Re: [Evolution-hackers] gcc 4.4 may be causing a number of bugs in Evolution

[Paul Smith <paul mad-scientist net>]

On Tue, 2010-02-02 at 14:30 -0500, Jeffrey Stedfast wrote:
> Matthew Barnes wrote:
> > On Tue, 2010-02-02 at 12:27 -0500, Paul Smith wrote:
> >   
> >> Anyway, I agree with you that if Evo makes use of this type of aliasing
> >> then we should definitely add that flag to the default makefile flags.
> >> Configure can check for it and use it if present.
> >>     
> >
> > Done.  Although, I imagine many distros have already disabled strict
> > aliasing optimization due to all the compiler warnings we used to have
> > about it.
> >
> > If GCC or even LLVM ever learns to detect cases like what Jeff ran into
> > and -warn- about them, I'd love to know about it so I can it to our
> > already lengthy list of warning flags we build with by default now.
> >   
> 
> If you want to get warnings about the aliasing stuff, it seems that
> -Wstrict-aliasing=2 is the one you want.

Yep, as Jeff points out GCC does provide warnings; in fact, -Wall
already includes -Wstrict-aliasing=3 which is the least aggressive
level.  Note this is another of those warnings (like variables used
before initialized) which only can be seen when you build with
optimization on.

You should check the GCC docs for details before choosing a particular
value.  The problem is that these warnings can be false positives,
that's why there are different levels of aggressiveness.