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[81.138.1.83]) by smtp.googlemail.com with ESMTPSA id l11sm1929420wms.45.2021.10.08.00.20.58 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Oct 2021 00:20:59 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.21\)) Subject: Re: libgfortran.so SONAME and powerpc64le-linux ABI changes From: Iain Sandoe In-Reply-To: <5533983c-f4d2-5041-75c9-9287e4e31f10@netcologne.de> Date: Fri, 8 Oct 2021 08:20:58 +0100 Cc: Jakub Jelinek , Michael Meissner , fortran@gcc.gnu.org, GCC Development , Tobias Burnus , Segher Boessenkool , David Edelsohn , Paul Thomas Content-Transfer-Encoding: quoted-printable Message-Id: <749ABCA1-5C3B-4EB8-8E4F-9B967A67AB07@googlemail.com> References: <20211004100754.GL304296@tucnak> <3dacfdf6-6b23-f307-969a-94265b506edb@netcologne.de> <20211007153306.GY304296@tucnak> <5533983c-f4d2-5041-75c9-9287e4e31f10@netcologne.de> To: Thomas Koenig X-Mailer: Apple Mail (2.3445.104.21) X-Spam-Status: No, score=-3.0 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 08 Oct 2021 07:21:02 -0000 > On 8 Oct 2021, at 07:35, Thomas Koenig via Fortran = wrote: >=20 >=20 > On 07.10.21 17:33, Jakub Jelinek wrote: >>> It will also be a compatibility issue if users have code compiled on = a LE >>> system with GCC 11 and earlier with KIND=3D16, it will not link with = GCC 12. >> libgfortran ABI changed multiple times in the past already, e.g. the >> so.1 -> so.2 transition in 4.2 >> so.2 -> so.3 transition in 4.3 >> so.3 -> so.4 transition in 7 >> so.4 -> so.5 transition in 8 >> and users have coped. >=20 > Yes, and it has always been a hassle for users, and we've been > criticized for it. >=20 > This is currently a change which brings users on non-POWER-systems > (the vast majority) all pain and no gain. If this cannot be > avoided, I would at least try to fit in as much of other improvements > as there are possible. If one wanted to prioritize library SO name stability - then, perhaps, = the approach Jonathan mentioned has been used for libstdc++ (add new symbols for ieee128 with a different mangling to the existing r/c_16 ..) would be preferable (the FE then has to choose the relevant symbol/ mangling depending on target). .. perhaps I missed where that idea was already ruled out (in which case sorry for the noise). Iain >=20 > There's a PR for it somewhere, but I can think of three areas, none > of the small, and all require an ABI change: >=20 > a) Get PDTs right (Paul?) > b) Make file descriptors conform to the C interop version > c) Remove the run-time parsing of I/O arguments and > replace them with a bit field. >=20 > What I mean by the last one is that >=20 > WRITE (unit,'(A)',ADVANCE=3D"NO") >=20 > we currently parse the "NO" at runtime, for every statement > execution. What we could be doing instead is to have >=20 > dt_parm.0.advance =3D __gfortran_evaluate_yesno ("NO") >=20 > where the latter function can be simplified at compile-time. >=20 > We should strive to break the ABI as few times as possible. >=20 > Best regards >=20 > Thomas