This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [C++1y] [PATCH 3/4] Ensure implicit template parameters have distinct canonical types.


On 22.09.2013 18:57, Adam Butcher wrote:
The following solves the canonical type issue in the general case
(pointers and refs) and makes it equivalent to the explicit template
case -- in terms of canonical type at least.

for (tree t = TREE_TYPE (TREE_VALUE (p)); t; t = TREE_CHAIN (t))
        TYPE_CANONICAL (t) = t;

The above is insufficient; the traversal doesn't handle function pointers. Currently, to get my local testcases passing, I have the following workaround that abuses find_type_usage. I intend for this to be replaced with a better solution but it will at least mean that people can start experimenting with this feature now (as they appear to be doing http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58500). This supports that testcase also.

Cheers,
Adam



Workaround implicit function template parameter canonical type issue.

* parser.c (add_implicit_template_parms): Workaround to fix up canonical type references left over from before substation of 'auto'. Better
        solution needed but this makes test cases functional.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index f3133f3..4171476 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -28987,6 +28987,25 @@ add_implicit_template_parms (cp_parser *parser, size_t expect_count,
       if (!generic_type_ptr)
        continue;

+ /* Make the canonical type of each part of the parameter distinct. + FIXME: A better solution is needed for this. Not least the abuse of + find_type_usage. Need foreach_type or similar for proper mutable + access. If something like this does turn out to be necessary then the + find_type_usage loop above can be replaced by a foreach_type that fixes
+        up the canonical types on the way to finding the 'auto'.  */
+
+      struct helper { static bool fixup_canonical_types (tree t) {
+         t = TREE_TYPE (t);
+         if (!t)
+           return false;
+         if (is_auto_or_concept (t))
+           return true;
+         TYPE_CANONICAL (t) = t;
+         return false;
+      }};
+      find_type_usage (TREE_VALUE (p), (bool (*)(const_tree))
+                      helper::fixup_canonical_types);
+
       ++synth_count;

       tree synth_id = make_generic_type_name ();


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]