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DateWed, 7 Jan 2009 16:00:25 +0100
FromIngo Molnar <>
SubjectRe: [RESEND][RFC PATCH v2] waitfd
* Casey Dahlin <cdahlin@redhat.com> wrote:

> >> +asmlinkage long sys_waitfd(int which, pid_t upid, int options, int unused)
> >> +{> >> +	int ufd;> >> +	struct waitfd_ctx *ctx;> >> +> >> +	/* Just to make sure we don't end up with a sys_waitfd4 */
> >> +	(void)unused;> > > > looks a bit silly ...> > > Do you mean the principle of having an unused argument around for future 
> use or the cast to void? The cast to void is there to suppress the 
> "Waning: unused argument" messages and make gcc happy.

gcc will not warn about unused function arguments - only about unused 
local variables. The 'unused' argument should either be removed 
altogether, or replaced with a properly named parameter and a check 
returning -ENOSYS if the argument is not zero (or something like that). 

(It's generally better to keep such syscalls extensible via such trivial 
means, if there's a remote chance for ever needing to extend that 
syscall.)

	Ingo


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