From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/13760 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: Bug in gets function? Date: Mon, 11 Feb 2019 22:51:06 -0500 Message-ID: <20190212035106.GI23599@brightrain.aerifal.cx> References: <20190212034838.GH23599@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="85812"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-13776-gllmg-musl=m.gmane.org@lists.openwall.com Tue Feb 12 04:51:22 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1gtP6P-000MFb-Gm for gllmg-musl@m.gmane.org; Tue, 12 Feb 2019 04:51:21 +0100 Original-Received: (qmail 24015 invoked by uid 550); 12 Feb 2019 03:51:19 -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 23997 invoked from network); 12 Feb 2019 03:51:19 -0000 Content-Disposition: inline In-Reply-To: <20190212034838.GH23599@brightrain.aerifal.cx> Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:13760 Archived-At: On Mon, Feb 11, 2019 at 10:48:38PM -0500, Rich Felker wrote: > On Mon, Feb 11, 2019 at 06:55:24PM -0800, Keyhan Vakil wrote: > > Hi. It seems that the gets function does not follow the C99 spec. In > > particular, if the input contains a null byte in the middle of the > > input, then the new-line character is not discarded. > > > > For reference, here's the relevant part in the C99 standard > > (7.19.7.7): > > > > > The gets function reads characters from the input stream pointed to > > > by stdin, into the array pointed to by s, until end-of-file is > > > encountered or a new-line character is read. Any new-line character > > > is discarded, and a null character is written immediately after the > > > last character read into the array. > > > > Here is an example: > > > > #include > > char s[8]; > > int main() { > > gets(s); > > for (int i = 0; i < sizeof s; i++) { > > printf("%02x ", s[i]); > > } > > printf("\n"); > > return 0; > > } > > > > When compiled against gcc: > > > > $ echo -e 'A\x00B' | ./a.out > > 41 00 42 00 00 00 00 00 > > > > When compiled against musl: > > > > $ echo -e 'A\x00B' | ./a.out > > 41 00 42 0a 00 00 00 00 > > > > Note the terminating newline, which contradicts the spec. > > I think this bug report is correct; however the gets function is > awful, removed in C11, and should never be used. :-) > > I will see what can be done to fix it though. Is gets(s) equivalent to scanf("%[^\n]%*1[\n]",s)? If so that would be an appropriately hideous way to implement it that avoids the current bug? :-) Rich