Multiple Ada task-specific breakpoints at the same address.

Multiple Ada task-specific breakpoints at the same address.

With the test changed as in the patch, against current mainline, we get:

 (gdb) PASS: gdb.ada/tasks.exp: info tasks before inserting breakpoint
 break break_me task 1
 Breakpoint 2 at 0x4030b0: file /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/tasks/foo.adb, line 27.
 (gdb) PASS: gdb.ada/tasks.exp: break break_me task 1
 break break_me task 3
 Note: breakpoint 2 also set at pc 0x4030b0.
 Breakpoint 3 at 0x4030b0: file /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/tasks/foo.adb, line 27.
 (gdb) PASS: gdb.ada/tasks.exp: break break_me task 3
 continue
 Continuing.
 [Switching to Thread 0x7ffff7dc7700 (LWP 27133)]

 Breakpoint 2, foo.break_me () at /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/tasks/foo.adb:27
 27	      null;
 (gdb) FAIL: gdb.ada/tasks.exp: continue to breakpoint
 info tasks
    ID       TID P-ID Pri State                  Name
     1    63b010       48 Waiting on RV with 3   main_task
     2    63bd80    1  48 Accept or Select Term  task_list(1)
 *   3    63f510    1  48 Accepting RV with 1    task_list(2)
     4    642ca0    1  48 Accept or Select Term  task_list(3)
 (gdb) PASS: gdb.ada/tasks.exp: info tasks after hitting breakpoint

The breakpoint that caused a stop is breakpoint 3, but GDB end up
reporting (and running breakpoint commands of) "Breakpoint 2" instead.

The issue is that the bpstat_check_breakpoint_conditions logic of
"wrong thread" is missing the "wrong task" check.  This is usually
harmless, because the thread hop code in infrun.c code that handles
wrong-task-hitting-breakpoint does check for task-specific breakpoints
(within breakpoint_thread_match):

      /* Check if a regular breakpoint has been hit before checking
         for a potential single step breakpoint.  Otherwise, GDB will
         not see this breakpoint hit when stepping onto breakpoints.  */
      if (regular_breakpoint_inserted_here_p (aspace, stop_pc))
	{
	  if (!breakpoint_thread_match (aspace, stop_pc, ecs->ptid))
	    thread_hop_needed = 1;
	}

IOW, usually, when one only has a task specific breakpoint at a given
address, things work correctly.  Put another task-specific or
non-task-specific breakpoint there, and things break.

A patch that eliminates the special thread hop code in infrun.c is
what exposed this, as after that GDB solely relies on
bpstat_check_breakpoint_conditions to know whether the right or wrong
task hit a breakpoint.  IOW, given the latent bug, Ada task-specific
breakpoints become non-task-specific, and that is caught by the
testsuite, as:

 break break_me task 3
 Breakpoint 2 at 0x4030b0: file /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/tasks/foo.adb, line 27.
 (gdb) PASS: gdb.ada/tasks.exp: break break_me task 3
 continue
 Continuing.
 [Switching to Thread 0x7ffff7fcb700 (LWP 17122)]

 Breakpoint 2, foo.break_me () at /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/tasks/foo.adb:27
 27	      null;
 (gdb) PASS: gdb.ada/tasks.exp: continue to breakpoint
 info tasks
    ID       TID P-ID Pri State                  Name
     1    63b010       48 Waiting on RV with 2   main_task
 *   2    63bd80    1  48 Accepting RV with 1    task_list(1)
     3    63f510    1  48 Accept or Select Term  task_list(2)
     4    642ca0    1  48 Accept or Select Term  task_list(3)
 (gdb) FAIL: gdb.ada/tasks.exp: info tasks after hitting breakpoint

It was after seeing this that I thought of how to expose the bug with
current mainline.

Tested on x86_64 Fedora 17.

gdb/
2014-02-26  Pedro Alves  <palves@redhat.com>

	* breakpoint.c (bpstat_check_breakpoint_conditions): Handle
	task-specific breakpoints.

gdb/testsuite/
2014-02-26  Pedro Alves  <palves@redhat.com>

	* gdb.ada/tasks.exp: Set a task-specific breakpoint at break_me
	that won't ever trigger.  Make sure that GDB reports the correct
	breakpoint that caused the stop.