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

Ben Pfaff blp at ovn.org
Wed Oct 2 14:46:13 UTC 2019


On Tue, Oct 01, 2019 at 06:40:10PM -0700, William Tu wrote:
> On Tue, Oct 1, 2019 at 4:19 PM William Tu <u9012063 at gmail.com> wrote:
> >
> > On Tue, Oct 01, 2019 at 08:29:41PM +0300, Ilya Maximets wrote:
> > > On 01.10.2019 19:56, Ben Pfaff wrote:
> > > >On Tue, Oct 01, 2019 at 07:46:10PM +0300, Ilya Maximets wrote:
> > > >>On 01.10.2019 19:17, Ben Pfaff wrote:
> > > >>>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.
> > > >>
> > > >>That's an interesting point.
> > > >>However, 'configure' script makes decision about building with libunwind
> > > >>and it needs to know  if we're going to build 32 or 64 bit binary to
> > > >>enable or disable the feature. Setting CFLAGS for configure script breaks
> > > >>it in a following way:
> > > >>
> > > >>$ CFLAGS='-m32' ./configure
> > > >>...
> > > >>checking for gcc... gcc
> > > >>checking whether the C compiler works... no
> > > >
> > > >Is this because the 32-bit C library isn't installed?  It should be easy
> > > >to fix with "sudo dnf install glibc-devel.i686" or the distro-specific
> > > >equivalent.
> > >
> > > Yes, you're right. It works after installation of gcc-multilib.
> > >
> > > I'll think about how to rework CI scripts tomorrow.
> > >
> > > >
> > > >I don't see how it's reasonable to run "configure" with a toolchain
> > > >different from the one we're going to use for building.  Adding -m32
> > > >changes the ABI and the API.
> > > >
> > > >My usual way to do this is actually to use CC="gcc -m32".  That way the
> > > >-m32, which is important, can't get separated at all!
> >
> > Thanks Ben and Ilya,
> >
> > I don't have a good solution, on my Xenial system, if I do 32-bit build
> >
> >   apt-get install libunwind-dev:i386
> >   CC="gcc -m32" ./configure
> >
> > then it correctly detects libunwind and pass, for x86_64, I have to
> >
> >   apt-get remove libunwind-dev:i386
> >   apt-get install libunwind-dev
> >   ./configure
> >
> > so like Ilya mentioned, the 32 and 64 bit libunwind-dev can not be installed
> > at the same time. To pass travis, we need to check whether it has '-m32' or not,
> > then install different libunwind-dev package.
> >
> > I'm also ok with disabling this feature on 32-bit system.
> >
> > Regards,
> > William
> >
> Hi,
> 
> How about this fix? So for 32-bit system, we have to install libunwind-dev:i386,
> in the meantime the libunwind-dev for 64-bit will be removed automatically.
> I tested it and passed.
> https://travis-ci.org/williamtu/ovs-travis/builds/592323952

Acked-by: Ben Pfaff <blp at ovn.org>

It might be worth waiting for Ilya's feedback, though.


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