[clang][Interp] Fix sizeof of reference types

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -1085,6 +1085,12 @@ bool ByteCodeExprGen<Emitter>::VisitUnaryExprOrTypeTraitExpr(
 
   if (Kind == UETT_SizeOf) {
     QualType ArgType = E->getTypeOfArgument();
+
+    // C++ [expr.sizeof]p2: "When applied to a reference or a reference type,
+    //   the result is the size of the referenced type."
+    if (const auto *Ref = ArgType->getAs<ReferenceType>())
+      ArgType = Ref->getPointeeType();
+
     CharUnits Size;
     if (ArgType->isVoidType() || ArgType->isFunctionType())
       Size = CharUnits::One();

clang/test/AST/Interp/literals.cpp

@@ -216,6 +216,8 @@ namespace PointerComparison {
 }
 
 namespace SizeOf {
+  static_assert(alignof(char&) == 1);
+
   constexpr int soint = sizeof(int);
   constexpr int souint = sizeof(unsigned int);
   static_assert(soint == souint, "");