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

Michael Snyder
2001-09-17T15:39:00Z

Don Howard wrote:
>
> [This is a repost with a few nits fixed, and addressed to the correct
> list =) ]
>
> Here is an other variation on how to deal with 'commands' scripts that
> delete their own breakpoint. The patch below makes a copy of the
> commands list before executing it and deletes the copy when finished.
> Comments?

You mean other than "the concept makes my head hurt"? ;-)

Well, let's see... seems like making a copy unconditionally
is going to slow down the execution of all command lists,
for the benefit of those few that delete themselves.

Can we think of a way to make the duplication conditional
on the need? That is, on the current command list being
deleted? Put off the cost until it becomes necessary?

I can think of one method, but it would require an extra pointer
in the breakpoint struct. "execute_control_command" would set
this pointer to point to its command list, and delete_breakpoint
would check the pointer. If it's non-null, then the duplication
would be done by delete_breakpoint, and the pointer updated to
point to the duplicate.

Is it worth the effort? Is this duplication costly
compared to everything else already being done by
bpstat_do_actions? Or am I worrying over nothing?

Michael

>
> 2001-09-14 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.
> * cli/cli-script.c (dup_command_lines): New function.
> * defs.h: Added declaration of new function.
>
> 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 2001/09/17 16:30:46
> @@ -1824,7 +1824,8 @@ top:
> breakpoint_proceeded = 0;
> for (; bs != NULL; bs = bs->next)
> {
> - cmd = bs->commands;
> + cmd = dup_command_lines (bs->commands);
> +
> while (cmd != NULL)
> {
> execute_control_command (cmd);
> @@ -1834,6 +1835,9 @@ top:
> else
> cmd = cmd->next;
> }
> +
> + free_command_lines (&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.
> Index: defs.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/defs.h,v
> retrieving revision 1.63
> diff -p -u -w -r1.63 defs.h
> --- defs.h 2001/09/07 21:33:08 1.63
> +++ defs.h 2001/09/17 16:30:47
> @@ -837,6 +837,7 @@ struct command_line
> extern struct command_line *read_command_lines (char *, int);
>
> extern void free_command_lines (struct command_line **);
> +extern struct command_line * dup_command_lines (struct command_line *);
>
> /* To continue the execution commands when running gdb asynchronously.
> A continuation structure contains a pointer to a function to be called
> Index: cli/cli-script.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/cli/cli-script.c,v
> retrieving revision 1.7
> diff -p -u -w -r1.7 cli-script.c
> --- cli-script.c 2001/06/17 15:16:12 1.7
> +++ cli-script.c 2001/09/17 16:30:47
> @@ -1005,6 +1005,59 @@ read_command_lines (char *prompt_arg, in
> return (head);
> }
>
> +/* Duplicate a chain of struct command_line's */
> +
> +struct command_line *
> +dup_command_lines (struct command_line *l)
> +{
> + struct command_line *dup = NULL;
> + register struct command_line *next = NULL;
> +
> +
> + for (; l ; l = l->next)
> + {
> + if (next == NULL)
> + {
> + dup = next = (struct command_line *)
> + xmalloc (sizeof (struct command_line));
> + }
> + else
> + {
> + next->next = (struct command_line *)
> + xmalloc (sizeof (struct command_line));
> +
> + next = next->next;
> + }
> +
> +
> + if (next == NULL)
> + return NULL;
> +
> +
> + next->next = NULL;
> + next->line = xstrdup (l->line);
> + next->control_type = l->control_type;
> + next->body_count = l->body_count;
> +
> +
> + if (l->body_count > 0)
> + {
> + int i;
> + struct command_line **blist = l->body_list;
> +
> + next->body_list =
> + (struct command_line **) xmalloc (sizeof (struct command_line *)
> + * l->body_count);
> +
> + for (i = 0; i < l->body_count; i++, blist++)
> + next->body_list[i] = dup_command_lines (*blist);
> + }
> + }
> +
> + return dup;
> +}
> +
> +
> /* Free a chain of struct command_line's. */
>
> void
>
> --
> -Don
> dhoward@redhat.com
> gdb engineering