In order to do that, the standard would have to define that dereferencing a null pointer must produce a deterministic behavior. There are only two possible behaviors:

1. The program successfully reads/writes that memory location and retrieves/overwrites whatever is there without crashing. Then the program can continue on and execute the if even if the pointer was null.

2. The program crashes immediate whenever a null pointer is read/written.

#1 is problematic, because NULL is a single pointer value that can be applied to a variety of pointer types. What happens if you first write to (long )NULL and then read from (FILE )NULL?

#2 is very useful, and most platforms already crash any program that tries to read or write NULL. But if the standard requires this behavior, then this introduces an even stronger guarantee that a dereferenced pointer is not null, so there's no reason to remove that optimization.