https://github.com/matthew-j-code updated 
https://github.com/llvm/llvm-project/pull/220864

>From fc53318a34d9dfceb79dc2b054b7a0754cecd061 Mon Sep 17 00:00:00 2001
From: "Jones, Matthew (DI SW SIM FRWK PLAT SIMFW HPC)"
 <[email protected]>
Date: Tue, 11 Aug 2026 03:13:24 -0700
Subject: [PATCH 1/4] [CodeGen] Added '*' to internal linkage types

RTTI typename for internal-linkage types lacked '*', which broke
type_info::operator== and dynamic_cast with libstdc++

Fixes #34255
---
 clang/docs/ReleaseNotes.md                    |  2 +
 clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp | 20 ++++++--
 clang/lib/CodeGen/ItaniumCXXABI.cpp           | 23 ++++++---
 .../CIR-internal-linkage-typeinfo-name.cpp    | 51 +++++++++++++++++++
 clang/test/CIR/CodeGenCXX/vtable-linkage.cpp  | 12 ++---
 .../internal-linkage-typeinfo-name.cpp        | 51 +++++++++++++++++++
 6 files changed, 142 insertions(+), 17 deletions(-)
 create mode 100644 
clang/test/CIR/CodeGen/CIR-internal-linkage-typeinfo-name.cpp
 create mode 100644 clang/test/CodeGenCXX/internal-linkage-typeinfo-name.cpp

diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index a49971adef86ff..fdbb12e653da5a 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -511,6 +511,8 @@ features cannot lower the translation-unit ABI level;
 - Fixed a crash when declaring a member template within a local class inside 
an OpenMP region. (#GH216052)
 - Fixed a bug where repeated #imports of modular headers in non-modular 
compilation were translated to #pragma clang module import. (#GH216924)
 - Fixed an assertion when `#pragma omp declare simd` or `#pragma omp declare 
variant` is followed by another OpenMP declarative directive containing a 
qualified identifier. (#GH217204)
+- Fixed RTTI name for internal-linkage types lacking '*', fixed breaking 
type_info::operator== and
+dynamic_cast with libstdc++ (#GH34255)
 
 #### Bug Fixes to Compiler Builtins
 
diff --git a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp 
b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
index 800f20ace0e703..2caabd9292db0e 100644
--- a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
@@ -1166,12 +1166,20 @@ 
CIRGenItaniumRTTIBuilder::getAddrOfTypeName(mlir::Location loc, QualType ty,
   llvm::raw_svector_ostream out(name);
   cgm.getCXXABI().getMangleContext().mangleCXXRTTIName(ty, out);
 
-  // We know that the mangled name of the type starts at index 4 of the
-  // mangled name of the typename, so we can just index into it in order to
-  // get the mangled name of the type.
+  // RTTI type-name symbol has form "_ZTS<mangled-string>". The string stored 
in
+  // type_info object excludes the "_ZTS" prefix. So we skip past the first 4
+  // characters. For types that do not have externally visible Clang/C++
+  // linkage, '*' is prepended to the type-name string so that within libstdc++
+  // RTTI names compare correctly via strcmp across translation units. LLVM
+  // internal linkage marks incomplete types as internal linkage, resulting in
+  // '*' being prepended incorrectly, thus Clang/C++ linkage is used, through
+  // isExternallyVisible.
+  SmallString<256> typeName;
+  if (!isExternallyVisible(ty->getLinkage()))
+    typeName += '*';
+  typeName += StringRef(name).substr(4);
   mlir::Attribute init = builder.getString(
-      name.substr(4), cgm.convertType(cgm.getASTContext().CharTy),
-      std::nullopt);
+      typeName, cgm.convertType(cgm.getASTContext().CharTy), std::nullopt);
 
   CharUnits align =
       cgm.getASTContext().getTypeAlignInChars(cgm.getASTContext().CharTy);
@@ -1181,6 +1189,8 @@ 
CIRGenItaniumRTTIBuilder::getAddrOfTypeName(mlir::Location loc, QualType ty,
   // So cast Init to a ConstArrayAttr should be safe.
   auto initStr = cast<cir::ConstArrayAttr>(init);
 
