[clang] [Clang] Fix: Handle member pointer in `EmitNullabilityChecks` (PR #227738)

[via cfe-commits]

https://github.com/def3r updated https://github.com/llvm/llvm-project/pull/227738

>From 3e85ab54be07e16a7929131a1c556d50c4c9aaf9 Mon Sep 17 00:00:00 2001
From: Ayaan Khan <ayaanandayaan2 at gmail.com>
Date: Wed, 30 Sep 2026 19:56:15 +0530
Subject: [PATCH 1/4] emit member ptr not null check

---
 clang/lib/CodeGen/CGDecl.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index e1ed66ae71243..10ca750426283 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -783,7 +783,14 @@ void CodeGenFunction::EmitNullabilityCheck(LValue LHS, llvm::Value *RHS,
   auto CheckOrdinal = SanitizerKind::SO_NullabilityAssign;
   auto CheckHandler = SanitizerHandler::TypeMismatch;
   SanitizerDebugLocation SanScope(this, {CheckOrdinal}, CheckHandler);
-  llvm::Value *IsNotNull = Builder.CreateIsNotNull(RHS);
+  llvm::Value *IsNotNull;
+  if (RHS->getType()->isAggregateType()) {
+    const MemberPointerType *MPT = LHS.getType()->getAs<MemberPointerType>();
+    assert(MPT && "Aggregate Type is not a Member Pointer Type");
+    IsNotNull = CGM.getCXXABI().EmitMemberPointerIsNotNull(*this, RHS, MPT);
+  } else {
+    IsNotNull = Builder.CreateIsNotNull(RHS);
+  }
   llvm::Constant *StaticData[] = {
       EmitCheckSourceLocation(Loc), EmitCheckTypeDescriptor(LHS.getType()),
       llvm::ConstantInt::get(Int8Ty, 0), // The LogAlignment info is unused.

>From 5a08ae381e989222e28ee29890c349e83c027bdf Mon Sep 17 00:00:00 2001
From: Ayaan Khan <ayaanandayaan2 at gmail.com>
Date: Thu, 1 Oct 2026 00:19:26 +0530
Subject: [PATCH 2/4] add test

---
 clang/test/CodeGenCXX/ubsan-nullability-assign.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp b/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp
index 08c7f0090220e..0897424a75e64 100644
--- a/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp
+++ b/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp
@@ -2,6 +2,7 @@
 
 struct S1 {
   int *_Nonnull p;
+  void q() {}
 };
 
 struct S2 {
@@ -29,6 +30,18 @@ void f1(int *p) {
   // CHECK: store
   u.s2.s1.p = p;
 
+  using MemberPtr = void (S1::*)(void);
+
+  // CHECK: br i1 true, label %cont{{.*}}, !nosanitize
+  // CHECK: call void @__ubsan_handle_type_mismatch{{.*}} !nosanitize
+  // CHECK: store
+  MemberPtr _Nonnull qptr = &S1::q;
+
+  // CHECK: br i1 false, label %cont{{.*}}, !nosanitize
+  // CHECK: call void @__ubsan_handle_type_mismatch{{.*}} !nosanitize
+  // CHECK: store
+  MemberPtr _Nonnull nqptr = nullptr;
+
   // CHECK-NOT: __ubsan_handle_type_mismatch
   // CHECK-NOT: store
   // CHECK: ret void

>From 7dab9303d28fa7cea3c09c8da8b735c10e987425 Mon Sep 17 00:00:00 2001
From: Ayaan Khan <ayaanandayaan2 at gmail.com>
Date: Thu, 1 Oct 2026 01:49:52 +0530
Subject: [PATCH 3/4] fix impl

---
 clang/lib/CodeGen/CGDecl.cpp | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 10ca750426283..35de80f55cbab 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -784,13 +784,11 @@ void CodeGenFunction::EmitNullabilityCheck(LValue LHS, llvm::Value *RHS,
   auto CheckHandler = SanitizerHandler::TypeMismatch;
   SanitizerDebugLocation SanScope(this, {CheckOrdinal}, CheckHandler);
   llvm::Value *IsNotNull;
-  if (RHS->getType()->isAggregateType()) {
-    const MemberPointerType *MPT = LHS.getType()->getAs<MemberPointerType>();
-    assert(MPT && "Aggregate Type is not a Member Pointer Type");
+  if (auto *MPT = LHS.getType()->getAs<MemberPointerType>())
     IsNotNull = CGM.getCXXABI().EmitMemberPointerIsNotNull(*this, RHS, MPT);
-  } else {
+  else
     IsNotNull = Builder.CreateIsNotNull(RHS);
-  }
+
   llvm::Constant *StaticData[] = {
       EmitCheckSourceLocation(Loc), EmitCheckTypeDescriptor(LHS.getType()),
       llvm::ConstantInt::get(Int8Ty, 0), // The LogAlignment info is unused.

>From 8c1496ee2bd4f395833a4168ee66145728577d3d Mon Sep 17 00:00:00 2001
From: Ayaan Khan <ayaanandayaan2 at gmail.com>
Date: Thu, 1 Oct 2026 10:20:24 +0530
Subject: [PATCH 4/4] test for -1

---
 clang/test/CodeGenCXX/ubsan-nullability-assign.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp b/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp
index 0897424a75e64..4b31b5c54c26a 100644
--- a/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp
+++ b/clang/test/CodeGenCXX/ubsan-nullability-assign.cpp
@@ -42,6 +42,16 @@ void f1(int *p) {
   // CHECK: store
   MemberPtr _Nonnull nqptr = nullptr;
 
+  // CHECK: br i1 true, label %cont{{.*}}, !nosanitize
+  // CHECK: call void @__ubsan_handle_type_mismatch{{.*}} !nosanitize
+  // CHECK: store
+  int* S1::* _Nonnull pptr = &S1::p;
+
+  // CHECK: br i1 false, label %cont{{.*}}, !nosanitize
+  // CHECK: call void @__ubsan_handle_type_mismatch{{.*}} !nosanitize
+  // CHECK: store
+  int* S1::* _Nonnull npptr = nullptr;
+
   // CHECK-NOT: __ubsan_handle_type_mismatch
   // CHECK-NOT: store
   // CHECK: ret void