r335925 - PR37979: integral promotions in C++ treat enum bit-fields like enums,
Galina Kistanova via cfe-commits
cfe-commits at lists.llvm.org
Fri Jun 29 11:24:19 PDT 2018
Hello Richard,
This commit broke tests at one of our builders:
http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/10599
Failing Tests (1):
Clang :: CXX/conv/conv.prom/p5.cpp
Please have a look?
Thanks
Galina
On Thu, Jun 28, 2018 at 2:17 PM, Richard Smith via cfe-commits <
cfe-commits at lists.llvm.org> wrote:
> Author: rsmith
> Date: Thu Jun 28 14:17:55 2018
> New Revision: 335925
>
> URL: http://llvm.org/viewvc/llvm-project?rev=335925&view=rev
> Log:
> 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.
>
> Added:
> cfe/trunk/test/CXX/conv/conv.prom/p5.cpp
> Modified:
> cfe/trunk/lib/AST/ASTContext.cpp
> cfe/trunk/lib/Sema/SemaOverload.cpp
>
> Modified: cfe/trunk/lib/AST/ASTContext.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/
> ASTContext.cpp?rev=335925&r1=335924&r2=335925&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/AST/ASTContext.cpp (original)
> +++ cfe/trunk/lib/AST/ASTContext.cpp Thu Jun 28 14:17:55 2018
> @@ -5456,6 +5456,12 @@ QualType ASTContext::isPromotableBitFiel
> if (E->isTypeDependent() || E->isValueDependent())
> return {};
>
> + // 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.
> + if (getLangOpts().CPlusPlus && E->getType()->isEnumeralType())
> + return {};
> +
> // FIXME: We should not do this unless E->refersToBitField() is true.
> This
> // matters in C where getSourceBitField() will find bit-fields for
> various
> // cases where the source expression is not a bit-field designator.
> @@ -5482,13 +5488,15 @@ QualType ASTContext::isPromotableBitFiel
> //
> // FIXME: C does not permit promotion of a 'long : 3' bitfield to int.
> // We perform that promotion here to match GCC and C++.
> + // FIXME: C does not permit promotion of an enum bit-field whose rank is
> + // greater than that of 'int'. We perform that promotion to
> match GCC.
> if (BitWidth < IntSize)
> return IntTy;
>
> if (BitWidth == IntSize)
> return FT->isSignedIntegerType() ? IntTy : UnsignedIntTy;
>
> - // Types bigger than int are not subject to promotions, and therefore
> act
> + // Bit-fields wider than int are not subject to promotions, and
> therefore act
> // like the base type. GCC has some weird bugs in this area that we
> // deliberately do not follow (GCC follows a pre-standard resolution to
> // C's DR315 which treats bit-width as being part of the type, and this
> leaks
>
> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/
> SemaOverload.cpp?rev=335925&r1=335924&r2=335925&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Thu Jun 28 14:17:55 2018
> @@ -2007,6 +2007,14 @@ bool Sema::IsIntegralPromotion(Expr *Fro
> 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 @@ bool Sema::IsIntegralPromotion(Expr *Fro
> // 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;
>
> Added: cfe/trunk/test/CXX/conv/conv.prom/p5.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/
> conv/conv.prom/p5.cpp?rev=335925&view=auto
> ============================================================
> ==================
> --- cfe/trunk/test/CXX/conv/conv.prom/p5.cpp (added)
> +++ cfe/trunk/test/CXX/conv/conv.prom/p5.cpp Thu Jun 28 14:17:55 2018
> @@ -0,0 +1,19 @@
> +// RUN: %clang_cc1 -verify %s
> +// expected-no-diagnostics
> +
> +// A prvalue for an integral bit-field can be converted to a prvalue of
> type
> +// int if int can represent all the values of the bit-field
> +struct X { long long e : 1; };
> +static_assert(sizeof(+X().e) == sizeof(int), "");
> +static_assert(sizeof(X().e + 1) == sizeof(int), "");
> +static_assert(sizeof(true ? X().e : 0) == sizeof(int), "");
> +
> +enum E { a = __LONG_LONG_MAX__ };
> +static_assert(sizeof(E{}) == sizeof(long long), "");
> +
> +// If the bit-field has an enumerated type, it is treated as any other
> value of
> +// that [enumerated] type for promotion purposes.
> +struct Y { E e : 1; };
> +static_assert(sizeof(+Y().e) == sizeof(long long), "");
> +static_assert(sizeof(Y().e + 1) == sizeof(long long), "");
> +static_assert(sizeof(true ? Y().e : 0) == sizeof(long long), "");
>
>
> _______________________________________________
> cfe-commits mailing list
> cfe-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20180629/c92e8b7b/attachment-0001.html>
More information about the cfe-commits
mailing list