+  // RTTI type-name object is still emitted with prefix "_ZTS" in the symbol
+  // name, so that it can be found by the linker.
   cir::GlobalOp gv = cgm.createOrReplaceCXXRuntimeVariable(
       loc, name, initStr.getType(), linkage, align);
   CIRGenModule::setInitializer(gv, init);
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp 
b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index c17813140b10f7..87a643c6412de3 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -3656,22 +3656,33 @@ llvm::GlobalVariable 
*ItaniumRTTIBuilder::GetAddrOfTypeName(
   llvm::raw_svector_ostream Out(Name);
   CGM.getCXXABI().getMangleContext().mangleCXXRTTIName(Ty, Out);
 
-  // We know that the mangled name of the type starts at index 4 of the
-  // mangled name of the typename, so we can just index into it in order to
-  // get the mangled name of the type.
+  // RTTI type-name symbol has form "_ZTS<mangled-string>". The string stored 
in
+  // type_info object excludes the "_ZTS" prefix. So we skip past the first 4
+  // characters. For types that do not have externally visible Clang/C++
+  // linkage, '*' is prepended to the type-name string so that within libstdc++
+  // RTTI names compare correctly via strcmp across translation units. LLVM
+  // internal linkage marks incomplete types as internal linkage, resulting in
+  // '*' being prepended incorrectly, thus Clang/C++ linkage is used, through
+  // isExternal
+  SmallString<256> TypeName;
+  if (!isExternallyVisible(Ty->getLinkage()))
+    TypeName += '*';
+  TypeName += StringRef(Name).substr(4);
   llvm::Constant *Init;
   if (CGM.getTriple().isOSzOS()) {
     // On z/OS, typename is stored as 2 encodings: EBCDIC followed by ASCII.
     SmallString<256> DualEncodedName;
-    llvm::ConverterEBCDIC::convertToEBCDIC(Name.substr(4), DualEncodedName);
+    llvm::ConverterEBCDIC::convertToEBCDIC(TypeName, DualEncodedName);
     DualEncodedName += '\0';
-    DualEncodedName += Name.substr(4);
+    DualEncodedName += TypeName;
     Init = llvm::ConstantDataArray::getString(VMContext, DualEncodedName);
   } else
-    Init = llvm::ConstantDataArray::getString(VMContext, Name.substr(4));
+    Init = llvm::ConstantDataArray::getString(VMContext, TypeName);
 
   auto Align = CGM.getContext().getTypeAlignInChars(CGM.getContext().CharTy);
 
+  // RTTI type-name object is still emitted with prefix "_ZTS" in the symbol
+  // name, so that it can be found by the linker.
   llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
       Name, Init->getType(), Linkage, Align.getAsAlign());
 
