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Fri, 20 Sep 2024 18:49:27 -0400 X-MC-Unique: RWP4zEb2Mn-BNu6-RtyCeQ-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (unknown [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B5DCA19792F5; Fri, 20 Sep 2024 22:49:26 +0000 (UTC) Received: from localhost (unknown [10.42.28.136]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1678F19560AA; Fri, 20 Sep 2024 22:49:25 +0000 (UTC) From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed] libstdc++: Document missing features for old std:string ABI [PR116777] Date: Fri, 20 Sep 2024 23:49:07 +0100 Message-ID: <20240920224924.929747-1-jwakely@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-13.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, 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 X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org Pushed to trunk. -- >8 -- There are several features that are not supported when using the old std::string ABI. It's possible that PR 81967 will get fixed, but the missing C++20 features almost certainly won't be. Document this in the manual. libstdc++-v3/ChangeLog: PR libstdc++/116777 * doc/xml/manual/using.xml: Document features that are not supported for the gcc4-compatible ABI. * doc/html/manual/using_dual_abi.html: Regenerate. --- .../doc/html/manual/using_dual_abi.html | 18 ++++++++++++- libstdc++-v3/doc/xml/manual/using.xml | 26 ++++++++++++++++++- 2 files changed, 42 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/doc/html/manual/using_dual_abi.html b/libstdc++-v3/doc/html/manual/using_dual_abi.html index 916ac575f64..939eedae362 100644 --- a/libstdc++-v3/doc/html/manual/using_dual_abi.html +++ b/libstdc++-v3/doc/html/manual/using_dual_abi.html @@ -22,7 +22,7 @@ of the macro is 1 which causes the new ABI to be active, so to use the old ABI you must explicitly define the macro to 0 before including any library headers. - (Be aware that some GNU/Linux distributions configure GCC 5 differently so + (Be aware that some GNU/Linux distributions configured GCC 5 differently so that the default value of the macro is 0 and users must define it to 1 to enable the new ABI.)

Although the changes were made for C++11 conformance, the choice of ABI @@ -72,6 +72,22 @@ Handlers for std::exception will always catch iostreams exceptions, because the old and new type both inherit from std::exception. +

+ Some features are not supported when using the old ABI, including: +

  • + Using std::string::const_iterator for + positional arguments to member functions such as + std::string::erase. +
  • + Allocator propagation in std::string. +
  • + Using std::string at compile-time in + constexpr functions. +
  • + Class std::chrono::time_zone and all related APIs. +
  • + The <syncstream> header. +

Troubleshooting

If you get linker errors about undefined references to symbols that involve types in the std::__cxx11 namespace or the tag [abi:cxx11] then it probably indicates that you are trying to diff --git a/libstdc++-v3/doc/xml/manual/using.xml b/libstdc++-v3/doc/xml/manual/using.xml index 4e1c70040b5..89119f6fb2d 100644 --- a/libstdc++-v3/doc/xml/manual/using.xml +++ b/libstdc++-v3/doc/xml/manual/using.xml @@ -1368,7 +1368,7 @@ g++ -Winvalid-pch -I. -include stdc++.h -H -g -O2 hello.cc -o test.exe of the macro is 1 which causes the new ABI to be active, so to use the old ABI you must explicitly define the macro to 0 before including any library headers. - (Be aware that some GNU/Linux distributions configure GCC 5 differently so + (Be aware that some GNU/Linux distributions configured GCC 5 differently so that the default value of the macro is 0 and users must define it to 1 to enable the new ABI.) @@ -1428,6 +1428,30 @@ g++ -Winvalid-pch -I. -include stdc++.h -H -g -O2 hello.cc -o test.exe std::exception. + + Some features are not supported when using the old ABI, including: + + + Using std::string::const_iterator for + positional arguments to member functions such as + std::string::erase. + + + Allocator propagation in std::string. + + + Using std::string at compile-time in + constexpr functions. + + + Class std::chrono::time_zone and all related APIs. + + + The <syncstream> header. + + + +

Troubleshooting If you get linker errors about undefined references to symbols