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| author | Ben Pfaff <blp@ovn.org> | 2018-09-18 02:11:20 -0700 |
|---|---|---|
| committer | Ben Pfaff <blp@ovn.org> | 2018-09-26 13:19:00 -0700 |
| commit | 4c1e8cb9423df8dfd53b0e8ffe58a3d4a9c5148a (patch) | |
| tree | c8ba797cabf6b8ac84468edb0936141612868611 /acinclude.m4 | |
| parent | 8821b212df5450799dfae8e9b4058b2cdacc49f0 (diff) | |
| download | openvswitch-4c1e8cb9423df8dfd53b0e8ffe58a3d4a9c5148a.tar.gz | |
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@ovn.org>
Acked-by: Aaron Conole <aconole@redhat.com>
Diffstat (limited to 'acinclude.m4')
| -rw-r--r-- | acinclude.m4 | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/acinclude.m4 b/acinclude.m4 index 0690baedf..8d8503498 100644 --- a/acinclude.m4 +++ b/acinclude.m4 @@ -996,7 +996,11 @@ AC_DEFUN([_OVS_CHECK_CC_OPTION], [dnl dnl gcc: unrecognized option '-Qunused-arguments' dnl 0 dnl % - CFLAGS="$CFLAGS $WERROR $1" + dnl + dnl In addition, GCC does not complain about a -Wno-<foo> option that + dnl it does not understand, unless it has another error to report, so + dnl instead of testing for -Wno-<foo>, test for the positive version. + CFLAGS="$CFLAGS $WERROR m4_bpatsubst([$1], [-Wno-], [-W])" AC_COMPILE_IFELSE( [AC_LANG_SOURCE([int x;])], [if test -s conftest.err && grep "unrecognized option" conftest.err |