Allocates an empty, unpopulated SDL_RWops structure.
Returns a pointer to the allocated memory on success, or NULL on error.
You must free any memory allocated with SDL_AllocRW with SDL_FreeRW. Depending on your operating system and compiler, there may be a difference between the malloc() and free() your program uses and the versions SDL calls internally. Trying to mix the two can cause crashing such as segmentation faults.
SDL_AllocRW allocates an empty, unpopulated SDL_RWops structure. You must fill out the fields yourself.