From: Jakub Jelinek <jakub@redhat.com>
Date: Sat, 6 Dec 2025 10:07:18 +0000 (+0100)
Subject: c++: is_late_template_attribute and tsubst_attribute fixes
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3b7e865779d03b4d29375a3c28dfaa2172eced4a;p=thirdparty%2Fgcc.git

c++: is_late_template_attribute and tsubst_attribute fixes

This has been discussed in the 1/9 Reflection thread, but doesn't depend on
reglection in any way.
cp_parser_std_attribute calls lookup_attribute_spec as:
    const attribute_spec *as
      = lookup_attribute_spec (TREE_PURPOSE (attribute));
so with TREE_LIST where TREE_VALUE is attribute name and TREE_PURPOSE
attribute ns.  Similarly c_parser_std_attribute.  And for
attribute_takes_identifier_p those do:
    else if (attr_ns == gnu_identifier
             && attribute_takes_identifier_p (attr_id))
and
        bool takes_identifier
          = (ns != NULL_TREE
             && strcmp (IDENTIFIER_POINTER (ns), "gnu") == 0
             && attribute_takes_identifier_p (name));
when handling std attributes (for GNU attributes they just call those
with the IDENTIFIER_NODE name.
is_late_template_attribute and tsubst_attribute pass to these functions
just get_attribute_name though, so handle attributes in all namespaces
as GNU attributes only, which means that lookup_attribute_spec can
return NULL or find a different attribute if it is not from gnu:: or
say standard attribute mapped to gnu::, or attribute_takes_identifier_p
can return true even for attributes for which it shouldn't.

I thought about changing attribute_takes_identifier_p to take optionally
TREE_LIST, but that would mean handling it in the target hooks too and
they only care about GNU attributes right now, so given the above
parser.cc/c-parser.cc snippets, the following patch just follow
what they do.

2025-12-06  Jakub Jelinek  <jakub@redhat.com>

	* decl2.cc (is_late_template_attribute): Call lookup_attribute_spec
	on TREE_PURPOSE (attr) rather than name.  Only call
	attribute_takes_identifier_p if get_attribute_namespace (attr) is
	gnu_identifier.
	* pt.cc (tsubst_attribute): Only call attribute_takes_identifier_p
	if get_attribute_namespace (t) is gnu_identifier.
---

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 9e135af41b3..8ec9740c8a9 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -1468,7 +1468,8 @@ is_late_template_attribute (tree attr, tree decl)
 {
   tree name = get_attribute_name (attr);
   tree args = TREE_VALUE (attr);
-  const struct attribute_spec *spec = lookup_attribute_spec (name);
+  const struct attribute_spec *spec
+    = lookup_attribute_spec (TREE_PURPOSE (attr));
   tree arg;
 
   if (!spec)
@@ -1512,7 +1513,9 @@ is_late_template_attribute (tree attr, tree decl)
 	 second and following arguments.  Attributes like mode, format,
 	 cleanup and several target specific attributes aren't late
 	 just because they have an IDENTIFIER_NODE as first argument.  */
-      if (arg == args && attribute_takes_identifier_p (name)
+      if (arg == args
+	  && get_attribute_namespace (attr) == gnu_identifier
+	  && attribute_takes_identifier_p (name)
 	  && identifier_p (t))
 	continue;
 
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 7a019d33bda..8498730b6e4 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -12386,7 +12386,8 @@ tsubst_attribute (tree t, tree *decl_p, tree args,
      pass it through tsubst.  Attributes like mode, format,
      cleanup and several target specific attributes expect it
      unmodified.  */
-  else if (attribute_takes_identifier_p (get_attribute_name (t)))
+  else if (get_attribute_namespace (t) == gnu_identifier
+	   && attribute_takes_identifier_p (get_attribute_name (t)))
     {
       tree chain
 	= tsubst_expr (TREE_CHAIN (val), args, complain, in_decl);