Yeah, I'm not sure. Technically, the only valid input should be a SDL_rwops structure allocated by malloc BUT common-usage will be that people allocate that structure by using a function to make it for them. We are implementing two of those functions (`SDL_RWFromConstMem` and `SDL_RWFromFile`).

I will say though that previously that  IMG_Load_RW only worked if it was called with the result of `SDL_RWFromFile`. No one would ever have passed a char * with a filename into IMG_Load_RW. This change continues to support that case.