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

Sun Apr 3 12:22:22 UTC 2022

On Saturday, 2 April 2022 at 18:54:58 UTC, Walter Bright wrote:
> You're right that the spec should add some commentary saying 
> that pointer arithmetic should be confined to being within the 
> same memory object.

What's the definition of memory object here? Does the C Standard 
treat malloc/calloc and co as special functions and memory 
objects are what is returned by them?