Issue with GCC 8

[spotrh]

It is not clear to me if this is a compiler issue or an asymptote issue, but when I try to build asymptote 2.41 for Fedora 28 (using gcc 8.0.1), the build succeeds, but asy dumps core during make all:

• make all
  ../asy -dir ../base -config "" -render=0 -h 2>&1 | grep -iv Asymptote > options
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc Hobbycontrol.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc binarytreetest.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc quartercircle.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc leastsquares.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc logo.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc join3.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc helix.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc loggrid.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc beziercurve.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc log2graph.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc monthaxis.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc exp.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc loggraph.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc cube.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc errorbars.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc generalaxis.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc tile.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc shadedtiling.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc lineargraph.asy
  ../asy -dir ../base -config "" -render=0 -f pdf -noprc secondaryaxis.asy
  make: *** [Makefile:42: secondaryaxis.pdf] Aborted (core dumped)

gdb backtrace looks like this:

Core was generated by `../asy -dir ../base -config  -render=0 -f pdf -noprc secondaryaxis.asy'.
Program terminated with signal SIGABRT, Aborted.
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
50	  return ret;
[Current thread is 1 (Thread 0x7efefef8f880 (LWP 7110))]
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x00007efefb126591 in __GI_abort () at abort.c:79
#2  0x0000562977da26c8 in std::__replacement_assert (
    __file=0x2 <error: Cannot access memory at address 0x2>, __line=-1874640560, __function=0x0, 
    __condition=0x0) at /usr/include/c++/8/x86_64-redhat-linux/bits/c++config.h:2389
#3  0x0000562977fcd5ff in std::__cxx11::basic_string<char, std::char_traits<char>, gc_allocator<char> >::operator[] (__pos=<optimized out>, this=<optimized out>) at /usr/include/c++/8/bits/char_traits.h:285
#4  camp::ifile::Read(std::__cxx11::basic_string<char, std::char_traits<char>, gc_allocator<char> >&) ()
    at fileio.cc:149
#5  0x0000562977eb0269 in camp::file::read<std::__cxx11::basic_string<char, std::char_traits<char>, gc_allocator<char> > > (this=0x562979832bb0, val="") at /usr/include/c++/8/bits/char_traits.h:285
#6  0x0000562977eb1ccc in run::readArray<std::__cxx11::basic_string<char, std::char_traits<char>, gc_allocator<char> > > (s=0x2, nx=0, ny=-1, nz=-1) at castop.h:109
#7  0x0000562977fb4127 in vm::stack::runWithOrWithoutClosure(vm::lambda*, vm::frame*, vm::frame*) ()
    at stack.cc:455
#8  0x0000562977fe8157 in runRunnable(absyntax::runnable*, trans::coenv&, vm::interactiveStack&, transMode) () at process.cc:168
#9  0x0000562977fefc9e in itree::run (this=0x56297947cd60, e=..., s=..., tm=TRANS_NORMAL)
    at process.cc:311
#10 0x0000562977fec9c7 in icore::doRun (this=0x7fff9043d000, purge=80, tm=TRANS_INTERACTIVE)
    at process.cc:234
#11 0x0000562977fe7991 in icore::process (purge=<optimized out>, this=<optimized out>) at process.cc:257
#12 ifile::process (purge=<optimized out>, this=<optimized out>) at process.cc:396
#13 processFile(std::__cxx11::basic_string<char, std::char_traits<char>, gc_allocator<char> > const&, bool) () at process.cc:877
#14 0x00005629780347df in asymain(void*) () at /usr/include/c++/8/bits/char_traits.h:320
#15 0x0000562977d87dcb in main () at main.cc:215
#16 0x00007efefb1281bb in __libc_start_main (main=0x562977d87d50 <main>, argc=10, argv=0x7fff9043d308, 
    init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff9043d2f8)
    at ../csu/libc-start.c:308
#17 0x0000562977d87f7a in _start () at drawpath.cc:165
(gdb) 

[mtasaka]

With -O0:

(gdb) up
#1  0x00007ffff44f15c1 in abort () from /lib64/libc.so.6
(gdb) 
#2  0x00005555555a0bbb in std::__replacement_assert (__file=0x55555588d760 "/usr/include/c++/8/bits/basic_string.h", __line=1048, 
    __function=0x55555588e860 <std::__cxx11::basic_string<char, std::char_traits<char>, gc_allocator<char> >::operator[](unsigned long)::__PRETTY_FUNCTION__> "std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::reference std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator[](std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type) [with _Ch"..., __condition=0x55555588d74c "__pos <= size()") at /usr/include/c++/8/x86_64-redhat-linux/bits/c++config.h:2389
2389	    __builtin_abort();
(gdb) 
#3  0x00005555555cbd20 in std::__cxx11::basic_string<char, std::char_traits<char>, gc_allocator<char> >::operator[] (this=0x7fffffff55d0, __pos=18446744073709551615)
    at /usr/include/c++/8/bits/basic_string.h:1048
1048		__glibcxx_assert(__pos <= size());
(gdb) 
#4  0x00005555557f995a in camp::ifile::Read (this=0x555556781bb0, val="") at fileio.cc:149
149	  if(s[pos] == '\r') s.erase(pos,1);
(gdb) p s
$1 = ""
(gdb) p pos
$2 = 18446744073709551615

So at https://github.com/vectorgraphics/asymptote/blob/master/fileio.cc#L149 , s is std::string "", pos is (size_t)-1 and now gcc8 checks the access of s[(size_t)-1] and it causes abort.
Now gcc8 checks this type of access (i.e. std::string str: a = str[pos]) every time and make it abort if access is illegal.

[johncbowman]

Thank you for tracking this bug down. It is fixed in commit 6ce2d6f.