Re: C standard compliance?

> Junio C Hamano <gitster@pobox.com> writes:
>
>> David Kastrup <dak@gnu.org> 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.
>
> The types intptr_t and uintptr_t are optional in ISO/IEC 9899:1999
> (C99).  So it would seem that I'd be covering fewer cases rather than
> more in that manner.
>
> I should think that architectures providing uintptr_t/intptr_t would
> have very little incentive _not_ to offer pointer inequalities
> equivalent to either the uintptr_t or intptr_t type conversion.
>