Adding -municode doesn't fix undefined references to `WinMain'

[aminya]

I have written a macro in project_options to try to fix the WinMain issue in MinGW. But adding -municode as a compile option doesn't fix the issue. Adding it as a link option causes linking to the fail with undefined reference to wWinMain. Other compilers don't need such flags, and I am not sure why we should do this for MinGW.

macro(mingw_unicode)
  is_mingw(_is_mingw)
  if(${_is_mingw})
    include(CheckCXXCompilerFlag)
    check_cxx_compiler_flag("-municode" _cxx_supports_municode)
    if(${_cxx_supports_municode})
      message(STATUS "Enabling Unicode for MinGW in the current project to fix undefined references to WinMain")
      add_compile_definitions("UNICODE" "_UNICODE")
      add_compile_options("-municode")
    endif()
  endif()
endmacro()

Blocks aminya/project_options#129

https://github.com/aminya/cpp_vcpkg_project/runs/6542106054?check_suite_focus=true#step:6:203

[6/18] Linking CXX executable my_exe\test\Debug\my_exe_helpers_tests.exe
FAILED: my_exe/test/Debug/my_exe_helpers_tests.exe 
cmd.exe /C "cd . && C:\Users\runneradmin\gcc\mingw64\bin\g++.exe -g  my_exe/test/CMakeFiles/my_exe_helpers_tests.dir/Debug/tests.cpp.obj -o my_exe\test\Debug\my_exe_helpers_tests.exe -Wl,--out-implib,my_exe\test\Debug\libmy_exe_helpers_tests.dll.a -Wl,--major-image-version,0,--minor-image-version,0  vcpkg_installed/x64-mingw-static/debug/lib/libfmtd.a  --coverage  -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 && cd ."
c:/users/runneradmin/gcc/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/11.3.0/../../../../x86_64-w64-mingw32/bin/ld.exe: c:/users/runneradmin/gcc/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/11.3.0/../../../../x86_64-w64-mingw32/lib/../lib/libmingw32.a(lib64_libmingw32_a-crt0_c.o):crt0_c.c:(.text+0x46): undefined reference to `WinMain'
collect2.exe: error: ld returned 1 exit status
[7/18] Linking CXX executable my_lib\test\Debug\my_lib_tests.exe
FAILED: my_lib/test/Debug/my_lib_tests.exe my_lib/test/my_lib_tests_tests-84286ba.cmake D:/a/cpp_vcpkg_project/cpp_vcpkg_project/build/my_lib/test/my_lib_tests_tests-84286ba.cmake 
cmd.exe /C "cd . && C:\Users\runneradmin\gcc\mingw64\bin\g++.exe -g  my_lib/test/CMakeFiles/my_lib_tests.dir/Debug/tests.cpp.obj -o my_lib\test\Debug\my_lib_tests.exe -Wl,--out-implib,my_lib\test\Debug\libmy_lib_tests.dll.a -Wl,--major-image-version,0,--minor-image-version,0  my_lib/Debug/libmy_lib.a  --coverage  vcpkg_installed/x64-mingw-static/debug/lib/libfmtd.a  -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 && cmd.exe /C "cd /D D:\a\cpp_vcpkg_project\cpp_vcpkg_project\build\my_lib\test && C:\Users\runneradmin\cmake\cmake-3.23.1-windows-x86_64\bin\cmake.exe -D TEST_TARGET=my_lib_tests -D TEST_EXECUTABLE=D:/a/cpp_vcpkg_project/cpp_vcpkg_project/build/my_lib/test/Debug/my_lib_tests.exe -D TEST_EXECUTOR= -D TEST_WORKING_DIR=D:/a/cpp_vcpkg_project/cpp_vcpkg_project/build/my_lib/test -D TEST_SPEC= -D TEST_EXTRA_ARGS= -D TEST_PROPERTIES= -D TEST_PREFIX= -D TEST_SUFFIX= -D TEST_LIST=my_lib_tests_TESTS -D TEST_REPORTER=xml -D TEST_OUTPUT_DIR= -D TEST_OUTPUT_PREFIX= -D TEST_OUTPUT_SUFFIX= -D CTEST_FILE=D:/a/cpp_vcpkg_project/cpp_vcpkg_project/build/my_lib/test/my_lib_tests_tests-84286ba.cmake -P D:/a/cpp_vcpkg_project/cpp_vcpkg_project/build/vcpkg_installed/x64-mingw-static/share/catch2/CatchAddTests.cmake""
c:/users/runneradmin/gcc/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/11.3.0/../../../../x86_64-w64-mingw32/bin/ld.exe: c:/users/runneradmin/gcc/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/11.3.0/../../../../x86_64-w64-mingw32/lib/../lib/libmingw32.a(lib64_libmingw32_a-crt0_c.o):crt0_c.c:(.text+0x46): undefined reference to `WinMain'
collect2.exe: error: ld returned 1 exit status
[8/18] Building CXX object my_header_lib/test/constexpr/CMakeFiles/my_header_lib_relaxed_constexpr_tests.dir/Debug/constexpr_tests.cpp.obj
Checking D:\a\cpp_vcpkg_project\cpp_vcpkg_project\my_header_lib\test\constexpr\constexpr_tests.cpp ...
Checking D:\a\cpp_vcpkg_project\cpp_vcpkg_project\my_header_lib\test\constexpr\constexpr_tests.cpp: CATCH_CONFIG_MAIN=1;CATCH_CONFIG_RUNTIME_STATIC_REQUIRE=1;FMT_LOCALE=1;UNICODE=1;_UNICODE=1;CMAKE_INTDIR="Debug"...
ninja: build stopped: subcommand failed.
task: Failed to run task "coverage": task: Failed to run task "build_template": exit status 1

[brechtsanders]

I'm not sure why you log this as a specific winlibs issue, it seems you have general MinGW-w64 issues with our project. These kind of questions are better asked on forums like https://stackoverflow.com/

A quick Internet search for your issue leads me to https://techstalking.com/solved-wwinmain-unicode-and-mingw/
Have you tried the suggestions there?

Also, why to you use WinMain()? Is that intentional, or did you mean to use main(). In the latter case you should use -mconsole (instead of -mwindows) when linking, so you get a console application.

[aminya]

Where is the repository that hosts the MinGW source code? This is not a StackOverflow question, it is a bug that is only present in MinGW.

Also, why to you use WinMain()? Is that intentional, or did you mean to use main(). In the latter case you should use -mconsole (instead of -mwindows) when linking, so you get a console application.

I don't know either. MinGW for some reason uses WinMain instead of the standard main function. This doesn't happen on other compilers. I can't detect the intention of the user in project_options, and so I can't work around this MinGW bug by adding -mconsole

[brechtsanders]

http://mingw-w64.sourceforge.net/

MinGW-w64 gcc uses main() for console applications, which is the default unless you specify you want a GUI application (-mwindows). So you probably have a flag like this somewhere...

[aminya]

Thanks. I'll open an issue there. In the above log I have included all the flags passed to g++

[aminya]

Reported here:
https://sourceforge.net/p/mingw-w64/bugs/942/

[brechtsanders]

I don't really understand why you try to fix the undefined reference to WinMain by doing a Unicode build.

Can you try to search the entire folder recursively after running cmake for mwindows and if you find it replace it with mconsole ?

Otherwise a dirty workaround could be to actually define WinMain like this:

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
  return main(_argc, _argv);
}

[aminya]

It seems like an issue with Catch2 + MinGW. The main function defined by Catch2 isn't working with MinGW
catchorg/Catch2#2437

[aminya]

This is a Catch2 issue. Found the reason:
catchorg/Catch2#2441