Author: Roy Jacobson Date: 2022-12-05T23:02:37+02:00 New Revision: 7d58c95635cce63ce6acd43c953b57f10bf5c686
URL: https://github.com/llvm/llvm-project/commit/7d58c95635cce63ce6acd43c953b57f10bf5c686 DIFF: https://github.com/llvm/llvm-project/commit/7d58c95635cce63ce6acd43c953b57f10bf5c686.diff LOG: [Clang] Don't consider default constructors ineligible if the more constrained constructor is a template Partially solves https://github.com/llvm/llvm-project/issues/59206: We now mark trivial constructors as eligible even if there's a more constrained templated default constructor. Although technically non-conformant, this solves problems with pretty reasonable uses cases like ``` template<int n> struct Foo { constexpr Foo() = default; template<class... Ts> Foo(Ts... vals) requires(sizeof...(Ts) == n) {} }; ``` where we currently consider the default constructor to be ineligible and therefor inheriting/containing classes have non trivial constructors. This is aligned with GCC: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=c75ebe76ae12ac4020f20a24f34606a594a40d15 This doesn't change `__is_trivial`. Although we're technically standard conformant in this regard, GCC/MSVC exhibit different behaviors that seem to make more sense. An issue has been filed to CWG and we await their response. Reviewed By: erichkeane, #clang-language-wg Differential Revision: https://reviews.llvm.org/D139038 Added: Modified: clang/lib/AST/DeclCXX.cpp clang/lib/Sema/SemaDecl.cpp clang/test/SemaCXX/constrained-special-member-functions.cpp Removed: ################################################################################ diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp index bc7589e418f2c..603075702a837 100644 --- a/clang/lib/AST/DeclCXX.cpp +++ b/clang/lib/AST/DeclCXX.cpp @@ -1378,7 +1378,11 @@ void CXXRecordDecl::addedSelectedDestructor(CXXDestructorDecl *DD) { } void CXXRecordDecl::addedEligibleSpecialMemberFunction(const CXXMethodDecl *MD, - unsigned SMKind) { + unsigned SMKind) { + // FIXME: We shouldn't change DeclaredNonTrivialSpecialMembers if `MD` is + // a function template, but this needs CWG attention before we break ABI. + // See https://github.com/llvm/llvm-project/issues/59206 + if (const auto *DD = dyn_cast<CXXDestructorDecl>(MD)) { if (DD->isUserProvided()) data().HasIrrelevantDestructor = false; diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index 96ea3fb402e74..0b6e2e5564870 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -18193,8 +18193,11 @@ static bool AreSpecialMemberFunctionsSameKind(ASTContext &Context, CXXMethodDecl *M1, CXXMethodDecl *M2, Sema::CXXSpecialMember CSM) { + // We don't want to compare templates to non-templates: See + // https://github.com/llvm/llvm-project/issues/59206 if (CSM == Sema::CXXDefaultConstructor) - return true; + return bool(M1->getDescribedFunctionTemplate()) == + bool(M2->getDescribedFunctionTemplate()); if (!Context.hasSameType(M1->getParamDecl(0)->getType(), M2->getParamDecl(0)->getType())) return false; diff --git a/clang/test/SemaCXX/constrained-special-member-functions.cpp b/clang/test/SemaCXX/constrained-special-member-functions.cpp index 33ed4050553b8..69d50eb04c572 100644 --- a/clang/test/SemaCXX/constrained-special-member-functions.cpp +++ b/clang/test/SemaCXX/constrained-special-member-functions.cpp @@ -225,3 +225,43 @@ void func() { S<2, 2> s2; } } + +namespace GH59206 { + +struct A { + A() = default; //eligible, second constructor unsatisfied + template<class... Args> + A(Args&&... args) requires (sizeof...(Args) > 0) {} +}; + +struct B { + B() = default; //ineligible, second constructor more constrained + template<class... Args> + B(Args&&... args) requires (sizeof...(Args) == 0) {} +}; + +struct C { + C() = default; //eligible, but + template<class... Args> //also eligible and non-trivial + C(Args&&... args) {} +}; + +struct D : B {}; + +static_assert(__is_trivially_copyable(A), ""); +static_assert(__is_trivially_copyable(B), ""); +static_assert(__is_trivially_copyable(C), ""); +static_assert(__is_trivially_copyable(D), ""); + +// FIXME: Update when https://github.com/llvm/llvm-project/issues/59206 is +// resolved. +static_assert(!__is_trivial(A), ""); +static_assert(!__is_trivial(B), ""); +static_assert(!__is_trivial(C), ""); +static_assert(__is_trivial(D), ""); +static_assert(__is_trivially_constructible(A), ""); +static_assert(__is_trivially_constructible(B), ""); +static_assert(__is_trivially_constructible(C), ""); +static_assert(__is_trivially_constructible(D), ""); + +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
