java_vm_ext.cc:570] JNI DETECTED ERROR IN APPLICATION: use of deleted local reference 0x75
        F droid.NET_Test: java_vm_ext.cc:570]     from void crc643df67da7b13bb6b1.TestInstrumentation_1.n_onCreate(android.os.Bundle)
        F droid.NET_Test: runtime.cc:630] Runtime aborting...
        F droid.NET_Test: runtime.cc:630] Dumping all threads without mutator lock held
        F droid.NET_Test: runtime.cc:630] All threads:
        F droid.NET_Test: runtime.cc:630] DALVIK THREADS (14):
        F droid.NET_Test: runtime.cc:630] "main" prio=5 tid=1 Runnable
        F droid.NET_Test: runtime.cc:630]   | group="" sCount=0 dsCount=0 flags=0 obj=0x729e9d98 self=0x7567e0f51000
        F droid.NET_Test: runtime.cc:630]   | sysTid=9143 nice=0 cgrp=default sched=0/0 handle=0x7567e14daed8
        F droid.NET_Test: runtime.cc:630]   | state=R schedstat=( 1270418000 334229000 139 ) utm=16 stm=110 core=0 HZ=100
        F droid.NET_Test: runtime.cc:630]   | stack=0x7ffcbb3e4000-0x7ffcbb3e6000 stackSize=8192KB
        F droid.NET_Test: runtime.cc:630]   | held mutexes= "abort lock" "mutator lock"(shared held)
        F droid.NET_Test: runtime.cc:630]   native: #00 pc 000000000048df4e  /apex/com.android.runtime/lib64/libart.so (art::DumpNativeStack(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, int, BacktraceMap*, char const*, art::ArtMethod*, void*, bool)+126)
        F droid.NET_Test: runtime.cc:630]   native: #1 pc 00000000005a77c3  /apex/com.android.runtime/lib64/libart.so (art::Thread::DumpStack(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, bool, BacktraceMap*, bool) const+675)
        F droid.NET_Test: runtime.cc:630]   native: #2 pc 00000000005c49cb  /apex/com.android.runtime/lib64/libart.so (art::DumpCheckpoint::Run(art::Thread*)+859)
        F droid.NET_Test: runtime.cc:630]   native: #3 pc 00000000005bcf28  /apex/com.android.runtime/lib64/libart.so (art::ThreadList::RunCheckpoint(art::Closure*, art::Closure*)+456)
        F droid.NET_Test: runtime.cc:630]   native: #4 pc 00000000005bc2e1  /apex/com.android.runtime/lib64/libart.so (art::ThreadList::Dump(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, bool)+1601)
        F droid.NET_Test: runtime.cc:630]   native: #5 pc 0000000000552eb9  /apex/com.android.runtime/lib64/libart.so (art::Runtime::Abort(char const*)+1529)
        F droid.NET_Test: runtime.cc:630]   native: #6 pc 000000000000c873  /system/lib64/libbase.so (android::base::LogMessage::~LogMessage()+611)
        F droid.NET_Test: runtime.cc:630]   native: #7 pc 00000000003ede84  /apex/com.android.runtime/lib64/libart.so (art::JavaVMExt::JniAbort(char const*, char const*)+1604)
        F droid.NET_Test: runtime.cc:630]   native: #8 pc 00000000003ee18a  /apex/com.android.runtime/lib64/libart.so (art::JavaVMExt::JniAbortF(char const*, char const*, ...)+234)
        F droid.NET_Test: runtime.cc:630]   native: #9 pc 00000000005adf31  /apex/com.android.runtime/lib64/libart.so (art::Thread::DecodeJObject(_jobject*) const+785)
        F droid.NET_Test: runtime.cc:630]   native: #10 pc 00000000003def9b  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::ScopedCheck::CheckInstance(art::ScopedObjectAccess&, art::(anonymous namespace)::ScopedCheck::InstanceKind, _jobject*, bool)+91)
        F droid.NET_Test: runtime.cc:630]   native: #11 pc 00000000003de205  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::ScopedCheck::CheckPossibleHeapValue(art::ScopedObjectAccess&, char, art::(anonymous namespace)::JniValueType)+485)
        F droid.NET_Test: runtime.cc:630]   native: #12 pc 00000000003dd732  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::ScopedCheck::Check(art::ScopedObjectAccess&, bool, char const*, art::(anonymous namespace)::JniValueType*)+690)
        F droid.NET_Test: runtime.cc:630]   native: #13 pc 00000000003ce865  /apex/com.android.runtime/lib64/libart.so (art::(anonymous namespace)::CheckJNI::GetObjectClass(_JNIEnv*, _jobject*)+837)
        F droid.NET_Test: runtime.cc:630]   native: #14 pc 0000000000017196  /data/app/Mono.Android.NET_Tests-LUUW792fOvX745oAS4jeRQ==/split_config.x86_64.apk (offset 331000) (???)
        F droid.NET_Test: runtime.cc:630]   at crc643df67da7b13bb6b1.TestInstrumentation_1.n_onCreate(Native method)

As per `native #13`, we're (somehow) passing an invalid JNI reference
to `JNIEnv::GetObjectClass()`.

***HOW*** are we passing an invalid JNI reference to
`JNIEnv::GetObjectClass()`?

Attempt to investigate (3) further, by:

 1. Reviewing all calls to `JNIEnv::GetObjectClass()` within this
    repo to see if we could potentially be passing an invalid value.
    The "most obvious" candidate is `TypeManager.CreateInstance()`,
    which calls `JNIEnv::GetObjectClass()` in a loop.

    I'm still not sure if that could possibly be the cause, but
    Just In Case™…

    "Cleanup" some C++ code so that calls to
    `JNIEnv::DeleteLocalReference()` are closer to the
    `JNIEnv::GetObjectClass()` calls.

 2. Update
    `tests/Mono.Android-Tests/Runtime-Microsoft.Android.Sdk/Mono.Android.NET-Tests.csproj`
    to add an `@(AndroidEnvironment)` item, which sets
    `debug.mono.log=gref+,lref+`.  This will enable LREF and GREF
    logging within `adb logcat`, which *may* allow us to track down
    where "local reference 0x75" came from.
@github-actions github-actions bot locked and limited conversation to collaborators Feb 2, 2024
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Labels
None yet
Projects
None yet
Development

Successfully merging this pull request may close these issues.

2 participants