https://github.com/cor3ntin created https://github.com/llvm/llvm-project/pull/89906
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p0609r3.pdf We support this feature in all language mode. maybe_unused applied to a binding makes the whole declaration unused. There maybe something more clever to do here but that can be explored as a separate PR. >From e87546f2bc0c7d213b6c1f2b414e0ce5335b3e47 Mon Sep 17 00:00:00 2001 From: Corentin Jabot <corentinja...@gmail.com> Date: Wed, 24 Apr 2024 11:53:28 +0200 Subject: [PATCH] [Clang] Implement C++26 Attributes for Structured Bindings (P0609R3) https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p0609r3.pdf We support this feature in all language mode. maybe_unused applied to a binding makes the whole declaration unused. There maybe something more clever to do here but that can be explored as a separate PR. --- clang/docs/LanguageExtensions.rst | 1 + clang/docs/ReleaseNotes.rst | 2 + clang/include/clang/Basic/Attr.td | 2 +- .../clang/Basic/DiagnosticParseKinds.td | 10 +++++ clang/include/clang/Sema/DeclSpec.h | 10 +++-- clang/include/clang/Sema/ParsedAttr.h | 1 + clang/lib/Frontend/InitPreprocessor.cpp | 2 +- clang/lib/Parse/ParseDecl.cpp | 41 ++++++++++++++----- clang/lib/Sema/DeclSpec.cpp | 4 +- clang/lib/Sema/SemaDecl.cpp | 2 +- clang/lib/Sema/SemaDeclCXX.cpp | 2 + clang/test/Lexer/cxx-features.cpp | 2 +- clang/test/Parser/cxx1z-decomposition.cpp | 38 +++++++++++++---- clang/test/SemaCXX/unused.cpp | 12 +++++- clang/www/cxx_status.html | 2 +- 15 files changed, 101 insertions(+), 30 deletions(-) diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst index 84fc4dee02fa80..49afd6c7f06bdd 100644 --- a/clang/docs/LanguageExtensions.rst +++ b/clang/docs/LanguageExtensions.rst @@ -1493,6 +1493,7 @@ Conditional ``explicit`` __cpp_conditional_explicit C+ ``if consteval`` __cpp_if_consteval C++23 C++20 ``static operator()`` __cpp_static_call_operator C++23 C++03 Attributes on Lambda-Expressions C++23 C++11 +Attributes on Structured Bindings __cpp_structured_bindings C++26 C++03 ``= delete ("should have a reason");`` __cpp_deleted_function C++26 C++03 -------------------------------------------- -------------------------------- ------------- ------------- Designated initializers (N494) C99 C89 diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 64526ed6d06f55..8c8ded8cde0837 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -131,6 +131,8 @@ C++2c Feature Support - Implemented `P2573R2: = delete("should have a reason"); <https://wg21.link/P2573R2>`_ +- Implemented `P0609R3: Attributes for Structured Bindings <https://wg21.link/P0609R3>`_ + Resolutions to C++ Defect Reports ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td index 4408d517e70e58..97e06fe7d2e6aa 100644 --- a/clang/include/clang/Basic/Attr.td +++ b/clang/include/clang/Basic/Attr.td @@ -3211,7 +3211,7 @@ def ObjCRequiresPropertyDefs : InheritableAttr { def Unused : InheritableAttr { let Spellings = [CXX11<"", "maybe_unused", 201603>, GCC<"unused">, C23<"", "maybe_unused", 202106>]; - let Subjects = SubjectList<[Var, ObjCIvar, Type, Enum, EnumConstant, Label, + let Subjects = SubjectList<[Var, Binding, ObjCIvar, Type, Enum, EnumConstant, Label, Field, ObjCMethod, FunctionLike]>; let Documentation = [WarnMaybeUnusedDocs]; } diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td index 38174cf3549f14..74ce0f8b53a48c 100644 --- a/clang/include/clang/Basic/DiagnosticParseKinds.td +++ b/clang/include/clang/Basic/DiagnosticParseKinds.td @@ -1056,11 +1056,21 @@ def ext_decl_attrs_on_lambda : ExtWarn< def ext_lambda_missing_parens : ExtWarn< "lambda without a parameter clause is a C++23 extension">, InGroup<CXX23>; + def warn_cxx20_compat_decl_attrs_on_lambda : Warning< "%select{an attribute specifier sequence|%1}0 in this position " "is incompatible with C++ standards before C++23">, InGroup<CXXPre23Compat>, DefaultIgnore; +def ext_decl_attrs_on_binding : ExtWarn< + "an attribute specifier sequence attached to a structured