[ovs-git] [openvswitch/ovs] 4c1e8c: acinclude.m4: Really check whether GCC support -Wn...
noreply at github.com
Wed Sep 26 20:24:15 UTC 2018
Author: Ben Pfaff <blp at ovn.org>
Date: 2018-09-26 (Wed, 26 Sep 2018)
acinclude.m4: Really check whether GCC support -Wno-null-pointer-arithmetic.
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>
Acked-by: Aaron Conole <aconole at redhat.com>
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