PR23833, DR2140: an lvalue-to-rvalue conversion on a glvalue of type

nullptr_t does not access memory.

We now reuse CK_NullToPointer to represent a conversion from a glvalue
of type nullptr_t to a prvalue of nullptr_t where necessary.

This reinstates r345562, reverted in r346065, now that CodeGen's
handling of non-odr-used variables has been fixed.

llvm-svn: 363337

1 files changed, 7 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 1a1d9347985..1301de4b111 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -7779,9 +7779,13 @@ ExprResult InitializationSequence::Perform(Sema &S,
 
     case SK_LValueToRValue: {
       assert(CurInit.get()->isGLValue() && "cannot load from a prvalue");
-      CurInit = ImplicitCastExpr::Create(S.Context, Step->Type,
-                                         CK_LValueToRValue, CurInit.get(),
-                                         /*BasePath=*/nullptr, VK_RValue);
+      // C++ [conv.lval]p3:
+      //   If T is cv std::nullptr_t, the result is a null pointer constant.
+      CastKind CK =
+          Step->Type->isNullPtrType() ? CK_NullToPointer : CK_LValueToRValue;
+      CurInit =
+          ImplicitCastExpr::Create(S.Context, Step->Type, CK, CurInit.get(),
+                                   /*BasePath=*/nullptr, VK_RValue);
       break;
     }