r328680 - [ObjC] Make C++ triviality type traits available to non-trivial C
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Wed Apr 4 16:40:27 PDT 2018
On 4 April 2018 at 16:37, Akira Hatanaka via cfe-commits <
cfe-commits at lists.llvm.org> wrote:
>
>
> On Apr 4, 2018, at 4:24 PM, Akira Hatanaka via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>
> On Apr 4, 2018, at 3:38 PM, Richard Smith <richard at metafoo.co.uk> wrote:
>
> Hi Akira,
>
> This change has broken the C++ versions of these type traits for classes
> with volatile members. Such classes are required to claim to be trivial per
> C++ DR 2094 (http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.
> html#2094) but return false from isNonTrivialToPrimitiveCopy().
>
>
> Oh that’s right. The function returns false when
> isNonTrivialToPrimitiveCopy() returns PCK_VolatileTrivial. That is wrong.
>
> Also, exposing these __has_* traits more widely seems like a backwards
> step to me: these traits are deprecated, near-useless, and we're trying to
> remove them. No code should be using them under any circumstances; the
> __is_* traits should be used instead.
>
>
> The __is_* traits (is_trivially_copy_constructible, etc.) are templates
> defined in libcxx, so it seems that we can’t use them when compiling in C
> mode. Is it OK to add their definitions to TokenKinds.def as non-C++
> keywords?
>
>
> Or perhaps redefine the six __has_* traits used here as non-C++ (KEYNOCXX
> or ‘KEYC99 | KEYC11') keywords?
>
I think __is_trivially_copy_constructible is a better name than
__has_trivial_copy_constructor in C, since C doesn't have constructors :)
I'd also like to avoid there being confusion about what the right trait to
use is in C and in C++ if possible.
> On 27 March 2018 at 17:12, Akira Hatanaka via cfe-commits <cfe-commits@
> lists.llvm.org> wrote:
>
>> Author: ahatanak
>> Date: Tue Mar 27 17:12:08 2018
>> New Revision: 328680
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=328680&view=rev
>> Log:
>> [ObjC] Make C++ triviality type traits available to non-trivial C
>> structs.
>>
>> r326307 and r327870 made changes that allowed using non-trivial C
>> structs with fields qualified with __strong or __weak. This commit makes
>> the following C++ triviality type traits available to non-trivial C
>> structs:
>>
>> __has_trivial_assign
>> __has_trivial_move_assign
>> __has_trivial_copy
>> __has_trivial_move_constructor
>> __has_trivial_constructor
>> __has_trivial_destructor
>>
>> rdar://problem/33599681
>>
>> Differential Revision: https://reviews.llvm.org/D44913
>>
>> Added:
>> cfe/trunk/test/SemaObjC/non-trivial-struct-traits.m
>> Modified:
>> cfe/trunk/include/clang/Basic/TokenKinds.def
>> cfe/trunk/lib/Sema/SemaExprCXX.cpp
>>
>> Modified: cfe/trunk/include/clang/Basic/TokenKinds.def
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/
>> TokenKinds.def?rev=328680&r1=328679&r2=328680&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/include/clang/Basic/TokenKinds.def (original)
>> +++ cfe/trunk/include/clang/Basic/TokenKinds.def Tue Mar 27 17:12:08 2018
>> @@ -433,12 +433,12 @@ TYPE_TRAIT_1(__has_nothrow_assign, HasNo
>> TYPE_TRAIT_1(__has_nothrow_move_assign, HasNothrowMoveAssign, KEYCXX)
>> TYPE_TRAIT_1(__has_nothrow_copy, HasNothrowCopy, KEYCXX)
>> TYPE_TRAIT_1(__has_nothrow_constructor, HasNothrowConstructor, KEYCXX)
>> -TYPE_TRAIT_1(__has_trivial_assign, HasTrivialAssign, KEYCXX)
>> -TYPE_TRAIT_1(__has_trivial_move_assign, HasTrivialMoveAssign, KEYCXX)
>> -TYPE_TRAIT_1(__has_trivial_copy, HasTrivialCopy, KEYCXX)
>> -TYPE_TRAIT_1(__has_trivial_constructor, HasTrivialDefaultConstructor,
>> KEYCXX)
>> -TYPE_TRAIT_1(__has_trivial_move_constructor, HasTrivialMoveConstructor,
>> KEYCXX)
>> -TYPE_TRAIT_1(__has_trivial_destructor, HasTrivialDestructor, KEYCXX)
>> +TYPE_TRAIT_1(__has_trivial_assign, HasTrivialAssign, KEYALL)
>> +TYPE_TRAIT_1(__has_trivial_move_assign, HasTrivialMoveAssign, KEYALL)
>> +TYPE_TRAIT_1(__has_trivial_copy, HasTrivialCopy, KEYALL)
>> +TYPE_TRAIT_1(__has_trivial_constructor, HasTrivialDefaultConstructor,
>> KEYALL)
>> +TYPE_TRAIT_1(__has_trivial_move_constructor, HasTrivialMoveConstructor,
>> KEYALL)
>> +TYPE_TRAIT_1(__has_trivial_destructor, HasTrivialDestructor, KEYALL)
>> TYPE_TRAIT_1(__has_virtual_destructor, HasVirtualDestructor, KEYCXX)
>> TYPE_TRAIT_1(__is_abstract, IsAbstract, KEYCXX)
>> TYPE_TRAIT_1(__is_aggregate, IsAggregate, KEYCXX)
>>
>> Modified: cfe/trunk/lib/Sema/SemaExprCXX.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/
>> Sema/SemaExprCXX.cpp?rev=328680&r1=328679&r2=328680&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/lib/Sema/SemaExprCXX.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaExprCXX.cpp Tue Mar 27 17:12:08 2018
>> @@ -4513,6 +4513,8 @@ static bool EvaluateUnaryTypeTrait(Sema
>> // does not correctly compute triviality in the presence of multiple
>> special
>> // members of the same kind. Revisit this once the g++ bug is fixed.
