Pick up WinMain with proper CC

[LemonBoy]

Closes #3712

[daurnimator]

Could we add a regression test?

[LemonBoy]

Could we add a regression test?

That's an exercise left to the reader :) You need some os-detection tricks to have a portable test case.

[andrewrk]

Async calling convention should be a compile error here, with a new test case in test/compile_errors.zig

add_fn_export implementation is wrong; it should be looking for stdcallcc rather than ccc to decide whether to check for these special Windows functions. The parameter should be changed from bool ccc to CallingConvention cc, and the function should look for CallingConventionStdcall.

This is all assuming that WinMain & friends are supposed to be stdcallcc and not ccc, which appears to be the case.

[JesseRMeyer]

This is all assuming that WinMain & friends are supposed to be stdcallcc and not ccc, which appears to be the case.

MSDN is inconsistent on this, but WINAPI is typedef'd to __stdcall on VS2019's version of Windows.h, which qualifies WinMain (and friends).

https://docs.microsoft.com/en-us/cpp/cpp/stdcall?redirectedfrom=MSDN&view=vs-2019

'The __stdcall calling convention is used to call Win32 API functions. The callee cleans the stack, so the compiler makes vararg functions __cdecl. Functions that use this calling convention require a function prototype.'

[andrewrk]

Thanks for the follow-up