[lttng-dev] [PATCH lttng-tools] Link test utilities against urcu-bp

[Jon Bernard]

* Mathieu Desnoyers <mathieu.desnoyers at efficios.com> wrote:
> * Jon Bernard (jbernard at debian.org) wrote:
> > * David Goulet <dgoulet at efficios.com> wrote:
> > > Hi Jon,
> > > 
> > > Can you enlighten us on what setup are you using?
> > > 
> > > This symbol is used by lttng-ust which is linked with -lurcu-bp so
> > > lttng-tools should not have an issue here.
> > > 
> > > Are you cross-compiling ?
> > 
> > Nothing unusual, I'm building lttng-tools (version 2.1.8~rc8) from source
> > against URCU version 0.7.5 and UST version 2.1.0~rc2.  During compilation
> > (configure with no additional parameters), I see the following:
> > 
> >     make[3]: Entering directory `tests/tools/streaming'
> >     CC     unit_tests.o
> >     CCLD   unit_tests
> >     CC     gen-ust-events.o
> >     CC     tp.o
> >     CCLD   gen-ust-events
> >     /usr/bin/ld: tp.o: undefined reference to symbol 'rcu_dereference_sym'
> > 
> > This link error occurs on each of the gen-events targets as there is no explicit
> > link against urcu-bp.  I must have something different, as I'm sure you'd have
> > noticed this earlier.  What additional information might you need?
> 
> Hi Jon,
> 
> It looks like something we already fixed in lttng-ust, but maybe the fix
> needs to be ported to tools also.
> 
> See lttng-ust:
> 
> commit faebb41808b9deda5ef5dfea0c035077407e7f9f
> Author: Christian Babeux <christian.babeux at efficios.com>
> Date:   Thu Aug 2 18:55:11 2012 -0400
> 
>     Fix: Libtool fails to find dependent libraries when cross-compiling lttng-ust
>     
>     This problem arise when cross compiling and linking libraries with
>     indirect libraries dependencies (such as liblttng-ust). This "bug" is
>     caused by an upstream modification in the libtool package on Debian
>     system. The libtool "link_all_deplibs" flag is set to "no" by default
>     on linux targets (AFAIK, other distros set it to "unknown").
>     
>     The chosen solution is to detect such cases via the configure script
>     and automagically patch the libtool.m4 by forcing the "link_all_deplibs"
>     to "unknown".
>     
>     This fixup can be disabled with the appropriate configure flag:
>     
>     ./configure --disable-libtool-linkdep-fixup
>     
>     Sample configure output on affected systems:
>     
>     checking for occurence(s) of link_all_deplibs = no in
>              ./config/libtool.m4... 3
>     configure: WARNING: the detected libtool will not link all
>                dependencies, forcing link_all_deplibs = unknown
>     
>     Fixes: #321
>     
>     Signed-off-by: Christian Babeux <christian.babeux at efficios.com>
>     Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> 
> Thoughts ?

Yep, it seems to be an issue with Debian's libtool, I think cross-compiling is
coincidental.  I'll prepare a port of this to tools, if someone doesn't beat me
to it.

Cheers,

-- 
Jon