Re: [PATCH] C undefined behavior fix

Paul Mackerras
2002-01-02T23:17:56Z

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.