Help with cross-compilation and CGO.

[Bruno Albuquerque]

I am trying to cross-compile this code that relies on several libraries with dependencies on C/C++ static libraries. Compaling the project locally on linux works without issues but I wanted to cross-compile the same project from Linux to Windows amd64.

To do that, i installed MXE and used it as the C/C++ cross-compiler. Compilation seems to work without issues but, when linking, I get errors about symbols being redefined:

$ CGO_ENABLED=1 CC=x86_64-w64-mingw32.static-gcc CXX=x86_64-w64-mingw32.static-g++ GOOS=windows GOARCH=amd64 go build -x test.go

[... all packages are compiled without issues but, then ...]

mkdir -p $WORK/command-line-arguments/_obj/

mkdir -p $WORK/command-line-arguments/_obj/exe/

cd /home/bga/development/go-dev/src

/usr/local/go/pkg/tool/linux_amd64/compile -o $WORK/command-line-arguments.a -trimpath $WORK -p main -complete -buildid dec769d8ff9c511dd002d6ccad0f5224169c5685 -D _/home/bga/development/go-dev/src -I $WORK -I /home/bga/development/go-dev/pkg/windows_amd64 -pack ./test.go

cd .

/usr/local/go/pkg/tool/linux_amd64/link -o $WORK/command-line-arguments/_obj/exe/a.out.exe -L $WORK -L /home/bga/development/go-dev/pkg/windows_amd64 -extld=x86_64-w64-mingw32.static-g++ -buildmode=exe -buildid=dec769d8ff9c511dd002d6ccad0f5224169c5685 $WORK/command-line-arguments.a

# command-line-arguments

/usr/local/go/pkg/tool/linux_amd64/link: running x86_64-w64-mingw32.static-g++ failed: exit status 1

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetGR':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:81: multiple definition of `_Unwind_GetGR'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:81: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_SetGR':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:91: multiple definition of `_Unwind_SetGR'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:91: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetCFA':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:102: multiple definition of `_Unwind_GetCFA'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:102: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetIP':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:110: multiple definition of `_Unwind_GetIP'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:110: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetIPInfo':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:123: multiple definition of `_Unwind_GetIPInfo'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:123: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_SetIP':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:131: multiple definition of `_Unwind_SetIP'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:131: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetLanguageSpecificData':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:137: multiple definition of `_Unwind_GetLanguageSpecificData'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:137: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetRegionStart':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:143: multiple definition of `_Unwind_GetRegionStart'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:143: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_FindEnclosingFunction':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:148: multiple definition of `_Unwind_FindEnclosingFunction'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:148: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetDataRelBase':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:161: multiple definition of `_Unwind_GetDataRelBase'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:161: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_GetTextRelBase':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:166: multiple definition of `_Unwind_GetTextRelBase'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:166: first defined here

/tmp/go-link-901845510/000002.o: In function `_GCC_specific_handler':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:196: multiple definition of `_GCC_specific_handler'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:196: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_RaiseException':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:330: multiple definition of `_Unwind_RaiseException'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:330: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_Resume':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:347: multiple definition of `_Unwind_Resume'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:347: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_Resume_or_Rethrow':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:396: multiple definition of `_Unwind_Resume_or_Rethrow'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:396: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_ForcedUnwind':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:409: multiple definition of `_Unwind_ForcedUnwind'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:409: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_DeleteException':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:427: multiple definition of `_Unwind_DeleteException'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:427: first defined here

/tmp/go-link-901845510/000002.o: In function `_Unwind_Backtrace':

/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:483: multiple definition of `_Unwind_Backtrace'

/tmp/go-link-901845510/000000.o:/home/bga/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.3/libgcc/unwind-seh.c:483: first defined here

collect2: error: ld returned 1 exit status

Any ideas about what may be causing this or, alternatively, any tips on how to debug this further?

$ go version

go version go1.5.1 linux/amd64

Thanks in advance.

[Ian Lance Taylor]

On Wed, Nov 25, 2015 at 2:55 AM, Bruno Albuquerque <b...@bug-br.org.br> wrote:
> I am trying to cross-compile this code that relies on several libraries with
> dependencies on C/C++ static libraries. Compaling the project locally on
> linux works without issues but I wanted to cross-compile the same project
> from Linux to Windows amd64.
>
> To do that, i installed MXE and used it as the C/C++ cross-compiler.
> Compilation seems to work without issues but, when linking, I get errors
> about symbols being redefined:

Looks like https://golang.org/issue/9510 . It should be fixed on tip
but unfortunately there may be no good workaround in 1.5.

Ian

[Bruno Albuquerque]

I guess this is exactly my problem. Thanks.

For now I can use dynamic linking although it would be great to not have to do that to avoid having to distribute other libraries with the binary file.

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[Péter Szilágyi]

Hey Bruno,

  As you didn't provide any packages you're trying to build I can't promise anything, but you might take a look at xgo for CGO enabled cross compilation. It's a suite of docker file based cross compilers that can currently target windows/linux/darwin/android/ios (latter two with limited experimental support). The only requirement is a valid docker installation (also it will download 1GB+ cross compiler container). It also supports building with various Go releases, including latest 1.5 develop branch and the main develop branch to test out recently fixed issues.

Cheers,

  Peter

[Bruno Albuquerque]

I actually tried xgo. It didn't quite work for me because some of the C/C++ dependencies had to be compiled with more than configure/make so it would fail with xgo. A way to provide an script for compiling a specific dependency would be great.

Other than that, xgo does look great.

-Bruno

[Péter Szilágyi]

Hmm, it's something to definitely keep in mind. I had on and off ideas about dependency specific build instructions, just haven't found a clean enough and easy enough solution yet :)