diff --git a/clang/test/CIR/CodeGen/CIR-internal-linkage-typeinfo-name.cpp 
b/clang/test/CIR/CodeGen/CIR-internal-linkage-typeinfo-name.cpp
new file mode 100644
index 00000000000000..3a43ea283ab153
--- /dev/null
+++ b/clang/test/CIR/CodeGen/CIR-internal-linkage-typeinfo-name.cpp
@@ -0,0 +1,51 @@
+//RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++11 -fclangir 
-emit-cir -o - %s | FileCheck %s
+
+// Check that RTTI type-name strings use a leading '*' for types that do not 
have externally visible Clang/C++ linkage,
+// and for it to be omitted from externally visible types.
+
+namespace std { class type_info; }
+
+//The following types have internal linkage, so their typeinfo names should 
have a leading '*'
+namespace { struct A {}; }
+const std::type_info &t1() { return typeid(A); }
+
+const std::type_info &t2() { struct L {}; return typeid(L); }
+
+const std::type_info &t3() { return typeid(A*); }
+
+template <class T> struct B {};
+const std::type_info &t4() { return typeid(B<A>); }
+
+namespace { struct C { int x; }; }
+const std::type_info &t5() { return typeid(int A::*); }
+
+//Following should not have a '*' prefix in the typeinfo name, since they have 
external linkage
+struct Ext {};
+
+const std::type_info &t6() { return typeid(Ext); }
+
+const std::type_info &t7() { return typeid(Ext*); }
+
+namespace NS2 { struct D {}; }
+
+const std::type_info &t8() { return typeid(NS2::D); }
+
+struct Fwd;
+const std::type_info &t9() { return typeid(Fwd*); }
+
+// The following checks emitted RTTI type-names. The global name is the 
ABI-mangled type-name object, 
+// while the string constant is the mangled type-name itself. For types 
without externally visible linkage,
+// Clang emits these as 'internal'. {{.*}} matches for array sizes, which is 
irrelevant to this test.
+
+// These checks are for types with internal linkage, which should have a '*' 
prefix in the typeinfo name.
+//CHECK-DAG: cir.global{{.*}}internal{{.*}}@_ZTSN12_GLOBAL__N_11AE = 
#cir.const_array<"*N12_GLOBAL__N_11AE"{{.*}}>
+//CHECK-DAG: cir.global{{.*}}internal{{.*}}@_ZTSZ2t2vE1L = 
#cir.const_array<"*Z2t2vE1L"{{.*}}>
+//CHECK-DAG: cir.global{{.*}}internal{{.*}}@_ZTSPN12_GLOBAL__N_11AE = 
#cir.const_array<"*PN12_GLOBAL__N_11AE"{{.*}}>
+//CHECK-DAG: cir.global{{.*}}internal{{.*}}@_ZTS1BIN12_GLOBAL__N_11AEE = 
#cir.const_array<"*1BIN12_GLOBAL__N_11AEE"{{.*}}>
+//CHECK-DAG: cir.global{{.*}}internal{{.*}}@_ZTSMN12_GLOBAL__N_11AEi = 
#cir.const_array<"*MN12_GLOBAL__N_11AEi"{{.*}}>
+
+// These checks are for types with external linkage, which should not have a 
'*' prefix in the typeinfo name.
+//CHECK-DAG: cir.global{{.*}}@_ZTS3Ext = #cir.const_array<"3Ext"{{.*}}>
+//CHECK-DAG: cir.global{{.*}}@_ZTSP3Ext = #cir.const_array<"P3Ext"{{.*}}>
+//CHECK-DAG: cir.global{{.*}}@_ZTSN3NS21DE = #cir.const_array<"N3NS21DE"{{.*}}>
+//CHECK-DAG: cir.global{{.*}}@_ZTSP3Fwd = #cir.const_array<"P3Fwd"{{.*}}>
\ No newline at end of file
diff --git a/clang/test/CIR/CodeGenCXX/vtable-linkage.cpp 
b/clang/test/CIR/CodeGenCXX/vtable-linkage.cpp
index 54f6f9c54a69c0..7bdb13252cfc2c 100644
--- a/clang/test/CIR/CodeGenCXX/vtable-linkage.cpp
+++ b/clang/test/CIR/CodeGenCXX/vtable-linkage.cpp
@@ -197,19 +197,19 @@ void use_F() {
 // The anonymous struct for e has no linkage, so the vtable should have
 // internal linkage.
 // CIR-DAG: cir.global "private" constant internal dso_local @_ZTV3$_0 = 
#cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, 
#cir.global_view<@_ZTI3$_0> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1D1fEv> : 
!cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 3>}> : !{{.*}}{alignment = 8 : 
i64}
-// CIR-DAG: cir.global constant internal dso_local @_ZTS3$_0 = 
#cir.const_array<"3$_0" : !cir.array<!s8i x 4>, trailing_zeros> : 
!cir.array<!s8i x 5> {alignment = 1 : i64}
+// CIR-DAG: cir.global constant internal dso_local @_ZTS3$_0 = 
#cir.const_array<"*3$_0" : !cir.array<!s8i x 5>, trailing_zeros> : 
!cir.array<!s8i x 6> {alignment = 1 : i64}
 // CIR-DAG: cir.global constant internal @_ZTI3$_0 = 
#cir.typeinfo<{#cir.global_view<@_ZTVN10__cxxabiv120__si_class_type_infoE, [2 : 
i32]> : !cir.ptr<!u8i>, #cir.global_view<@_ZTS3$_0> : !cir.ptr<!u8i>, 
#cir.global_view<@_ZTI1D> : !cir.ptr<!u8i>}> : !{{.*}}{alignment = 8 : i64}
-// LLVM-DAG: @"_ZTV3$_0" = internal constant { [3 x ptr] } { [3 x ptr] [ptr 
null, ptr @"_ZTI3$_0", ptr @_ZN1D1fEv] }, align 8
-// LLVM-DAG: @"_ZTS3$_0" = internal constant [5 x i8] c"3$_0\00", align 1
+// LLVM-DAG: @"_ZTV3$_0" = internal constant {{.*}}{ [3 x ptr] } { [3 x ptr] 
[ptr null, ptr @"_ZTI3$_0", ptr @_ZN1D1fEv] }, align 8
+// LLVM-DAG: @"_ZTS3$_0" = internal constant {{.*}}[6 x i8] c"*3$_0\00", align 
1
 // LLVM-DAG: @"_ZTI3$_0" = internal constant { ptr, ptr, ptr } { ptr 
getelementptr {{.*}}({{.*}}, ptr @_ZTVN10__cxxabiv120__si_class_type_infoE, i64 
{{.*}}), ptr @"_ZTS3$_0", ptr @_ZTI1D }, align 8
 
