svn commit: r187805 - head/lib/libc/stdio

Tom Rhodes trhodes at
Wed Jan 28 04:02:35 PST 2009

On Wed, 28 Jan 2009 22:15:22 +1100 (EST)
Bruce Evans <brde at> wrote:

> On Wed, 28 Jan 2009, Roman Divacky wrote:
> > On Wed, Jan 28, 2009 at 01:11:21AM +0000, Tom Rhodes wrote:
> >> Log:
> >>   Remove comment about clearerr() being the only method of clearing
> >>   the EOF indicator, fseek() may also be used for this.
> fseek() can't always be used for this, since fseek() fails for unseekable
> files (even SEEK_CUR fails then).  However, when it works, it has the
> advantage(?) of not clobbering the error indicator.
> The comment was also wrong because the EOF indicator can also be cleared
> by clearerr_unlocked() in some cases and by fseeko() in the same cases as
> by fseek().
> > why not saying what you state in the commit message in the man page
> > instead of removing the info entirely?
> Well, neither C99 nor POSIX say this for feof().
> The man page still says that the error indicator can only be cleared by
> clearerr().  This is false since a sucessful rewind() clears both
> indicators, and the indicator can be cleared by clearerr_unlocked() in
> some cases.
> I think the man page is trying to make the false claims that the
> indicators are not cleared as side effects and is not trying to list
> all the functions that do clear the indicators as side effects, and
> that it shouldn't try to do the latter.  The list for the EOF indicator
> may be quite long and system-and-time-dependent since it includes the
> closure of all functions that call fseek(), or fseeko()).  For both
> indicators, the list includes the closure of all functions that call
> clearerr() or clearerr_unlocked().  Perhaps no such functions in
> standard libraries are permitted to operate on application streams,
> but this is unclear.
> Bruce

Exactly, listing every possible method is a bit much I think.
Anyway, I picked off the last mention of it, which I missed
earlier.  Thanks!

Tom Rhodes

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