cvs commit: src/sys/kern sys_generic.c
ache at nagual.pp.ru
Tue Jan 25 03:15:48 PST 2005
On Tue, Jan 25, 2005 at 12:02:23PM +0100, Poul-Henning Kamp wrote:
> >> >"This volume of IEEE Std 1003.1-2001 requires that no action be taken for
> >> >read() or write() when nbyte is zero. This is not intended to take
> >> >precedence over detection of errors (such as invalid buffer pointers or
> >> >file descriptors). This is consistent with the rest of this volume of IEEE
> >> >Std 1003.1-2001, but the phrasing here could be misread to require
> >> >detection of the zero case before any other errors."
> Std 1003.1-2001, but the phrasing here could be misread to require
> detection of the zero case before any other errors."
> Does not say you are not allowed to check for the zero case first, only that
> you are not required to do so.
The quote above is not complete, last phrase slips in the exchange:
"A value of zero is to be considered a correct value, for which the
semantics are a no-op."
For any correct value read() checks some FS-dependent errors conditions
and may return errors, but not for zero value now. It means we can't now
call zero value "correct". "No-op" does not means error conditions should
be skipped. Instead, it means that non-error case operation is empty.
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