c++: Fix up handling of dependent (late) attributes on function/method types [PR116175]

When working on unsequenced/reproducible attributes, I've noticed that on
templates for some attributes decl_attributes isn't called at all, so they
are kept in TYPE_ATTRIBUTES without any verification/transformations and
also without argument substitution.

The following patch fixes that for FUNCTION/METHOD_TYPE attributes.
The included testcase ICEs without the pt.cc changes.

2024-08-07  Jakub Jelinek  <jakub@redhat.com>

	PR c++/116175
	* pt.cc (apply_late_template_attributes): For function/method types
	call cp_build_type_attribute_variant on the non-dependent attributes.
	(rebuild_function_or_method_type): Add ARGS argument.  Use
	apply_late_template_attributes rather than
	cp_build_type_attribute_variant.
	(maybe_rebuild_function_decl_type): Add ARGS argument, pass it to
	rebuild_function_or_method_type.
	(tsubst_function_decl): Adjust caller.
	(tsubst_function_type): Adjust rebuild_function_or_method_type caller.

	* g++.dg/ext/attr-format4.C: New test.

2 files changed, 28 insertions, 8 deletions

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 2db5921..542962b 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -12201,6 +12201,8 @@ apply_late_template_attributes (tree *decl_p, tree attributes, int attr_flags,
          to our attributes parameter.  */
       gcc_assert (*p == attributes);
     }
+  else if (FUNC_OR_METHOD_TYPE_P (*decl_p))
+    p = NULL;
   else
     {
       p = &TYPE_ATTRIBUTES (*decl_p);
@@ -12219,7 +12221,10 @@ apply_late_template_attributes (tree *decl_p, tree attributes, int attr_flags,
   tree nondep = t;
 
   /* Apply any non-dependent attributes.  */
-  *p = nondep;
+  if (p)
+    *p = nondep;
+  else if (nondep)
+    *decl_p = cp_build_type_attribute_variant (*decl_p, nondep);
 
   if (nondep == attributes)
     return true;
@@ -14377,8 +14382,9 @@ lookup_explicit_specifier (tree v)
    identical to T.  */
 
 static tree
-rebuild_function_or_method_type (tree t, tree return_type, tree arg_types,
-				 tree raises, tsubst_flags_t complain)
+rebuild_function_or_method_type (tree t, tree args, tree return_type,
+				 tree arg_types, tree raises,
+				 tsubst_flags_t complain)
 {
   gcc_assert (FUNC_OR_METHOD_TYPE_P (t));
 
@@ -14411,7 +14417,9 @@ rebuild_function_or_method_type (tree t, tree return_type, tree arg_types,
       new_type = build_method_type_directly (r, return_type,
 					     TREE_CHAIN (arg_types));
     }
-  new_type = cp_build_type_attribute_variant (new_type, TYPE_ATTRIBUTES (t));
+  if (!apply_late_template_attributes (&new_type, TYPE_ATTRIBUTES (t), 0,
+				       args, complain, NULL_TREE))
+    return error_mark_node;
 
   cp_ref_qualifier rqual = type_memfn_rqual (t);
   bool late_return_type_p = TYPE_HAS_LATE_RETURN_TYPE (t);
@@ -14424,7 +14432,7 @@ rebuild_function_or_method_type (tree t, tree return_type, tree arg_types,
    resolution for Core issues 1001/1322.  */
 
 static void
-maybe_rebuild_function_decl_type (tree decl)
+maybe_rebuild_function_decl_type (tree decl, tree args)
 {
   bool function_type_needs_rebuilding = false;
   if (tree parm_list = FUNCTION_FIRST_USER_PARM (decl))
@@ -14476,7 +14484,7 @@ maybe_rebuild_function_decl_type (tree decl)
     *q = void_list_node;
 
   TREE_TYPE (decl)
-    = rebuild_function_or_method_type (fntype,
+    = rebuild_function_or_method_type (fntype, args,
 				       TREE_TYPE (fntype), new_parm_type_list,
 				       TYPE_RAISES_EXCEPTIONS (fntype), tf_none);
 }
@@ -14659,7 +14667,7 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
   DECL_ARGUMENTS (r) = parms;
   DECL_RESULT (r) = NULL_TREE;
 
-  maybe_rebuild_function_decl_type (r);
+  maybe_rebuild_function_decl_type (r, args);
 
   TREE_STATIC (r) = 0;
   TREE_PUBLIC (r) = TREE_PUBLIC (t);
@@ -15927,7 +15935,7 @@ tsubst_function_type (tree t,
     }
 
   /* Construct a new type node and return it.  */
-  return rebuild_function_or_method_type (t, return_type, arg_types,
+  return rebuild_function_or_method_type (t, args, return_type, arg_types,
 					  /*raises=*/NULL_TREE, complain);
 }
 
diff --git a/gcc/testsuite/g++.dg/ext/attr-format4.C b/gcc/testsuite/g++.dg/ext/attr-format4.C
new file mode 100644
index 0000000..29d39ba
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attr-format4.C
@@ -0,0 +1,12 @@
+// PR c++/116175
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wformat" }
+
+template <typename ...T>
+int foo (T ...args, const char *fmt, ...)
+[[gnu::format (printf, 1 + sizeof... (T), 2 + sizeof... (T))]];
+
+int a = foo <> ("%d", 1);
+int b = foo <int, int, int, int, int> (1, 2, 3, 4, 5, "%d", 1);
+int c = foo <> ("%f", 1);	// { dg-warning "format '%f' expects argument of type 'double', but argument 2 has type 'int'" }
+int d = foo <int, int, int, int, int> (1, 2, 3, 4, 5, "%f", 1);	// { dg-warning "format '%f' expects argument of type 'double', but argument 7 has type 'int'" }