[PATCH 2/3] [Ada] Add field "thread-id" in -ada-task-info output

[Joel Brobecker <brobecker at adacore dot com>]

This patch enhances the -ada-task-info command, adding a new
field called "thread-id" in the command output.  This field
provides the ID of the task's corresponding thread (if that
information could not be determined, the field is omitted).

This field is useful in the context of GDB/MI users, because
it allows a quick translation from Ada task to thread, and
thus easy use of all the commands that take a --thread argument.

gdb/ChangeLog:

        * ada-tasks.c (print_ada_task_info): Add "thread-id" field
        in output of -ada-task-info GDB/MI command.

Tested on x86_64-linux.

---
 gdb/ada-tasks.c |   33 +++++++++++++++++++++++++++++++--
 1 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index 7dff8f8..2673fed 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -938,6 +938,7 @@ print_ada_task_info (struct ui_out *uiout,
   int taskno, nb_tasks;
   int taskno_arg = 0;
   struct cleanup *old_chain;
+  int nb_columns;
 
   if (ada_build_task_list () == 0)
     {
@@ -949,14 +950,29 @@ print_ada_task_info (struct ui_out *uiout,
   if (arg_str != NULL && arg_str[0] != '\0')
     taskno_arg = value_as_long (parse_and_eval (arg_str));
 
+  if (ui_out_is_mi_like_p (uiout))
+    /* In GDB/MI mode, we want to provide the thread ID corresponding
+       to each task.  This allows clients to quickly find the thread
+       associated to any task, which is helpful for commands that
+       take a --thread argument.  However, in order to be able to
+       provide that thread ID, the thread list must be up to date
+       first.  */
+    target_find_new_threads ();
+
   data = get_ada_tasks_inferior_data (inf);
   nb_tasks = VEC_length (ada_task_info_s, data->task_list);
 
-  old_chain = make_cleanup_ui_out_table_begin_end (uiout, 7, nb_tasks,
-                                                   "tasks");
+  nb_columns = ui_out_is_mi_like_p (uiout) ? 8 : 7;
+  old_chain = make_cleanup_ui_out_table_begin_end (uiout, nb_columns,
+						   nb_tasks, "tasks");
   ui_out_table_header (uiout, 1, ui_left, "current", "");
   ui_out_table_header (uiout, 3, ui_right, "id", "ID");
   ui_out_table_header (uiout, 9, ui_right, "task-id", "TID");
+  /* The following column is provided in GDB/MI mode only because
+     it is only really useful in that mode, and also because it
+     allows us to keep the CLI output shorter and more compact.  */
+  if (ui_out_is_mi_like_p (uiout))
+    ui_out_table_header (uiout, 4, ui_right, "thread-id", "");
   ui_out_table_header (uiout, 4, ui_right, "parent-id", "P-ID");
   ui_out_table_header (uiout, 3, ui_right, "priority", "Pri");
   ui_out_table_header (uiout, 22, ui_left, "state", "State");
@@ -996,6 +1012,19 @@ print_ada_task_info (struct ui_out *uiout,
       /* Print the Task ID.  */
       ui_out_field_fmt (uiout, "task-id", "%9lx", (long) task_info->task_id);
 
+      /* Print the associated Thread ID.  */
+      if (ui_out_is_mi_like_p (uiout))
+        {
+	  const int thread_id = pid_to_thread_id (task_info->ptid);
+
+	  if (thread_id != 0)
+	    ui_out_field_int (uiout, "thread-id", thread_id);
+	  else
+	    /* This should never happen unless there is a bug somewhere,
+	       but be resilient when that happens.  */
+	    ui_out_field_skip (uiout, "thread-id");
+	}
+
       /* Print the ID of the parent task.  */
       parent_id = get_task_number_from_id (task_info->parent, inf);
       if (parent_id)
-- 
1.7.1