alexander-shaposhnikov updated this revision to Diff 490313. alexander-shaposhnikov added a comment.
@aaron.ballman - thanks for the review, I've updated the release notes. Regarding LanguageExtensions.rst - somehow I don't see any appropriate sections in LanguageExtensions.rst (either about our builtin std::move and friends or [[clang::lifetimebound]]) - didn't change that. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D141744/new/ https://reviews.llvm.org/D141744 Files: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaDecl.cpp clang/test/SemaCXX/attr-lifetimebound.cpp clang/test/SemaCXX/builtin-std-move.cpp clang/test/SemaCXX/builtins.cpp
Index: clang/test/SemaCXX/builtins.cpp =================================================================== --- clang/test/SemaCXX/builtins.cpp +++ clang/test/SemaCXX/builtins.cpp @@ -40,7 +40,7 @@ struct U { int n : 5; } u; int *pbf = __builtin_addressof(u.n); // expected-error {{address of bit-field requested}} - S *ptmp = __builtin_addressof(S{}); // expected-error {{taking the address of a temporary}} + S *ptmp = __builtin_addressof(S{}); // expected-error {{taking the address of a temporary}} expected-warning {{temporary whose address is used as value of local variable 'ptmp' will be destroyed at the end of the full-expression}} } namespace function_start { Index: clang/test/SemaCXX/builtin-std-move.cpp =================================================================== --- clang/test/SemaCXX/builtin-std-move.cpp +++ clang/test/SemaCXX/builtin-std-move.cpp @@ -85,7 +85,7 @@ A &forward_rval_as_lval() { std::forward<A&&>(A()); // expected-warning {{const attribute}} - return std::forward<A&>(A()); // expected-note {{instantiation of}} + return std::forward<A&>(A()); // expected-note {{instantiation of}} expected-warning {{returning reference}} } struct B {}; Index: clang/test/SemaCXX/attr-lifetimebound.cpp =================================================================== --- clang/test/SemaCXX/attr-lifetimebound.cpp +++ clang/test/SemaCXX/attr-lifetimebound.cpp @@ -113,3 +113,77 @@ std::map<std::string, std::string> m; const std::string &v = findOrDefault(m, "foo"s, "bar"s); // expected-warning {{temporary bound to local reference 'v'}} } + +// definitions for std::move, std::forward et al. +namespace std { +inline namespace foo { + +template <class T> struct remove_reference { + typedef T type; +}; +template <class T> struct remove_reference<T &> { + typedef T type; +}; +template <class T> struct remove_reference<T &&> { + typedef T type; +}; + +template <class T> constexpr typename remove_reference<T>::type &&move(T &&t) { + return static_cast<typename remove_reference<T>::type>(t); +} + +template <class T> +constexpr T &&forward(typename remove_reference<T>::type &t) { + return static_cast<T &&>(t); +} + +template <class T> +constexpr T &&forward(typename remove_reference<T>::type &&t) { + return static_cast<T &&>(t); +} + +template <class T> constexpr const T &as_const(T &x) { return x; } + +template <class T, bool RValueRef> struct PickRef { + using type = typename remove_reference<T>::type &; +}; +template <class T> struct PickRef<T, true> { + using type = typename remove_reference<T>::type &&; +}; + +template <class T> +auto move_if_noexcept(T &t) -> + typename PickRef<T, noexcept(T(static_cast<T &&>(t)))>::type { + return static_cast< + typename PickRef<T, noexcept(T(static_cast<T &&>(t)))>::type>(t); +} + +template <class T> T *addressof(T &arg) { + return reinterpret_cast<T *>( + &const_cast<char &>(reinterpret_cast<const volatile char &>(arg))); +} + +} // namespace foo +} // namespace std + +namespace move_forward_et_al_examples { + struct S { + S &self() [[clang::lifetimebound]] { return *this; } + }; + + S &&Move = std::move(S{}); // expected-warning {{temporary bound to local reference 'Move' will be destroyed at the end of the full-expression}} + S MoveOk = std::move(S{}); + + S &&Forward = std::forward<S &&>(S{}); // expected-warning {{temporary bound to local reference 'Forward' will be destroyed at the end of the full-expression}} + S ForwardOk = std::forward<S &&>(S{}); + + const S &Const = std::as_const(S{}.self()); // expected-warning {{temporary bound to local reference 'Const' will be destroyed at the end of the full-expression}} + const S ConstOk = std::as_const(S{}.self()); + + S &&MoveIfNoExcept = std::move_if_noexcept(S{}.self()); // expected-warning {{temporary bound to local reference 'MoveIfNoExcept' will be destroyed at the end of the full-expression}} + S MoveIfNoExceptOk = std::move_if_noexcept(S{}.self()); + + S *AddressOf = std::addressof(S{}.self()); // expected-warning {{temporary whose address is used as value of local variable 'AddressOf' will be destroyed at the end of the full-expression}} + S X; + S *AddressOfOk = std::addressof(X); +} // namespace move_forward_et_al_examples Index: clang/lib/Sema/SemaDecl.cpp =================================================================== --- clang/lib/Sema/SemaDecl.cpp +++ clang/lib/Sema/SemaDecl.cpp @@ -16182,6 +16182,24 @@ default: break; } + + // Add lifetime attribute to std::move, std::fowrard et al. + switch (BuiltinID) { + case Builtin::BIaddressof: + case Builtin::BI__addressof: + case Builtin::BI__builtin_addressof: + case Builtin::BIas_const: + case Builtin::BIforward: + case Builtin::BImove: + case Builtin::BImove_if_noexcept: + if (ParmVarDecl *P = FD->getParamDecl(0u); + !P->hasAttr<LifetimeBoundAttr>()) + P->addAttr( + LifetimeBoundAttr::CreateImplicit(Context, FD->getLocation())); + break; + default: + break; + } } AddKnownFunctionAttributesForReplaceableGlobalAllocationFunction(FD); Index: clang/docs/ReleaseNotes.rst =================================================================== --- clang/docs/ReleaseNotes.rst +++ clang/docs/ReleaseNotes.rst @@ -456,6 +456,9 @@ only when ``x`` is a string literal. - Clang will now reject the GNU extension address of label in coroutines explicitly. This fixes `Issue 56436 <https://github.com/llvm/llvm-project/issues/56436>`_. +- Clang now automatically adds ``[[clang::lifetimebound]]`` to the parameters of + ``std::move, std::forward`` et al, this enables Clang to diagnose more cases + where the returned reference outlives the object. Non-comprehensive list of changes in this release -------------------------------------------------
_______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits