Installing a breakpoint on top of a dprintf makes GDB lose control.

While the full fix for PR 15180 isn't in, it's best if we at least
make sure that GDB doesn't lose control when a breakpoint is set at
the same address as a dprintf.

gdb/
2014-06-02  Pedro Alves  <palves@redhat.com>

	* breakpoint.c (build_target_command_list): Don't build a command
	list if we have any duplicate location that isn't a dprintf.

gdb/testsuite/
2014-06-02  Pedro Alves  <palves@redhat.com>

	* gdb.base/dprintf-bp-same-addr.c: New file.
	* gdb.base/dprintf-bp-same-addr.exp: New file.

gdb/breakpoint.c

@@ -2351,14 +2351,26 @@ build_target_command_list (struct bp_location *bl)
   /* Release commands left over from a previous insert.  */
   VEC_free (agent_expr_p, bl->target_info.tcommands);
 
-  /* For now, limit to agent-style dprintf breakpoints.  */
-  if (bl->owner->type != bp_dprintf
-      || strcmp (dprintf_style, dprintf_style_agent) != 0)
-    return;
-
   if (!target_can_run_breakpoint_commands ())
     return;
 
+  /* For now, limit to agent-style dprintf breakpoints.  */
+  if (dprintf_style != dprintf_style_agent)
+    return;
+
+  /* For now, if we have any duplicate location that isn't a dprintf,
+     don't install the target-side commands, as that would make the
+     breakpoint not be reported to the core, and we'd lose
+     control.  */
+  ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
+    {
+      loc = (*loc2p);
+      if (is_breakpoint (loc->owner)
+	  && loc->pspace->num == bl->pspace->num
+	  && loc->owner->type != bp_dprintf)
+	return;
+    }
+
   /* Do a first pass to check for locations with no assigned
      conditions or conditions that fail to parse to a valid agent expression
      bytecode.  If any of these happen, then it's no use to send conditions