void_cast.h

// In C, a void* can be implicitly cast to any other kind of pointer, while in C++ you need an explicit cast. In most
// cases, the explicit cast works for both C and C++, but if we consider the case where we have nested structs, then
// the way you refer to them differs between C and C++ (in C++, `parent_type::nested_type`, in C just `nested_type`).
// In addition, with the automatic cast in C, it is possible to use unnamed nested structs and still dynamically 
// allocate arrays of that type - this would be desirable when the code is compiled from C++ as well.
// This VOID_CAST macro allows for automatic cast from void* in C++. In C, it does nothing, but for C++ it uses a 
// simple template function to define a cast-to-anything operator.
// Use like this:
//      struct {
//          struct {
//              int x;
//          } *nested;
//      } parent;
//      parent.nested = VOID_CAST( malloc( sizeof( *parent.nested ) * count ) );

#ifdef __cplusplus
    struct void_cast {
        inline void_cast( void* x_ ) : x( x_ ) { }
        inline void_cast( void const* x_ ) : x( (void*) x_ ) { }
        template< typename T > inline operator T() { return (T)x; } // cast to whatever requested
        void* x;
    };
    #define VOID_CAST( x ) void_cast( x )
#else
    #define VOID_CAST( x ) x
#endif