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[FYI/pushed] ada-tasks.c::read_atcb: start from a cleared ada_task_info result

Message ID 1541626357-41376-2-git-send-email-brobecker@adacore.com
State New
Headers show

Commit Message

Joel Brobecker Nov. 7, 2018, 9:32 p.m. UTC
The purpose of this patch is not to fix a bug per se, but rather
to robustify this function to make sure it never returns a struct
ada_task_info where some of the fields are left uninitialized.
Reading the current implementation, it attempts to methodically
set them all one by one: but it's not excluded that a future
change might miss something. A memset is cheap and make sure that
this function returns repeatable results.

This in turns allows us to remove some assignments which have become
redundant.

gdb/ChangeLog:

        * ada-tasks.c (read_atcb): Clear task_info before computing
        the value of each of its fields.
---
 gdb/ChangeLog   |  5 +++++
 gdb/ada-tasks.c | 16 ++++++----------
 2 files changed, 11 insertions(+), 10 deletions(-)
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Patch

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f7d1de5..c94321b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@ 
+2018-11-07  Joel Brobecker  <brobecker@adacore.com>
+
+	* ada-tasks.c (read_atcb): Clear task_info before computing
+	the value of each of its fields.
+
 2018-11-07  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* dwarf2read.c (dwarf2_init_integer_type): Check for name being
diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index 566eae5..5b97e93 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -611,6 +611,10 @@  read_atcb (CORE_ADDR task_id, struct ada_task_info *task_info)
   const struct ada_tasks_pspace_data *pspace_data
     = get_ada_tasks_pspace_data (current_program_space);
 
+  /* Clear the whole structure to start with, so that everything
+     is always initialized the same.  */
+  memset (task_info, 0, sizeof (struct ada_task_info));
+
   if (!pspace_data->initialized_p)
     {
       const char *err_msg = ada_get_tcb_types_info ();
@@ -704,9 +708,6 @@  read_atcb (CORE_ADDR task_id, struct ada_task_info *task_info)
     task_info->parent =
       value_as_address (value_field (common_value,
 				     pspace_data->atcb_fieldno.parent));
-  else
-    task_info->parent = 0;
-  
 
   /* If the ATCB contains some information about entry calls, then
      compute the "called_task" as well.  Otherwise, zero.  */
@@ -732,15 +733,10 @@  read_atcb (CORE_ADDR task_id, struct ada_task_info *task_info)
         value_as_address (value_field (entry_calls_value_element,
                                        called_task_fieldno));
     }
-  else
-    {
-      task_info->called_task = 0;
-    }
 
-  /* If the ATCB cotnains some information about RV callers,
-     then compute the "caller_task".  Otherwise, zero.  */
+  /* If the ATCB cotnains some information about RV callers, then
+     compute the "caller_task".  Otherwise, leave it as zero.  */
 
-  task_info->caller_task = 0;
   if (pspace_data->atcb_fieldno.call >= 0)
     {
       /* Get the ID of the caller task from Common_ATCB.Call.all.Self.