Date: Sun, 25 Jan 2009 20:11:22 +0100 From: Christoph Mallon <christoph.mallon@gmx.de> To: Jeff Roberson <jroberson@jroberson.net> Cc: svn-src-head@freebsd.org, Jeff Roberson <jeff@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org Subject: Re: svn commit: r187693 - head/sys/kern Message-ID: <497CB95A.109@gmx.de> In-Reply-To: <20090125085419.O983@desktop> References: <200901251838.n0PIcgXk024858@svn.freebsd.org> <20090125085419.O983@desktop>
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Jeff Roberson schrieb: > On Sun, 25 Jan 2009, Jeff Roberson wrote: > >> Author: jeff >> Date: Sun Jan 25 18:38:42 2009 >> New Revision: 187693 >> URL: http://svn.freebsd.org/changeset/base/187693 >> >> Log: >> - bit has to be fd_mask to work properly on 64bit platforms. Constants >> must also be cast even though the result ultimately is promoted >> to 64bit. >> - Correct a loop index upper bound in selscan(). > > Sorry about that, should've tested my earlier patch for more than a > couple of days. I seldom remember c's integer promotion rules as they > relate to constants. You'd think they'd make it easy on us and just > promote it to the largest type in the expression/lvalue. I'm not sure > why they don't. Perhaps the more careful among you knows the answer. The rule for operations is quite simple: An operation never cares for the type of its user. It only uses the type of the operand(s) to determine its result type. So for a = b + c the type of the result of + only depends on the types of b and c, but never on a. Integer literals have a bit ugly rules what type they are: It depends on the base (!) and on the magnitude of the literal. If in doubt and you need a specific type (and maybe making it more clear for a reader) then cast.
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