From: Patrick Palka <ppalka@redhat.com>
Date: Mon, 15 Dec 2025 20:03:36 +0000 (-0500)
Subject: c++: restrict TYPE_POLYMORPHIC_P to class types
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=09a9ae0dcb34ef7c57ef997f017eb5a2ddb926d4;p=thirdparty%2Fgcc.git

c++: restrict TYPE_POLYMORPHIC_P to class types

Since TYPE_POLYMORPHIC_P shares the same storage as other flags for
TYPENAME_TYPE and DECLTYPE_TYPE, we should avoid accidentally using
this accessor on those tree codes.  This patch restricts the accessor
to RECORD/UNION_TYPE which allows callers to conveniently guard any
uses with CLASS_TYPE_P.  Otherwise with the next patch applied that
rearranges TYPENAME_TYPE flags, noexcept_override_late_checks would
not skip over a TYPENAME_TYPE base for which TYPE_POLYMORPHIC_P
nonsensically returns true, leading to an eventual ICE.

gcc/cp/ChangeLog:

	* cp-tree.h (CLASSTYPE_LAMBDA_EXPR): Check CLASS_TYPE_P before
	inspecting TYPE_POLYMORPHIC_P.
	(TYPE_POLYMORPHIC_P): Restrict to RECORD_TYPE or UNION_TYPE.
	Document its use of TREE_LANG_FLAG_2.
	* parser.cc (noexcept_override_late_checks): Only
	check TYPE_POLYMORPHIC_P on CLASS_TYPE_P types.
	* rtti.cc (build_headof): Likewise.
	(get_tinfo_ptr_dynamic): Likewise.
	(build_typeid): Likewise.

Reviewed-by: Jason Merrill <jason@redhat.com>
---

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 180c0cad593..6f244a8bdfd 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -481,6 +481,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
       DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (in VAR_DECL)
       STATEMENT_LIST_TRY_BLOCK (in STATEMENT_LIST)
       TYPENAME_IS_RESOLVING_P (in TYPENAME_TYPE)
+      TYPE_POLYMORPHIC_P (in RECORD_TYPE and UNION_TYPE)
       TARGET_EXPR_DIRECT_INIT_P (in TARGET_EXPR)
       FNDECL_USED_AUTO (in FUNCTION_DECL)
       DECLTYPE_FOR_LAMBDA_PROXY (in DECLTYPE_TYPE)
@@ -2815,7 +2816,7 @@ struct GTY(()) lang_type {
 
 /* The associated LAMBDA_EXPR that made this class.  */
 #define CLASSTYPE_LAMBDA_EXPR(NODE) \
-  (TYPE_POLYMORPHIC_P (NODE)				\
+  (CLASS_TYPE_P (NODE) && TYPE_POLYMORPHIC_P (NODE)	\
    ? NULL_TREE						\
    : LANG_TYPE_CLASS_CHECK (NODE)->key_method)
 #define SET_CLASSTYPE_LAMBDA_EXPR(NODE, VALUE) \
@@ -4570,7 +4571,8 @@ get_vec_init_expr (tree t)
 
    A class that declares or inherits a virtual function is called a
    polymorphic class.  */
-#define TYPE_POLYMORPHIC_P(NODE) (TREE_LANG_FLAG_2 (NODE))
+#define TYPE_POLYMORPHIC_P(NODE) \
+  (TREE_LANG_FLAG_2 (RECORD_OR_UNION_CHECK (NODE)))
 
 /* Nonzero if this class has a virtual function table pointer.  */
 #define TYPE_CONTAINS_VPTR_P(NODE)		\
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 74c08f23188..17199e013ba 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -31060,7 +31060,7 @@ noexcept_override_late_checks (tree fndecl, tree class_type)
     {
       tree basetype = BINFO_TYPE (base_binfo);
 
-      if (!TYPE_POLYMORPHIC_P (basetype))
+      if (!CLASS_TYPE_P (basetype) || !TYPE_POLYMORPHIC_P (basetype))
 	continue;
 
       tree fn = look_for_overrides_here (basetype, fndecl);
diff --git a/gcc/cp/rtti.cc b/gcc/cp/rtti.cc
index c06a18b3ff1..1e787157b7b 100644
--- a/gcc/cp/rtti.cc
+++ b/gcc/cp/rtti.cc
@@ -166,7 +166,7 @@ build_headof (tree exp)
   gcc_assert (TYPE_PTR_P (type));
   type = TREE_TYPE (type);
 
-  if (!TYPE_POLYMORPHIC_P (type))
+  if (!CLASS_TYPE_P (type) || !TYPE_POLYMORPHIC_P (type))
     return exp;
 
   /* We use this a couple of times below, protect it.  */
@@ -280,7 +280,9 @@ get_tinfo_ptr_dynamic (tree exp, tsubst_flags_t complain)
     return error_mark_node;
 
   /* If exp is a reference to polymorphic type, get the real type_info.  */
-  if (TYPE_POLYMORPHIC_P (type) && ! resolves_to_fixed_type_p (exp, 0))
+  if (CLASS_TYPE_P (type)
+      && TYPE_POLYMORPHIC_P (type)
+      && ! resolves_to_fixed_type_p (exp, 0))
     {
       /* build reference to type_info from vtable.  */
       tree index;
@@ -353,7 +355,8 @@ build_typeid (tree exp, tsubst_flags_t complain)
   if (processing_template_decl)
     return build_min (TYPEID_EXPR, const_type_info_type_node, exp);
 
-  if (TYPE_POLYMORPHIC_P (TREE_TYPE (exp))
+  if (CLASS_TYPE_P (TREE_TYPE (exp))
+      && TYPE_POLYMORPHIC_P (TREE_TYPE (exp))
       && ! resolves_to_fixed_type_p (exp, &nonnull)
       && ! nonnull)
     {