[clang] [clang][bytecode] Fix initializing base casts (PR #104901)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/104901

Use delegate() there. To fix a follow-up problem, abort when a cast ends up on a valid Pointer that isn't a base class.

>From cd2cc98cecc1f237da4a2aa30a9c07b07ae4c804 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Tue, 20 Aug 2024 09:28:37 +0200
Subject: [PATCH] [clang][bytecode] Fix initializing base casts

Use delegate() there. To fix a follow-up problem, abort when a cast ends
up on a valid Pointer that isn't a base class.
---
 clang/lib/AST/ByteCode/Compiler.cpp      | 8 ++++----
 clang/lib/AST/ByteCode/Interp.h          | 4 ++--
 clang/test/Modules/merge-using-decls.cpp | 1 +
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index 53144a50ccf4a9..d84da1efb97695 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -214,7 +214,7 @@ bool Compiler<Emitter>::VisitCastExpr(const CastExpr *CE) {
     unsigned DerivedOffset = collectBaseOffset(QualType(ToMP->getClass(), 0),
                                                QualType(FromMP->getClass(), 0));
 
-    if (!this->visit(SubExpr))
+    if (!this->delegate(SubExpr))
       return false;
 
     return this->emitGetMemberPtrBasePop(DerivedOffset, CE);
@@ -229,14 +229,14 @@ bool Compiler<Emitter>::VisitCastExpr(const CastExpr *CE) {
     unsigned DerivedOffset = collectBaseOffset(QualType(FromMP->getClass(), 0),
                                                QualType(ToMP->getClass(), 0));
 
-    if (!this->visit(SubExpr))
+    if (!this->delegate(SubExpr))
       return false;
     return this->emitGetMemberPtrBasePop(-DerivedOffset, CE);
   }
 
   case CK_UncheckedDerivedToBase:
   case CK_DerivedToBase: {
-    if (!this->visit(SubExpr))
+    if (!this->delegate(SubExpr))
       return false;
 
     const auto extractRecordDecl = [](QualType Ty) -> const CXXRecordDecl * {
@@ -265,7 +265,7 @@ bool Compiler<Emitter>::VisitCastExpr(const CastExpr *CE) {
   }
 
   case CK_BaseToDerived: {
-    if (!this->visit(SubExpr))
+    if (!this->delegate(SubExpr))
       return false;
 
     unsigned DerivedOffset =
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 5aa3d24ebc7582..3c1fa0f93273d4 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -1568,7 +1568,7 @@ inline bool GetPtrBase(InterpState &S, CodePtr OpPC, uint32_t Off) {
   if (!CheckSubobject(S, OpPC, Ptr, CSK_Base))
     return false;
   const Pointer &Result = Ptr.atField(Off);
-  if (Result.isPastEnd())
+  if (Result.isPastEnd() || !Result.isBaseClass())
     return false;
   S.Stk.push<Pointer>(Result);
   return true;
@@ -1581,7 +1581,7 @@ inline bool GetPtrBasePop(InterpState &S, CodePtr OpPC, uint32_t Off) {
   if (!CheckSubobject(S, OpPC, Ptr, CSK_Base))
     return false;
   const Pointer &Result = Ptr.atField(Off);
-  if (Result.isPastEnd())
+  if (Result.isPastEnd() || !Result.isBaseClass())
     return false;
   S.Stk.push<Pointer>(Result);
   return true;
diff --git a/clang/test/Modules/merge-using-decls.cpp b/clang/test/Modules/merge-using-decls.cpp
index e9794a40837ef9..b678eb4e0f851f 100644
--- a/clang/test/Modules/merge-using-decls.cpp
+++ b/clang/test/Modules/merge-using-decls.cpp
@@ -8,6 +8,7 @@
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -x c++ -I%S/Inputs/merge-using-decls -verify -std=c++11 %s -DORDER=2
 
 // RUN: %clang_cc1 -fexperimental-new-constant-interpreter -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -x c++ -I%S/Inputs/merge-using-decls -verify -std=c++17 %s -DORDER=2
+// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -fmodules -fimplicit-module-maps -fexperimental-new-constant-interpreter -fmodules-cache-path=%t -x c++ -I%S/Inputs/merge-using-decls -verify -std=c++98 %s -DORDER=1
 
 #if ORDER == 1
 #include "a.h"