Is D's pointer subtraction more permissive than C (and C++)?

[Elronnd]

On Friday, 1 April 2022 at 17:39:24 UTC, Steven Schveighoffer 
wrote:
> In practice, I don't see how it affects the behavior *of the 
> compiler*. When you subtract two pointers, I don't see how the 
> compiler/optimizer can make some other decision based on the 
> subtraction not being between two pointers to the same block of 
> memory.

Unfortunately, they can and do.  For instance, consider this 
snippet of c code:

#include <stddef.h>
#include <stdlib.h>
int f() {
	int *x = malloc(1), *y = malloc(1);
	ptrdiff_t d = y - x;
	return y == x + d;
}

GCC compiles this to the same code as:

int f() { return 1; }

This is intertwined with issues of provenance.