Date: Tue, 9 Jul 2013 09:13:12 +0100 From: David Chisnall <theraven@FreeBSD.org> To: Tim Kientzle <tim@kientzle.com> Cc: dt71@gmx.com, freebsd-current@FreeBSD.org Subject: Re: another -Wunsequenced topic Message-ID: <374FC203-F5FB-4C7C-84D3-76A7AD507D90@FreeBSD.org> In-Reply-To: <6AC1186D-3D9C-4B7A-B5E4-4EA9CB120517@kientzle.com> References: <51CEEC34.2010308@gmx.com> <51D03D27.3020100@gmx.com> <51DAA5FE.4040505@gmx.com> <6AC1186D-3D9C-4B7A-B5E4-4EA9CB120517@kientzle.com>
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[-- Attachment #1 --] On 9 Jul 2013, at 05:40, Tim Kientzle <tim@kientzle.com> wrote: > However, this does have an implicit redundant store, > so changing it to > > ptr = func(ptr + 1); > > is still a good idea, just not for the reason Clang was claiming. If the compiler can tell that ptr has not escaped, then it will elide the redundant store (typically, it will be gone as long as ptr is a local and its address has not been passed out of the function), so there should be no change to the generated code. However, I still agree that it is good style, because if I read the original code I would be left wondering what the original programmer expected the incremented value of ptr++ to be visible to and suspect a more subtle error. David [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.18 (Darwin) Comment: GPGTools - http://gpgtools.org iQIcBAEBAgAGBQJR28YYAAoJEKx65DEEsqIdj6gP/jdC6pgahOjH/rP+cKoSuo2p Z5S3BcaFn7d0VNeqFxN29lxfqjvnqwXLcZg2G/p7u4Vkn78sXwUNqX9XjIk5QmVY 5LQ1qez6QLrpPKcmwC3yHaKuiPm0yThy4I/v/sRmEXgkFYw4JMuvOsfq0aWO4guj h7CtRXHkvxH7xx5RY4miWnow76W39IUSZFbidSWYmDydHrzIy/zgBzlQgnWg7NWI GGa6ESM7L7/1EQ61jSSBGxlW39Rfw8qQsBsrpg61rQs/7u/ZpKNpS9x3Cqy7npww eqwCePVa6DeVMYJgd3Lx8TNOR7jND7qjw4GcsLBk5zXK5lkpyK1tVc1AlL4eiEJJ wPiq91SIvwJgoNUT2qGYhlAxrDCqtkucPK46MG2hOD+tAv0FCCZKTcF/VtjA12uP eQnPDwyAIDHDGWJVBuRMny7mMv4jn+TpHIe1D+5NNYkQw8kPUbqCddsRgj3hJfaA og9hoV3EhKEbJTS574XjPw7AQaJrosJR8sRTKcm/fjMbEn7xylw0B0CU+NK/eH9s lQvBWRPwldzYONRq6FCMyaKMSD8U1ZsMQMg82hjN53e16PYU8dZGrkrxFU3OhBWf yFxeqWM5ez0x3YK/3lG7lqgDqzYm3m3IzdLfaogz/4ksdj4uzdObueCfnqVJCRBz 2dfonQ6HcbHM2B5H81/j =qg4B -----END PGP SIGNATURE-----
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