binding declaration " + "is a C++2c extension">, InGroup<CXX26>; + +def warn_cxx23_compat_decl_attrs_on_binding : Warning< + "an attribute specifier sequence attached to a structured binding declaration " + "is incompatible with C++ standards before C++2c">, + InGroup<CXXPre26Compat>, DefaultIgnore; + // C++17 lambda expressions def err_expected_star_this_capture : Error< "expected 'this' following '*' in lambda capture list">; diff --git a/clang/include/clang/Sema/DeclSpec.h b/clang/include/clang/Sema/DeclSpec.h index c9eecdafe62c7c..760c7980be52bd 100644 --- a/clang/include/clang/Sema/DeclSpec.h +++ b/clang/include/clang/Sema/DeclSpec.h @@ -36,6 +36,7 @@ #include "llvm/ADT/SmallVector.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/ErrorHandling.h" +#include <optional> namespace clang { class ASTContext; @@ -1790,6 +1791,7 @@ class DecompositionDeclarator { struct Binding { IdentifierInfo *Name; SourceLocation NameLoc; + std::optional<ParsedAttributes> Attrs; }; private: @@ -2339,10 +2341,10 @@ class Declarator { } /// Set the decomposition bindings for this declarator. - void - setDecompositionBindings(SourceLocation LSquareLoc, - ArrayRef<DecompositionDeclarator::Binding> Bindings, - SourceLocation RSquareLoc); + void setDecompositionBindings( + SourceLocation LSquareLoc, + MutableArrayRef<DecompositionDeclarator::Binding> Bindings, + SourceLocation RSquareLoc); /// AddTypeInfo - Add a chunk to this declarator. Also extend the range to /// EndLoc, which should be the last token of the chunk. diff --git a/clang/include/clang/Sema/ParsedAttr.h b/clang/include/clang/Sema/ParsedAttr.h index 25a5fa05b21c7d..8368d9ce61466d 100644 --- a/clang/include/clang/Sema/ParsedAttr.h +++ b/clang/include/clang/Sema/ParsedAttr.h @@ -948,6 +948,7 @@ class ParsedAttributes : public ParsedAttributesView { ParsedAttributes(AttributeFactory &factory) : pool(factory) {} ParsedAttributes(const ParsedAttributes &) = delete; ParsedAttributes &operator=(const ParsedAttributes &) = delete; + ParsedAttributes(ParsedAttributes &&G) = default; AttributePool &getPool() const { return pool; } diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp index 4f44c3b7b89d4d..fb6435a30cc656 100644 --- a/clang/lib/Frontend/InitPreprocessor.cpp +++ b/clang/lib/Frontend/InitPreprocessor.cpp @@ -704,7 +704,7 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts, Builder.defineMacro("__cpp_nested_namespace_definitions", "201411L"); Builder.defineMacro("__cpp_variadic_using", "201611L"); Builder.defineMacro("__cpp_aggregate_bases", "201603L"); - Builder.defineMacro("__cpp_structured_bindings", "201606L"); + Builder.defineMacro("__cpp_structured_bindings", "202403L"); Builder.defineMacro("__cpp_nontype_template_args", "201411L"); // (not latest) Builder.defineMacro("__cpp_fold_expressions", "201603L"); diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp index 05ad5ecbfaa0cf..a7846e102a43c7 100644 --- a/clang/lib/Parse/ParseDecl.cpp +++ b/clang/lib/Parse/ParseDecl.cpp @@ -7038,18 +7038,23 @@ void Parser::ParseDirectDeclarator(Declarator &D) { void Parser::ParseDecompositionDeclarator(Declarator &D) { assert(Tok.is(tok::l_square)); + TentativeParsingAction PA(*this); + BalancedDelimiterTracker T(*this, tok::l_square); + T.consumeOpen(); + + if (isCXX11AttributeSpecifier()) + DiagnoseAndSkipCXX11Attributes(); + // If this doesn't look like a structured binding, maybe it's a misplaced // array declarator. - // FIXME: Consume the l_square first so we don't need extra lookahead for - // this. - if (!(NextToken().is(tok::identifier) && - GetLookAheadToken(2).isOneOf(tok::comma, tok::r_square)) && - !(NextToken().is(tok::r_square) && - GetLookAheadToken(2).isOneOf(tok::equal, tok::l_brace))) + if (!(Tok.is(tok::identifier) && + NextToken().isOneOf(tok::comma, tok::r_square, tok::kw_alignas, + tok::l_square)) && + !