Re: [RFA] deleting breakpoints inside of 'commands'

[Don Howard <dhoward@redhat.com>]

I've attempted to implement your sugesstion in the patch below.  I need
some feedback from folks who are familiar with the breakpoint code.  I
think it maybe as you say, that a copy of the commands list should be
allocated.  With this patch, gdb no longer dumps core when a command
list deletes it's breakpoint, but commands lists get lost after hitting
the associated breakpoint once or twice.

If someone can explain to me what gdb does with bpstat structures when
the target continues, (and how that may interact with this patch) that
would be most useful.



2001-09-12  Don Howard  <dhoward@redhat.com>

        * breakpoint.c (bpstat_do_actions): Avoid deleting a 'commands'
        list while executing that list.  Thanks to Pierre Muller
        <muller@ics.u-strasbg.fr> for suggesting this implementation.


Index: breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.52
diff -p -u -w -r1.52 breakpoint.c
--- breakpoint.c	2001/08/02 11:58:28	1.52
+++ breakpoint.c	2001/09/13 20:16:18
@@ -1824,7 +1824,24 @@ top:
   breakpoint_proceeded = 0;
   for (; bs != NULL; bs = bs->next)
     {
-      cmd = bs->commands;
+      /* It is possible that the list of commands we are executing
+         includes a command to delete the current breakpoint, which
+         will also delete the current command list (oops!).
+
+         Pierre Muller <muller at cerbere dot u-strasbg dot fr>
+         suggested that the commands list could be disconnected from
+         it's associated breakpoint structure during execution of the
+         list.  Once execution is complete, we check for the
+         non-existence of the breakpoint. If the breakpoint has been
+         deleted, we free the associated command list. */
+
+      struct command_line *head_cmd;
+
+      head_cmd = cmd = bs->commands;
+      bs->commands = NULL;
+      if (bs->breakpoint_at)
+        bs->breakpoint_at->commands = NULL;
+
       while (cmd != NULL)
 	{
 	  execute_control_command (cmd);
@@ -1834,6 +1851,31 @@ top:
 	  else
 	    cmd = cmd->next;
 	}
+
+      /* Detect if the command list has deleted the current
+         breakpoint. */
+      {
+        int deleted = 1;
+        struct breakpoint *b;
+
+        ALL_BREAKPOINTS (b)
+	  if (bs->breakpoint_at == b)
+	    {
+	      deleted = 0;
+	      break;
+	    }
+
+        if (deleted)
+          free_command_lines (&head_cmd);
+        else
+          {
+            bs->commands = head_cmd;
+            if (bs->breakpoint_at)
+              bs->breakpoint_at->commands = head_cmd;
+          }
+      }
+
+
       if (breakpoint_proceeded)
 	/* The inferior is proceeded by the command; bomb out now.
 	   The bpstat chain has been blown away by wait_for_inferior.


-- 
-Don
dhoward@redhat.com
gdb engineering