From: Jason Merrill <jason@redhat.com>
Date: Wed, 1 Jul 2026 15:49:39 +0000 (-0400)
Subject: c++: naming typedef and incomplete class [PR126031]
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b6825a7ce698b65657e952e437ab9edd655fe5a5;p=thirdparty%2Fgcc.git

c++: naming typedef and incomplete class [PR126031]

We can't look at the bases and members of a forward-declared nested class,
and such a forward declaration can't contain problematic constructs, so
treat it as OK.

	PR c++/126031
	PR c++/121552

gcc/cp/ChangeLog:

	* decl.cc (maybe_diagnose_non_c_class_typedef_for_linkage): Handle
	incomplete type.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/typedef2.C: New test.
---

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 79247302608..a2233107317 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -13775,6 +13775,8 @@ diagnose_non_c_class_typedef_for_linkage (tree type, tree orig)
 static bool
 maybe_diagnose_non_c_class_typedef_for_linkage (tree type, tree orig, tree t)
 {
+  if (!COMPLETE_TYPE_P (t))
+    return false;
   if (!BINFO_BASE_BINFOS (TYPE_BINFO (t))->is_empty ())
     {
       auto_diagnostic_group d;
diff --git a/gcc/testsuite/g++.dg/cpp2a/typedef2.C b/gcc/testsuite/g++.dg/cpp2a/typedef2.C
new file mode 100644
index 00000000000..e4a8195ce18
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/typedef2.C
@@ -0,0 +1,5 @@
+// PR c++/126031
+
+typedef struct {
+  struct S;
+} s;