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Re: Bug in loop optimize (invalid postinc to preinc transformation)
- To: aoliva at redhat dot com, egcs at tantalophile dot demon dot co dot uk
- Subject: Re: Bug in loop optimize (invalid postinc to preinc transformation)
- From: dewar at gnat dot com (Robert Dewar)
- Date: Thu, 28 Dec 2000 01:39:58 -0500 (EST)
- Cc: denisc at overta dot ru, dkorn at pixelpower dot com, gcc at gcc dot gnu dot org,peter dot osterlund at mailbox dot swipnet dot se
<<Overflow of unsigned integers has defined behaviour -- they wrap. The
question is, what rule applies to pointer comparisons?
>>
This is a malformed question. Any pointer increment is constrained
to require that the resulting pointer be valid. Wrapping is simply
not an issue.
If p points to a valid address in an allocated array, then P+1 is also
valid, and there is no question of wrap. But P+2 may be beyond the
array and therefore ill-defined, and this has nothing to do with wrapping.