From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/9129 Path: news.gmane.org!not-for-mail From: Felix Janda Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] add _DIRENT_HAVE_D_* constants to dirent.h Date: Fri, 15 Jan 2016 17:20:27 +0100 Message-ID: <20160115162027.GB296@nyan> References: <20160113180919.GA11433@nyan> <20160114224449.GX238@brightrain.aerifal.cx> <20160115022713.GC238@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1452875012 7496 80.91.229.3 (15 Jan 2016 16:23:32 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 15 Jan 2016 16:23:32 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-9142-gllmg-musl=m.gmane.org@lists.openwall.com Fri Jan 15 17:23:24 2016 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1aK79l-0004eN-7g for gllmg-musl@m.gmane.org; Fri, 15 Jan 2016 17:23:21 +0100 Original-Received: (qmail 28532 invoked by uid 550); 15 Jan 2016 16:23:19 -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 28514 invoked from network); 15 Jan 2016 16:23:18 -0000 Mail-Followup-To: musl@lists.openwall.com Content-Disposition: inline In-Reply-To: <20160115022713.GC238@brightrain.aerifal.cx> User-Agent: Mutt/1.5.23 (2014-03-12) Xref: news.gmane.org gmane.linux.lib.musl.general:9129 Archived-At: Rich Felker wrote: > On Thu, Jan 14, 2016 at 05:44:49PM -0500, Rich Felker wrote: > > On Wed, Jan 13, 2016 at 07:09:19PM +0100, Felix Janda wrote: > > > they can be used for checking existence of non-standard fields of > > > struct dirent, are used by various programs to avoid configure > > > checks and are at least present on glibc, uclibc, dietlibc and > > > newlib. > > > --- > > > The motivation for this patch is > > > > > > http://oss.sgi.com/archives/xfs/2016-01/msg00388.html > > > --- > > > include/dirent.h | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/include/dirent.h b/include/dirent.h > > > index 5aa8510..b2ffe8a 100644 > > > --- a/include/dirent.h > > > +++ b/include/dirent.h > > > @@ -57,6 +57,9 @@ int getdents(int, struct dirent *, size_t); > > > #endif > > > > > > #ifdef _GNU_SOURCE > > > +#define _DIRENT_HAVE_D_OFF > > > +#define _DIRENT_HAVE_D_RECLEN > > > +#define _DIRENT_HAVE_D_TYPE > > > int versionsort(const struct dirent **, const struct dirent **); > > > #endif > > > > I like the concept of defining macros to publish the availability of > > extensions like this, but I don't think they should be dependent on > > _GNU_SOURCE. At the very least they should also be available under > > _DEFAULT_SOURCE (_BSD_SOURCE), but since they're in the reserved > > namespace (underscore followed by capital) I'd prefer to have them > > exposed unconditionally. I see. > > I'm also skeptical of whether d_off and d_reclen should be promoted as > > public APIs. They don't seem to be useful (unlike d_type which is > > highly useful) and may lock down some assumptions about > > implementation. > > Perhaps to make a discussion of this more concrete: is there other > software that's using the d_reclen or d_off fields conditionally on > having the above macros defined? What is is using them for? I had not checked specifically how much each macro is used. (I'm using debian codesearch.) _DIRENT_HAVE_D_TYPE seems to be used the most often. The only other (apart from xfsprogs) use of the others is in glusterfs: http://sources.debian.net/src/glusterfs/3.7.6-1/api/src/glfs-fops.c It seems to be used in the glfs_readdir* functions to convert the internal gf_dirent structure to the usual dirent. Likely few people rely on the d_reclen or d_off from a dirent received via glfs_readdir*... > I read the above-linked mailing list discussion and I think the > autoconf test is a better approach than depending on the macros (since > they're not present on older musl or on other non-glibc libcs/systems) They seem to be present on most libcs on linux. > but we should probably add at least _DIRENT_HAVE_D_TYPE and perhaps > the others too. Thanks, Felix