From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp78.iad3a.emailsrvr.com (smtp78.iad3a.emailsrvr.com [173.203.187.78]) by sourceware.org (Postfix) with ESMTPS id E91CD385840A for ; Sun, 24 Jul 2022 04:46:07 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E91CD385840A X-Auth-ID: tom@honermann.net Received: by smtp10.relay.iad3a.emailsrvr.com (Authenticated sender: tom-AT-honermann.net) with ESMTPSA id 5B3755D8D; Sun, 24 Jul 2022 00:46:07 -0400 (EDT) Message-ID: <48aa78ed-6ba6-95f4-206c-d6b462d31b49@honermann.net> Date: Sun, 24 Jul 2022 00:46:06 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH v4 2/3] stdlib: Implement mbrtoc8(), c8rtomb(), and the char8_t typedef. Content-Language: en-US To: Adhemerval Zanella Netto , Joseph Myers Cc: libc-alpha@sourceware.org References: <20220630125215.6052-1-tom@honermann.net> <20220630125215.6052-3-tom@honermann.net> <6cf42820-86cb-f3ee-e4cf-3310de2e0bd1@honermann.net> <9940d0fb-0907-7ab2-2dc0-29236fc286a3@honermann.net> <68dad418-f607-e0af-1983-df01ed1e422f@linaro.org> From: Tom Honermann In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Classification-ID: d22be978-82cc-4dcb-bba2-ff47da580e4d-1-1 X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00, BODY_8BITS, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, KAM_SHORT, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, 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 X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 24 Jul 2022 04:46:10 -0000 On 7/22/22 1:24 AM, Tom Honermann via Libc-alpha wrote: > On 7/21/22 4:56 PM, Adhemerval Zanella Netto wrote: >> >> On 21/07/22 17:51, Tom Honermann wrote: >>> On 7/21/22 3:22 PM, Adhemerval Zanella Netto wrote: >>>> On 20/07/22 13:47, Tom Honermann wrote: >>>>> Confirmed that this issue can be easily reproduced outside the >>>>> testsuite. >>>>> >>>>> $ cat t.cpp >>>>> #include >>>>> >>>>> $ g++ --version >>>>> g++ (GCC) 13.0.0 20220720 (experimental) >>>>> ... >>>>> >>>>> $ g++ -c -I/path/to/glibc-char8_t/include -std=c++17 >>>>> -Werror=c++20-compat t.cpp >>>>> In file included from t.cpp:1: >>>>> /home/tom/products/glibc-char8_t/include/uchar.h:38:23: error: >>>>> identifier ‘char8_t’ is a keyword in C++20 [-Werror=c++20-compat] >>>>>      38 | typedef unsigned char char8_t; >>>>>         |                       ^~~~~~~ >>>>> cc1plus: some warnings being treated as errors >>>>> >>>>> The char8_t typedef is currently guarded by: >>>>> >>>>> /* Declare the C2x char8_t typedef in C2x modes, but only if the C++ >>>>>     __cpp_char8_t feature test macro is not defined.  */ >>>>> #if __GLIBC_USE (ISOC2X) && !defined __cpp_char8_t >>>>> /* Define the 8-bit character type.  */ >>>>> typedef unsigned char char8_t; >>>>> #endif >>>>> >>>>> __GLIBC_USE (ISOC2X) evaluates to true because gcc unconditionally >>>>> defines _GNU_SOURCE. I believe otherwise, C++17 mode would only >>>>> (or should only) imply __GLIBC_USE (ISOC11). >>>>> >>>>> Regardless, it seems that directives should be added to suppress >>>>> the diagnostic. I tried prototyping such a fix, but it doesn't >>>>> seem to work for me. I don't understand why. >>>> I have tried as well and I can't get to work either.  It would >>>> expect to work >>>> as we have done bits/stdlib-bsearch.h, could it be a gcc issue? >>> Yes, this appears to be a gcc issue. I spent some time looking at >>> gcc source code, but didn't find anything obvious. I verified the >>> same technique does work to suppress the similar warning issued for >>> use of, e.g., constexpr, as an identifier when -Wc++11-compat is >>> enabled. I found tests that exercise #pragma GCC diagnostic ignored >>> "-Wc++-compat", but none for -Wc++20-compat (or -Wc++11-compat). >>> >>> Tom. >>> >> In any case I think the fix below is the correct way (in fact I don't >> see >> another way so I am assuming a compiler issue here). > I agree. I debugged gcc tonight and discovered what the problem was. > I'll submit a patch to gcc. A patch has been submitted to gcc to correct '#pragma GCC diagnostic ignored' based suppression for -Wc++20-compat diagnostics. See the thread at https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598736.html. Tom.