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[130.44.159.43]) by smtp.gmail.com with ESMTPSA id fb16-20020a05622a481000b003a4cda52c95sm7848464qtb.63.2022.11.15.15.36.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Nov 2022 15:36:40 -0800 (PST) Message-ID: Date: Tue, 15 Nov 2022 18:36:38 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH] c++, v2: Implement C++23 P2647R1 - Permitting static constexpr variables in constexpr functions To: Jakub Jelinek Cc: gcc-patches@gcc.gnu.org, Marek Polacek , Jonathan Wakely References: From: Jason Merrill In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-6.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 11/13/22 01:45, Jakub Jelinek wrote: > On Fri, Nov 11, 2022 at 06:07:04PM +0100, Jakub Jelinek wrote: >> The following patch on top of Marek's P2448 PR106649 patch >> (mainly because that patch implements the previous __cpp_constexpr >> feature test macro bump so this can't go in earlier; OT, >> P2280R4 doesn't have any feature test macro?) implements this >> simple paper. >> >> Ok for trunk if it passes bootstrap/regtest and is voted into C++23? > > Here is an updated patch that passed bootstrap/regtest, the only > change is another testcase tweak. > > 2022-11-13 Jakub Jelinek > > gcc/c-family/ > * c-cppbuiltin.cc (c_cpp_builtins): Bump __cpp_constexpr > value from 202207L to 202211L. > gcc/cp/ > * constexpr.cc (cxx_eval_constant_expression): Implement C++23 > P2647R1 - Permitting static constexpr variables in constexpr functions. > Allow decl_maybe_constant_var_p static or thread_local vars for > C++23. This was accepted as a DR, so it shouldn't be limited to C++23 mode. Certainly it should be allowed in C++20 mode; I don't have a strong opinion about C++14/17. Jonathan, do you? > (potential_constant_expression_1): Likewise. > gcc/testsuite/ > * g++.dg/cpp23/constexpr-nonlit17.C: New test. > * g++.dg/cpp23/feat-cxx2b.C: Adjust expected __cpp_constexpr > value. > * g++.dg/ext/stmtexpr19.C: Don't expect an error for C++23 or later. > > --- gcc/c-family/c-cppbuiltin.cc.jj 2022-11-11 17:14:52.021613271 +0100 > +++ gcc/c-family/c-cppbuiltin.cc 2022-11-11 17:17:45.065265246 +0100 > @@ -1074,7 +1074,7 @@ c_cpp_builtins (cpp_reader *pfile) > /* Set feature test macros for C++23. */ > cpp_define (pfile, "__cpp_size_t_suffix=202011L"); > cpp_define (pfile, "__cpp_if_consteval=202106L"); > - cpp_define (pfile, "__cpp_constexpr=202207L"); > + cpp_define (pfile, "__cpp_constexpr=202211L"); > cpp_define (pfile, "__cpp_multidimensional_subscript=202110L"); > cpp_define (pfile, "__cpp_named_character_escapes=202207L"); > cpp_define (pfile, "__cpp_static_call_operator=202207L"); > --- gcc/cp/constexpr.cc.jj 2022-11-11 17:14:52.024613231 +0100 > +++ gcc/cp/constexpr.cc 2022-11-11 17:16:54.384952917 +0100 > @@ -7085,7 +7085,8 @@ cxx_eval_constant_expression (const cons > && (TREE_STATIC (r) > || (CP_DECL_THREAD_LOCAL_P (r) && !DECL_REALLY_EXTERN (r))) > /* Allow __FUNCTION__ etc. */ > - && !DECL_ARTIFICIAL (r)) > + && !DECL_ARTIFICIAL (r) > + && (cxx_dialect < cxx23 || !decl_maybe_constant_var_p (r))) > { > if (!ctx->quiet) > { > @@ -9577,7 +9578,10 @@ potential_constant_expression_1 (tree t, > tmp = DECL_EXPR_DECL (t); > if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp)) > { > - if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp)) > + if (CP_DECL_THREAD_LOCAL_P (tmp) > + && !DECL_REALLY_EXTERN (tmp) > + && (cxx_dialect < cxx23 > + || !decl_maybe_constant_var_p (tmp))) > { > if (flags & tf_error) > constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p, > @@ -9585,7 +9589,9 @@ potential_constant_expression_1 (tree t, > "% context", tmp); > return false; > } > - else if (TREE_STATIC (tmp)) > + else if (TREE_STATIC (tmp) > + && (cxx_dialect < cxx23 > + || !decl_maybe_constant_var_p (tmp))) > { > if (flags & tf_error) > constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p, > --- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C.jj 2022-11-11 17:59:59.972852793 +0100 > +++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C 2022-11-11 17:59:38.725141231 +0100 > @@ -0,0 +1,12 @@ > +// P2647R1 - Permitting static constexpr variables in constexpr functions > +// { dg-do compile { target c++23 } } > + > +constexpr char > +test () > +{ > + static const int x = 5; > + static constexpr char c[] = "Hello World"; > + return *(c + x); > +} > + > +static_assert (test () == ' '); > --- gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C.jj 2022-11-11 17:14:52.194610922 +0100 > +++ gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C 2022-11-11 17:48:56.038865825 +0100 > @@ -134,8 +134,8 @@ > > #ifndef __cpp_constexpr > # error "__cpp_constexpr" > -#elif __cpp_constexpr != 202207 > -# error "__cpp_constexpr != 202207" > +#elif __cpp_constexpr != 202211 > +# error "__cpp_constexpr != 202211" > #endif > > #ifndef __cpp_decltype_auto > --- gcc/testsuite/g++.dg/ext/stmtexpr19.C.jj 2020-01-14 20:02:46.839608995 +0100 > +++ gcc/testsuite/g++.dg/ext/stmtexpr19.C 2022-11-12 09:17:40.706245495 +0100 > @@ -8,7 +8,7 @@ const test* setup() > { > static constexpr test atest = > { > - ({ static const int inner = 123; &inner; }) // { dg-error "static" } > + ({ static const int inner = 123; &inner; }) // { dg-error "static" "" { target c++20_down } } > }; > > return &atest; > > > Jakub >