Messages in this thread | | | Date | Thu, 3 Jan 2002 15:08:43 +1100 | From | Cameron Simpson <> | Subject | Re: C undefined behavior fix |
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On Wed, Jan 02, 2002 at 12:09:10PM -0700, Tom Rini <trini@kernel.crashing.org> wrote: | On Wed, Jan 02, 2002 at 01:03:25AM +0200, Momchil Velikov wrote: | > The GCC tries to replace the strcpy from a constant string source with | > a memcpy, since the length is know at compile time. | | 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.
Dudes, maybe I'm missing something here, but why don't you just mark the source data as volatile? Then it _can't_ assume it knows the length of the strcpy because it can't assume it knows the content:
If PTRRELOC cast the pointer type to
volatile void *
or something else suitable generic but volatile then this discussion might not be happening. It would at least move the optimisation into "definite compiler bug" if it still happens. -- Cameron Simpson, DoD#743 cs@zip.com.au http://www.zip.com.au/~cs/
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