 // The A vtable should have internal linkage since it is inside an anonymous 
 // namespace.
 // CIR-DAG: cir.global "private" constant internal dso_local 
@_ZTVN12_GLOBAL__N_11AE = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : 
!cir.ptr<!u8i>, #cir.global_view<@_ZTIN12_GLOBAL__N_11AE> : !cir.ptr<!u8i>, 
#cir.global_view<@_ZN12_GLOBAL__N_11A1fEv> : !cir.ptr<!u8i>]> : 
!cir.array<!cir.ptr<!u8i> x 3>}> : !{{.*}}{alignment = 8 : i64}
-// CIR-DAG: cir.global constant internal dso_local @_ZTSN12_GLOBAL__N_11AE = 
#cir.const_array<"N12_GLOBAL__N_11AE" : !cir.array<!s8i x 18>, trailing_zeros> 
: !cir.array<!s8i x 19> {alignment = 1 : i64}
+// CIR-DAG: cir.global constant internal dso_local @_ZTSN12_GLOBAL__N_11AE = 
#cir.const_array<"*N12_GLOBAL__N_11AE" : !cir.array<!s8i x 19>, trailing_zeros> 
: !cir.array<!s8i x 20> {alignment = 1 : i64}
 // CIR-DAG: cir.global constant internal @_ZTIN12_GLOBAL__N_11AE = 
#cir.typeinfo<{#cir.global_view<@_ZTVN10__cxxabiv117__class_type_infoE, [2 : 
i32]> : !cir.ptr<!u8i>, #cir.global_view<@_ZTSN12_GLOBAL__N_11AE> : 
!cir.ptr<!u8i>}> : !{{.*}}{alignment = 8 : i64}
-// LLVM-DAG: @_ZTVN12_GLOBAL__N_11AE = internal constant { [3 x ptr] } { [3 x 
ptr] [ptr null, ptr @_ZTIN12_GLOBAL__N_11AE, ptr @_ZN12_GLOBAL__N_11A1fEv] }, 
align 8
-// LLVM-DAG: @_ZTSN12_GLOBAL__N_11AE = internal constant [19 x i8] 
c"N12_GLOBAL__N_11AE\00", align 1
+// LLVM-DAG: @_ZTVN12_GLOBAL__N_11AE = internal constant {{.*}}{ [3 x ptr] } { 
[3 x ptr] [ptr null, ptr @_ZTIN12_GLOBAL__N_11AE, ptr @_ZN12_GLOBAL__N_11A1fEv] 
}, align 8
+// LLVM-DAG: @_ZTSN12_GLOBAL__N_11AE = internal constant {{.*}}[20 x i8] 
c"*N12_GLOBAL__N_11AE\00", align 1
 // LLVM-DAG: @_ZTIN12_GLOBAL__N_11AE = internal constant { ptr, ptr } { ptr 
getelementptr {{.*}}({{.*}}, ptr @_ZTVN10__cxxabiv117__class_type_infoE, i64 
{{.*}}), ptr @_ZTSN12_GLOBAL__N_11AE }, align 8
 