(Tok.is(tok::r_square) && + NextToken().isOneOf(tok::equal, tok::l_brace))) { + PA.Revert(); return ParseMisplacedBracketDeclarator(D); - - BalancedDelimiterTracker T(*this, tok::l_square); - T.consumeOpen(); + } SmallVector<DecompositionDeclarator::Binding, 32> Bindings; while (Tok.isNot(tok::r_square)) { @@ -7074,13 +7079,27 @@ void Parser::ParseDecompositionDeclarator(Declarator &D) { } } + if (isCXX11AttributeSpecifier()) + DiagnoseAndSkipCXX11Attributes(); + if (Tok.isNot(tok::identifier)) { Diag(Tok, diag::err_expected) << tok::identifier; break; } - Bindings.push_back({Tok.getIdentifierInfo(), Tok.getLocation()}); + IdentifierInfo *II = Tok.getIdentifierInfo(); + SourceLocation Loc = Tok.getLocation(); ConsumeToken(); + + ParsedAttributes Attrs(AttrFactory); + if (isCXX11AttributeSpecifier()) { + Diag(Tok, getLangOpts().CPlusPlus26 + ? diag::warn_cxx23_compat_decl_attrs_on_binding + : diag::ext_decl_attrs_on_binding); + MaybeParseCXX11Attributes(Attrs); + } + + Bindings.push_back({II, Loc, std::move(Attrs)}); } if (Tok.isNot(tok::r_square)) @@ -7095,6 +7114,8 @@ void Parser::ParseDecompositionDeclarator(Declarator &D) { T.consumeClose(); } + PA.Commit(); + return D.setDecompositionBindings(T.getOpenLocation(), Bindings, T.getCloseLocation()); } diff --git a/clang/lib/Sema/DeclSpec.cpp b/clang/lib/Sema/DeclSpec.cpp index b79683bb32a69e..5f63c857c43067 100644 --- a/clang/lib/Sema/DeclSpec.cpp +++ b/clang/lib/Sema/DeclSpec.cpp @@ -293,7 +293,7 @@ DeclaratorChunk DeclaratorChunk::getFunction(bool hasProto, void Declarator::setDecompositionBindings( SourceLocation LSquareLoc, - ArrayRef<DecompositionDeclarator::Binding> Bindings, + MutableArrayRef<DecompositionDeclarator::Binding> Bindings, SourceLocation RSquareLoc) { assert(!hasName() && "declarator given multiple names!"); @@ -317,7 +317,7 @@ void Declarator::setDecompositionBindings( new DecompositionDeclarator::Binding[Bindings.size()]; BindingGroup.DeleteBindings = true; } - std::uninitialized_copy(Bindings.begin(), Bindings.end(), + std::uninitialized_move(Bindings.begin(), Bindings.end(), BindingGroup.Bindings); } } diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index 452e00fa32b102..2e27e031b8fabd 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -1974,7 +1974,7 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions &LangOpts, // it is, by the bindings' expressions). bool IsAllPlaceholders = true; for (const auto *BD : DD->bindings()) { - if (BD->isReferenced()) + if (BD->isReferenced() || BD->hasAttr<UnusedAttr>()) return false; IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts); } diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp index abdbc9d8830c03..1a71a37c0732aa 100644 --- a/clang/lib/Sema/SemaDeclCXX.cpp +++ b/clang/lib/Sema/SemaDeclCXX.cpp @@ -910,6 +910,8 @@ Sema::ActOnDecompositionDeclarator(Scope *S, Declarator &D, auto *BD = BindingDecl::Create(Context, DC, B.NameLoc, VarName); + ProcessDeclAttributeList(S, BD, *B.Attrs); + // Find the shadowed declaration before filtering for scope. NamedDecl *ShadowedDecl = D.getCXXScopeSpec().isEmpty() ? getShadowedDeclaration(BD, Previous) diff --git a/clang/test/Lexer/cxx-features.cpp b/clang/test/Lexer/cxx-features.cpp index baaa9d4434e9b7..4a08eb61cd3978 100644 --- a/clang/test/Lexer/cxx-features.cpp +++ b/clang/test/Lexer/cxx-features.cpp @@ -222,7 +222,7 @@ #error "wrong value for __cpp_aggregate_bases" #endif -#if check(structured_bindings, 0, 0, 0, 201606, 201606, 201606, 201606) +#if check(structured_bindings, 0, 0, 0, 202403L, 202403L, 202403L, 202403L) #error "wrong value for __cpp_structured_bindings" #endif diff --git a/clang/test/Parser/cxx1z-decomposition.cpp b/clang/test/Parser/cxx1z-decomposition.cpp index 90d60df2e47fe8..81ad13e2381bc1 100644 --- a/clang/test/Parser/cxx1z-decomposition.cpp +++ b/clang/test/Parser/cxx1z-decomposition.cpp @@ -1,5 +1,6 @@ -// RUN: %clang_cc1 -std=c++17 %s -verify=expected,cxx17 -fcxx-exceptions -// RUN: %clang_cc1 -std=c++2b %s -verify=expected,cxx2b -fcxx-exceptions +// RUN: %clang_cc1 -std=c++17 %s -verify=expected,cxx17,pre2c -fcxx-exceptions +// RUN: %clang_cc1 -std=c++2b %s -verify=expected,cxx2b,pre2c,post2b -fcxx-exceptions +// RUN: %clang_cc1 -std=c++2c %s -verify=expected,cxx2c,post2b -fcxx-exceptions // RUN: not %clang_cc1 -std=c++17 %s -emit-llvm-only -fcxx-exceptions struct S { int a, b, c; }; @@ -58,7 +59,7 @@ namespace OtherDecl { namespace GoodSpecifiers { void f() { int n[1]; - const volatile auto &[a] = n; // cxx2b-warning {{volatile qualifier in structured binding declaration is deprecated}} + const volatile auto &[a] = n; // post2b-warning {{volatile qualifier in structured binding declaration is deprecated}} } } @@ -97,8 +98,8 @@ namespace BadSpecifiers { S [a] = s; // expected-error {{cannot be declared with type 'S'}} decltype(auto) [b] = s; // expected-error {{cannot be declared with type 'decltype(auto)'}} auto ([c2]) = s; // cxx17-error {{decomposition declaration cannot be declared with parenthese}} \ - // cxx2b-error {{use of undeclared identifier 'c2'}} \ - // cxx2b-error {{expected body of lambda expression}} \ + // post2b-error {{use of undeclared identifier 'c2'}} \ + // post2b-error {{expected body of lambda expression}} \ // FIXME: This error is not very good. auto [d]() = s; // expected-error {{expected ';'}} expected-error {{expected expression}} @@ -119,9 +120,6 @@ namespace BadSpecifiers { [[]] auto [ok_3] = s; alignas(S) auto [ok_4] = s; - // ... but not after the identifier or declarator. - // FIXME: These errors are not very good. - auto [bad_attr_1 [[]]] = s; // expected-error {{attribute list cannot appear here}} expected-error 2{{}} auto [bad_attr_2] [[]] = s; // expected-error {{expected ';'}} expected-error {{}} } } @@ -156,3 +154,27 @@ namespace Init { S [goodish4] { 4 }; // expected-error {{cannot be declared with type 'S'}} } } + + +namespace attributes { + +struct S{ + int a; + int b = 0; +}; + +void err() { + auto [[]] = S{0}; // expected-error {{expected unqualified-id}} + auto [ alignas(42) a, foo ] = S{0}; // expected-error {{an attribute list cannot appear here}} + auto [ c, [[]] d ] = S{0}; // expected-error {{an attribute list cannot appear here}} + auto [ e, alignas(42) f ] = S{0}; // expected-error {{an attribute list cannot appear here}} +} + +void ok() { + auto [ a alignas(42) [[]], b alignas(42) [[]]] = S{0}; // expected-error 2{{'alignas' attribute only applies to variables, data members and tag types}} \ + // pre2c-warning 2{{an attribute specifier sequence attached to a structured binding declaration is a C++2c extension}} + auto [ c [[]] alignas(42), d [[]] alignas(42) [[]]] = S{0}; // expected-error 2{{'alignas' attribute only applies to variables, data members and tag types}} \ + // pre2c-warning 2{{an attribute specifier sequence attached to a structured binding declaration is a C++2c extension}} +} + +} diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp index 0af9e5b68b00df..1f40c1b1ca903d 100644 --- a/clang/test/SemaCXX/unused.cpp +++ b/clang/test/SemaCXX/unused.cpp @@ -102,11 +102,21 @@ namespace PR33839 { for (auto [x] : a) { // expected-warning {{unused variable '[x]'}} } } - void use() { + void use() { f<int>(); // expected-note {{instantiation of}} g<true>(); g<false>(); h<int>(); // expected-note {{instantiation of}} } } + +namespace maybe_unused_binding { + +void test() { + struct X { int a, b; } x; + auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute specifier sequence attached to a structured binding declaration is a C++2c extension}} +} + +} + #endif diff --git a/clang/www/cxx_status.html b/clang/www/cxx_status.html index c233171e63c811..0d796597d05c0e 100755 --- a/clang/www/cxx_status.html +++ b/clang/www/cxx_status.html @@ -187,7 +187,7 @@ <h2 id="cxx26">C++2c implementation status</h2> <tr> <td>Trivial infinite loops are not Undefined Behavior</td> <td><a href="https://wg21.link/P2809R3";>P2809R3</a> (<a href="#dr">DR</a>)</td> - <td class="none" align="center">No</td> + <td class="unreleased" align="center">Clang 19</td> </tr> <tr> <td>Erroneous behaviour for uninitialized reads</td> _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
