[clang][bytecode] Fix returne value of array CXXNewExprs

[tbaederr]

Just like with the __builtin_operator_new version, we need to point to the first array element, not the array element itself.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

Changes

Just like with the __builtin_operator_new version, we need to point to the first array element, not the array element itself.

---

Full diff: https://github.com/llvm/llvm-project/pull/127526.diff

3 Files Affected:

• (modified) clang/lib/AST/ByteCode/Interp.cpp (+2-1)
• (modified) clang/lib/AST/ByteCode/Interp.h (+11-2)
• (modified) clang/test/AST/ByteCode/new-delete.cpp (+14)

diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index c80be094856b0..0310870f7372e 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -1063,7 +1063,8 @@ bool Free(InterpState &S, CodePtr OpPC, bool DeleteIsArrayForm,
       return false;
     }
 
-    if (!Ptr.isRoot() || Ptr.isOnePastEnd() || Ptr.isArrayElement()) {
+    if (!Ptr.isRoot() || Ptr.isOnePastEnd() ||
+        (Ptr.isArrayElement() && Ptr.getIndex() != 0)) {
       const SourceInfo &Loc = S.Current->getSource(OpPC);
       S.FFDiag(Loc, diag::note_constexpr_delete_subobject)
           << Ptr.toDiagnosticString(S.getASTContext()) << Ptr.isOnePastEnd();
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 73cc107b7dbff..10cf21e28437c 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -2915,13 +2915,17 @@ inline bool AllocN(InterpState &S, CodePtr OpPC, PrimType T, const Expr *Source,
     S.Stk.push<Pointer>(0, nullptr);
     return true;
   }
+  assert(NumElements.isPositive());
 
   DynamicAllocator &Allocator = S.getAllocator();
   Block *B =
       Allocator.allocate(Source, T, static_cast<size_t>(NumElements),
                          S.Ctx.getEvalID(), DynamicAllocator::Form::Array);
   assert(B);
-  S.Stk.push<Pointer>(B);
+  if (NumElements.isZero())
+    S.Stk.push<Pointer>(B);
+  else
+    S.Stk.push<Pointer>(Pointer(B).atIndex(0));
   return true;
 }
 
@@ -2941,13 +2945,18 @@ inline bool AllocCN(InterpState &S, CodePtr OpPC, const Descriptor *ElementDesc,
     S.Stk.push<Pointer>(0, ElementDesc);
     return true;
   }
+  assert(NumElements.isPositive());
 
   DynamicAllocator &Allocator = S.getAllocator();
   Block *B =
       Allocator.allocate(ElementDesc, static_cast<size_t>(NumElements),
                          S.Ctx.getEvalID(), DynamicAllocator::Form::Array);
   assert(B);
-  S.Stk.push<Pointer>(B);
+  if (NumElements.isZero())
+    S.Stk.push<Pointer>(B);
+  else
+    S.Stk.push<Pointer>(Pointer(B).atIndex(0));
+
   return true;
 }
 
diff --git a/clang/test/AST/ByteCode/new-delete.cpp b/clang/test/AST/ByteCode/new-delete.cpp
index e9850d27666e5..7e5f6ab8815ea 100644
--- a/clang/test/AST/ByteCode/new-delete.cpp
+++ b/clang/test/AST/ByteCode/new-delete.cpp
@@ -922,6 +922,20 @@ namespace NonConstexprArrayCtor {
                          // both-note {{in call to}}
 }
 
+namespace ArrayBaseCast {
+  struct A {};
+  struct B : A {};
+  constexpr bool test() {
+    B *b = new B[2];
+
+    A* a = b;
+
+    delete[] b;
+    return true;
+  }
+  static_assert(test());
+}
+
 #else
 /// Make sure we reject this prior to C++20
 constexpr int a() { // both-error {{never produces a constant expression}}