Building OpenGL emits tons of warnings on Win7 x86-64 GHC 7.6.1

[ghost]

The build is still successful. The issue is that the FFI bindings use the stdcall convention, but this convention doesn't exist on x85-64 windows. The solution is to export the bindings with the ccall convention for 64-bit windows platforms.

Alternatively, these warnings could be suppressed because there is exactly one calling convention on this platform anyway.

I'm not sure which solution is better.

[svenpanne]

OpenGLRaw.cabal contains the lines:

if os(windows) && flag(UseNativeWindowsLibraries)
   cpp-options: "-DCALLCONV=stdcall"
   cc-options: "-DUSE_WGLGETPROCADDRESS"
   extra-libraries: opengl32

Fixing this would be trivial if we could somehow detect that we are on a 64bit Windows platform. Can we do this somehow? Cabal experts to the rescue!

GLURaw.cabal and GLUT.cabal contain similar lines, BTW, and should be fixed similarly.

[shelarcy]

Cabal could detect architechture by using arch condition.

• http://www.haskell.org/cabal/users-guide/developing-packages.html#conditions
• http://www.haskell.org/ghc/docs/7.6.3/html/libraries/base-4.6.0.1/System-Info.html

And 32 bit Windows' arch is i386.

I think we should just add three lines for fixing this problem:

if os(windows) && flag(UseNativeWindowsLibraries)
  if arch(i386)
    cpp-options: "-DCALLCONV=stdcall"
  else
    cpp-options: "-DCALLCONV=ccall"
  cc-options: "-DUSE_WGLGETPROCADDRESS"
  extra-libraries: opengl32

[svenpanne]

Those lines seem to make sense, I think I'll try them when I am back at a Windows box.

One question regarding 32bit/64bit Windows executables: 32bit executables exclusively call 32bit DLLs, and 64bit executables exclusively call 64bit DLLs, correct? Or put another way: It never happens that e.g. and executable calls a 64bit OpenGL DLL and uses a 32bit GLUT DLL at the same time, correct? I really hope that this is the case, otherwise I don't know how we should handle the calling convention correctly.

[svenpanne]

I've fixed this as suggested above for the OpenGLRaw, GLURaw and GLUT packages. Hmmm, probably I should do something similar for my OpenAL/ALUT package, too...