Date: Tue, 09 Oct 2012 22:24:56 +0400 From: Andrey Chernov <ache@freebsd.org> To: Eitan Adler <eadler@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, theraven@freebsd.org Subject: Re: svn commit: r241373 - head/lib/libc/stdlib Message-ID: <50746BF8.5010307@freebsd.org> In-Reply-To: <CAF6rxgkDbyrCHfY-5eMjJ%2B7nP9ZCnXsjLgEBB1Q_p=QJ3tCkfg@mail.gmail.com> References: <201210091425.q99EPFS6020787@svn.freebsd.org> <507451DE.9060909@freebsd.org> <CAF6rxgkDbyrCHfY-5eMjJ%2B7nP9ZCnXsjLgEBB1Q_p=QJ3tCkfg@mail.gmail.com>
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On 09.10.2012 21:47, Eitan Adler wrote: > On 9 October 2012 12:33, Andrey Chernov <ache@freebsd.org> wrote: >> Do you check assembler output for _both_ cases? > > Yes. ... > http://blog.eitanadler.com/2012/10/reduced-entropy-in-rand-and-random.html At this URL I see only already known buggy assembler without 'volatile' keyword (which is fixed by adding 'volatile' in srandomdev()). As I already mention, adding 'volatile' helps any gcc and clang finally generated assembler code (checked by cc -S ...). What happens with LLVM intermediate code, I mean mentioned by David call void @srand(i32 undef) is a big question and perhaps clang bug. Please note that we use 'volatile' a lot in the kernel, just 'grep -r volatile /sys'. Some of that potentially can hit the same (probably) bug. And, in case it is the bug, it should be fixed in clang. > volatile is still undefined: see 5.1.2.2.3 and 6.7.2.4 of ISO9899 I don't have ISO9899 nearby, could you directly quote mentioned sections, please? Do you against 'volatile' usage at all? It seems whole kernel (see above) contradicts with such point of view.home | help
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