Windows GNU Toolchain doesn't find gcc anymore

[CryZe]

Starting with rustc 1.19.0-nightly (6684d176c 2017-06-03) the compiler is not able to find gcc anymore when targeting x86_64-pc-windows-gnu, at least on AppVeyor.

  Compiling odds v0.2.25
   Compiling itoa v0.3.1
   Compiling quote v0.2.3
   Compiling color_quant v1.0.0
   Compiling winapi-build v0.1.1
   Compiling lzw v0.10.0
   Compiling libc v0.2.23
   Compiling num_cpus v1.5.1
   Compiling deque v0.3.2
   Compiling scoped_threadpool v0.1.7
   Compiling rayon-core v1.0.2
error: could not exec the linker `gcc`: The system cannot find the file specified. (os error 2)
  |
  = note: "gcc" "-Wl,--enable-long-section-names" "-fno-use-linker-plugin" "-Wl,--nxcompat" "-nostdlib" "-m64" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\crt2.o" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\rsbegin.o" "-L" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib" "C:\\projects\\livesplit-core\\target\\debug\\build\\rayon-core-c51968ef174e14dd\\build_script_build-c51968ef174e14dd.0.o" "-o" "C:\\projects\\livesplit-core\\target\\debug\\build\\rayon-core-c51968ef174e14dd\\build_script_build-c51968ef174e14dd.exe" "-Wl,--gc-sections" "-nodefaultlibs" "-L" "C:\\projects\\livesplit-core\\target\\debug\\deps" "-L" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib" "-Wl,-Bstatic" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libstd-5a958d157a8d8d98.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\librand-ce86047000b56785.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libcollections-b8b9a576d130e244.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libstd_unicode-9fbe5d3bbc85c563.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libpanic_unwind-14e8bb7ca07ebf2c.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libunwind-a4bc20050f473f79.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\liblibc-892bd58ec617c3bd.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\liballoc-b9c9173c47c20c41.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\liballoc_system-141f235246f01712.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libcore-3a6338503b91076c.rlib" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\libcompiler_builtins-e9e280acad4314a4.rlib" "-Wl,-Bdynamic" "-l" "advapi32" "-l" "ws2_32" "-l" "userenv" "-l" "shell32" "-Wl,-Bstatic" "-l" "gcc_eh" "-l" "pthread" "-Wl,-Bdynamic" "-lmingwex" "-lmingw32" "-lgcc" "-lmsvcrt" "-luser32" "-lkernel32" "C:\\Users\\appveyor\\.rustup\\toolchains\\nightly-x86_64-pc-windows-gnu\\lib\\rustlib\\x86_64-pc-windows-gnu\\lib\\rsend.o"

I assume the switch to the MSVC 2017 linker could've caused this: #38584

[ollie27]

Yeah looks like #42225 caused this (cc. @brson). Specifically https://github.com/rust-lang/rust/pull/42225/files#diff-1b71e145dde424ac83e674eef22373d8L710 removed the call to command_path which was used to find gcc.

[brson]

I'll look into this tomorrow.

[brson]

I've got a patch, but so far having a hard time producing the proper compiler locally to test.

[CryZe]

And now it's a beta regression too, so the fix needs to be backported.

[lilianmoraru]

This didn't trickle down to beta yet.

[CryZe]

Yeah, it should be in the next beta. They are bumping the beta version right now in #42609 it seems.