[ltt-dev] SystemTAP support in tracepoints

[mjw@redhat.com (Mark Wielaard)]

On Wed, 2011-04-13 at 11:38 -0400, Mathieu Desnoyers wrote:
> * Mark Wielaard (mjw at redhat.com) wrote:
> > I have just been using the following configure check:
> > 
> > AC_CHECK_HEADER([sys/sdt.h], [SDT_H_FOUND='yes'],
> >                 [SDT_H_FOUND='no';
> >                    AC_MSG_ERROR([systemtap support needs sys/sdt.h header])])
> > 
> > Which you can adapt to your needs with/without error message, including
> > an test to see if it fully works for your environment.
> 
> Thanks for the hint, but adding this test in the UST build system don't
> really make sense, because both systemtap and UST don't have dependency
> on each other, and thus the build order between the two packages is not
> fixed. So the detection should be done when the UST header is being
> included into an application rather than at UST configuration time. And
> I don't want to require all applications that want to use tracepoint to
> use autoconf neither.

Sure autoconf is optional. But if you want UST tracepoints to be
recognized by other consumers that use SDT probe points, then just
depending on the availability of sys/sdt.h in UST seems to make the most
sense. Note that sys/sdt.h is kind of independent from systemtap proper.
It can be installed independently from the systemtap stap translator or
runtime. And it is only a build dependency, not a runtime dependency.
All consumers just parse the notes section to get the addresses to place
their probes and extract the arguments. There is even a binutils bfd
extractor now.

Cheers,

Mark