Re: RFC: lazily call save_current_space_and_thread

[Tom Tromey <tromey at redhat dot com>]

>>>>> "Tom" == Tom Tromey <tromey@redhat.com> writes:

Tom> This patch makes make_cleanup_restore_current_thread more efficient, by
Tom> having it not compute the current frame when there is no selected frame.
Tom> This approach let me remove another hack I had in my tree.

I am checking in this revised version.  I made the changes Jan and Pedro
suggested.

Built and regtested on x86-64 (compile farm).

Tom

2011-03-09  Tom Tromey  <tromey@redhat.com>

	* thread.c (restore_selected_frame): Handle frame_level == -1.
	(make_cleanup_restore_current_thread): Use
	get_selected_frame_if_set.
	* frame.h (get_selected_frame_if_set): Declare.
	* frame.c (get_selected_frame_if_set): New function.

Index: frame.c
===================================================================
RCS file: /cvs/src/src/gdb/frame.c,v
retrieving revision 1.291
diff -u -r1.291 frame.c
--- frame.c	7 Jan 2011 19:36:17 -0000	1.291
+++ frame.c	9 Mar 2011 14:21:33 -0000
@@ -1247,6 +1247,14 @@
   return selected_frame;
 }
 
+/* If there is a selected frame, return it.  Otherwise, return NULL.  */
+
+struct frame_info *
+get_selected_frame_if_set (void)
+{
+  return selected_frame;
+}
+
 /* This is a variant of get_selected_frame() which can be called when
    the inferior does not have a frame; in that case it will return
    NULL instead of calling error().  */
Index: frame.h
===================================================================
RCS file: /cvs/src/src/gdb/frame.h,v
retrieving revision 1.188
diff -u -r1.188 frame.h
--- frame.h	27 Feb 2011 16:25:37 -0000	1.188
+++ frame.h	9 Mar 2011 14:21:33 -0000
@@ -260,6 +260,9 @@
    and then return that thread's previously selected frame.  */
 extern struct frame_info *get_selected_frame (const char *message);
 
+/* If there is a selected frame, return it.  Otherwise, return NULL.  */
+extern struct frame_info *get_selected_frame_if_set (void);
+
 /* Select a specific frame.  NULL, apparently implies re-select the
    inner most frame.  */
 extern void select_frame (struct frame_info *);
Index: thread.c
===================================================================
RCS file: /cvs/src/src/gdb/thread.c,v
retrieving revision 1.136
diff -u -r1.136 thread.c
--- thread.c	21 Feb 2011 23:40:46 -0000	1.136
+++ thread.c	9 Mar 2011 14:21:33 -0000
@@ -1019,6 +1019,13 @@
   struct frame_info *frame = NULL;
   int count;
 
+  /* This means there was no selected frame.  */
+  if (frame_level == -1)
+    {
+      select_frame (NULL);
+      return;
+    }
+
   gdb_assert (frame_level >= 0);
 
   /* Restore by level first, check if the frame id is the same as
@@ -1137,7 +1144,14 @@
 	  && target_has_registers
 	  && target_has_stack
 	  && target_has_memory)
-	frame = get_selected_frame (NULL);
+	{
+	  /* When processing internal events, there might not be a
+	     selected frame.  If we naively call get_selected_frame
+	     here, then we can end up reading debuginfo for the
+	     current frame, but we don't generally need the debuginfo
+	     at this point.  */
+	  frame = get_selected_frame_if_set ();
+	}
       else
 	frame = NULL;