Re: Question about building hash values from pointers

["Richard Guenther" <richard dot guenther at gmail dot com>]

On Mon, Jun 2, 2008 at 5:59 AM, Ian Lance Taylor <iant@google.com> wrote:
> Andrew Haley <aph@redhat.com> writes:
>
>> Ian Lance Taylor wrote:
>>> Andrew Haley <aph@redhat.com> writes:
>>>
>>>> Richard Guenther wrote:
>>>>> On Fri, May 30, 2008 at 10:57 AM, Kai Tietz <Kai.Tietz@onevision.com> wrote:
>>>>>> Hi,
>>>>>>
>>>>>> as I noticed, most hash value calculations are trying to use pointer
>>>>>> values for building the value and assume that a long/unsigned long scalar
>>>>>> is wide enough for a pointer. This is at least for w64 target not true. So
>>>>>> I want to know, if it would be good to introduce an gcc specific type for
>>>>>> those kind of casts, or to use ssize_t/size_t.?
>>>>> it's uintptr_t which should be used, if only as an intermediate cast -
>>>>> (unsigned long)(uintptr_t)ptr.
>>>> That's not possible because, IIRC, gcc must compile on C90 systems.
>>>
>>> We can just test for it with autoconf and typedef it if we don't have
>>> it.  We can figure out what to typedef it to by comparing the sizeof
>>> void* to the sizeof the integer types--we already gather these sizes
>>> in the configure script anyhow, and use them in hwint.h.
>>
>> Given that all this seems to be about is avoiding warning messages on
>> some extremely unlikely architectures on which gcc may not run, I have
>> to question the sens of such heavyweight measures.  Why not simply use
>> size_t?  It would be adequate on every architecture anyone here knows
>> about.
>
> I don't personally find these measures to be heavyweight.  I find them
> to be fairly routine for the kind of portability we aim for.  Only one
> person has to get them right once.
>
> But I'm fine with using size_t also, if it does the right thing on
> W64.

If size_t is fine then long is also fine if W64 is compatible with C90
(guess what - it is not).  So I'd rather go the full lenghth of using
C99 uintptr_t which is what even W64 would be compatible with (C99, that is).

Richard.