 // F<char> is an explicit specialization without a key function, so
diff --git a/clang/test/CodeGenCXX/internal-linkage-typeinfo-name.cpp 
b/clang/test/CodeGenCXX/internal-linkage-typeinfo-name.cpp
new file mode 100644
index 00000000000000..3c8d1c1d0aa62a
--- /dev/null
+++ b/clang/test/CodeGenCXX/internal-linkage-typeinfo-name.cpp
@@ -0,0 +1,51 @@
+//RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++11 -emit-llvm -o - 
%s | FileCheck %s
+
+// Check that RTTI type-name strings use a leading '*' for types that do not 
have externally visible Clang/C++ linkage,
+// and for it to be omitted from externally visible types.
+
+namespace std { class type_info; }
+
+//The following types have internal linkage, so their typeinfo names should 
have a leading '*'
+namespace { struct A {}; }
+const std::type_info &t1() { return typeid(A); }
+
+const std::type_info &t2() { struct L {}; return typeid(L); }
+
+const std::type_info &t3() { return typeid(A*); }
+
+template <class T> struct B {};
+const std::type_info &t4() { return typeid(B<A>); }
+
+namespace { struct C { int x; }; }
+const std::type_info &t5() { return typeid(int A::*); }
+
+//Following should not have a '*' prefix in the typeinfo name, since they have 
external linkage
+struct Ext {};
+
+const std::type_info &t6() { return typeid(Ext); }
+
+const std::type_info &t7() { return typeid(Ext*); }
+
+namespace NS2 { struct D {}; }
+
+const std::type_info &t8() { return typeid(NS2::D); }
+
+struct Fwd;
+const std::type_info &t9() { return typeid(Fwd*); }
+
+// The following checks emitted RTTI type-names. The global name is the 
ABI-mangled type-name object, 
+// while the string constant is the mangled type-name itself. For types 
without externally visible linkage,
+// Clang emits these as 'internal constant'. {{.*}} matches for array sizes, 
which is irrelevant to this test.
+
+// These checks are for types with internal linkage, which should have a '*' 
prefix in the typeinfo name.
+//CHECK-DAG: @_ZTSN12_GLOBAL__N_11AE = internal constant 
{{.*}}c"*N12_GLOBAL__N_11AE\00"
+//CHECK-DAG: @_ZTSZ2t2vE1L = internal constant {{.*}}c"*Z2t2vE1L\00"
+//CHECK-DAG: @_ZTSPN12_GLOBAL__N_11AE = internal constant 
{{.*}}c"*PN12_GLOBAL__N_11AE\00"
+//CHECK-DAG: @_ZTS1BIN12_GLOBAL__N_11AEE = internal constant 
{{.*}}c"*1BIN12_GLOBAL__N_11AEE\00"
+//CHECK-DAG: @_ZTSMN12_GLOBAL__N_11AEi = internal constant 
{{.*}}c"*MN12_GLOBAL__N_11AEi\00"
+
+// These checks are for types with external linkage, which should not have a 
'*' prefix in the typeinfo name.
+//CHECK-DAG: @_ZTS3Ext = {{.*}}constant {{.*}}c"3Ext\00"
+//CHECK-DAG: @_ZTSP3Ext = {{.*}}constant {{.*}}c"P3Ext\00"
+//CHECK-DAG: @_ZTSN3NS21DE = {{.*}}constant {{.*}}c"N3NS21DE\00"
+//CHECK-DAG: @_ZTSP3Fwd = {{.*}}constant {{.*}}c"P3Fwd\00"
\ No newline at end of file

>From 48e9903af518f3c051a49eb2d3dd6f6582206cee Mon Sep 17 00:00:00 2001
From: "Jones, Matthew (DI SW SIM FRWK PLAT SIMFW HPC)"
 <[email protected]>
Date: Tue, 22 Sep 2026 08:59:28 -0700
Subject: [PATCH 2/4] removed * prefix from rtti name() to match libstdc++,
 resulting in no change to libc++. Also added a test to verify this

---
 libcxx/include/typeinfo                       |  3 +-
 .../type_info.name.internal_linkage.pass.cpp  | 30 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 
libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.name.internal_linkage.pass.cpp

diff --git a/libcxx/include/typeinfo b/libcxx/include/typeinfo
index aca6b91768d095..58ae6ece281855 100644
--- a/libcxx/include/typeinfo
+++ b/libcxx/include/typeinfo
@@ -309,7 +309,8 @@ protected:
 public:
   virtual ~type_info();
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const char* name() const _NOEXCEPT {
-    return __impl::__type_name_to_string(__type_name);
+    const char* __str = __impl::__type_name_to_string(__type_name);
+    return __str[0] == '*' ? __str + 1 : __str;
   }
 
