c++: Relax attribute on friend declaration checking [PR100596]

It turned out that there are codebases that profusely use GNU attributes
on friend declarations, so we have to dial back our checking and allow
them.  And for C++11 attributes let's just warn instead of giving
errors.

	PR c++/100596

gcc/cp/ChangeLog:

	* cp-tree.h (any_non_type_attribute_p): Remove.
	* decl.c (grokdeclarator): Turn an error into a warning and only
	warn for standard attributes.
	* decl2.c (any_non_type_attribute_p): Remove.
	* parser.c (cp_parser_elaborated_type_specifier): Turn an error
	into a warning and only warn for standard attributes.
	(cp_parser_member_declaration): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/friend7.C: Turn a few dg-warnings into dg-errors.
	Remove dg-errors for GNU attributes.
	* g++.dg/ext/attrib63.C: Remove dg-error.
	* g++.dg/cpp0x/friend8.C: New test.

4 files changed, 28 insertions, 30 deletions

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 3c900dc..860ed79 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6761,7 +6761,6 @@ extern tree grokbitfield (const cp_declarator *, cp_decl_specifier_seq *,
 			  tree, tree, tree);
 extern tree splice_template_attributes		(tree *, tree);
 extern bool any_dependent_type_attributes_p	(tree);
-extern bool any_non_type_attribute_p		(tree);
 extern tree cp_reconstruct_complex_type		(tree, tree);
 extern bool attributes_naming_typedef_ok	(tree);
 extern void cplus_decl_attributes		(tree *, tree, int);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 4f2fc2e..28052df 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13731,11 +13731,15 @@ grokdeclarator (const cp_declarator *declarator,
 
 	if (friendp)
 	  {
-	    if (attrlist && !funcdef_flag
-		/* Hack to allow attributes like vector_size on a friend.  */
-		&& any_non_type_attribute_p (*attrlist))
-	      error_at (id_loc, "attribute appertains to a friend "
-			"declaration that is not a definition");
+	    /* Packages tend to use GNU attributes on friends, so we only
+	       warn for standard attributes.  */
+	    if (attrlist && !funcdef_flag && cxx11_attribute_p (*attrlist))
+	      {
+		*attrlist = NULL_TREE;
+		if (warning_at (id_loc, OPT_Wattributes, "attribute ignored"))
+		  inform (id_loc, "an attribute that appertains to a friend "
+			  "declaration that is not a definition is ignored");
+	      }
 	    /* Friends are treated specially.  */
 	    if (ctype == current_class_type)
 	      ;  /* We already issued a permerror.  */
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 8e4dd6b..89f874a 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -1331,20 +1331,6 @@ any_dependent_type_attributes_p (tree attrs)
   return false;
 }
 
-/* True if ATTRS contains any attribute that does not require a type.  */
-
-bool
-any_non_type_attribute_p (tree attrs)
-{
-  for (tree a = attrs; a; a = TREE_CHAIN (a))
-    {
-      const attribute_spec *as = lookup_attribute_spec (get_attribute_name (a));
-      if (as && !as->type_required)
-	return true;
-    }
-  return false;
-}
-
 /* Return true iff ATTRS are acceptable attributes to be applied in-place
    to a typedef which gives a previously unnamed class or enum a name for
    linkage purposes.  */
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index f3503b1..bc0505d 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -19774,9 +19774,12 @@ cp_parser_elaborated_type_specifier (cp_parser* parser,
 	       && ! processing_explicit_instantiation)
 	warning (OPT_Wattributes,
 		 "attributes ignored on template instantiation");
-      else if (is_friend && attributes)
-	error ("attribute appertains to a friend declaration that is not "
-	       "a definition");
+      else if (is_friend && cxx11_attribute_p (attributes))
+	{
+	  if (warning (OPT_Wattributes, "attribute ignored"))
+	    inform (input_location, "an attribute that appertains to a friend "
+		    "declaration that is not a definition is ignored");
+	}
       else if (is_declaration && cp_parser_declares_only_class_p (parser))
 	cplus_decl_attributes (&type, attributes, (int) ATTR_FLAG_TYPE_IN_PLACE);
       else
@@ -26064,17 +26067,23 @@ cp_parser_member_declaration (cp_parser* parser)
 		   if (type && TREE_CODE (type) == TYPE_DECL)
 		     type = TREE_TYPE (type);
 		 }
+	       /* Warn if an attribute cannot appear here, as per
+		  [dcl.attr.grammar]/5.  But not when declares_class_or_enum:
+		  we ignore attributes in elaborated-type-specifiers.  */
+	       if (!declares_class_or_enum
+		   && cxx11_attribute_p (decl_specifiers.attributes))
+		 {
+		   decl_specifiers.attributes = NULL_TREE;
+		   if (warning_at (decl_spec_token_start->location,
+				   OPT_Wattributes, "attribute ignored"))
+		     inform (decl_spec_token_start->location, "an attribute "
+			     "that appertains to a friend declaration that "
+			     "is not a definition is ignored");
+		 }
 	       if (!type || !TYPE_P (type))
 		 error_at (decl_spec_token_start->location,
 			   "friend declaration does not name a class or "
 			   "function");
-	       /* Give an error if an attribute cannot appear here, as per
-		  [dcl.attr.grammar]/5.  But not when declares_class_or_enum:
-		  we ignore attributes in elaborated-type-specifiers.  */
-	       else if (!declares_class_or_enum && decl_specifiers.attributes)
-		 error_at (decl_spec_token_start->location,
-			   "attribute appertains to a friend declaration "
-			   "that is not a definition");
 	       else
 		 make_friend_class (current_class_type, type,
 				    /*complain=*/true);