Re: -pipe passed to gcc via Automake

[Ralf Corsepius]

On Sun, 2007-10-21 at 16:24 -0500, Bob Friesenhahn wrote:
> On Sun, 21 Oct 2007, Benoit SIGOURE wrote:
> 
> > On Oct 21, 2007, at 7:13 PM, NightStrike wrote:
> >
> >> If I wanted -pipe passed in to gcc all the time, do I put that in
> >> AM_CPPFLAGS or AM_CFLAGS?
> >
> > I usually do this in my configure.ac:
> >
> > AC_PROG_CXX
> > # Speed GCC compilation up.
> > if test "$GXX" = yes; then
> >  CXXFLAGS="$CXXFLAGS -pipe"
> > fi
> 
> Sounds great, but I have yet to see -pipe actually speed up 
> compilation. 
I performed some measurements several years ago - It really does speed
up compilation.

But ... IMO, such tricks should be left to the user and do not belong
into configure.ac

Also, you really want to append it to CC and not to CPPFLAGS, because
--pipe is not a cpp option.

> Sometimes pipes may not be supported.  In that case hopefully GCC 
> simply ignores the request rather than refusing to run.
... very old GCCs (<< 3.x) don't support it.

Ralf