X-Recipient: archive-cygwin AT delorie DOT com X-SWARE-Spam-Status: No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,TW_YM,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Message-ID: <4F717637.80703@lysator.liu.se> Date: Tue, 27 Mar 2012 10:11:35 +0200 From: Peter Rosin User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2 MIME-Version: 1.0 To: cygwin AT cygwin DOT com Subject: Re: rcs 5.8-1 checks out wrong version of file when using similar mark symbols References:

In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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 Csaba Raduly skrev 2012-03-27 09:37: > On Mon, Mar 26, 2012 at 9:29 PM, Richard Gribble wrote: >> Using rcs 5.8-1: >> >> Synopsis: >> Given two mark symbols, abc (version 1.1) and abcd (version 1.2), >> executing "co -rabc " will check out version 1.2, when it >> should check out version 1.1. >> >> I set the mark symbols as follows: >> rcs -nabc:1.1 -nabcd:1.2 >> >> >> I dug into it, and found the following (rcsrev.c): >> >> 01: static char const * >> 02: rev_from_symbol (struct cbuf const *id) >> 03: /* Look up "id" in the list of symbolic names starting with pointer >> 04: "GROK (symbols)", and return a pointer to the corresponding >> 05: revision number. Return NULL if not present. */ >> 06: { >> 07: for (struct link *ls = GROK (symbols); ls; ls = ls->next) >> 08: { >> 09: struct symdef const *d = ls->entry; >> 10: >> 11: if (!strncmp (d->meaningful, id->string, id->size)) >> 12: return d->underlying; >> 13: } >> 14: return NULL; >> 15: } >> >> Note that line 11 tests the name of the requested mark symbol >> (id->string) against each element of a linked-list (ls) containing all >> the mark symbols for the file. The problem is that it will only test >> the first 'id->size' characters - so R25 (from the command line) matches >> R25a (from the list) because the first three characters match and it >> won't test any more than that (strncmp). >> >> I recommend modifying line 11 as follows: >> if ((strlen(d->meaningful) == strlen(id->size)) && !strncmp >> (d->meaningful, id->string, id->size)) > > I think strlen(id->size) is overkill :) > > If both strings (d->meaningful and id->string) are NULL-terminated , > then a simple call to strlen would do the job: You mean a simple call to strcmp here. > if (!strcmp(d->meaningful, id->string)) > > It would do the right thing w.r.t. different lengths. > >> Of course, since you now know that the two strings are the same size, >> you could use strcmp - but that assumes that the && short-circuits, and >> I don't know if that's guaranteed. > > Yes, it required by the C standard. But...careful! You have to assume that the original authors were not idiots! Maybe the obvious strcmp was not used for a *good* reason? I can't tell if d->meaningful is guaranteed to be zero-terminated from the limited context, but it sure is suspect. Assuming that the original authors were not idiots but instead made an off-by one error missing a corner-case, the safer approach is to replace line 11 with: 11: if (!strncmp (d->meaningful, id->string, id->size + 1)) That is, if id->string is guaranteed to be zero-terminated, which is not clear either, but perhaps easier to verify... Cheers, Peter -- 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