[RFA 2/4] Improved linker-debugger interface

[Gary Benson <gbenson at redhat dot com>]

Hi all,

This patch implements the basics of the improved runtime linker
interface in GDB--everything except the incremental library
list loading, basically.  It is an updated version of the patch
I posted here in May:

  http://www.cygwin.com/ml/gdb-patches/2012-05/msg00130.html

The changes I've made since then are as follows:

 - All references to SystemTap have been removed; the patch
   now uses GDB's generic probe API, and can work with any
   system which allows named probes with arguments.

 - The probe names have been changed.  The previous version
   prefixed the names with "rtld_", but I didn't realise at
   the time that probes exist within providers which serve
   as namespaces (the probes are all in the "rtld" provider).
   Some Fedora and RHEL systems have the original, prefixed
   probe names, so the patch makes GDB try these names if
   the unprefixed probes are not found.  Not doing this
   would cause GDB to regress PR 2328 on these systems.

 - I've used ARRAY_SIZE to define NUM_PROBES rather than
   calculating it explicitly.

 - I've made a new function, free_probes, to collect some
   code I'd repeated in several places.

 - I've made a new function, solib_event_probe_at, which is
   used only once in this patch, but which is also used by
   the last patch in this series.

 - I've written a simple testcase to check that solib-event
   stops work when probes are used.  (It will XFAIL if probes
   are not available).

 - Various formatting nits were fixed.

I did not suffix the "mandatory" field of struct probe_info
with "_p", as the consensus seemed to be that it was better
without.  I also didn't make it a bitfield as I wasn't sure
if that was desirable, but I can easily do so if necessary.

Cheers,
Gary

-- 
http://gbenson.net/

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