Re: [dpdk-dev] [PATCH v2] build: avoid --as-needed as it causes overlinking

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

On Wed, Sep 4, 2019 at 11:18 AM Bruce Richardson
<bruce.richardson@intel.com> wrote:
>
> On Wed, Sep 04, 2019 at 11:13:34AM +0200, Christian Ehrhardt wrote:
> > On Mon, Sep 2, 2019 at 9:09 AM Christian Ehrhardt
> > <christian.ehrhardt@canonical.com> wrote:
> > >
> > > On Thu, Aug 29, 2019 at 6:02 PM Luca Boccassi <bluca@debian.org> wrote:
> > > >
> > > > On Thu, 2019-08-29 at 16:34 +0100, Bruce Richardson wrote:
> > > > > On Thu, Aug 29, 2019 at 05:30:03PM +0200, Christian Ehrhardt wrote:
> > > > > > A while ago telemetry was added in 57ae0ec6 and it also added as-
> > > > > > needed
> > > > > > to config/meson.build. This seems no more needed these days as due
> > > > > > to other
> > > > > > build changes the ordering in buildlogs is:
> > > > > >   [...] -lrte_telemetry [...] -Wl,--no-as-needed [...]
> > > > > > Which means telemetry no more benefits from --no-as-needed anyway.
> > > > > >
> > > > > > Overlinking problems get triggered by the meson generated pkgconfig
> > > > > > which
> > > > > > will have:
> > > > > >    [...] -Wl,--no-as-needed <somelibsusedbydpdk>
> > > > > > This will overlink <somelibs> and in addition anything that follows
> > > > > > as it also doesn't wrap back to --as-needed. So if a projects
> > > > > > includes
> > > > > > dpdk libs + <other> it will also consider <other> with --no-as-
> > > > > > needed.
> > > > > >
> > > > > > Fixes:
> > > > > > https://bugs.launchpad.net/ubuntu/+source/dpdk/+bug/1841759
> > > > > >
> > > > > >
> > > > > > Signed-off-by: Christian Ehrhardt <
> > > > > > christian.ehrhardt@canonical.com
> > > > > > >
> > > > > > Acked-by: Luca Boccassi <
> > > > > > bluca@debian.org
> > > > > > >
> > > > > > ---
> > > > > >  config/meson.build | 1 -
> > > > > >  1 file changed, 1 deletion(-)
> > > > > >
> > > > > > diff --git a/config/meson.build b/config/meson.build
> > > > > > index 2bafea530..a27f731f8 100644
> > > > > > --- a/config/meson.build
> > > > > > +++ b/config/meson.build
> > > > > > @@ -94,7 +94,6 @@ dpdk_conf.set('RTE_TOOLCHAIN_' +
> > > > > > toolchain.to_upper(), 1)
> > > > > >  dpdk_conf.set('RTE_ARCH_64', cc.sizeof('void *') == 8)
> > > > > >
> > > > > >  add_project_link_arguments('-Wl,--no-as-needed', language: 'c')
> > > > > > -dpdk_extra_ldflags += '-Wl,--no-as-needed'
> > > > > >
> > > > >
> > > > > This seems strange to me. What is it about linking the dpdk apps that
> > > > > require the argument, but makes it safe for non-builtin apps to avoid
> > > > > having the arg?
> > > >
> > > > We've been wondering about that for a while :-) It also seems to be not
> > > > reproducible on Ubuntu 18.04/gcc 7.4.
> > > >
> > > > Can the verbose linking log be shared here, so that we can have a look
> > > > at where no-as-needed lands? Might provide some clue
> > >
> > > That would be the verbose linking log of the Travis CI run right?
> > > I currently have no idea which knob to turn to get this :-/
> > >
> > > Having it accepted in upstream would make it more easy to fix this in
> > > the soon to be released Ubuntu 19.10.
> > > Is there a path to consider taking this fix as-is and continue the
> > > debug/discussion how the removal of the second line can even cause the
> > > symptoms that we have seen later?
> >
> > re-ping for the above ^^
> >
>
> I'm ok with what you propose above.

Thanks Bruce!

Is there anything else we'd need to do to get this committed?

-- 
Christian Ehrhardt
Software Engineer, Ubuntu Server
Canonical Ltd