What is dwmain?

[1e9t8m29]

I'm having trouble to understand what is dwmain. I run gcc -E with the following snippet and it prints nothing. It seems it can't interpret them.

Code:

if defined(__WIN32__)
#define dwmain(a, b) \
_dwmain(a, b); \
char ** API _dw_convertargs(int *count, char *start, HINSTANCE hInstance); \
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {\
   int argc; \
   char **argv = _dw_convertargs(&argc, lpCmdLine, hInstance); \
   return _dwmain(argc, argv); } \
int _dwmain(a, b)