Build failure with MinGW-w64 gcc 5.2.0

[alexcrichton]

Updated description

We need to document that the standard MSYS2 package for gcc will not work when building Rust, you have to install a custom toolchain with a known good version and the win32 threading model, not the pthread threading model.

Original report

Looks related to #29177, perhaps the gcc_eh library picked up new dependencies in 5.2.0?

cc @vadimcn

error: linking with `gcc` failed: exit code: 1
note: "gcc" "-Wl,--enable-long-section-names" "-fno-use-linker-plugin" "-Wl,--nxcompat" "-nostdlib" "-Wl,--large-address-aware" "C:\\msys64\\home\\ale\\rust2\\i686-pc-windows-gnu\\stage1\\lib\\rustlib\\i686-pc-windows-gnu\\lib\\dllcrt2.o" "C:\\msys64\\home\\ale\\rust2\\i686-pc-windows-gnu\\stage1\\lib\\rustlib\\i686-pc-windows-gnu\\lib\\rsbegin.o" "-L" "C:\\msys64\\home\\ale\\rust2\\i686-pc-windows-gnu\\stage1\\lib\\rustlib\\i686-pc-windows-gnu\\lib" "i686-pc-windows-gnu/stage1/lib/rustlib/i686-pc-windows-gnu/lib\\std-71b07a99.0.o" "-o" "i686-pc-windows-gnu/stage1/lib/rustlib/i686-pc-windows-gnu/lib\\std-71b07a99.dll" "i686-pc-windows-gnu/stage1/lib/rustlib/i686-pc-windows-gnu/lib\\std-71b07a99.metadata.o" "-nodefaultlibs" "-L" "i686-pc-windows-gnu/rt" "-L" "C:\\msys64\\home\\ale\\rust2\\i686-pc-windows-gnu\\llvm\\Release/lib" "-L" "C:\\msys64\\home\\ale\\rust2\\i686-pc-windows-gnu\\stage1\\lib\\rustlib\\i686-pc-windows-gnu\\lib" "-L" "C:\\msys64\\home\\ale\\rust2\\.rust\\lib\\i686-pc-windows-gnu" "-L" "C:\\msys64\\home\\ale\\rust2\\lib\\i686-pc-windows-gnu" "-Wl,-Bstatic" "-Wl,--whole-archive" "-l" "backtrace" "-Wl,--no-whole-archive" "-Wl,-Bdynamic" "-l" "gcc_eh" "-l" "gcc_eh" "-l" "ws2_32" "-l" "userenv" "-l" "shell32" "-l" "advapi32" "-Wl,--whole-archive" "C:\\msys64\\tmp\\rustc.hZLinbW19bbD\\libcollections-71b07a99.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "C:\\msys64\\tmp\\rustc.hZLinbW19bbD\\liballoc-71b07a99.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "C:\\msys64\\tmp\\rustc.hZLinbW19bbD\\librustc_unicode-71b07a99.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "C:\\msys64\\tmp\\rustc.hZLinbW19bbD\\liballoc_jemalloc-71b07a99.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "C:\\msys64\\tmp\\rustc.hZLinbW19bbD\\liblibc-71b07a99.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "C:\\msys64\\tmp\\rustc.hZLinbW19bbD\\librand-71b07a99.rlib" "-Wl,--no-whole-archive" "-Wl,--whole-archive" "C:\\msys64\\tmp\\rustc.hZLinbW19bbD\\libcore-71b07a99.rlib" "-Wl,--no-whole-archive" "-shared" "-l" "compiler-rt" "-lmingwex" "-lmingw32" "-lgcc" "-lmsvcrt" "-luser32" "-lkernel32" "C:\\msys64\\home\\ale\\rust2\\i686-pc-windows-gnu\\stage1\\lib\\rustlib\\i686-pc-windows-gnu\\lib\\rsend.o"
note: C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2.o):(.text+0x1a4b): undefined reference to `pthread_once'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x1a3): undefined reference to `pthread_mutex_init'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0xf99): undefined reference to `pthread_once'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0xfa5): undefined reference to `pthread_mutex_lock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x10b4): undefined reference to `pthread_once'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x10c0): undefined reference to `pthread_mutex_lock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x118b): undefined reference to `pthread_once'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x1197): undefined reference to `pthread_mutex_lock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x11f9): undefined reference to `pthread_mutex_unlock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x1228): undefined reference to `pthread_mutex_unlock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x12af): undefined reference to `pthread_once'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x12bb): undefined reference to `pthread_mutex_lock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x12f7): undefined reference to `pthread_mutex_unlock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x13b6): undefined reference to `pthread_mutex_unlock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0xfc4): undefined reference to `pthread_mutex_unlock'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/5.2.0/libgcc_eh.a(unwind-dw2-fde.o):(.text+0x10df): undefined reference to `pthread_mutex_unlock'
collect2.exe: error: ld returned 1 exit status

error: aborting due to previous error

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
/home/ale/rust2/mk/target.mk:231: recipe for target 'i686-pc-windows-gnu/stage1/lib/rustlib/i686-pc-windows-gnu/lib/stamp.std' failed
make: *** [i686-pc-windows-gnu/stage1/lib/rustlib/i686-pc-windows-gnu/lib/stamp.std] Error 3

[vadimcn]

Huh. Could this be due to the difference between the 'win32' and 'posix' flavors of mingw-w64? If it's the latter,we are probably missing libpthread link dependency.

[alexcrichton]

Oh, right, of course!

Hm that kinda sucks though because it means that the default gcc packages in MinGW are no longer usable to build Rust. Does MSYS2 provide win32 threaded gcc implementations?

[vadimcn]

Nope, the only way (that I've found) to install win32-threaded gcc is through mingw-builds installer.
I suppose we could detect gcc flavor in configure and pass --cfg use_libpthread to rustc. This would be prone to bit-rot though.

[alexcrichton]

Hm ok, in that case I'm gonna switch this to a docs bug, we basically need to document that using an external package is not only recommended but it's the only option in a case like this as it's not something upstream's gonna fix (unlike the LLVM-wont-build-and-may-segfault bug)

[DanielKeep]

Same problem here with 4.9.0. I haven't touched my install in ages.

[steveklabnik]

Can someone help me out here? I'm assuming this needs to be in the README, yeah? What exactly do we need to say?

[vadimcn]

Basically, we need to remove this line (and the next) and instead instruct devs to download mingw-builds installer, and choose the threads=win32,exceptions=dwarf/seh flavor (and probably version < 5.0 for now - because of #28260). Finally, they'll need to add its \mingw32\bin (or ...\mingw64\bin - depending on bit-ness) to search path.

[davidkazlauskas]

I'm building MXE ( http://mxe.cc/ ) and I'd like to link with some code cross compiled with rust. My MXE is mingw-gcc build is posix threads and dwarf exceptions. Is it a good idea to if I call some code from a dll that has win32 threading model ( rust ) from a code with posix model or it doesn't matter?