1 files changed, 15 insertions, 5 deletions
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 8d2fc5331a0d..985005d0b79b 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2092,7 +2092,7 @@ static void CheckPoppedLabel(LabelDecl *L, Sema &S) {
 }
 
 void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
-  S->mergeNRVOIntoParent();
+  S->applyNRVO();
 
   if (S->decl_empty()) return;
   assert((S->getFlags() & (Scope::DeclScope | Scope::TemplateParamScope)) &&
@@ -18899,14 +18899,24 @@ void Sema::ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
     const llvm::APSInt &InitVal = ECD->getInitVal();
 
     // Keep track of the size of positive and negative values.
-    if (InitVal.isUnsigned() || InitVal.isNonNegative())
-      NumPositiveBits = std::max(NumPositiveBits,
-                                 (unsigned)InitVal.getActiveBits());
-    else
+    if (InitVal.isUnsigned() || InitVal.isNonNegative()) {
+      // If the enumerator is zero that should still be counted as a positive
+      // bit since we need a bit to store the value zero.
+      unsigned ActiveBits = InitVal.getActiveBits();
+      NumPositiveBits = std::max({NumPositiveBits, ActiveBits, 1u});
+    } else {
       NumNegativeBits = std::max(NumNegativeBits,
                                  (unsigned)InitVal.getMinSignedBits());
+    }
   }
 
+  // If we have have an empty set of enumerators we still need one bit.
+  // From [dcl.enum]p8
+  // If the enumerator-list is empty, the values of the enumeration are as if
+  // the enumeration had a single enumerator with value 0
+  if (!NumPositiveBits && !NumNegativeBits)
+    NumPositiveBits = 1;
+
   // Figure out the type that should be used for this enum.
   QualType BestType;
   unsigned BestWidth;