Re: [PATCH] configure: Fix default -O2 being added when CFLAGS not set

[Glenn Washburn]

Hi Paul,

On Fri, 25 Mar 2022 07:53:29 +0100
Paul Menzel <pmenzel@molgen.mpg.de> wrote:

> Dear Glenn,
> 
> 
> Thank you for your tireless awesome work on GRUB.

Sincerely, thank you. It seems to me that you're also deserving of this
compliment and probably more so. 

> Am 24.03.22 um 23:31 schrieb Glenn Washburn:
> > Autoconf will set a default CFLAGS of "-g -O2" if CFLAGS is not set. CFLAGS
> > was defaulted to "" early in configure to prevent this. Apparently something
> > changed in autoconf and now AC_USE_SYSTEM_EXTENSIONS, which is before the
> > default setting of CFLAGS, will pull in this check. Move the default
> > setting of CFLAGS to before this so that if will see CFLAGS as set and not
> > give it a default.
> 
> Could you please mention the Autoconf version you use? I guess, it’d be 
> great to know, when this behavior started, so to make sure, that the 
> last X years all the tests were done like this, and reverting the 
> behavior would actually break things (though shouldn’t).

I'm generally testing on Debian 11 and have an autoconf version
of 2.69. However, I was wrong in the commit message as Robbie pointed
out. The issue wasn't from a change in autoconf, but in a very recent
change in GRUB's usage of autoconf. So this shouldn't have affected any
previous testing.

> With Debian sid/unstable and GNU Autoconf 2.71 I can reproduce your 
> behavior:
> 
>      $ grep '^CFLAGS=' config.log
>      CFLAGS='-g -O2'
> 
> > Signed-off-by: Glenn Washburn <development@efficientek.com>
> > ---
> >   configure.ac | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/configure.ac b/configure.ac
> > index 3ffbc7c57b..c1e50c9d75 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -36,12 +36,12 @@ dnl description of the relationships between them.
> >   
> >   AC_INIT([GRUB],[2.11],[bug-grub@gnu.org])
> >   
> > -AC_USE_SYSTEM_EXTENSIONS
> > -AC_CONFIG_AUX_DIR([build-aux])
> > -
> >   # We don't want -g -O2 by default in CFLAGS
> >   : ${CFLAGS=""}
> >   
> > +AC_USE_SYSTEM_EXTENSIONS
> > +AC_CONFIG_AUX_DIR([build-aux])
> > +
> >   # Checks for build, host and target systems.
> >   AC_CANONICAL_BUILD
> >   AC_CANONICAL_HOST
> 
> Tested-by: Paul Menzel <pmenzel@molgen.mpg.de>

Thank you for testing this.

Glenn

> 
>      $ git am … && ./autogen.sh && ./configure --with-platform=coreboot
>      $ grep '^CFLAGS=' config.log
>      CFLAGS=''
> 
> 
> Kind regards,
> 
> Paul