[Clang][Sema] placement new initializes typedef array with correct size

Author: mahtohappy

clang/lib/Sema/TreeTransform.h

@@ -12731,7 +12731,7 @@ TreeTransform<Derived>::TransformCXXNewExpr(CXXNewExpr *E) {
   }
 
   QualType AllocType = AllocTypeInfo->getType();
-  if (!ArraySize) {
+  if (ArraySize) {
     // If no array size was specified, but the new expression was
     // instantiated with an array type (e.g., "new T" where T is
     // instantiated with "int[4]"), extract the outer bound from the

clang/test/CodeGen/instantiate-new-placement-size.cpp

@@ -0,0 +1,19 @@
+// RUN: %clang++ -S -emit-llvm -o - %s | FileCheck %s
+#include <new>
+
+// CHECK: call void @llvm.memset.p0.i64(ptr align 1 %x, i8 0, i64 8, i1 false)
+// CHECK: call void @llvm.memset.p0.i64(ptr align 16 %x, i8 0, i64 32, i1 false)
+template <typename TYPE>
+void f()
+{
+    typedef TYPE TArray[8];
+
+    TArray x;
+    new(&x) TArray();
+}
+
+int main()
+{
+    f<char>();
+    f<int>();
+}