[PATCH util-macros 1/2] Don't disable strict aliasing (-fno-strict-aliasing) globally

[Gaetan Nadon]

On Mon, 2010-11-01 at 13:40 -0700, Jeremy Huddleston wrote:

> I don't think that's the correct model.  -fstrict-aliasing is on by
> default (for many users), and -fno-strict-aliasing should be what is
> opted into in order to disable optimizations that rely on correctly
> written C code.
> 
> >> XORG_CWARNFLAGS would be updated to call these two and set
> CWARNFLAGS="$(CFLAGS_WARNINGS) $(CFLAGS_NO_STRICT_ALIASING)"
> > 
> > Nope. Our good old CWARNFLAGS would remain untouched for eternity
> and
> > will eventually fall off the radar screen.
> 
> Well, I think that in the spirit of abstraction and code-reuse, it
> would be best to have it call the two new macros... but I guess that
> is contingent on our dispute over opting-in to -fno-strict-aliasing
> versus -fstrict-aliasing.
> 
> ...
> 
> >> For modules that did have it historically, we'll leave them alone
> initially.  
> >> As we audit them, we'll change CWARNFLAGS to either CFLAGS_WARNINGS
> or CFLAGS_WARNINGS CFLAGS_NO_STRICT_ALIASI.  
> >> This will help us keep track of what has been audited to determine
> what really needs 
> >> the flag versus what might've inherited it by accident.
> > 
> > Those modules would use both the new CFLAGS_WARNINGS and the new
> > CFLAGS_STRICT_ALIASING, under an opt-in principle
> 
> I'm confused now.  If they actually *NEED* -fno-strict-aliasing, how
> are you proposing adding -fno-strict-aliasing?  This is why I was
> suggesting a CFLAGS_NO_STRICT_ALIASING
> 

Sorry, I got confused. I forgot -O brings strict aliasing by default. We
need one new variable for "real warnings" and one variable for
-fno-strict-aliasing. Modules would typically use the new "real
warnings" variable and some would pick the new "-fno-strict-aliasing"
variable (the server and drivers for example). The CWARNFLAGS is
untouched for backward compatibility. I hope I got it right :-)

For the server, it would be $(CFLAGS_WARNINGS) +
$(CFLAGS_NO_STRICT_ALIASING)
For libXxf86vm, it would be $(CFLAGS_WARNINGS)












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