Cross compilation Linux -> Windows (mingw) fails: undefined reference to __imp_isblank

[tg--]

I'm trying to cross compile a giu application for windows.
This worked before the change to cimgui-go, but now fails:

GOOS=windows GOARCH=amd64 CGO_ENABLED=1 CC=/usr/lib/mingw64-toolchain/bin/x86_64-w64-mingw32-gcc CXX=/usr/lib/mingw64-toolchain/bin/x86_64-w64-mingw32-g++ HOST=x86_64-w64thomasg@fortress eGUI % GOOS=windows GOARCH=amd64 CGO_ENABLED=1 CC=/usr/lib/mingw64-toolchain/bin/x86_64-w64-mingw32-gcc CXX=/usr/lib/mingw64-toolchain/bin/x86_64-w64-mingw32-g++ HOST=x86_64-w64-mingw32 go build -ldflags "-s -w -H=windowsgui -extldflags=-static" -p 4 -v -o app.exe


/usr/lib/go/pkg/tool/linux_amd64/link: running /usr/lib/mingw64-toolchain/bin/x86_64-w64-mingw32-g++ failed: exit status 1
/usr/lib/mingw64-toolchain/bin/x86_64-w64-mingw32-g++ -m64 -s -mwindows -Wl,--tsaware -Wl,--nxcompat -Wl,--major-os-version=6 -Wl,--minor-os-version=1 -Wl,--major-subsystem-version=6 -Wl,--minor-subsystem-version=1 -Wl,--dynamicbase -Wl,--high-entropy-va -o $WORK/b001/exe/a.out.exe -Wl,--no-insert-timestamp /tmp/go-link-2518725268/go.o /tmp/go-link-2518725268/000000.o /tmp/go-link-2518725268/000001.o /tmp/go-link-2518725268/000002.o /tmp/go-link-2518725268/000003.o /tmp/go-link-2518725268/000004.o /tmp/go-link-2518725268/000005.o /tmp/go-link-2518725268/000006.o /tmp/go-link-2518725268/000007.o /tmp/go-link-2518725268/000008.o /tmp/go-link-2518725268/000009.o /tmp/go-link-2518725268/000010.o /tmp/go-link-2518725268/000011.o /tmp/go-link-2518725268/000012.o /tmp/go-link-2518725268/000013.o /tmp/go-link-2518725268/000014.o /tmp/go-link-2518725268/000015.o /tmp/go-link-2518725268/000016.o /tmp/go-link-2518725268/000017.o /tmp/go-link-2518725268/000018.o /tmp/go-link-2518725268/000019.o /tmp/go-link-2518725268/000020.o /tmp/go-link-2518725268/000021.o /tmp/go-link-2518725268/000022.o /tmp/go-link-2518725268/000023.o /tmp/go-link-2518725268/000024.o /tmp/go-link-2518725268/000025.o /tmp/go-link-2518725268/000026.o /tmp/go-link-2518725268/000027.o /tmp/go-link-2518725268/000028.o /tmp/go-link-2518725268/000029.o /tmp/go-link-2518725268/000030.o /tmp/go-link-2518725268/000031.o /tmp/go-link-2518725268/000032.o /tmp/go-link-2518725268/000033.o /tmp/go-link-2518725268/000034.o /tmp/go-link-2518725268/000035.o /tmp/go-link-2518725268/000036.o /tmp/go-link-2518725268/000037.o /tmp/go-link-2518725268/000038.o /tmp/go-link-2518725268/000039.o /tmp/go-link-2518725268/000040.o /tmp/go-link-2518725268/000041.o /tmp/go-link-2518725268/000042.o /tmp/go-link-2518725268/000043.o /tmp/go-link-2518725268/000044.o /tmp/go-link-2518725268/000045.o /tmp/go-link-2518725268/000046.o /tmp/go-link-2518725268/000047.o /tmp/go-link-2518725268/000048.o /tmp/go-link-2518725268/000049.o /tmp/go-link-2518725268/000050.o /tmp/go-link-2518725268/000051.o /tmp/go-link-2518725268/000052.o /tmp/go-link-2518725268/000053.o /tmp/go-link-2518725268/000054.o /tmp/go-link-2518725268/000055.o /tmp/go-link-2518725268/000056.o /tmp/go-link-2518725268/000057.o /tmp/go-link-2518725268/000058.o /tmp/go-link-2518725268/000059.o /tmp/go-link-2518725268/000060.o /tmp/go-link-2518725268/000061.o /tmp/go-link-2518725268/000062.o /tmp/go-link-2518725268/000063.o /tmp/go-link-2518725268/000064.o /tmp/go-link-2518725268/000065.o /tmp/go-link-2518725268/000066.o /tmp/go-link-2518725268/000067.o /tmp/go-link-2518725268/000068.o /tmp/go-link-2518725268/000069.o /tmp/go-link-2518725268/000070.o /tmp/go-link-2518725268/000071.o /tmp/go-link-2518725268/000072.o /tmp/go-link-2518725268/000073.o /tmp/go-link-2518725268/000074.o /tmp/go-link-2518725268/000075.o /tmp/go-link-2518725268/000076.o /tmp/go-link-2518725268/000077.o /tmp/go-link-2518725268/000078.o -O2 -g -static -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/imgui/../lib/windows/x64 -l:cimgui.a -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/backend/../lib/windows/x64 -l:cimgui.a -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/backend/glfwbackend/../../lib/windows/x64 -l:cimgui.a -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/backend/glfwbackend/../../lib/windows/x64 -l:libglfw3.a -lgdi32 -lopengl32 -limm32 -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/ImGuiColorTextEdit/../lib/windows/x64 -l:cimgui.a -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/implot/../lib/windows/x64 -l:cimgui.a -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/imguizmo/../lib/windows/x64 -l:cimgui.a -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/immarkdown/../lib/windows/x64 -l:cimgui.a -O2 -g -L/home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/imnodes/../lib/windows/x64 -l:cimgui.a -O2 -g -O2 -g -O2 -g -static -Wl,-T,/tmp/go-link-2518725268/fix_debug_gdb_scripts.ld -Wl,--start-group -lmingwex -lmingw32 -Wl,--end-group -lkernel32
/usr/lib/mingw64-toolchain/lib/gcc/x86_64-w64-mingw32/14/../../../../x86_64-w64-mingw32/bin/ld: /home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/imgui/../lib/windows/x64/cimgui.a(TextEditor.cpp.obj):TextEditor.cpp:(.text+0xf564): undefined reference to `__imp_isblank'
/usr/lib/mingw64-toolchain/lib/gcc/x86_64-w64-mingw32/14/../../../../x86_64-w64-mingw32/bin/ld: /home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/imgui/../lib/windows/x64/cimgui.a(LanguageDefinitions.cpp.obj):LanguageDefinitions.cpp:(.text+0x2df): undefined reference to `__imp_isblank'
/usr/lib/mingw64-toolchain/lib/gcc/x86_64-w64-mingw32/14/../../../../x86_64-w64-mingw32/bin/ld: /home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/imgui/../lib/windows/x64/cimgui.a(LanguageDefinitions.cpp.obj):LanguageDefinitions.cpp:(.text+0x6bf): undefined reference to `__imp_isblank'
/usr/lib/mingw64-toolchain/lib/gcc/x86_64-w64-mingw32/14/../../../../x86_64-w64-mingw32/bin/ld: /home/thomasg/go/pkg/mod/github.com/!allen!dang/cimgui-go@v1.3.1/imgui/../lib/windows/x64/cimgui.a(LanguageDefinitions.cpp.obj):LanguageDefinitions.cpp:(.text+0x8ef): undefined reference to `__imp_isblank'
collect2: error: ld returned 1 exit status

