c++: Fix friend attributes [PR51344]

51344 was a problem with calling save_template_attributes twice for the same
friend function: once from do_friend and once from grokmethod.  The 2012
patch for the bug avoided creating an infinite loop when this happens, but
it's better to avoid the duplication in the first place.  This also restores
the dependent attributes to the beginning of the attribute list, as
originally intended.  And then apply_late_template_attributes can avoid
copying the non-dependent attributes.

gcc/cp/ChangeLog:

	PR c++/51344
	* decl2.c (grokfield): Call cplus_decl_attributes for friend.
	(save_template_attributes): Use chainon.
	* friend.c (do_friend): Remove attrlist parm.
	* cp-tree.h (do_friend): Adjust.
	* class.c (add_implicitly_declared_members): Adjust.
	* decl.c (grokdeclarator): Adjust.
	* pt.c (apply_late_template_attributes): Optimize.

6 files changed, 34 insertions, 43 deletions

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index d693b43..dad3849 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -3314,7 +3314,7 @@ add_implicitly_declared_members (tree t, tree* access_decls,
 	bool is_friend = DECL_CONTEXT (space) != t;
 	if (is_friend)
 	  do_friend (NULL_TREE, DECL_NAME (eq), eq,
-		     NULL_TREE, NO_SPECIAL, true);
+		     NO_SPECIAL, true);
 	else
 	  {
 	    add_method (t, eq, false);
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index d3639e3..368d9f5 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6848,7 +6848,7 @@ extern void mark_exp_read			(tree);
 extern int is_friend				(tree, tree);
 extern void make_friend_class			(tree, tree, bool);
 extern void add_friend				(tree, tree, bool);
-extern tree do_friend				(tree, tree, tree, tree,
+extern tree do_friend				(tree, tree, tree,
 						 enum overload_flags, bool);
 
 extern void set_global_friend			(tree);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index e51c1b0..d1e7337 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13758,8 +13758,7 @@ grokdeclarator (const cp_declarator *declarator,
 		  }
 
 		decl = do_friend (ctype, unqualified_id, decl,
-				  *attrlist, flags,
-				  funcdef_flag);
+				  flags, funcdef_flag);
 		return decl;
 	      }
 	    else
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index a82960f..89f874a 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -974,7 +974,11 @@ grokfield (const cp_declarator *declarator,
   if ((TREE_CODE (value) == FUNCTION_DECL
        || TREE_CODE (value) == TEMPLATE_DECL)
       && DECL_CONTEXT (value) != current_class_type)
-    return value;
+    {
+      if (attrlist)
+	cplus_decl_attributes (&value, attrlist, 0);
+      return value;
+    }
 
   /* Need to set this before push_template_decl.  */
   if (VAR_P (value))
@@ -1278,9 +1282,9 @@ save_template_attributes (tree *attr_p, tree *decl_p, int flags)
 
   tree old_attrs = *q;
 
-  /* Merge the late attributes at the beginning with the attribute
+  /* Place the late attributes at the beginning of the attribute
      list.  */
-  late_attrs = merge_attributes (late_attrs, *q);
+  late_attrs = chainon (late_attrs, *q);
   if (*q != late_attrs
       && !DECL_P (*decl_p)
       && !(flags & ATTR_FLAG_TYPE_IN_PLACE))
diff --git a/gcc/cp/friend.c b/gcc/cp/friend.c
index ee73adb..4f62884 100644
--- a/gcc/cp/friend.c
+++ b/gcc/cp/friend.c
@@ -475,7 +475,7 @@ make_friend_class (tree type, tree friend_type, bool complain)
 
 tree
 do_friend (tree ctype, tree declarator, tree decl,
-	   tree attrlist, enum overload_flags flags,
+	   enum overload_flags flags,
 	   bool funcdef_flag)
 {
   gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);
@@ -488,13 +488,6 @@ do_friend (tree ctype, tree declarator, tree decl,
     error ("friend declaration %qD may not have virt-specifiers",
 	   decl);
 
-  /* Unfortunately, we have to handle attributes here.  Normally we would
-     handle them in start_decl_1, but since this is a friend decl start_decl_1
-     never gets to see it.  */
-
-  /* Set attributes here so if duplicate decl, will have proper attributes.  */
-  cplus_decl_attributes (&decl, attrlist, 0);
-
   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
     {
       declarator = TREE_OPERAND (declarator, 0);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index fc5065b..116bdd2 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -11659,7 +11659,6 @@ static bool
 apply_late_template_attributes (tree *decl_p, tree attributes, int attr_flags,
 				tree args, tsubst_flags_t complain, tree in_decl)
 {
-  tree last_dep = NULL_TREE;
   tree t;
   tree *p;
 
@@ -11685,39 +11684,35 @@ apply_late_template_attributes (tree *decl_p, tree attributes, int attr_flags,
 	p = &TREE_CHAIN (*p);
     }
 
+  /* save_template_attributes puts the dependent attributes at the beginning of
+     the list; find the non-dependent ones.  */
   for (t = attributes; t; t = TREE_CHAIN (t))
-    if (ATTR_IS_DEPENDENT (t))
-      {
-	last_dep = t;
-	attributes = copy_list (attributes);
-	break;
-      }
+    if (!ATTR_IS_DEPENDENT (t))
+      break;
+  tree nondep = t;
 
-  *p = attributes;
-  if (last_dep)
-    {
-      tree late_attrs = NULL_TREE;
-      tree *q = &late_attrs;
+  /* Apply any non-dependent attributes.  */
+  *p = nondep;
 
-      for (; *p; )
+  /* And then any dependent ones.  */
+  tree late_attrs = NULL_TREE;
+  tree *q = &late_attrs;
+  for (t = attributes; t != nondep; t = TREE_CHAIN (t))
+    {
+      *q = tsubst_attribute (t, decl_p, args, complain, in_decl);
+      if (*q == error_mark_node)
+	return false;
+      if (*q == t)
 	{
-	  t = *p;
-	  if (ATTR_IS_DEPENDENT (t))
-	    {
-	      *q = tsubst_attribute (t, decl_p, args, complain, in_decl);
-	      if (*q == error_mark_node)
-		return false;
-	      *p = TREE_CHAIN (t);
-	      TREE_CHAIN (t) = NULL_TREE;
-	      while (*q)
-		q = &TREE_CHAIN (*q);
-	    }
-	  else
-	    p = &TREE_CHAIN (t);
+	  *q = copy_node (t);
+	  TREE_CHAIN (*q) = NULL_TREE;
 	}
-
-      cplus_decl_attributes (decl_p, late_attrs, attr_flags);
+      while (*q)
+	q = &TREE_CHAIN (*q);
     }
+
+  cplus_decl_attributes (decl_p, late_attrs, attr_flags);
+
   return true;
 }