[U-Boot] [PATCH 2/3] md5: Fix gcc-4.7 build problem in md5

[Pavel Machek]

On Tue 2012-11-06 01:56:50, Marek Vasut wrote:
> Dear Pavel Machek,
> 
> > Hi!
> > 
> >     In message <20121105200340.GA15821 at xo-6d-61-c0.localdomain> you wrote:
> > >    > > > >         /* Append length in bits and transform */
> > >    > > > > 
> > >    > > > > -       ctx->in32[14] = ctx->bits[0];
> > >    > > > > -       ctx->in32[15] = ctx->bits[1];
> > >    > > > > +       memcpy(ctx->in + 14 * sizeof(__u32), ctx->bits, 2 *
> > >    
> > >    sizeof(__u32));
> > Is there some alternate solution? The memcpy is really ugly...
> > 
> > Plus... does it solve the issue? The code does not look like being
> > compatible with strict pointer aliasing... and I don't think memcpy()
> > helps.
> > 
> > arch/nds32/config.mk:PLATFORM_RELFLAGS  += -fno-strict-aliasing
> > -fno-common -mrelax
> > arch/x86/config.mk:PLATFORM_CPPFLAGS += -fno-strict-aliasing
> > 
> > We should really do that globally.
> 
> Were you even able to replicate this problem in the first place? Isn't this 
> whole "problem" a problem of a broken (ubuntu/linaro) toolchain again?

This is not something you can replicate. At least md5 code is unsafe
with strict aliasing, probably most of u-boot, because low-level
people write code like that. Thus we should do
-fno-strict-aliasing. Otherwise compiler may decide in future to
"miscompile" our code, even if it compiles it correctly now.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html