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[130.44.159.43]) by smtp.gmail.com with ESMTPSA id bw13-20020a05622a098d00b0031f36cd1958sm8728053qtb.81.2022.08.31.09.14.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 31 Aug 2022 09:14:24 -0700 (PDT) Message-ID: Date: Wed, 31 Aug 2022 12:14:22 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.13.0 Subject: Re: [PATCH] c++, v2: Implement C++23 P2071R2 - Named universal character escapes [PR106648] To: Jakub Jelinek Cc: Joseph Myers , gcc-patches@gcc.gnu.org References: <4fcd7e74-6f1c-dbec-a42c-e4e3fd13470b@redhat.com> <5da578e7-9c43-99ea-15c1-aefc641a0654@redhat.com> 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: 8bit X-Spam-Status: No, score=-6.6 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,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE 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 8/31/22 11:07, Jakub Jelinek wrote: > On Wed, Aug 31, 2022 at 10:52:49AM -0400, Jason Merrill wrote: >> It could be more explicit, but I think we can assume that from the existing >> wording; it says it designates the named character. If there is no such >> character, that cannot be satisfied, so it must be ill-formed. > > Ok. > >>> So, we could reject the int h case above and accept silently the others? >> >> Why not warn on the others? > > We were always silent for the cases like \u123X or \U12345X. > Do you think we should emit some warnings (but never pedwarns/errors in that > case) that it is universal character name like but not completely? I think that would be helpful, at least for \u{ and \N{. > The following patch let's us silently accept: > #define z(x) 0 > #define a z( > int b = a\u{}); > int c = a\u{); > int d = a\N{}); > int e = a\N{); > int f = a\u123); > int g = a\U1234567); > int h = a\N); > int i = a\NARG); > int j = a\N{abc}); > int k = a\N{ABC.123}); > > The following 2 will be still rejected with errors: > int l = a\N{ABC}); > int m = a\N{LATIN SMALL LETTER A WITH ACUTE}); > the first one because ABC is not valid Unicode name and the latter because > it will be int m = aá); and will trigger other errors later. > > Given what you said above, I think that is what we want for the last 2 > for C++23, the question is if it is ok also for C++20/C17 etc. and whether > it should depend on -pedantic or -pedantic-errors or GNU vs. ISO mode > or not in that case. We could handle those 2 also differently, just > warn instead of error for the \N{ABC} case if not in C++23 mode when > identifier_pos. That sounds right. > Here is an incremental version of the patch which will make valid > \u{123} and \N{LATIN SMALL LETTER A WITH ACUTE} an extension in GNU > modes before C++23 and split it as separate tokens in ISO modes. Looks good. Jason