Re: AC_CHECK_FUNCS and gcc with -Werror

[Ralf Corsepius]

On 03/03/2010 02:44 PM, Eric Blake wrote:
> According to Steffen Dettmer on 3/3/2010 6:33 AM:
> > > > > what to do best here?
> > > > Not using -Werror
> > >
> > > That's been the standard advice for years now.
> >
> > Do I understand correctly that it is generally adviced to not use
> > the option -Werror?
>
> Not quite.  The advice is to not mix -Werror and configure.
> Post-configure, you can use -Werror to your heart's content, and I do it
> all the time in packages that I maintain.  And it is even possible to let
> configure check whether -Werror works, and if so, automatically add it to
> CFLAGS.  It's just that configure checks themselves are not guaranteed to
> be warning-free, so converting warnings to errors during configure is a
> recipe for disaster.  In other words, the advice is that you shouldn't use
> './configure CFLAGS=-Werror'.

Another aspect is -Wall and -Werror are moving (and architecture 
dependent) targets. I.e. the number of warnings GCC will issue changes 
over time, triggering different kind of warnings.

I.e. when using -Werror a configure script will fail for different kinds 
of reasons at different places depending on your toolchain.

I.e. the best your "Development Rules" will be able to achieve is 
"warning free" compilation in a very narrowly pre-defined setup, with a 
well defined toolchain.

> > > Don't do something if it hurts.
> >
> > mmm... (I think the idea is to make a warning hurting to ensure
> > that it is fixed instantly and cannot be overseen / forgotten).
>
> The problem is that no one has submitted a patch to make configure and
> -Werror try to play nicely, until last month; and even then, it is not the
> easiest thing in the world to do.
There is another aspect: There exist configure-checks which rely on 
switching on/off -Werror. I haven't checked how this recent submission 
co-exists with such kind of configure-checks.

Ralf