[RFA] Reverse Debugging, 4/5

[Michael Snyder <msnyder at vmware dot com>]

This patch (#4), adds special handling for the "finish" command
when executing in reverse.  The new code can't actually be 
invoked until patch #5 is added, and so has no user visible
effect.

Tested under RHEL native with no change in results.

2008-09-30  Michael Snyder  <msnyder@vmware.com>

	* breakpoint.h (breakpoint_silence): Export.
	* breakpoint.c (breakpoint_silence): New function.
	* infcmd.c (finish_command): Check for reverse exec direction.
	(finish_backward): New function, handle finish cmd in reverse.

Index: breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.352
diff -u -p -r1.352 breakpoint.c
--- breakpoint.c	16 Sep 2008 18:55:01 -0000	1.352
+++ breakpoint.c	30 Sep 2008 23:53:41 -0000
@@ -7741,6 +7741,13 @@ breakpoint_clear_ignore_counts (void)
     b->ignore_count = 0;
 }
 
+void
+breakpoint_silence (struct breakpoint *b)
+{
+  /* Silence the breakpoint.  */
+  b->silent = 1;
+}
+
 /* Command to set ignore-count of breakpoint N to COUNT.  */
 
 static void
Index: breakpoint.h
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.h,v
retrieving revision 1.79
diff -u -p -r1.79 breakpoint.h
--- breakpoint.h	22 Sep 2008 15:26:53 -0000	1.79
+++ breakpoint.h	30 Sep 2008 23:53:41 -0000
@@ -884,4 +884,7 @@ extern int breakpoints_always_inserted_m
    in our opinion won't ever trigger.  */
 extern void breakpoint_retire_moribund (void);
 
+/* Tell a breakpoint to be quiet.  */
+extern void breakpoint_silence (struct breakpoint *);
+
 #endif /* !defined (BREAKPOINT_H) */
Index: infcmd.c
===================================================================
RCS file: /cvs/src/src/gdb/infcmd.c,v
retrieving revision 1.212
diff -u -p -r1.212 infcmd.c
--- infcmd.c	22 Sep 2008 15:20:08 -0000	1.212
+++ infcmd.c	30 Sep 2008 23:53:41 -0000
@@ -1369,6 +1369,8 @@ finish_command_continuation_free_arg (vo
 /* "finish": Set a temporary breakpoint at the place the selected
    frame will return to, then continue.  */
 
+static void finish_backwards (struct symbol *, struct thread_info *);
+
 static void
 finish_command (char *arg, int from_tty)
 {
@@ -1412,13 +1414,6 @@ finish_command (char *arg, int from_tty)
 
   clear_proceed_status ();
 
-  sal = find_pc_line (get_frame_pc (frame), 0);
-  sal.pc = get_frame_pc (frame);
-
-  breakpoint = set_momentary_breakpoint (sal, get_frame_id (frame), bp_finish);
-
-  old_chain = make_cleanup_delete_breakpoint (breakpoint);
-
   /* Find the function we will return from.  */
 
   function = find_pc_function (get_frame_pc (get_selected_frame (NULL)));
@@ -1427,10 +1422,29 @@ finish_command (char *arg, int from_tty)
      source.  */
   if (from_tty)
     {
-      printf_filtered (_("Run till exit from "));
+      if (target_get_execution_direction () == EXEC_REVERSE)
+	printf_filtered ("Run back to call of ");
+      else
+	printf_filtered ("Run till exit from ");
+
       print_stack_frame (get_selected_frame (NULL), 1, LOCATION);
     }
 
+  if (target_get_execution_direction () == EXEC_REVERSE)
+    {
+      /* Split off at this point.  */
+      finish_backwards (function, tp);
+      return;
+    }
+
+  sal = find_pc_line (get_frame_pc (frame), 0);
+  sal.pc = get_frame_pc (frame);
+
+  breakpoint = set_momentary_breakpoint (sal, get_frame_id (frame), 
+					 bp_finish);
+
+  old_chain = make_cleanup_delete_breakpoint (breakpoint);
+
   tp->proceed_to_finish = 1;	/* We want stop_registers, please...  */
   make_cleanup_restore_integer (&suppress_stop_observer);
   suppress_stop_observer = 1;
@@ -1514,6 +1528,66 @@ It stopped at a breakpoint that has sinc
 Type \"info stack\" or \"info registers\" for more information.\n"));
     }
 }
+
+static void
+finish_backwards (struct symbol *function, struct thread_info *tp)
+{
+  struct symtab_and_line sal;
+  struct breakpoint *breakpoint;
+  struct cleanup *old_chain;
+  CORE_ADDR func_addr;
+  int back_up;
+
+  if (find_pc_partial_function (get_frame_pc (get_current_frame ()),
+				NULL, &func_addr, NULL) == 0)
+    internal_error (__FILE__, __LINE__,
+		    "Finish: couldn't find function.");
+
+  sal = find_pc_line (func_addr, 0);
+
+  /* TODO: Let's not worry about async until later.  */
+
+  /* We don't need a return value.  */
+  tp->proceed_to_finish = 0;
+  /* Special case: if we're sitting at the function entry point,
+     then all we need to do is take a reverse singlestep.  We
+     don't need to set a breakpoint, and indeed it would do us
+     no good to do so.
+
+     Note that this can only happen at frame #0, since there's
+     no way that a function up the stack can have a return address
+     that's equal to its entry point.  */
+
+  if (sal.pc != read_pc ())
+    {
+      /* Set breakpoint and continue.  */
+      breakpoint =
+	set_momentary_breakpoint (sal,
+				  get_frame_id (get_selected_frame (NULL)),
+				  bp_breakpoint);
+      /* Tell the breakpoint to keep quiet.  We won't be done
+         until we've done another reverse single-step.  */
+      breakpoint_silence (breakpoint);
+      old_chain = make_cleanup_delete_breakpoint (breakpoint);
+      proceed ((CORE_ADDR) -1, TARGET_SIGNAL_DEFAULT, 0);
+      /* We will be stopped when proceed returns.  */
+      back_up = bpstat_find_breakpoint (tp->stop_bpstat, breakpoint) != NULL;
+      do_cleanups (old_chain);
+    }
+  else
+    back_up = 1;
+  if (back_up)
+    {
+      /* If in fact we hit the step-resume breakpoint (and not
+	 some other breakpoint), then we're almost there --
+	 we just need to back up by one more single-step.  */
+      /* (Kludgy way of letting wait_for_inferior know...) */
+      tp->step_range_start = tp->step_range_end = 1;
+      proceed ((CORE_ADDR) -1, TARGET_SIGNAL_DEFAULT, 1);
+    }
+  return;
+}
+
 
 static void
 environment_info (char *var, int from_tty)