[patch] Fix for gdb.threads/staticthreads.exp failure on Linux

[ppluzhnikov@google.com (Paul Pluzhnikov)]

Greetings,

The following tests always fail for us:

FAIL: gdb.threads/staticthreads.exp: running to main in runto
FAIL: gdb.threads/staticthreads.exp: Continue to main's call of sem_post
FAIL: gdb.threads/staticthreads.exp: handle SIG32 helps

This is happening because when loading a statically-linked executable, gdb
detects threads right away, but attempt to enumerate threads at that time
fails, because "thread subsystem" in the inferior has not been initialized
yet. This causes spurious error:

  [Thread debugging using libthread_db enabled]
  find_new_threads_callback: cannot get thread info: generic error

and makes subsequent debugging impossible.

Attached patch silently ignores such errors, and makes staticthreads PASS.

Tested on Linux/x86_64.

Ok to check in?

Thanks,

--
Paul Pluzhnikov

2009-06-05  Paul Pluzhnikov  <ppluzhnikov@google.com>

	* linux-thread-db.c (thread_db_find_new_threads_silently):
	New function.
	(try_thread_db_load_1): Call it.


Index: linux-thread-db.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-thread-db.c,v
retrieving revision 1.60
diff -u -p -u -r1.60 linux-thread-db.c
--- linux-thread-db.c	24 May 2009 21:06:53 -0000	1.60
+++ linux-thread-db.c	5 Jun 2009 22:01:37 -0000
@@ -588,6 +588,25 @@ enable_thread_event_reporting (void)
     }
 }
 
+/* Same as thread_db_find_new_threads_1, but silently ignore errors.  */
+
+static void
+thread_db_find_new_threads_silently (ptid_t ptid)
+{
+  volatile struct gdb_exception except;
+
+  TRY_CATCH (except, RETURN_MASK_ERROR)
+    {
+      thread_db_find_new_threads_1 (ptid);
+    }
+
+  if (except.reason < 0 && info_verbose)
+  {
+    exception_fprintf (gdb_stderr, except,
+                       "Warning: thread_db_find_new_threads_silently: ");
+  }
+}
+
 /* Lookup a library in which given symbol resides.
    Note: this is looking in GDB process, not in the inferior.
    Returns library name, or NULL.  */
@@ -705,7 +724,7 @@ try_thread_db_load_1 (struct thread_db_i
     push_target (&thread_db_ops);
 
   enable_thread_event_reporting ();
-  thread_db_find_new_threads_1 (inferior_ptid);
+  thread_db_find_new_threads_silently (inferior_ptid);
   return 1;
 }