cmd/cgo: support clang on Windows

[nadiasvertex]

What version of Go are you using (go version)?

go version devel +0cff219 Wed Sep 7 10:43:13 2016 +0000 windows/amd64

What operating system and processor architecture are you using (go env)?

Windows 10 / AMD64

What did you do?

I used CGO with Clang for Windows 3.8.1 (http://llvm.org/releases/3.8.1/LLVM-3.8.1-win64.exe) like this:

set CC=clang
set CGO_CFLAGS="-m64 -Ipath/to/my/includes"
set CGO_LDFLAGS = "-v -Xlinker -libpath:path/to/libs -lwldap32 -ladvapi32 -lws2_32 -ldbghelp -luser32"

go build

What did you expect to see?

Expected to see nothing (ie, successful compile)

What did you see instead?

# editor/dom
clang version 3.8.1 (branches/release_38)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\LLVM\bin
 "C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\bin\\amd64\\link.exe" "-out:C:\\Users\\CHRIST~1\\AppData\\Local\\Temp\\go-build406860094\\editor\\dom\\_obj\\_cgo_.o" -defaultlib:libcmt "-libpath:C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\lib\\amd64" "-libpath:C:\\Program Files (x86)\\Windows Kits\\10\\Lib\\10.0.10240.0\\ucrt\\x64" "-libpath:C:\\Program Files (x86)\\Windows Kits\\8.1\\Lib\\winv6.3\\um\\x64" -nologo "C:\\Users\\CHRIST~1\\AppData\\Local\\Temp\\go-build406860094\\editor\\dom\\_obj\\_cgo_main.o" "C:\\Users\\CHRIST~1\\AppData\\Local\\Temp\\go-build406860094\\editor\\dom\\_obj\\_cgo_export.o" "C:\\Users\\CHRIST~1\\AppData\\Local\\Temp\\go-build406860094\\editor\\dom\\_obj\\binding.cgo2.o" "-libpath:c:\\temp\\go\\src\\editor\\.mm\\windows\\amd64\\release\\lib" core-static.lib ssl-static.lib crypto-static.lib ssh2-static.lib c-ares-static.lib user32.lib ws2_32.lib wldap32.lib advapi32.lib dbghelp.lib
   Creating library $WORK\editor\dom\_obj\_cgo_.lib and object $WORK\editor\dom\_obj\_cgo_.exp
core-static.lib(node.obj) : warning LNK4049: locally defined symbol xmlFree imported
core-static.lib(xml.obj) : warning LNK4049: locally defined symbol xmlFree imported
# editor/dom
clang version 3.8.1 (branches/release_38)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\LLVM\bin
 "C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\bin\\amd64\\link.exe" "-out:C:\\Users\\CHRIST~1\\AppData\\Local\\Temp\\go-build406860094\\editor\\dom\\_obj\\_all.o" "-libpath:C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\lib\\amd64" "-libpath:C:\\Program Files (x86)\\Windows Kits\\10\\Lib\\10.0.10240.0\\ucrt\\x64" "-libpath:C:\\Program Files (x86)\\Windows Kits\\8.1\\Lib\\winv6.3\\um\\x64" -nologo "C:\\Users\\CHRIST~1\\AppData\\Local\\Temp\\go-build406860094\\editor\\dom\\_obj\\_cgo_export.o" "C:\\Users\\CHRIST~1\\AppData\\Local\\Temp\\go-build406860094\\editor\\dom\\_obj\\binding.cgo2.o" -Wl,-r
LINK : warning LNK4044: unrecognized option '/Wl,-r'; ignored
LINK : fatal error LNK1561: entry point must be defined
clang.exe: error: linker command failed with exit code 1561 (use -v to see invocation)

[bradfitz]

I don't believe clang is supported yet. Our installation docs only mention mingw.

That said, we should probably support clang on Windows at some point.

/cc @ianlancetaylor @alexbrainman @crawshaw

[alexbrainman]

I have nothing against clang support. I have never had it installed on my computer. I will try install clang when I have some time.

Alex

[DmitriyMV]

I did some digging around and found out that with -Xlinker /subsystem:console it actually gets past entry point must be defined. But now I'm getting this error:

