From: Jakub Jelinek Date: Tue, 7 May 2024 20:38:01 +0000 (+0200) Subject: c++: Implement C++26 P2893R3 - Variadic friends [PR114459] X-Git-Tag: basepoints/gcc-16~9249 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=17458d2bc74b904968e6bdc12527eb040c8d2370;p=thirdparty%2Fgcc.git c++: Implement C++26 P2893R3 - Variadic friends [PR114459] The following patch imeplements the C++26 P2893R3 - Variadic friends paper. The paper allows for the friend type declarations to specify more than one friend type specifier and allows to specify ... at the end of each. The patch doesn't introduce tentative parsing of friend-type-declaration non-terminal, but rather just extends existing parsing where it is a friend declaration which ends with ; after the declaration specifiers to the cases where it ends with ...; or , or ..., In that case it pedwarns for cxx_dialect < cxx26, handles the ... and if there is , continues in a loop to parse the further friend type specifiers. 2024-05-07 Jakub Jelinek PR c++/114459 gcc/c-family/ * c-cppbuiltin.cc (c_cpp_builtins): Predefine __cpp_variadic_friend=202403L for C++26. gcc/cp/ * parser.cc (cp_parser_member_declaration): Implement C++26 P2893R3 - Variadic friends. Parse friend type declarations with ... or with more than one friend type specifier. * friend.cc (make_friend_class): Allow TYPE_PACK_EXPANSION. * pt.cc (instantiate_class_template): Handle PACK_EXPANSION_P in friend classes. gcc/testsuite/ * g++.dg/cpp26/feat-cxx26.C (__cpp_variadic_friend): Add test. * g++.dg/cpp26/variadic-friend1.C: New test. --- diff --git a/gcc/c-family/c-cppbuiltin.cc b/gcc/c-family/c-cppbuiltin.cc index b6f25e4db3c..d9b84a0f1b9 100644 --- a/gcc/c-family/c-cppbuiltin.cc +++ b/gcc/c-family/c-cppbuiltin.cc @@ -1093,6 +1093,7 @@ c_cpp_builtins (cpp_reader *pfile) cpp_define (pfile, "__cpp_placeholder_variables=202306L"); cpp_define (pfile, "__cpp_structured_bindings=202403L"); cpp_define (pfile, "__cpp_deleted_function=202403L"); + cpp_define (pfile, "__cpp_variadic_friend=202403L"); } if (flag_concepts) { diff --git a/gcc/cp/friend.cc b/gcc/cp/friend.cc index 758ea87b172..2e70d0160c4 100644 --- a/gcc/cp/friend.cc +++ b/gcc/cp/friend.cc @@ -279,7 +279,8 @@ make_friend_class (tree type, tree friend_type, bool complain) } if (! MAYBE_CLASS_TYPE_P (friend_type) - && TREE_CODE (friend_type) != TEMPLATE_TEMPLATE_PARM) + && TREE_CODE (friend_type) != TEMPLATE_TEMPLATE_PARM + && TREE_CODE (friend_type) != TYPE_PACK_EXPANSION) { /* N1791: If the type specifier in a friend declaration designates a (possibly cv-qualified) class type, that class is declared as a diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc index 775067ed4bc..c4191200291 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -28100,8 +28100,17 @@ cp_parser_member_declaration (cp_parser* parser) && cp_parser_parse_and_diagnose_invalid_type_name (parser)) goto out; /* If there is no declarator, then the decl-specifier-seq should - specify a type. */ - if (cp_lexer_next_token_is (parser->lexer, CPP_SEMICOLON)) + specify a type. For C++26 Variadic friends don't just check for + a semicolon, but also for a comma and in both cases optionally + preceded by ellipsis. */ + if (cp_lexer_next_token_is (parser->lexer, CPP_SEMICOLON) + || (cp_parser_friend_p (&decl_specifiers) + && cxx_dialect >= cxx11 + && (cp_lexer_next_token_is (parser->lexer, CPP_COMMA) + || (cp_lexer_next_token_is (parser->lexer, CPP_ELLIPSIS) + && (cp_lexer_nth_token_is (parser->lexer, 2, CPP_SEMICOLON) + || cp_lexer_nth_token_is (parser->lexer, 2, + CPP_COMMA)))))) { /* If there was no decl-specifier-seq, and the next token is a `;', then we have something like: @@ -28136,44 +28145,81 @@ cp_parser_member_declaration (cp_parser* parser) { /* If the `friend' keyword was present, the friend must be introduced with a class-key. */ - if (!declares_class_or_enum && cxx_dialect < cxx11) - pedwarn (decl_spec_token_start->location, OPT_Wpedantic, - "in C++03 a class-key must be used " - "when declaring a friend"); - /* In this case: - - template struct A { - friend struct A::B; - }; - - A::B will be represented by a TYPENAME_TYPE, and - therefore not recognized by check_tag_decl. */ - if (!type) - { - type = decl_specifiers.type; - if (type && TREE_CODE (type) == TYPE_DECL) - type = TREE_TYPE (type); - } - /* Warn if an attribute cannot appear here, as per - [dcl.attr.grammar]/5. But not when declares_class_or_enum: - we ignore attributes in elaborated-type-specifiers. */ - if (!declares_class_or_enum - && cxx11_attribute_p (decl_specifiers.attributes)) - { - decl_specifiers.attributes = NULL_TREE; - if (warning_at (decl_spec_token_start->location, - OPT_Wattributes, "attribute ignored")) - inform (decl_spec_token_start->location, "an attribute " - "that appertains to a friend declaration that " - "is not a definition is ignored"); - } - if (!type || !TYPE_P (type)) - error_at (decl_spec_token_start->location, - "friend declaration does not name a class or " - "function"); - else - make_friend_class (current_class_type, type, - /*complain=*/true); + if (!declares_class_or_enum && cxx_dialect < cxx11) + pedwarn (decl_spec_token_start->location, OPT_Wpedantic, + "in C++03 a class-key must be used " + "when declaring a friend"); + if (!cp_lexer_next_token_is (parser->lexer, CPP_SEMICOLON) + && cxx_dialect < cxx26) + pedwarn (cp_lexer_peek_token (parser->lexer)->location, + OPT_Wc__26_extensions, + "variadic friends or friend type declarations with " + "multiple types only available with " + "%<-std=c++2c%> or %<-std=gnu++2c%>"); + location_t friend_loc = decl_specifiers.locations[ds_friend]; + do + { + /* In this case: + + template struct A { + friend struct A::B; + }; + + A::B will be represented by a TYPENAME_TYPE, and + therefore not recognized by check_tag_decl. */ + if (!type) + { + type = decl_specifiers.type; + if (type && TREE_CODE (type) == TYPE_DECL) + type = TREE_TYPE (type); + } + /* Warn if an attribute cannot appear here, as per + [dcl.attr.grammar]/5. But not when + declares_class_or_enum: we ignore attributes in + elaborated-type-specifiers. */ + if (!declares_class_or_enum + && cxx11_attribute_p (decl_specifiers.attributes)) + { + decl_specifiers.attributes = NULL_TREE; + if (warning_at (decl_spec_token_start->location, + OPT_Wattributes, "attribute ignored")) + inform (decl_spec_token_start->location, "an attribute " + "that appertains to a friend declaration that " + "is not a definition is ignored"); + } + bool ellipsis = cp_lexer_next_token_is (parser->lexer, + CPP_ELLIPSIS); + if (ellipsis) + cp_lexer_consume_token (parser->lexer); + if (!type || !TYPE_P (type)) + error_at (decl_spec_token_start->location, + "friend declaration does not name a class or " + "function"); + else + { + if (ellipsis) + type = make_pack_expansion (type); + if (type != error_mark_node) + make_friend_class (current_class_type, type, + /*complain=*/true); + } + if (!cp_lexer_next_token_is (parser->lexer, CPP_COMMA)) + break; + cp_lexer_consume_token (parser->lexer); + clear_decl_specs (&decl_specifiers); + decl_specifiers.locations[ds_friend] = friend_loc; + decl_specifiers.any_specifiers_p = true; + declares_class_or_enum = false; + cp_parser_type_specifier (parser, + CP_PARSER_FLAGS_TYPENAME_OPTIONAL, + &decl_specifiers, + /*is_declaration=*/true, + &declares_class_or_enum, NULL); + type = check_tag_decl (&decl_specifiers, + /*explicit_type_instantiation_p=*/ + false); + } + while (1); } /* If there is no TYPE, an error message will already have been issued. */ diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 7a3a4e7d77e..1816bfd1f40 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -12693,6 +12693,22 @@ instantiate_class_template (tree type) tf_warning_or_error, NULL_TREE); --processing_template_decl; } + else if (PACK_EXPANSION_P (friend_type)) + { + friend_type = tsubst_pack_expansion (friend_type, args, + tf_warning_or_error, + NULL_TREE); + if (friend_type != error_mark_node) + { + unsigned int len = TREE_VEC_LENGTH (friend_type); + for (unsigned int idx = 0; idx < len; ++idx) + if (TREE_VEC_ELT (friend_type, idx) != error_mark_node) + make_friend_class (type, + TREE_VEC_ELT (friend_type, idx), + /*complain=*/false); + } + friend_type = error_mark_node; + } else if (uses_template_parms (friend_type)) /* friend class C; */ friend_type = tsubst (friend_type, args, diff --git a/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C b/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C index de66dcccd02..8a5fd64d396 100644 --- a/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C +++ b/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C @@ -615,3 +615,9 @@ #elif __cpp_deleted_function != 202403 # error "__cpp_deleted_function != 202403" #endif + +#ifndef __cpp_variadic_friend +# error "__cpp_variadic_friend" +#elif __cpp_variadic_friend != 202403 +# error "__cpp_variadic_friend != 202403" +#endif diff --git a/gcc/testsuite/g++.dg/cpp26/variadic-friend1.C b/gcc/testsuite/g++.dg/cpp26/variadic-friend1.C new file mode 100644 index 00000000000..25c6c456f6b --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp26/variadic-friend1.C @@ -0,0 +1,58 @@ +// P2893R3 - Variadic friends +// { dg-do compile { target c++11 } } +// { dg-options "" } + +template +class A { + class X {}; + friend Ts...; // { dg-warning "variadic friends or friend type declarations with multiple types only available with" "" { target c++23_down } } +}; +template +class A, A> { + class X {}; + friend +#if __cplusplus < 202002L + typename +#endif + Ts::Y..., Us...; // { dg-warning "variadic friends or friend type declarations with multiple types only available with" "" { target c++23_down } } +}; +template +class B { + class X {}; + friend T, U; // { dg-warning "variadic friends or friend type declarations with multiple types only available with" "" { target c++23_down } } +}; +template +class C { + class X {}; + friend U, Vs..., T; // { dg-warning "variadic friends or friend type declarations with multiple types only available with" "" { target c++23_down } } +}; +class E; +class F; +class G; +class H; +class I; +class J; +class K; +class L; +class M; +class N; +class O; +class P; +class E : A::X {}; +class F : A::X {}; +class G : B::X {}; +class H : B::X {}; +class I : C::X {}; +class J : C::X {}; +class K : C::X {}; +class L : C::X {}; +class M : C::X {}; +class N : C::X {}; +class O : C::X {}; +struct Q { class Y : A, A>::X {}; }; +class P : A, A>::X {}; +struct R { class Y; }; +struct S { class Y; }; +class R::Y : A, A>::X {}; +class S::Y : A, A>::X {}; +A a;