[libvirt] [PATCH WIP] build: add a warning when configure is executed with -Werror

[Eric Blake]

On 09/19/2012 04:28 PM, Marcelo Cerri wrote:
> Some tests performed by configure to check what is supported can be
> broken if -Werror is defined in CFLAGS variable when configure is
> executed.
> 
> This patch checks if CFLAGS contains -Werror and shows a warning for
> user recommending to use --enable-compile-warnings=error instead.
> ---
> 
> Please, note that this is a work in progress patch and suggestions are
> welcome.
> 
>  configure.ac | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/configure.ac b/configure.ac
> index 3e90672..38d6263 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -3232,3 +3232,10 @@ AC_MSG_NOTICE([Privileges])
>  AC_MSG_NOTICE([])
>  AC_MSG_NOTICE([      QEMU: $QEMU_USER:$QEMU_GROUP])
>  AC_MSG_NOTICE([])
> +
> +# -Werror can break some configure tests
> +if echo "$CFLAGS" | sed -e 's/\s\+/\n/g' | grep -E '^-Werror$' >/dev/null 2>&1; then

Eeek.  Much simpler as:

case " $CFLAGS " in
  *" -Werror "*) AC_MSG_WARN(...) ;;
esac

> +    AC_MSG_WARN([CFLAGS contains -Werror flag. This might break some tests performed by])
> +    AC_MSG_WARN([configure and cause some compilation errors.])
> +    AC_MSG_WARN([Please use --enable-compile-warnings=error instead.])
> +fi

Other than that, I very much like the idea.  I also sparked a discussion
on the upstream autoconf list on whether future autoconf 2.70 should
make this sort of thing easier; although we won't be able to rely on
that until we no longer support things like RHEL 5 that will probably
never upgrade to new enough autoconf to use that type of feature.

https://lists.gnu.org/archive/html/autoconf/2012-09/msg00029.html

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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