On Fri, 24 May 2013, Richard Biener wrote: > On Thu, May 23, 2013 at 9:47 PM, Marc Glisse <marc.gli...@inria.fr> wrote: > > Hello, > > > > this is a simple patch to reduce a bit the noise in PR57324 (undefined > > behavior flagged by clang). I only handled some of the most obvious ones. > > Passes bootstrap+testsuite on x86_64-linux-gnu. > > Hm, so ISO C99 says in 6.5.7/4 that (E1 << E2) "If E1 has signed type > and nonnegative > value, and E1 * 2^E2 is representable in the result type, then that is the > resulting value; otherwise, the behavior is undefined." > > While seriously underspecified for signed negative values (always undefined?! > or well-defined?!), I wonder why CLang requires
Always undefined for signed negative values (compared to the implementation-defined of C90; DR#081). -- Joseph S. Myers jos...@codesourcery.com