>> case UTT_HasTrivialDefaultConstructor:
>> + if (T.isNonTrivialToPrimitiveDefaultInitialize())
>> + return false;
>> // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
>> // If __is_pod (type) is true then the trait is true, else if type
>> is
>> // a cv class or union type (or array thereof) with a trivial
>> default
>> @@ -4524,6 +4526,8 @@ static bool EvaluateUnaryTypeTrait(Sema
>> !RD->hasNonTrivialDefaultConstructor();
>> return false;
>> case UTT_HasTrivialMoveConstructor:
>> + if (T.isNonTrivialToPrimitiveDestructiveMove())
>> + return false;
>> // This trait is implemented by MSVC 2012 and needed to parse the
>> // standard library headers. Specifically this is used as the logic
>> // behind std::is_trivially_move_constructible (20.9.4.3).
>> @@ -4533,6 +4537,8 @@ static bool EvaluateUnaryTypeTrait(Sema
>> return RD->hasTrivialMoveConstructor() &&
>> !RD->hasNonTrivialMoveConstructor();
>> return false;
>> case UTT_HasTrivialCopy:
>> + if (T.isNonTrivialToPrimitiveCopy())
>> + return false;
>> // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
>> // If __is_pod (type) is true or type is a reference type then
>> // the trait is true, else if type is a cv class or union type
>> @@ -4545,6 +4551,8 @@ static bool EvaluateUnaryTypeTrait(Sema
>> !RD->hasNonTrivialCopyConstructor();
>> return false;
>> case UTT_HasTrivialMoveAssign:
>> + if (T.isNonTrivialToPrimitiveDestructiveMove())
>> + return false;
>> // This trait is implemented by MSVC 2012 and needed to parse the
>> // standard library headers. Specifically it is used as the logic
>> // behind std::is_trivially_move_assignable (20.9.4.3)
>> @@ -4554,6 +4562,8 @@ static bool EvaluateUnaryTypeTrait(Sema
>> return RD->hasTrivialMoveAssignment() &&
>> !RD->hasNonTrivialMoveAssignment();
>> return false;
>> case UTT_HasTrivialAssign:
>> + if (T.isNonTrivialToPrimitiveCopy())
>> + return false;
>> // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
>> // If type is const qualified or is a reference type then the
>> // trait is false. Otherwise if __is_pod (type) is true then the
>> @@ -4624,6 +4634,8 @@ static bool EvaluateUnaryTypeTrait(Sema
>> return true;
>>
>> case UTT_HasTrivialDestructor:
>> + if (T.isDestructedType() == QualType::DK_nontrivial_c_struct)
>> + return false;
>> // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html
>> // If __is_pod (type) is true or type is a reference type
>> // then the trait is true, else if type is a cv class or union
>>
>> Added: cfe/trunk/test/SemaObjC/non-trivial-struct-traits.m
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Se
>> maObjC/non-trivial-struct-traits.m?rev=328680&view=auto
>> ============================================================
>> ==================
>> --- cfe/trunk/test/SemaObjC/non-trivial-struct-traits.m (added)
>> +++ cfe/trunk/test/SemaObjC/non-trivial-struct-traits.m Tue Mar 27
>> 17:12:08 2018
>> @@ -0,0 +1,25 @@
>> +// RUN: %clang_cc1 -fsyntax-only -fobjc-arc -verify %s
>> +
>> +// expected-no-diagnostics
>> +
>> +struct Trivial {
>> + int x;
>> +};
>> +
>> +struct NonTrivial {
>> + id x;
>> +};
>> +
>> +int trivial_assign[__has_trivial_assign(struct Trivial) ? 1 : -1];
>> +int trivial_move_assign[__has_trivial_move_assign(struct Trivial) ? 1 :
>> -1];
>> +int trivial_copy_constructor[__has_trivial_copy(struct Trivial) ? 1 :
>> -1];
>> +int trivial_move_constructor[__has_trivial_move_constructor(struct
>> Trivial) ? 1 : -1];
>> +int trivial_constructor[__has_trivial_constructor(struct Trivial) ? 1 :
>> -1];
>> +int trivial_destructor[__has_trivial_destructor(struct Trivial) ? 1 :
>> -1];
>> +
>> +int non_trivial_assign[__has_trivial_assign(struct NonTrivial) ? -1 :
>> 1];
>> +int non_trivial_move_assign[__has_trivial_move_assign(struct
>> NonTrivial) ? -1 : 1];
>> +int non_trivial_copy_constructor[__has_trivial_copy(struct NonTrivial)
>> ? -1 : 1];
>> +int non_trivial_move_constructor[__has_trivial_move_constructor(struct
>> NonTrivial) ? -1 : 1];
>> +int non_trivial_constructor[__has_trivial_constructor(struct
>> NonTrivial) ? -1 : 1];
>> +int non_trivial_destructor[__has_trivial_destructor(struct NonTrivial)
>> ? -1 : 1];
>>
>>
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