Should (p - q) be disallowed in @safe code?

[Walter Bright]

On 1/1/2026 7:18 AM, Timon Gehr wrote:
> In C, subtracting pointers to different memory objects is undefined behavior, 
> hence side-effecting.
> 
> Subtracting pointers can be `@safe` iff it is always defined behavior. (Even if 
> the defined behavior is to yield a nonsense value.)

Getting a nonsense value is memory safe, but is almost certainly a bug.


> I am not sure how GDC and LDC are currently treating this.

Since the same front end is used, I'd be surprised if they behaved differently.