Re: [PATCH 1/5] Makeconf: add -fno-strict-aliasing to CFLAGS

[Samuel Thibault]

Thomas Schwinge, le Fri 25 Oct 2013 15:09:48 +0200, a écrit :
> On Fri, 25 Oct 2013 10:30:20 +0200, Justus Winter 
> <4winter@informatik.uni-hamburg.de> wrote:
> > If gcc is used with optimizations -O2, -O3, or -Os, it will enable
> > optimizations that assume that pointers of different type do not
> > alias, i.e. point to the same address. However, we use this a lot,
> > e.g. in code using libports.

Which code, more precisely?

> > Add -fno-strict-aliasing to CFLAGS to disable optimizations based on
> > the strict aliasing rule.
> > 
> > * Makeconf: Add -fno-strict-aliasing to CFLAGS.
> 
> <http://www.gnu.org/software/hurd/open_issues/strict_aliasing.html>.  So,
> generally OK, but please, at the same time, revert my commit
> c856c99d06a20a4a69eba4c044144384d87f3142 (pfinet only,
> <https://savannah.gnu.org/bugs/?17124>)

Mmm, I disagree: they would have -fno-strict-aliasing for different
reasons: pfinet because it's Linux code which has always been built so,
hurd because in some places it may abuse strict aliasing, but I believe
these are rare, and fixable.

Samuel