Minor Ada task cleanups

While working on the Ada task code, I noticed a few things that could
be cleaned up:

* task_list_valid_p was not set in all cases in ada_build_task_list.
  This causes many needless re-fetches of the task list.

* task_list_valid_p can be bool, and various functions can also return
  bool.

* Nothing checks the return value of read_known_tasks, so it can be
  changed to return void.

* The call to ada_build_task_list in
  ravenscar_thread_target::update_thread_list is redundant, because
  this is the first thing done by iterate_over_live_ada_tasks.

Tested using the internal AdaCore test suite against a ravenscar
target.

gdb/ChangeLog
2019-02-19  Tom Tromey  <tromey@adacore.com>

	* ravenscar-thread.c
	(ravenscar_thread_target::update_thread_list): Don't call
	ada_build_task_list.
	* ada-lang.h (ada_build_task_list): Don't declare.
	* ada-tasks.c (struct ada_tasks_inferior_data)
	<task_list_valid_p>: Now bool.
	(read_known_tasks, ada_task_list_changed)
	(ada_tasks_invalidate_inferior_data): Update.
	(read_known_tasks_array): Return bool.
	(read_known_tasks_list): Likewise.
	(read_known_tasks): Return void.
	(ada_build_task_list): Now static.

4 files changed, 42 insertions, 32 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1cf2f07..4e429f4 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,18 @@
+2019-02-19  Tom Tromey  <tromey@adacore.com>
+
+	* ravenscar-thread.c
+	(ravenscar_thread_target::update_thread_list): Don't call
+	ada_build_task_list.
+	* ada-lang.h (ada_build_task_list): Don't declare.
+	* ada-tasks.c (struct ada_tasks_inferior_data)
+	<task_list_valid_p>: Now bool.
+	(read_known_tasks, ada_task_list_changed)
+	(ada_tasks_invalidate_inferior_data): Update.
+	(read_known_tasks_array): Return bool.
+	(read_known_tasks_list): Likewise.
+	(read_known_tasks): Return void.
+	(ada_build_task_list): Now static.
+
 2019-02-18  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdbtypes.c (type_align): Allow alignment of TYPE_CODE_METHODPTR
diff --git a/gdb/ada-lang.h b/gdb/ada-lang.h
index 14470d5..ee03dbd 100644
--- a/gdb/ada-lang.h
+++ b/gdb/ada-lang.h
@@ -411,8 +411,6 @@ extern void iterate_over_live_ada_tasks
 
 extern const char *ada_get_tcb_types_info (void);
 
-extern int ada_build_task_list (void);
-
 extern void print_ada_task_info (struct ui_out *uiout,
 				 char *taskno_str,
 				 struct inferior *inf);
diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index 440e32b..ccabc631 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -26,6 +26,8 @@
 #include "progspace.h"
 #include "objfiles.h"
 
+static int ada_build_task_list ();
+
 /* The name of the array in the GNAT runtime where the Ada Task Control
    Block of each task is stored.  */
 #define KNOWN_TASKS_NAME "system__tasking__debug__known_tasks"
@@ -230,7 +232,7 @@ struct ada_tasks_inferior_data
   /* When nonzero, this flag indicates that the task_list field
      below is up to date.  When set to zero, the list has either
      not been initialized, or has potentially become stale.  */
-  int task_list_valid_p = 0;
+  bool task_list_valid_p = false;
 
   /* The list of Ada tasks.
 
@@ -803,9 +805,9 @@ add_ada_task (CORE_ADDR task_id, struct inferior *inf)
 }
 
 /* Read the Known_Tasks array from the inferior memory, and store
-   it in the current inferior's TASK_LIST.  Return non-zero upon success.  */
+   it in the current inferior's TASK_LIST.  Return true upon success.  */
 
-static int
+static bool
 read_known_tasks_array (struct ada_tasks_inferior_data *data)
 {
   const int target_ptr_byte = TYPE_LENGTH (data->known_tasks_element);
@@ -826,13 +828,13 @@ read_known_tasks_array (struct ada_tasks_inferior_data *data)
         add_ada_task (task_id, current_inferior ());
     }
 
-  return 1;
+  return true;
 }
 
 /* Read the known tasks from the inferior memory, and store it in
-   the current inferior's TASK_LIST.  Return non-zero upon success.  */
+   the current inferior's TASK_LIST.  Return true upon success.  */
 
-static int
+static bool
 read_known_tasks_list (struct ada_tasks_inferior_data *data)
 {
   const int target_ptr_byte = TYPE_LENGTH (data->known_tasks_element);
@@ -843,7 +845,7 @@ read_known_tasks_list (struct ada_tasks_inferior_data *data)
 
   /* Sanity check.  */
   if (pspace_data->atcb_fieldno.activation_link < 0)
-    return 0;
+    return false;
 
   /* Build a new list by reading the ATCBs.  Read head of the list.  */
   read_memory (data->known_tasks_addr, known_tasks, target_ptr_byte);
@@ -864,7 +866,7 @@ read_known_tasks_list (struct ada_tasks_inferior_data *data)
                                 pspace_data->atcb_fieldno.activation_link));
     }
 
-  return 1;
+  return true;
 }
 
 /* Set all fields of the current inferior ada-tasks data pointed by DATA.
@@ -962,11 +964,10 @@ ada_tasks_inferior_data_sniffer (struct ada_tasks_inferior_data *data)
 }
 
 /* Read the known tasks from the current inferior's memory, and store it
-   in the current inferior's data TASK_LIST.
-   Return non-zero upon success.  */
+   in the current inferior's data TASK_LIST.  */
 
-static int
-read_known_tasks (void)
+static void
+read_known_tasks ()
 {
   struct ada_tasks_inferior_data *data =
     get_ada_tasks_inferior_data (current_inferior ());
@@ -983,29 +984,27 @@ read_known_tasks (void)
   ada_tasks_inferior_data_sniffer (data);
   gdb_assert (data->known_tasks_kind != ADA_TASKS_UNKNOWN);
 
+  /* Step 3: Set task_list_valid_p, to avoid re-reading the Known_Tasks
+     array unless needed.  */
   switch (data->known_tasks_kind)
     {
-      case ADA_TASKS_NOT_FOUND: /* Tasking not in use in inferior.  */
-        return 0;
-      case ADA_TASKS_ARRAY:
-        return read_known_tasks_array (data);
-      case ADA_TASKS_LIST:
-        return read_known_tasks_list (data);
+    case ADA_TASKS_NOT_FOUND: /* Tasking not in use in inferior.  */
+      break;
+    case ADA_TASKS_ARRAY:
+      data->task_list_valid_p = read_known_tasks_array (data);
+      break;
+    case ADA_TASKS_LIST:
+      data->task_list_valid_p = read_known_tasks_list (data);
+      break;
     }
-
-  /* Step 3: Set task_list_valid_p, to avoid re-reading the Known_Tasks
-     array unless needed.  Then report a success.  */
-  data->task_list_valid_p = 1;
-
-  return 1;
 }
 
 /* Build the task_list by reading the Known_Tasks array from
    the inferior, and return the number of tasks in that list
    (zero means that the program is not using tasking at all).  */
 
-int
-ada_build_task_list (void)
+static int
+ada_build_task_list ()
 {
   struct ada_tasks_inferior_data *data;
 
@@ -1361,7 +1360,7 @@ ada_task_list_changed (struct inferior *inf)
 {
   struct ada_tasks_inferior_data *data = get_ada_tasks_inferior_data (inf);
 
-  data->task_list_valid_p = 0;
+  data->task_list_valid_p = false;
 }
 
 /* Invalidate the per-program-space data.  */
@@ -1380,7 +1379,7 @@ ada_tasks_invalidate_inferior_data (struct inferior *inf)
   struct ada_tasks_inferior_data *data = get_ada_tasks_inferior_data (inf);
 
   data->known_tasks_kind = ADA_TASKS_UNKNOWN;
-  data->task_list_valid_p = 0;
+  data->task_list_valid_p = false;
 }
 
 /* The 'normal_stop' observer notification callback.  */
diff --git a/gdb/ravenscar-thread.c b/gdb/ravenscar-thread.c
index 05a8320..cb4f26a 100644
--- a/gdb/ravenscar-thread.c
+++ b/gdb/ravenscar-thread.c
@@ -374,8 +374,6 @@ ravenscar_add_thread (struct ada_task_info *task)
 void
 ravenscar_thread_target::update_thread_list ()
 {
-  ada_build_task_list ();
-
   /* Do not clear the thread list before adding the Ada task, to keep
      the thread that the process stratum has included into it
      (m_base_ptid) and the running thread, that may not have been included