Re: [bug] gcc-4.[23] miscompiling causing networking to bugger up

[Kyle McMartin <kyle@mcmartin.ca>]

On Wed, May 28, 2008 at 06:55:29PM -0400, Carlos O'Donell wrote:
> On Wed, May 28, 2008 at 4:00 PM, Kyle McMartin <kyle@mcmartin.ca> wrote:
> > On Wed, May 28, 2008 at 03:09:46PM -0400, Kyle McMartin wrote:
> >> So I've narrowed the regression down to a miscompilation (presumably) of
> >> net/ipv4/ip_output.o, in the sense that
> >>
> >>       cp linux-2.6-gcc34/net/ipv4/ip_output.o
> >>               linux-2.6-gcc43/net/ipv4/ip_output.o
> >>       touch linux-2.6-gcc43/net/ipv4/ip_output.o
> >>       make vmlinux
> >>
> >> fixes the issue.
> >>
> >
> > Apparently I was on glue and gcc-4.2 is not problematic.
> 
> If you compile ip_output.c with -O0 does it work with gcc-4.3?
> 

Building the kernel without optimization is very tetchy... if you can
guess what passes to remove, I can try... one of the optimization
effects that must go is DCE though, otherwise we'll have undefined
references to things (ie: kmalloc_too_much in a switch that should have
been eliminated except the constant case.)

r, Kyle