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Re: Question about building hash values from pointers
- From: Kai Tietz <Kai dot Tietz at onevision dot com>
- To: Andrew Haley <aph at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Fri, 30 May 2008 11:54:40 +0200
- Subject: Re: Question about building hash values from pointers
Andrew,
Andrew Haley <aph@redhat.com> wrote on 30.05.2008 11:45:50:
> Kai Tietz wrote:
>
> > 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.?
>
> Why would it matter? Are there any circumstances is which not using the
> upper part of an address will reduce performance or break something?
>
First of all it matters about warnings. The native build of w64 gcc is
full of 'cast from pointer to integer of different size. The second, IMHO
the more important reason, is that a general type to express a host
pointer scalar size would prevent such bugs as in PR/36386.
Cheers,
Kai
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