Resolve WinMain linking issues with CMake

[ccawley2011]

Follow up to PR #77. SDL2 now works, but D3D9 is still broken.

Possibly related:

• https://forum.qt.io/topic/126534/qt-6-undefined-reference-to-winmain-on-mingw
• https://bugreports.qt.io/browse/QTBUG-93671

[madebr]

You need to add a call to SDL_SetMainReady in main/WinMain.
See https://wiki.libsdl.org/SDL_SetMainReady

[madebr]

I just checked the implementation of SDL_SetMainReady.
It looks like SDL2main is needed (for some platforms).
On e.g. Windows, it does something: https://github.com/libsdl-org/SDL/blob/main/src/main/windows/SDL_windows_main.c

Other platforms also use it: https://github.com/libsdl-org/SDL/tree/main/src/main

[ccawley2011]

This only seems to be needed on platforms that define SDL_MAIN_NEEDED, while Windows defines SDL_MAIN_AVAILABLE instead. For Windows, what SDL2main provides is equivalent to what both the skeleton and MinGW already provide, so calling SDL_SetMainReady shouldn't be necessary on Windows.

[madebr]

We don't use the SDL2main library, so perhaps all logic related to SDL2main can be removed from this cmake script?

[madebr]

I created a branch on my fork that adds mingw CI with github actions: https://github.com/madebr/librw/tree/ga_mingw
Github actions result at https://github.com/madebr/librw/actions/runs/1002476846
It has the behavior described in your initial comment: glfw/SDL2 works, d3d9 does not.

I find it weird that glfw works while d3d9 does not.
Their respective librw_skeletonlibraries are both providing a WinMain symbol in a static library.
What is different between them?

[ccawley2011]

I find it weird that glfw works while d3d9 does not.
Their respective librw_skeletonlibraries are both providing a WinMain symbol in a static library.
What is different between them?

I think it's because the GLFW backend has a standard main() function that can be used with MinGW's default WinMain implementation, while the Win32 backend doesn't have one and the one in the SDL backend gets renamed when SDL_MAIN_HANDLED is not defined.

[madebr]

@ccawley2011
Please re-check my ga_mingw branch at https://github.com/madebr/librw/tree/ga_mingw
I got it working in a (so I believe) cleaner way by using linker options.
github action results at https://github.com/madebr/librw/actions/runs/1002584126

[ccawley2011]

@ccawley2011
Please re-check my ga_mingw branch at https://github.com/madebr/librw/tree/ga_mingw
I got it working in a (so I believe) cleaner way by using linker options.
github action results at https://github.com/madebr/librw/actions/runs/1002584126

This seems to work with the 64-bit mingw-w64 toolchain, but not with MinGW32 or the 32-bit mingw-w64 toolchain.

[madebr]

@ccawley2011
Please re-check my ga_mingw branch at https://github.com/madebr/librw/tree/ga_mingw
I got it working in a (so I believe) cleaner way by using linker options.
github action results at https://github.com/madebr/librw/actions/runs/1002584126

This seems to work with the 64-bit mingw-w64 toolchain, but not with MinGW32 or the 32-bit mingw-w64 toolchain.

I got it working for all configs.
See https://github.com/madebr/librw/actions/runs/1006420251 for the logs.
I also added the ability to switch between static and shared runtime (this also includes static SDL2/glfw).
Is it okay for you if I open a pr with these commits (I have to rewrite the commit history)?

[ccawley2011]

I got it working for all configs.
See https://github.com/madebr/librw/actions/runs/1006420251 for the logs.
I also added the ability to switch between static and shared runtime (this also includes static SDL2/glfw).

Thanks, I've tested the new changes and it works for me as well. I just have one additional suggested change for building with clang:

index 7c7c27c..572e4b2 100644
--- a/cmake/UseStaticRuntime.cmake
+++ b/cmake/UseStaticRuntime.cmake
@@ -6,6 +6,8 @@ endif()

 if(CMAKE_C_COMPILER_ID MATCHES "^GNU$")
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static-libgcc -static-libstdc++ -static")
+elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static")
 endif()

 if(WIN32)

Is it okay for you if I open a pr with these commits (I have to rewrite the commit history)?

Sure, go ahead.

[madebr]

+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static")

Thanks. I wasn't sure whether -static also meant static libgcc and libstdc++

Is it okay for you if I open a pr with these commits (I have to rewrite the commit history)?

Sure, go ahead.

I will post it in the coming days and tag you.