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

[Paul Menzel]

Dear Glenn,


Thank you for your tireless awesome work on GRUB.

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).

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>

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


Kind regards,

Paul