From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 18 Dec 2025 15:41:10 +0000 (+0100)
Subject: c++: Fix up recent cp_parser_template_id regression [PR123186]
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1c555ba67a34ced2460a065eac05ae2e2693ca4d;p=thirdparty%2Fgcc.git

c++: Fix up recent cp_parser_template_id regression [PR123186]

On Fri, Dec 12, 2025 at 09:39:18AM -0500, Patrick Palka wrote:
> +      TREE_TYPE (templ)
> +     = build_typename_type (TYPE_CONTEXT (TREE_TYPE (templ)),
> +                            TYPE_NAME (TREE_TYPE (templ)),
> +                            fullname,
> +                            get_typename_type_tag (TREE_TYPE (templ)));
>        template_id = templ;
>      }
>    else

This change causes ICE e.g. on the following testcase.

The problem is that build_typename_type expects IDENTIFIER_NODE as the
second argument, e.g. it uses it as
      tree d = build_decl (input_location, TYPE_DECL, name, t);
argument.  But TYPE_NAME doesn't have to be an IDENTIFIER_NODE, it can
be a TYPE_DECL too and when we build a TYPE_DECL with TYPE_DECL as
DECL_NAME, it breaks all kinds of assumptions everywhere in the FE as well
as middle-end.

Fixed by using TYPE_IDENTIFIER instead.

2025-12-18  Jakub Jelinek  <jakub@redhat.com>

	PR c++/123186
	* parser.cc (cp_parser_template_id): Use TYPE_IDENTIFIER instead of
	TYPE_NAME in second build_typename_type argument.

	* g++.dg/template/crash133.C: New test.
---

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 18df3b1014e..521c05549f1 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -20435,7 +20435,7 @@ cp_parser_template_id (cp_parser *parser,
 				   fullname, arguments);
       TREE_TYPE (templ)
 	= build_typename_type (TYPE_CONTEXT (TREE_TYPE (templ)),
-			       TYPE_NAME (TREE_TYPE (templ)),
+			       TYPE_IDENTIFIER (TREE_TYPE (templ)),
 			       fullname,
 			       get_typename_tag (TREE_TYPE (templ)));
       template_id = templ;
diff --git a/gcc/testsuite/g++.dg/template/crash133.C b/gcc/testsuite/g++.dg/template/crash133.C
new file mode 100644
index 00000000000..9a1a6b136c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/crash133.C
@@ -0,0 +1,6 @@
+// PR c++/123186
+
+template <class T>
+struct A : T {
+  typename A <T>::template B <42> C;
+};