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Re: [PATCH] C undefined behavior fix
- From: Paul Mackerras <paulus at samba dot org>
- To: Tom Rini <trini at kernel dot crashing dot org>
- Cc: Momchil Velikov <velco at fadata dot bg>, linux-kernel at vger dot kernel dot org,gcc at gcc dot gnu dot org, linuxppc-dev at lists dot linuxppc dot org,Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>,Benjamin Herrenschmidt <benh at kernel dot crashing dot org>,Corey Minyard <minyard at acm dot org>
- Date: Thu, 3 Jan 2002 10:11:53 +1100 (EST)
- Subject: Re: [PATCH] C undefined behavior fix
- References: <87g05py8qq.fsf@fadata.bg><20020102190910.GG1803@cpe-24-221-152-185.az.sprintbbd.net>
- Reply-to: paulus at samba dot org
Tom Rini writes:
> Okay, here's a summary of all of the options we have:
> 1) Change this particular strcpy to a memcpy
> 2) Add -ffreestanding to the CFLAGS of arch/ppc/kernel/prom.o (If this
> optimization comes back on with this flag later on, it would be a
> compiler bug, yes?)
> 3) Modify the RELOC() marco in such a way that GCC won't attempt to
> optimize anything which touches it [1]. (Franz, again by Jakub)
> 4) Introduce a function to do the calculations [2]. (Corey Minyard)
> 5) 'Properly' set things up so that we don't need the RELOC() macros
> (-mrelocatable or so?), and forget this mess altogether.
I would add:
6) change strcpy to string_copy so gcc doesn't think it knows what the
function does
7) code RELOC etc. in assembly, which would let us get rid of the
offset = reloc_offset();
at the beginning of each function which uses RELOC.
Maybe 7 is the way to go, at least it will shut the bush-lawyers up.
Paul.