[ovs-dev] [PATCH] m4: Fix 32bit build with 64bit version of libunwind-dev installed.

Ben Pfaff blp at ovn.org
Tue Oct 1 16:17:53 UTC 2019

On Tue, Oct 01, 2019 at 02:22:20PM +0300, Ilya Maximets wrote:
> 32 and 64 bit versions of libunwind-dev package can not be installed
> at the same time at least in Debian and Ubuntu.  AC_CHECK_LIB macro
> doesn't know if we have '-m32' in OVS_CFLAGS, so we need to
> additionally check for actual compiling possibility before enabling
> the feature.  Otherwise 'make' will fail due to inability to
> build with 64bit libunwind headers:
>     https://travis-ci.org/openvswitch/ovs/jobs/590580374
>     /usr/include/libunwind.h:23:28: fatal error:
>         libunwind-x86.h: No such file or directory
> CC: William Tu <u9012063 at gmail.com>
> Fixes: e2ed6fbeb18c ("fatal-signal: Catch SIGSEGV and print backtrace.")
> Signed-off-by: Ilya Maximets <i.maximets at ovn.org>

I think there's some confusion here on the use of options.  CFLAGS is
for the user, OVS_CFLAGS is for the OVS configure script to use itself.
.cirrus.yml and .travis/linux-build.sh are setting OVS_CFLAGS, but they
should not because they are the "user", not the configure script.  If
they set CFLAGS, instead, I believe that there would be no problem here.

See commit 95626395a3db ("build: Respect CFLAGS and LDFLAGS passed to
make") and the documentation it references.

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