[ovs-dev] [PATCH] acinclude.m4: Really check whether GCC support -Wno-null-pointer-arithmetic.

Ben Pfaff blp at ovn.org
Wed Sep 26 20:24:14 UTC 2018


On Wed, Sep 26, 2018 at 01:26:46PM -0400, Aaron Conole wrote:
> Ben Pfaff <blp at ovn.org> writes:
> 
> > I've noticed recently an annoying quantity of error messages like the
> > following in builds in various places:
> >
> >     gcc: error: unrecognized command line option ‘-Wunknown-warning-option’
> >
> > This didn't really make sense because OVS checks whether the compiler
> > supports warning options before it uses them.  Looking closer, the GCC
> > manual has a note that explains the issue:
> >
> >      When an unrecognized warning option is requested (e.g.,
> >     '-Wunknown-warning'), GCC emits a diagnostic stating that the
> >     option is not recognized.  However, if the '-Wno-' form is used,
> >     the behavior is slightly different: no diagnostic is produced for
> >     '-Wno-unknown-warning' unless other diagnostics are being
> >     produced.  This allows the use of new '-Wno-' options with old
> >     compilers, but if something goes wrong, the compiler warns that
> >     an unrecognized option is present.
> >
> > Thus, we can properly check only for the *positive* version of a warning
> > option, so this commit makes the OVS tests do that.
> >
> > Fixes: a7021b08b0d5 ("configure: Disable -Wnull-pointer-arithmetic Clang warning.")
> > Signed-off-by: Ben Pfaff <blp at ovn.org>
> > ---
> 
> I didn't get a chance to test this out, but the change looks sane.
> 
> Acked-by: Aaron Conole <aconole at redhat.com>

Thanks.  I applied this to master.


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