From: Jeff King Date: Tue, 26 Mar 2013 18:55:59 GMT Subject: Re: [PATCH 2/4] dir.c::match_basename(): pay attention to the length of string parameters Message-ID: <20130326185559.GB26462@sigill.intra.peff.net> In-Reply-To: <1364323171-20299-3-git-send-email-gitster@pobox.com> On Tue, Mar 26, 2013 at 11:39:29AM -0700, Junio C Hamano wrote: > The function takes two counted strings ( and > ) as parameters, together with prefix (the > length of the prefix in pattern that is to be matched literally > without globbing against the basename) and EXC_* flags that tells it > how to match the pattern against the basename. > > However, it did not pay attention to the length of these counted > strings. Update them to do the following: > > * When the entire pattern is to be matched literally, the pattern > matches the basename only when the lengths of them are the same, > and they match up to that length. > > * When the pattern is "*" followed by a string to be matched > literally, make sure that the basenamelen is equal or longer than > the "literal" part of the pattern, and the tail of the basename > string matches that literal part. > > * Otherwise, make sure we use only the counted part of the strings > when calling fnmatch_icase(). Because these counted strings are > full strings most of the time, avoid unnecessary allocation. I think this is OK, with the intention that we would eventually drop the allocations from your third bullet point in favor of using a byte-counted version of fnmatch (i.e., nwildmatch). But until then we're going to see a performance drop. The pattern is usually going to be NUL-terminated at the length counter, but every time we feed a directory, it's going to run into this allocation. And we do it once for _every_ directory against _every_ wildcard gitignore pattern. So I think it is probably going to be measurable. I guess we can try measuring it on something like WebKit, which has plenty of both directories and gitattributes. -Peff