# runtime/cgo
clang version 3.9.0 (branches/release_39)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Dmitry\LLVM_\bin
 "C:\\Program Files (x86)\\Microsoft Visual Studio\\VS15Preview\\Common7\\IDE\\VC\\bin\\amd64\\link.exe" "-out:C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\_cgo_.o" -defaultlib:libcmt -nologo "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\_cgo_main.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\_cgo_export.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\cgo.cgo2.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_context.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_libinit_windows.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_util.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_windows_amd64.o" "
subsystem:console wldap32.lib advapi32.lib ws2_32.lib dbghelp.lib user32.lib kernel32.lib winmm.lib ntdll.lib
cmd/go
# runtime/cgo
clang version 3.9.0 (branches/release_39)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Dmitry\LLVM_\bin
 "C:\\Program Files (x86)\\Microsoft Visual Studio\\VS15Preview\\Common7\\IDE\\VC\\bin\\amd64\\link.exe" "-out:C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\_all.o" -nologo "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\_cgo_export.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\cgo.cgo2.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_context.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_libinit_windows.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_util.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_windows_amd64.o" "C:\\Users\\Dmitry\\AppData\\Local\\Temp\\go-build586540150\\runtime\\cgo\\_obj\\gcc_amd64.o" /subsystem:console -r
LINK : warning LNK4044: unrecognized option '/r'; ignored
gcc_context.o : error LNK2019: unresolved external symbol __stdio_common_vsprintf referenced in function _vsnprintf_l
gcc_libinit_windows.o : error LNK2001: unresolved external symbol __stdio_common_vsprintf
gcc_util.o : error LNK2001: unresolved external symbol __stdio_common_vsprintf
gcc_windows_amd64.o : error LNK2001: unresolved external symbol __stdio_common_vsprintf
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __imp_CreateEventA referenced in function _cgo_preinit_init
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __acrt_iob_func referenced in function _cgo_preinit_init
gcc_util.o : error LNK2001: unresolved external symbol __acrt_iob_func
gcc_windows_amd64.o : error LNK2001: unresolved external symbol __acrt_iob_func
gcc_libinit_windows.o : error LNK2019: unresolved external symbol abort referenced in function _cgo_preinit_init
gcc_util.o : error LNK2001: unresolved external symbol abort
gcc_windows_amd64.o : error LNK2001: unresolved external symbol abort
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __imp_InitializeCriticalSection referenced in function _cgo_preinit_init
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __imp_Sleep referenced in function _cgo_maybe_run_preinit
gcc_libinit_windows.o : error LNK2019: unresolved external symbol _beginthread referenced in function x_cgo_sys_thread_create
gcc_windows_amd64.o : error LNK2001: unresolved external symbol _beginthread
gcc_libinit_windows.o : error LNK2019: unresolved external symbol _errno referenced in function x_cgo_sys_thread_create
gcc_windows_amd64.o : error LNK2001: unresolved external symbol _errno
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __imp_EnterCriticalSection referenced in function _cgo_is_runtime_initialized
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __imp_LeaveCriticalSection referenced in function _cgo_is_runtime_initialized
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __imp_WaitForSingleObject referenced in function _cgo_wait_runtime_init_done
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __imp_SetEvent referenced in function x_cgo_notify_runtime_init_done
gcc_libinit_windows.o : error LNK2019: unresolved external symbol __stdio_common_vfprintf referenced in function _vfprintf_l
gcc_util.o : error LNK2001: unresolved external symbol __stdio_common_vfprintf
gcc_windows_amd64.o : error LNK2001: unresolved external symbol __stdio_common_vfprintf
gcc_util.o : error LNK2019: unresolved external symbol malloc referenced in function x_cgo_thread_start
gcc_windows_amd64.o : error LNK2019: unresolved external symbol free referenced in function threadentry
LINK : error LNK2001: unresolved external symbol mainCRTStartup
C:\Users\Dmitry\AppData\Local\Temp\go-build586540150\runtime\cgo\_obj\_all.o : fatal error LNK1120: 16 unresolved externals
clang.exe: error: linker command failed with exit code 1120 (use -v to see invocation)

With:
set CGO_LDFLAGS=-v -Xlinker /subsystem:console -lwldap32 -ladvapi32 -lws2_32 -ldbghelp -luser32 -lkernel32 -lwinmm -lntdll

I guess, it cannot find the C libs, but then when I tried to add -libpath:"C:\Program Files (x86)\Microsoft Visual Studio\VS15Preview\Common7\IDE\VC\lib\" I'm sure I did something wrong because it started to produce this:

# runtime/cgo
clang version 3.9.0 (branches/release_39)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Dmitry\LLVM_\bin
clang.exe: error: no such file or directory: 'Files'
clang.exe: error: no such file or directory: '(x86)/Microsoft'
clang.exe: error: no such file or directory: 'Visual'
clang.exe: error: no such file or directory: 'Studio/VS15Preview/Common7/IDE/VC/lib"'

@nadiasvertex I would really appreciate an advice on proper libpath setting.

[mattn]

Maybe it's related on #16455 ?

[DmitriyMV]

Yes - I created symlink because of that. It solved the second part of the problem, but the first(and main) remains.

[nadiasvertex]

@DmitriyMV I don't have much to tell you. The fundamental problem is that clang for Windows uses Microsoft's LIB as its backend. You do not need to tell LIB where to find the C library, it already knows that. I believe that the problem is that Go does not currently pass paths to clang in a way that LIB knows how to consume. I have not had success getting clang to compile with Go by playing with the commands. I think that the Go backend needs to be modified to send different values in order to make this work.

Sorry. I haven't had much time to work on this, but it is something that I would like to get working, or see someone else get working. :-)

[minux]

I think core issue is that the target for clang is: x86_64-pc-windows-msvc i.e. it's meant to be MSVC compatible. However, Go on windows rely on mingw for cgo. If we want to do anything here, it's probably to support msvc directly, rather than clang's emulation of it.

[nadiasvertex]

I prefer Clang's emulation. It makes the compiler part simpler since MSVC
is notoriously slow to get up to date with the standard, among other
frustrations. It would be really nice to be able to create MSVC-compatible
binaries without having to use MSVC. Not that I'm against also supporting
MSVC. We support a lot of C++ code that must compile under MSVC for now,
but we are very interested in dropping MSVC as soon as it is feasible.

On Tue, Nov 8, 2016, 2:48 AM Minux Ma notifications@github.com wrote:

I think core issue is that the target for clang is: x86_64-pc-windows-msvc
i.e. it's meant to be MSVC compatible.

However, Go on windows rely on mingw for cgo.

If we want to do anything here, it's probably to support msvc directly,
rather than clang's emulation of it.

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