Re: redboot fconfig crash with gcc 4.3.2

[Jose Vasconcellos <jvasco at verizon dot net>]

Gary Thomas wrote:
> Jose Vasconcellos wrote:
> > Redboot gets an exception when trying to set any IP address with fconfig
> > when using gcc-4.3.2 on an ixp425 target (armeb). The issue seems to be
> > an alignment problem as val_ptr contains an odd address; it looks 
> > like gcc
> > is optimizing and trying to do a copy on a word boundary. The removal of
> > the cast fixes the problem.
> >
> >
> > --- fconfig.c    2009-01-18 14:34:11.000000000 -0500
> > +++ fconfig.c.new    2009-01-18 14:35:22.000000000 -0500
> > @@ -388,7 +388,7 @@
> >        break;
> > #ifdef CYGPKG_REDBOOT_NETWORKING
> >    case CONFIG_IP:
> > -        memcpy(&hold_ip_val.s_addr, &((in_addr_t *)val_ptr)->s_addr, 
> > sizeof(in_addr_t));
> > +        memcpy(&hold_ip_val.s_addr, val_ptr, sizeof(in_addr_t));
> >        if (!_gethostbyname(line, &new_ip_val)) {
> >            return CONFIG_BAD;
> >        }
>
> Sounds like a *BUG* in the compiler.  Have you reported it?
>
> This does more than remove the cast :-)  What if the s_addr field is not
> at the start of the structure?  I know it hasn't moved in 25+ years, but
> I don't like tossing correctness [even if only pedantic] away.
>
> Maybe there's another way to solve this.  Does it happen on arm[el]?
This doesn't look like a compiler bug to me. I suspect that this problem
affects other arm variants but I only have access to an ixp425. The code
is incorrect as val_ptr is pointing to a place in a configuration buffer for
the raw data. Imposing (via a cast) the structure is not the right solution.
Note that a few lines down in the source, the copy in the other direction
does not have such a cast.

Jose