Fix PR19548: Breakpoint re-set inserts breakpoints when it shouldn't

PR19548 shows that we still have problems related to 13fd3ff34329:

 [PR17431: following execs with "breakpoint always-inserted on"]
 https://sourceware.org/ml/gdb-patches/2014-09/msg00733.html

The problem this time is that we currently update the global location
list and try to insert breakpoint locations after re-setting _each_
breakpoint in turn.

Say:

 - We have _more_ than one breakpoint set.  Let's assume 2.

 - There's a breakpoint with a pre-exec address that ends up being an
   unmapped address after the exec.

 - That breakpoint is NOT the first in the breakpoint list.

Then when handling an exec, and we re-set the first breakpoint in the
breakpoint list, we mistakently try to install the old pre-exec /
un-re-set locations of the other breakpoint, which fails:

 (gdb) continue
 Continuing.
 process 28295 is executing new program: (...)/execl-update-breakpoints2
 Error in re-setting breakpoint 1: Warning:
 Cannot insert breakpoint 2.
 Cannot access memory at address 0x1000764

 Breakpoint 1, main (argc=1, argv=0x7fffffffd368) at /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.base/execl-update-breakpoints.c:34
 34        len = strlen (argv[0]);
 (gdb)

Fix this by deferring the global location list update till after all
breakpoints are re-set.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/ChangeLog:
2016-02-09  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19548
	* breakpoint.c (create_overlay_event_breakpoint): Don't update
	global location list here.
	(create_longjmp_master_breakpoint)
	(create_std_terminate_master_breakpoint)
	(create_exception_master_breakpoint, create_jit_event_breakpoint)
	(update_breakpoint_locations):
	(breakpoint_re_set): Update global location list after all
	breakpoints are re-set.

gdb/testsuite/ChangeLog:
2016-02-09  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19548
	* gdb.base/execl-update-breakpoints.c (some_function): New
	function.
	(main): Call it.
	* gdb.base/execl-update-breakpoints.exp: Add a second breakpoint.
	Tighten expected GDB output.

1 files changed, 10 insertions, 15 deletions

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index afd9065..c059861 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -3488,7 +3488,6 @@ create_overlay_event_breakpoint (void)
          overlay_events_enabled = 0;
        }
     }
-  update_global_location_list (UGLL_MAY_INSERT);
 }
 
 static void
@@ -3602,7 +3601,6 @@ create_longjmp_master_breakpoint (void)
 	}
     }
   }
-  update_global_location_list (UGLL_MAY_INSERT);
 
   do_cleanups (old_chain);
 }
@@ -3661,8 +3659,6 @@ create_std_terminate_master_breakpoint (void)
     }
   }
 
-  update_global_location_list (UGLL_MAY_INSERT);
-
   do_cleanups (old_chain);
 }
 
@@ -3766,8 +3762,6 @@ create_exception_master_breakpoint (void)
       b->location = new_explicit_location (&explicit_loc);
       b->enable_state = bp_disabled;
     }
-
-  update_global_location_list (UGLL_MAY_INSERT);
 }
 
 void
@@ -7807,12 +7801,8 @@ struct lang_and_radix
 struct breakpoint *
 create_jit_event_breakpoint (struct gdbarch *gdbarch, CORE_ADDR address)
 {
-  struct breakpoint *b;
-
-  b = create_internal_breakpoint (gdbarch, address, bp_jit_event,
-				  &internal_breakpoint_ops);
-  update_global_location_list_nothrow (UGLL_MAY_INSERT);
-  return b;
+  return create_internal_breakpoint (gdbarch, address, bp_jit_event,
+				     &internal_breakpoint_ops);
 }
 
 /* Remove JIT code registration and unregistration breakpoint(s).  */
@@ -14278,7 +14268,6 @@ update_breakpoint_locations (struct breakpoint *b,
       /* Ranged breakpoints have only one start location and one end
 	 location.  */
       b->enable_state = bp_disabled;
-      update_global_location_list (UGLL_MAY_INSERT);
       printf_unfiltered (_("Could not reset ranged breakpoint %d: "
 			   "multiple locations found\n"),
 			 b->number);
@@ -14376,8 +14365,6 @@ update_breakpoint_locations (struct breakpoint *b,
 
   if (!locations_are_equal (existing_locations, b->loc))
     observer_notify_breakpoint_modified (b);
-
-  update_global_location_list (UGLL_MAY_INSERT);
 }
 
 /* Find the SaL locations corresponding to the given LOCATION.
@@ -14617,6 +14604,11 @@ breakpoint_re_set (void)
   save_input_radix = input_radix;
   old_chain = save_current_space_and_thread ();
 
+  /* Note: we must not try to insert locations until after all
+     breakpoints have been re-set.  Otherwise, e.g., when re-setting
+     breakpoint 1, we'd insert the locations of breakpoint 2, which
+     hadn't been re-set yet, and thus may have stale locations.  */
+
   ALL_BREAKPOINTS_SAFE (b, b_tmp)
   {
     /* Format possible error msg.  */
@@ -14637,6 +14629,9 @@ breakpoint_re_set (void)
   create_longjmp_master_breakpoint ();
   create_std_terminate_master_breakpoint ();
   create_exception_master_breakpoint ();
+
+  /* Now we can insert.  */
+  update_global_location_list (UGLL_MAY_INSERT);
 }
 
 /* Reset the thread number of this breakpoint: