Re: Question about building hash values from pointers

[Ian Lance Taylor <iant at google dot com>]

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.

Ian