Date: Thu, 5 Feb 2015 09:29:01 +0000 From: David Chisnall <theraven@FreeBSD.org> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: Konstantin Belousov <kostikbel@gmail.com>, "freebsd-current@freebsd.org" <freebsd-current@freebsd.org>, Peter Wemm <peter@wemm.org> Subject: Re: PSA: If you run -current, beware! Message-ID: <FE51D754-7B35-48A5-8B8D-CA957194D48C@FreeBSD.org> In-Reply-To: <CA%2BhQ2%2BiVE53PJs0noc_SPHpwDZVLX-tHpgYmzO9tGzJzDXwXWg@mail.gmail.com> References: <8089702.oYScRm8BTN@overcee.wemm.org> <20150204142941.GE42409@kib.kiev.ua> <2509923.ondFvsFdql@overcee.wemm.org> <CA%2BhQ2%2BiVE53PJs0noc_SPHpwDZVLX-tHpgYmzO9tGzJzDXwXWg@mail.gmail.com>
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On 5 Feb 2015, at 07:48, Luigi Rizzo <rizzo@iet.unipi.it> wrote: > > Rather than depending on a compiler option, wouldn't it be better/more > robust to change ticks to unsigned, which has specified wrapping behavior? Especially if we want to extend support for external toolchains. gcc and clang support -fwrapv (though occasionally versions of both will not fully support it), but other compilers may well not have an equivalent. Translating the code into C is a far more robust solution than the band-aid of telling the compiler to accept a language that is a bit like C and hoping that this will keep working across compiler implementations and versions. Adding -fwrapv also defeats a number of compiler optimisations, so we are going to generate worse code for places where people used signed types correctly to work around places where they were used incorrectly. Davidhome | help
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