[Bug rtl-optimization/98692] Unitialized Values reported only with -Os

[mark at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98692

--- Comment #10 from Mark Wielaard <mark at gcc dot gnu.org> ---
(In reply to Will Schmidt from comment #9)
> (In reply to Segher Boessenkool from comment #5)
> > Have you tried a new valgrind?
> > 
> > Either this is (or was) a known problem in valgrind, or it is related to
> > one.  Cc:ing Aaron, he might know more (he wrote the GCC optimisations
> > that expose the problem).
> 
> 
> I've recreated against new (built out of upstream git) valgrind:
> with --track-origins=yes
> 
> 
> ==37507== 
> argv[0]=./a.out
> ==37507== Use of uninitialised value of size 8
> ==37507==    at 0x10000618: main (pr9862.C:16)
> ==37507==  Uninitialised value was created by a stack allocation
> ==37507==    at 0x100007D4: isVariable(char*) (pr9862.C:5)

Trying to get hold of a ppc64 setup. But could you try with --vgdb-error=0 and
then (in another window) gdb ./a.out and target remote | vgdb and continue till
you get the TRAP. Then disassamble so we can see the exact instruction that
generates the use of uninitialised value?