Re: C standard compliance?

David Kastrup [off-list ref] writes:

Hi, I am wondering if I may compare pointers with < that have been
created using different calls of malloc.

The C standard does not allow this (inequalities are only allowed for
pointers into the same structure) to allow for some cheapskate sort of
comparison in segmented architectures.

Hmm... if you were to implement a set of pointers in such a way that
you can cheaply tell if an unknown pointer belongs to that set, you
would use a hashtable, keyed with something that is derived from the
value of the pointer casted to uintptr_t, I would think.  Is such a
use of ((uintptr_t)ptr) unallowed?  If it is allowed, comparing two
unrelated pointers after casting them to uintptr_t would equally be
valid, I would have to think.