I'm very unhappy that they chose to make it UB rather than mandating a behavior, but in portable C89 calling `realloc(ptr, 0)` is always a bug in your code, and

I'm very unhappy that they chose to make it UB rather than mandating a behavior, but in portable C89 calling `realloc(ptr, 0)` is always a bug in your code, and it was an insane thing to declare implementation-defined originally.