From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael Kerrisk (man-pages)" Subject: Re: "man 3 vsprintf" : simple bug in EXAMPLE section Date: Sat, 11 Apr 2015 09:30:29 +0200 Message-ID: <5528CD95.7010204@gmail.com> References: <551584DE020000D400069A4C@relay2.provo.novell.com> <5515C2F9020000D400069A6F@relay2.provo.novell.com> <55152F0A.7090708@bfs.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55152F0A.7090708-fPG8STNUNVg@public.gmane.org> Sender: linux-man-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: wharms-fPG8STNUNVg@public.gmane.org, Zhen Ren Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-man List-Id: linux-man@vger.kernel.org On 03/27/2015 11:20 AM, walter harms wrote: > > hi Zhen Ren, > i tried to create a more simple example. Do you think this is more > helpful for you ? Walter, Your version seems better. See comments below. > re, > wh > > char * > make_message2 (const char *fmt, ...) > { > int n,size = 0; > char *p = NULL; > va_list ap; > > /* figure our required size */ > va_start (ap, fmt); > size = vsnprintf (p, size, fmt, ap); > va_end (ap); > > if (size < 0) > return NULL; > > /* leave room for \0 */ > size++; > p = malloc (size); > if (p == NULL) > return NULL; > > va_start (ap, fmt); > n = vsnprintf (p, size, fmt, ap); What's missing here is a check on the return value from the vsnprintf() call. I added one. I've put your code into the page, replacing the existing example, with the fix noted above. Thanks, Michael > va_end (ap); > > return p; > } > Am 27.03.2015 10:52, schrieb Zhen Ren: >> Hi Michael, >> >> I'm so sorry for this negative report. >> >> Yeah, you're right. It'll fall through,loop again,do "vsprintf" and return if done. >> >> -- >> Best regards, >> Eric, Ren >> HA team, SUSE >> >> >>>>> >>> Hello Zhen Ren, >>> >>> On 27 March 2015 at 06:27, Zhen Ren wrote: >>>> Hi, >>>> There is simple bug in EXAMPLE section of "man 3 vsprintf". >>>> >>>> Function will return nothing if it steps into the last "else {}". >>>> >>>> ------------------ example code ----------------- >>>> char * >>>> make_message(const char *fmt, ...) >>>> { >>>> int n; >>>> int size = 100; /* Guess we need no more than 100 bytes */ >>>> char *p, *np; >>>> va_list ap; >>>> . >>>> .cut off >>>> . >>>> np = realloc(p, size); >>>> if (np == NULL) { >>>> free(p); >>>> return NULL; >>>> } else { >>>> p = np; >>>> + return p; >>>> } >>>> } >>>> } >>> >>> I have not looked too closely at the code, but the above report >>> appears incorrect to me. The function should NOT be returning at that >>> point. It should be falling through and then round the loop once more. >>> If I've missed something, could you elaborate a little more on the >>> problem, please? >>> >>> Cheers, >>> >>> Michael >>> >>> >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-man" in >> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-man" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html