Question

I was reading opengl es book and in the source code i found this Macro

///
//  Macros
//
#define ESUTIL_API
#define ESCALLBACK

later in the implementation file .c

void ESUTIL_API esInitContext ( ESContext *esContext )
{
   if ( esContext != NULL )
   {
     memset( esContext, 0, sizeof( ESContext) );
   }
}

from what I understand macros, they just replace what is defined by the macro.. although i don’t understand what it is the point in this case.

Thanks.

Answer 1

This kind of macro is used to change the calling convention that is used by the compiler:

#define ESUTIL_API  // nothing, use the standard calling convention

or

#define ESUTIL_API __fastcall // use the fastcall calling convention

The call type calling convention has usually to be put in a function definition between the return type and the function identifier name.