From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/9256 Path: news.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: fread, fwrite with size 0 Date: Wed, 3 Feb 2016 23:39:48 -0500 Message-ID: <20160204043948.GM9349@brightrain.aerifal.cx> References: <56B1C001.7020603@gmx.at> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1454560808 15861 80.91.229.3 (4 Feb 2016 04:40:08 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 4 Feb 2016 04:40:08 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-9269-gllmg-musl=m.gmane.org@lists.openwall.com Thu Feb 04 05:40:08 2016 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1aRBi8-0005fQ-TS for gllmg-musl@m.gmane.org; Thu, 04 Feb 2016 05:40:05 +0100 Original-Received: (qmail 26584 invoked by uid 550); 4 Feb 2016 04:40:02 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 26566 invoked from network); 4 Feb 2016 04:40:01 -0000 Content-Disposition: inline In-Reply-To: <56B1C001.7020603@gmx.at> User-Agent: Mutt/1.5.21 (2010-09-15) Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:9256 Archived-At: On Wed, Feb 03, 2016 at 09:53:21AM +0100, hombre wrote: > Hello, > > I think that fread and fwrite does not return 0 when parameter size > is 0 (when nmemb is 0, it does). > Clib spec says: If size or nmemb is zero, fread/fwrite returns zero > > I did the following changes to make it work: > > fread: > from > return nmemb; > to > return len == 0 ? 0 : nmemb; > > fwrite: > from > return k == l ? nmemb : k / size; > to > if (l == 0) > return 0; > else > return k == l ? nmemb : k / size; > > Regards, > Erwin Thanks. Sadly the POSIX version of the text is contradictory on this: "Upon successful completion, fread() shall return the number of elements successfully read which is less than nitems only if a read error or end-of-file is encountered. If size or nitems is 0, fread() shall return 0 and the contents of the array and the state of the stream remain unchanged." First it says that the return value can be less than nitems only if an error of EOF happens, but then it gives another way the return value can be less than nitems (if size is 0). Fortunately the ISO C text is not so broken and agrees with you: "The fread function returns the number of elements successfully read, which may be less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero, fread returns zero and the contents of the array and the state of the stream remain unchanged." There's another issue I want to fix here too, but I might do it in two commits. Thanks for the report. Rich