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool before(const type_info& __arg) 
const _NOEXCEPT {
diff --git 
a/libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.name.internal_linkage.pass.cpp
 
b/libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.name.internal_linkage.pass.cpp
new file mode 100644
index 00000000000000..8d5e487fd598e7
--- /dev/null
+++ 
b/libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.name.internal_linkage.pass.cpp
@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: no-rtti
+
+// Compilers may prefix the type_info::name() result with a '*' to indicate 
that the type has internal linkage. This test checks that libc++ strips the '*' 
prefix from the name() result.
+
+#include <typeinfo>
+#include <cassert>
+
+namespace {
+struct AnonymousType {};
+} // namespace
+
+const std::type_info& local_type() {
+  struct LocalType {};
+  return typeid(LocalType);
+}
+
+int main(int, char**) {
+  assert(typeid(AnonymousType).name()[0] != '*');
+  assert(typeid(AnonymousType*).name()[0] != '*');
+  assert(local_type().name()[0] != '*');
+  return 0;
+}

>From 4588416e8d62d4ff0fa739fea5980650249bec43 Mon Sep 17 00:00:00 2001
From: "Jones, Matthew (DI SW SIM FRWK PLAT SIMFW HPC)"
 <[email protected]>
Date: Tue, 22 Sep 2026 09:18:51 -0700
Subject: [PATCH 3/4] Moved release notes into ABI changes

---
 clang/docs/ReleaseNotes.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index e25586458f23cc..c1fc79c959d396 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -112,6 +112,9 @@ features cannot lower the translation-unit ABI level;
   for homogeneous aggregate classification.
   `-fclang-abi-compat=23` restores the previous behavior. (#GH218799)
 
+- Fixed RTTI name for internal-linkage types lacking '*', fixed breaking 
type_info::operator== and
+  dynamic_cast with libstdc++ (#GH34255)
+
 ### AST Dumping Potentially Breaking Changes
 
 ### Clang Frontend Potentially Breaking Changes

>From 53e2dc8cf4aaccf98ad20ad2bc7df9551bbc4c25 Mon Sep 17 00:00:00 2001
From: "Jones, Matthew (DI SW SIM FRWK PLAT SIMFW HPC)"
 <[email protected]>
Date: Wed, 23 Sep 2026 07:21:49 -0700
Subject: [PATCH 4/4] fixed non_unique_impl incorrectly compared internally
 linked types via strcmp, fixed test which incorrectly sets two internally
 linked typeinfo names as equal

---
 libcxx/include/typeinfo                             | 13 +++++++++++--
 .../type.info/type_info.comparison.unmerged.sh.cpp  |  2 +-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/libcxx/include/typeinfo b/libcxx/include/typeinfo
index 58ae6ece281855..9afec27ea4e6ea 100644
--- a/libcxx/include/typeinfo
+++ b/libcxx/include/typeinfo
@@ -221,10 +221,19 @@ struct __non_unique_impl : __string_impl_base {
     return __hash;
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_ALWAYS_INLINE static bool __eq(__type_name_t 
__lhs, __type_name_t __rhs) _NOEXCEPT {
-    return __lhs == __rhs || __builtin_strcmp(__lhs, __rhs) == 0;
+    // Internal linkage types (marked with '*') cannot compare equal via 
strcmp.
+    // They are only equal if they refer to the same RTTI object.
+    return __lhs == __rhs || (__lhs[0] != '*' && __builtin_strcmp(__lhs, 
__rhs) == 0);
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_ALWAYS_INLINE static bool __lt(__type_name_t 
__lhs, __type_name_t __rhs) _NOEXCEPT {
-    return __builtin_strcmp(__lhs, __rhs) < 0;
+    int __r = __builtin_strcmp(__lhs, __rhs);
+    if (__r != 0)
+      return __r < 0;
+    // Internal linkage types (marked with '*') are ordered via pointer 
address.
+    if (__lhs[0] == '*') {
+      return reinterpret_cast<uintptr_t>(__lhs) < 
reinterpret_cast<uintptr_t>(__rhs);
+    }
+    return false;
   }
 };
 
diff --git 
a/libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.comparison.unmerged.sh.cpp
 
b/libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.comparison.unmerged.sh.cpp
index 9b94fcbc1c92a8..937b5057a1f984 100644
--- 
a/libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.comparison.unmerged.sh.cpp
+++ 
b/libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.comparison.unmerged.sh.cpp
@@ -37,7 +37,7 @@ void register2();
     register2();
 
     assert(registry.size() == 2);
-    assert(registry[0] == registry[1]);
+    assert(registry[0] != registry[1]);
     return 0;
   }
 #else

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