From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20096 invoked by alias); 13 Dec 2005 09:05:44 -0000 Received: (qmail 20074 invoked by alias); 13 Dec 2005 09:05:40 -0000 Date: Tue, 13 Dec 2005 09:05:00 -0000 Message-ID: <20051213090540.20073.qmail@sourceware.org> From: "michael dot kerrisk at gmx dot net" To: glibc-bugs@sources.redhat.com In-Reply-To: <20051208155151.1997.michael.kerrisk@gmx.net> References: <20051208155151.1997.michael.kerrisk@gmx.net> Reply-To: sourceware-bugzilla@sourceware.org Subject: [Bug manual/1997] opern_memstream() buffer should be freed X-Bugzilla-Reason: CC Mailing-List: contact glibc-bugs-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: glibc-bugs-owner@sourceware.org X-SW-Source: 2005-12/txt/msg00070.txt.bz2 List-Id: ------- Additional Comments From michael dot kerrisk at gmx dot net 2005-12-13 09:05 ------- Subject: Re: opern_memstream() buffer should be freed > Von: "decimal at us dot ibm dot com" > I took a look in the linux man pages and in the glibc manual and I found > that while the man page for strdup(3) does say > > The strdup() function returns a pointer to a new string which is a > duplicate of the string s. Memory for the new string is obtained with > malloc(3), and can be freed with free(3). > > the glibc manual info entry for strdup() says > > This function copies the null-terminated string s into a newly allocated > string. > The string is allocated using malloc; see Unconstrained Allocation. If > malloc > cannot allocate space for the new string, strdup returns a null pointer. > Otherwise it returns a pointer to the new string. > > The section on Unconstrained Allocation includes a section "Freeing after > Malloc" which discusses free(). > > The current section in the glibc manual on open_memstream() says > > This function opens a stream for writing to a buffer. The buffer is > allocated > dynamically (as with malloc; see Unconstrained Allocation) and grown as > necessary. > > So is it really necessary to explicitly mention free() next to every > function > which uses malloc()? I'm asking to see if anyone else has a strong > opinion. Being the Linux manual page maintainer (but I didn't write that strdup(2)) text, I'm inclined to the view that it is useful to mention free() when describing these interfaces. It is just too easy to create memory leaks in C: giving people more direct hints (instead of suggesting a hyperlink in the doc, in which it only becomes clear that free() is needed after quite a bit of reading) alerts people to the issue. There is a second reason for doing this in the case of open_memstream(): the interface is non-standard. I can determine from any number of places (my own knowledge, the SUSv3 spec, manual pages on various systems) that glibc's strdup() must be followed with a free(). However, those sources of information are not available for open_memstream(). I realise there are differences on documentation philosophy for "info" and the manual pages, but I do think an explicit mention of free() could be valuable here (and perhaps in a few other places). Cheers, Michael -- http://sourceware.org/bugzilla/show_bug.cgi?id=1997 ------- You are receiving this mail because: ------- You are on the CC list for the bug, or are watching someone who is.