X-Recipient: archive-cygwin AT delorie DOT com DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:date:from:to:subject:message-id:references :mime-version:content-type:in-reply-to; q=dns; s=default; b=KSyy q9ib+YA1dUjnOQOwD/Pc5EEy6PkOSoXGWRr0uNTzhDuTk7kepw+oXSIKqbFinxLL x29SnCbl2SIxiTFu++wrAO98Q4G9QX32F1hESrnciCc+mqQLVbrhDF3B8g/oLeGY V70RLjMu9v5/FwzVtmGNe9UxvWPux8pVBelr9Ac= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:date:from:to:subject:message-id:references :mime-version:content-type:in-reply-to; s=default; bh=RDmUe5d9md Hf9k6KMZ2urO8wf7w=; b=NzgFB+S+92jinGWfCunrY0XCaabHN8fZ34Y73B9jWi d1RlRdD5Hm05IP/EZbSRt1Ft02AtF3qPDigawxJCD0YW1knXYFg6JEmlk2xtgfzT brS4uCSPouuB+CWJmBRNLU9421zvXzYMyTSVLox199crhlbPdejlS/PWUdWj1sZ+ A= Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.2 required=5.0 tests=AWL,BAYES_05,RP_MATCHES_RCVD,SPF_PASS autolearn=ham version=3.3.2 spammy=develop-help.com, UD:develop-help.com, develophelpcom, defensiveness X-HELO: mars.tony.develop-help.com Date: Tue, 12 Apr 2016 20:56:58 +1000 From: Tony Cook To: cygwin AT cygwin DOT com Subject: Re: strxfrm() returns an incorrect value on a short buffer Message-ID: <20160412105658.GF12445@mars.tony.develop-help.com> References: <20160412050722 DOT GE12445 AT mars DOT tony DOT develop-help DOT com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-IsSubscribed: yes On Tue, Apr 12, 2016 at 10:20:13AM +0000, Achim Gratz wrote: > Tony Cook develop-help.com> writes: > > strxfrm() returns an incorrect value if you supply an output buffer > > and that buffer is too short for the result. > > The text in the C standard is: > > >>>>> > The strxfrm function returns the length of the transformed string (not > including the > terminating null character). If the value returned is n or more, the > contents of the array > pointed to by s1 are indeterminate. > > EXAMPLE The value of the following expression is the size of the array > needed to hold the > transformation of the string pointed to by s. > 1 + strxfrm(NULL, s, 0) > <<<<< > > It doesn't really provide for an explanation of what should happen if you > start with a buffer that is too small, but from the standpoint of > defensiveness, if you are getting the size of your buffer or larger, then > you should ask again with a size of zero to get the actual minimum size > needed or try again with a larger buffer until the returned value is smaller > than the buffer size. > > > It appears that strxfrm() is just returning the size of the output > > buffer on an overflow error rather than calling LCMapString() again > > with cchDest set to zero to get the required buffer length that > > strxfrm() is meant to return on a short buffer. > > So, you may be expecting something that the standard doesn't explicitly > specify, although you might reasonhably invoke that Cygwin should behave > like Linux in this case. The specification of strxfrm() in the standard doesn't special-case a length of zero beyond allowing for s1 to be NULL. If an implementation were permitted to return the lesser of the full length of the transformed string and the size of the buffer the example in the standard wouldn't return what the description says it does. Tony -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple