bin/181153: sscanf doesn't skip whitespace properly

[Andrey Chernov]

The following reply was made to PR kern/181153; it has been noted by GNATS.

From: Andrey Chernov <ache at freebsd.org>
To: Garrett Cooper <yaneurabeya at gmail.com>
Cc: "FreeBSD-gnats-submit at FreeBSD.org" <freebsd-gnats-submit at freebsd.org>
Subject: Re: bin/181153: sscanf doesn't skip whitespace properly
Date: Fri, 09 Aug 2013 06:15:55 +0400

 On 09.08.2013 6:03, Garrett Cooper wrote:
 >> I doubt this exampe should skip whitespace. POSIX says:
 >> "A directive that is an ordinary character shall be executed as follows:
 >> the next byte shall be read from the input and compared with the byte
 >> that comprises the directive; if the comparison shows that they are not
 >> equivalent, the directive shall fail, and the differing and subsequent
 >> bytes shall remain unread."
 >> %% is the ordinary % character and no isspace(3) skipping mentioned in
 >> this explanation.
 > 
 > What about this line [*]?
 > 
 > "
 > A directive composed of one or more white-space characters is executed
 > by reading input until no more valid input can be read, or up to the
 > first byte which is not a white-space character which remains unread.
 > "
 > 
 > I think this is what the NetBSD test developer was shooting for originally.
 > 
 > FWIW I did print out the value previously and it was (char)0, or '\0'.
 > 
 > Thanks!
 > 
 > * http://pubs.opengroup.org/onlinepubs/7908799/xsh/fscanf.html
 > 
 
 I see another line here:
 http://pubs.opengroup.org/onlinepubs/9699919799/functions/sscanf.html
 (2013 Edition)
 
 "A directive that is a conversion specification defines a set of
 matching input sequences, as described below for each conversion
 character. A conversion specification shall be executed in the following
 steps.
 Input white-space characters (as specified by isspace) shall be skipped,
 unless the conversion specification includes a [, c, C, or n conversion
 specifier."
 
 Which is clearly not our case because %% is not a conversion, just
 ordinary character. And don't see there line your mentioned.
 Probably there still are skipping bugs with other %-modifiers, I don't
 inspect it carefully, but not with %%.
 
 -- 
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