gdb: Restore selected frame in print_frame_local_vars

PR gdb/23203 reports 'bt full' causing the currently selected frame to
change, this issue is fixed in this commit.

Add a new class scoped_restore_selected_frame that saves and restores
the selected frame.  Make use of this in print_frame_local_vars to
restore the selected frame on exit.

gdb/ChangeLog:

	PR gdb/23203
	* frame.c
	(scoped_restore_selected_frame::scoped_restore_selected_frame):
	Define.
	(scoped_restore_selected_frame::~scoped_restore_selected_frame):
	Define.
	* frame.h (class scoped_restore_selected_frame): New class.
	* stack.c (print_frame_local_vars): Remove catching and rethrowing
	of any exception, use scoped_restore_selected_frame to restore the
	frame instead.

gdb/testsuite/ChangeLog:

	PR gdb/23203
	* gdb.base/bt-selected-frame.c: New file.
	* gdb.base/bt-selected-frame.exp: New file.
	* lib/gdb.exp (get_current_frame_number): New function.

1 files changed, 4 insertions, 20 deletions

diff --git a/gdb/stack.c b/gdb/stack.c
index 74c92537da4..98a21842e77 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -2018,7 +2018,6 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs,
   struct print_variable_and_value_data cb_data;
   const struct block *block;
   CORE_ADDR pc;
-  struct gdb_exception except = exception_none;
 
   if (!get_frame_pc_if_available (frame, &pc))
     {
@@ -2042,27 +2041,12 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs,
   /* Temporarily change the selected frame to the given FRAME.
      This allows routines that rely on the selected frame instead
      of being given a frame as parameter to use the correct frame.  */
+  scoped_restore_selected_frame restore_selected_frame;
   select_frame (frame);
 
-  TRY
-    {
-      iterate_over_block_local_vars (block,
-				     do_print_variable_and_value,
-				     &cb_data);
-    }
-  CATCH (ex, RETURN_MASK_ALL)
-    {
-      except = ex;
-    }
-  END_CATCH
-
-  /* Restore the selected frame, and then rethrow if there was a problem.  */
-  select_frame (frame_find_by_id (cb_data.frame_id));
-  if (except.reason < 0)
-    throw_exception (except);
-
-  /* do_print_variable_and_value invalidates FRAME.  */
-  frame = NULL;
+  iterate_over_block_local_vars (block,
+				 do_print_variable_and_value,
+				 &cb_data);
 
   if (!cb_data.values_printed)
     fprintf_filtered (stream, _("No locals.\n"));