Re: [PATCH 3/3 v2] Implement completion limiting

[Doug Evans <xdje42@gmail.com>]

Gary Benson <gbenson@redhat.com> writes:
> This commit adds a new exception, TOO_MANY_COMPLETIONS_ERROR, to be
> thrown whenever the completer has generated too many possibilities to
> be useful.  A new user-settable variable, "max_completions", is added
> to control this behaviour.  A top-level completion limit is added to
> complete_line_internal, as the final check to ensure the user never
> sees too many completions.  An additional limit is added to
> default_make_symbol_completion_list_break_on, to halt time-consuming
> symbol table expansions.
>
> gdb/ChangeLog:
>
> 	PR cli/9007
> 	PR cli/11920
> 	PR cli/15548
> 	* common/common-exceptions.h (enum errors)
> 	<TOO_MANY_COMPLETIONS_ERROR>: New value.
> 	* completer.h (completion_tracker_t): New typedef.
> 	(new_completion_tracker): New declaration.
> 	(make_cleanup_free_completion_tracker): Likewise.
> 	(maybe_limit_completions): Likewise.
> 	* completer.c [TUI]: Include tui/tui.h and tui/tui-io.h.
> 	(max_completions): New static variable.
> 	(new_completion_tracker): New function.
> 	(make_cleanup_free_completion_tracker): Likewise.
> 	(maybe_limit_completions): Likewise.
> 	(complete_line_internal): Do not generate any completions if
> 	max_completions = 0.  Limit the number of completions if
> 	max_completions >= 0.
> 	(line_completion_function): Handle TOO_MANY_COMPLETIONS_ERROR.
> 	(_initialize_completer): New declaration and function.
> 	* symtab.c: Include completer.h.
> 	(completion_tracker): New static variable.
> 	(completion_list_add_name): Call maybe_limit_completions.
> 	(default_make_symbol_completion_list_break_on): Maintain
> 	completion_tracker across calls to completion_list_add_name.
> 	* NEWS (New Options): Mention set/show max-completions.

Hi.

I only skimmed this patch set.
I want to give it a more thorough look
once the patch has been updated to apply
to current HEAD.

Thanks very much for working on this!

> +void
> +maybe_limit_completions (completion_tracker_t tracker, char *name)
> +{
> +  if (max_completions < 0)
> +    return;
> +
> +  if (tracker != NULL)
> +    {
> +      void **slot = htab_find_slot (tracker, name, INSERT);
> +
> +      if (*slot != HTAB_EMPTY_ENTRY)
> +	return;
> +
> +      if (htab_elements (tracker) <= max_completions)
> +	{
> +	  *slot = name;
> +	  return;
> +	}
> +    }
> +
> +  throw_error (TOO_MANY_COMPLETIONS_ERROR,
> +	       _("Too many possibilities."));
> +}

This will throw an error if tracker == NULL.
Is that intended?