PR37979: integral promotions in C++ treat enum bit-fields like enums,
not like bit-fields.
We used to get this right "by accident", because conversions for the
selected built-in overloaded operator would convert the enum bit-field
to its corresponding underlying type early. But after DR1687 that no
longer happens.
Technically this change should also apply to C, where bit-fields only
have special promotion rules if the bit-field's declared type is
_Bool, int, signed int, or unsigned int, but for GCC compatibility we
only look at the bit-width and not the underlying type when performing
bit-field integral promotions in C.
llvm-svn: 335925
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index e9d2eb6..6f01f19 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -2007,6 +2007,14 @@
isCompleteType(From->getLocStart(), FromType))
return Context.hasSameUnqualifiedType(
ToType, FromEnumType->getDecl()->getPromotionType());
+
+ // C++ [conv.prom]p5:
+ // If the bit-field has an enumerated type, it is treated as any other
+ // value of that type for promotion purposes.
+ //
+ // ... so do not fall through into the bit-field checks below in C++.
+ if (getLangOpts().CPlusPlus)
+ return false;
}
// C++0x [conv.prom]p2:
@@ -2054,6 +2062,11 @@
// other value of that type for promotion purposes (C++ 4.5p3).
// FIXME: We should delay checking of bit-fields until we actually perform the
// conversion.
+ //
+ // FIXME: In C, only bit-fields of types _Bool, int, or unsigned int may be
+ // promoted, per C11 6.3.1.1/2. We promote all bit-fields (including enum
+ // bit-fields and those whose underlying type is larger than int) for GCC
+ // compatibility.
if (From) {
if (FieldDecl *MemberDecl = From->getSourceBitField()) {
llvm::APSInt BitWidth;