From: Simon Martin <simon@nasilyan.com>
Date: Sun, 18 Jan 2026 10:07:10 +0000 (+0100)
Subject: c++: don't crash determining linkage of invalid TYPE_DECL [PR122391]
X-Git-Tag: basepoints/gcc-17~1921
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e3bb887b3ee2baf118a67082c2bed2c8cc262875;p=thirdparty%2Fgcc.git

c++: don't crash determining linkage of invalid TYPE_DECL [PR122391]

We currently ICE in decl_linkage for the following invalid input
because we access the TYPE_MAIN_VARIANT of error_mark_node

===
extern "C" {
  template <a> class b;
  struct {
    typedef b:
===

This patch fixes this by returning no linkage for any TYPE_DECL with an
erroneous type.

	PR c++/122391

gcc/cp/ChangeLog:

	* tree.cc (decl_linkage): Return lk_none for TYPE_DECLs with
	erroneous type.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/bitfield10.C: New test.
---

diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index a57eefaf11f..030af4d219d 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -6440,10 +6440,13 @@ decl_linkage (tree decl)
     {
       /* But this could be a typedef name for linkage purposes, in which
 	 case we're interested in the linkage of the main decl.  */
-      if (decl == TYPE_NAME (TYPE_MAIN_VARIANT (TREE_TYPE (decl)))
-	  /* Likewise for the injected-class-name.  */
-	  || DECL_SELF_REFERENCE_P (decl))
-	decl = TYPE_MAIN_DECL (TREE_TYPE (decl));
+      tree type = TREE_TYPE (decl);
+      if (type == error_mark_node)
+	return lk_none;
+      else if (decl == TYPE_NAME (TYPE_MAIN_VARIANT (type))
+	       /* Likewise for the injected-class-name.  */
+	       || DECL_SELF_REFERENCE_P (decl))
+	decl = TYPE_MAIN_DECL (type);
       else
 	return lk_none;
     }
diff --git a/gcc/testsuite/g++.dg/parse/bitfield10.C b/gcc/testsuite/g++.dg/parse/bitfield10.C
new file mode 100644
index 00000000000..c5ab75932e7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/bitfield10.C
@@ -0,0 +1,9 @@
+/* PR c++/122391 */
+/* { dg-do "compile" } */
+
+extern "C" {
+  template <int> class b; /* { dg-error "with C linkage" } */
+  struct {
+    typedef b: /* { dg-error "at end of input" } */
+
+/* { dg-excess-errors "" } */