[ovs-dev] [PATCH] configure: Properly handle case where libunwind.h is not available.

[Yi-Hung Wei]

On Wed, Oct 16, 2019 at 6:50 PM Ben Pfaff <blp at ovn.org> wrote:
>
> On Tue, Oct 15, 2019 at 04:49:33PM -0700, Yi-Hung Wei wrote:
> > On Tue, Oct 15, 2019 at 3:25 PM Ben Pfaff <blp at ovn.org> wrote:
> > >
> > > On Tue, Oct 15, 2019 at 02:30:48PM -0700, Yi-Hung Wei wrote:
> > > > It is possible that user install libunwind but not libunwind-devel,
> > > > and it will run into a compilation error.  So check the existence
> > > > of the header file instead of the library.
> > > >
> > > > Fixes: e2ed6fbeb18c ("fatal-signal: Catch SIGSEGV and print backtrace.")
> > > > Signed-off-by: Yi-Hung Wei <yihung.wei at gmail.com>
> > > > ---
> > > >  m4/openvswitch.m4 | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/m4/openvswitch.m4 b/m4/openvswitch.m4
> > > > index 79e0be5a33dd..da7119951484 100644
> > > > --- a/m4/openvswitch.m4
> > > > +++ b/m4/openvswitch.m4
> > > > @@ -640,7 +640,7 @@ AC_DEFUN([OVS_CHECK_UNBOUND],
> > > >
> > > >  dnl Checks for libunwind.
> > > >  AC_DEFUN([OVS_CHECK_UNWIND],
> > > > -  [AC_CHECK_LIB(unwind, unw_backtrace, [HAVE_UNWIND=yes], [HAVE_UNWIND=no])
> > > > +  [AC_CHECK_HEADERS([libunwind.h], [HAVE_UNWIND=yes], [HAVE_UNWIND=no])
> > >
> > > It might be wise to check for both, e.g.:
> > >
> > > AC_CHECK_LIB([unwind], [unw_backtrace],
> > >   [AC_CHECK_HEADERS([libunwind.h], [HAVE_UNWIND=yes], [HAVE_UNWIND=no])],
> > >   [HAVE_UNWIND=no])
> > >
> >
> > Hi Ben,
> >
> > In most distros, libunwind-devel (or libunwind-dev) depends on
> > libunwind.  Is it necessary for us to check both?
>
> Not if everyone installs from a distro package.  If you install from a
> tarball, it's easy to provide configure options that make the header
> available but not the library, or vice versa.  It's better to catch that
> at configure time.

Thanks for explanation.   It's better to check both.  I will send out v2 soon.

Thanks,

-Yi-Hung