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Re: optimization/7799: [3.2/3.3 regression] Loop bug with optimization flag -Os in gcc
- From: Joern Rennecke <amylaar at onetel dot net dot uk>
- To: segher at koffie dot nl (Segher Boessenkool)
- Cc: ehrhardt at mathematik dot uni-ulm dot de (Christian Ehrhardt), nejataydin at superonline dot com, gcc-gnats at gcc dot gnu dot org, gcc at gcc dot gnu dot org, gcc-bugs at gcc dot gnu dot org
- Date: Fri, 20 Dec 2002 06:17:18 +0000 (GMT)
- Subject: Re: optimization/7799: [3.2/3.3 regression] Loop bug with optimization flag -Os in gcc
> 6.2.5.19:
> ... An array type describes a contiguously allocated nonempty set of
> objects with a particular member object type, called the element
> type. ...
>
> So an array can not wrap around address 0.
It can't wrap around there, but if pointers are signed, it might straddle 0
nonetheless. This requires, of course, for an aligned start address
that the address 0 is not the same as NULL, which AFAICR is something gcc
doesn't currently support.
OTOH, if the start address is not aligned to a multiple of the types size,
you can have the array straddle address 0 without it ever being a valid
address. Well, that is if character pointers have a different
representation ;-)