[C PATCH] Make attributes accept enum values (PR c/50459)

[Marek Polacek]

On Tue, Apr 15, 2014 at 09:59:10AM -0400, Jason Merrill wrote:
> On 04/14/2014 11:10 AM, Marek Polacek wrote:
> >+  else if (TREE_CODE (val) == IDENTIFIER_NODE)
> >+    {
> >+      tree t = lookup_name (val);
> >+      if (t && TREE_CODE (t) == CONST_DECL)
> >+	return DECL_INITIAL (t);
> >+    }
> 
> I'm uncomfortable with this; we should have looked up any attributes
> in the parser.  Does the testsuite hit this code?

Thanks for looking at it.

So the newer version of the patch contains:

+      else if (TREE_CODE (val) == IDENTIFIER_NODE)
+	{
+	  tree t = lookup_name (val);
+	  if (t && TREE_CODE (t) == CONST_DECL)
+	    val = default_conversion (t);
+	}

The testsuite doesn't hit this code with C++, but does hit this code
with C.  The thing is, if we have e.g.
enum { A = 128 };
void *fn1 (void) __attribute__((assume_aligned (A)));
then handle_assume_aligned_attribute walks the attribute arguments
and gets the argument via TREE_VALUE.  If this argument is an enum
value, then for C the argument is identifier_node that contains const_decl,
but for C++ the argument is directly const_decl.  That means for C++ in
get_attrib_value we just call default_conversion as before, but for C we
call lookup_name firstly.
Does this answer your question?

	Marek