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From: Daniel Jacobowitz <drow@mvista.com> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, Subject: Re: optimization/8300: [3.2/3.3/3.4 regression] [sparc] ICE in gen_reg_rtx, at emit-rtl.c:662 Date: Mon, 17 Mar 2003 14:36:00 -0000 [thread overview] Message-ID: <20030317143600.16934.qmail@sources.redhat.com> (raw) The following reply was made to PR optimization/8300; it has been noted by GNATS. From: Daniel Jacobowitz <drow@mvista.com> To: Robert Schiele <rschiele@uni-mannheim.de> Cc: Richard Henderson <rth@redhat.com>, gcc-bugs@gcc.gnu.org, tneumann@pi3.informatik.uni-mannheim.de, gcc-gnats@gcc.gnu.org Subject: Re: optimization/8300: [3.2/3.3/3.4 regression] [sparc] ICE in gen_reg_rtx, at emit-rtl.c:662 Date: Mon, 17 Mar 2003 09:29:37 -0500 On Mon, Mar 17, 2003 at 10:25:04AM +0100, Robert Schiele wrote: > On Mon, Mar 17, 2003 at 01:05:55AM -0800, Richard Henderson wrote: > > On Mon, Mar 17, 2003 at 06:08:21AM +0100, Robert Schiele wrote: > > > *(&c + 1) is also well defined. > > > > How's that? > > It's pointer arithmetic: > > Assume you have the following memory layout... > > | | > +---+ > | | <== ... then the contents of that address is *(&c + 1) > +---+ > | c | > +---+ > | | > > It is: > > c: The contents of the variable c on the stack. > > &c: The address where c is located on the stack. > > &c + 1: That address plus 4 byte. (sizeof(int) == 4 on sparc) > > *(&c + 1): The contents of the above address. > > > > 1. My rewritten example is legal code with no doubt and produces an > > > ICE whit optimization. > > > > Nyet. > > Well, I still don't see why this is illegal. Can you give me the > paragraph of the C standard that prohibits this sort of pointer > arithmetic? If you have a copy of the standard, it's 6.5.6#8. Once a pointer is adjusted to point outside of the original object it must not be dereferenced. Accessing memory in this way produces undefined behavior. -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer
next reply other threads:[~2003-03-17 14:36 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2003-03-17 14:36 Daniel Jacobowitz [this message] -- strict thread matches above, loose matches on Subject: below -- 2003-04-24 4:23 rth 2003-03-18 20:29 ebotcazou 2003-03-17 17:16 Robert Schiele 2003-03-17 17:06 Falk Hueffner 2003-03-17 16:56 Joseph S. Myers 2003-03-17 16:26 Robert Schiele 2003-03-17 15:56 Robert Schiele 2003-03-17 15:36 Andreas Schwab 2003-03-17 15:26 Robert Schiele 2003-03-17 15:26 Falk Hueffner 2003-03-17 9:26 Robert Schiele 2003-03-17 9:16 Richard Henderson 2003-03-17 5:16 Robert Schiele 2003-03-16 23:27 rth 2003-03-16 23:26 rth
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