cimgui version: 1.3.1
toolchain: ming-w64 12.0.0
OS: gentoo

[tg--]

I've tried to build in a windows VM now, too, with mingw toolchain v14.2.0 and seeing the same errors, so this appears to be a general error with mingw and not restricted to cross compiling.

[tg--]

One more update: Switching the windows C runtime from msvcrt to ucrt fixes the build on windows.
Just have to figure out how to try that with the cross-compiler as well.

[gucio321]

@tg-- the problem is, that cimgui-go uses pre-compiled cimgui-go shared library to boost build time. This shared library is built with msys2 (instead of mingw) so cross-compilation (and compilation on windows itself) with mingw does not work.

[gucio321]

@tg-- btw, works on my machine 😄

what versions of gcc are you using?

CGO_ENABLED="1" CC="x86_64-w64-mingw32-gcc" CXX="x86_64-w64-mingw32-g++" GOOS="windows" GOARCH="amd64" go build -v main.go 

[~ (0) ]$ x86_64-w64-mingw32-gcc --version
x86_64-w64-mingw32-gcc (GCC) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[~ (0) ]$ x86_64-w64-mingw32-g++ --version
x86_64-w64-mingw32-g++ (GCC) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[tg--]

I rebuilt my cross-compile toolchain with ucrt support instead of msvcrt-os, which fixes the issues for me.
Cross-compiling works now.

In case someone else stumbles upon this:
mingw64-headers and mingw64-runtime have to be configured with the --with-default-msvcrt=ucrt flag.

[ioxenus]

Adding my two cents because I encountered the same problem on Windows after upgrading to cimgui-go to 1.3.1.

There are also standalone builds with a UCRT runtime available at https://winlibs.com/ (or https://github.com/brechtsanders/winlibs_mingw/releases). Didn't want to re-build mingw64 myself, so might be helpful to someone as lazy as me :D

However, my project is also using gocv/opencv, and building it with a UCRT runtime failed - apparently, it didn't like either UCRT or mingw64 gcc 14.2.0 build I had (not sure about that, not competent enough).

So looks like I'm stuck with MSVCRT, so I had to re-build the imgui library myself. Didn't want to fork cimgui-go and change dependencies in my project, so i took a glance at .github/workflows/build.yml, went to GOPATH's cimgui-go package and re-compiled it (PowerShell):

cd $env:GOPATH\pkg\mod\github.com\!allen!dang\cimgui-go@v1.3.1\lib
cmake -G Ninja -B build
cmake --build build -j 4
cp .\build\cimgui.a .\lib\windows\x64

Was really surprised that it worked out easily and fixed the building issue for me.

I wish I was competent enough to help out and modify the project to take into account the msys2/mingw64 differences :C