Re: [C++ PATCH]: make cp_tree_equal unequivocal

[Nathan Sidwell <nathan at codesourcery dot com>]

Mark Mitchell wrote:

> Wow, this is very exciting -- lots of cruft going away.
>
> How did you get away with assuming comp_target_types never sees an
> ARRAY_TYPE?  What about something like "int (*p)[5]"?
Yes, it took me ages to satisfy myself that was safe. comp_target_types
looks like this

	if (is_pointer(t) && count > 0)
	{
	  ...
	  if (is_array (TREE_TYPE (t))
		return something else
	}
	
	if (is_an_array) {/*unreachable*/}

Then it was a small matter of proving that all entry points into the
(recursive) comp_target_types call graph had count > 0, and never had
an array.

> Also, I think this patch is a little too aggressive in cp_tree_equal:
>
> !     case COMPONENT_REF:
> !       if (TREE_OPERAND (t1, 1) != TREE_OPERAND (t2, 1))
> !       return false;
>
> I think we should continue to recur on that operand; I'm pretty sure we
> have COMPONENT_REFs and/or SCOPE_REFs with TEMPLATE_ID_EXPRs as the
> field, and better safe than sorry...
I agree, but I have not changed that behaviour. I refactored
	if (OP1(t1) == OP1(t2)) recurse
	return false;
to
	if (OP1(t1) != OP1(t2))
	  return false
	recurse

which is similar to the formatting on other cases. I will try and see if
I can find a test case where that first test should use cp_tree_equal, rather
than ==

> Thanks; this cleanup will make some of that code a lot simpler...
you bet!

nathan

--
Nathan Sidwell    ::   http://www.codesourcery.com   ::     CodeSourcery LLC
         The voices in my head said this was stupid too
nathan@codesourcery.com    ::     http://www.planetfall.pwp.blueyonder.co.uk