Date: Fri, 24 Jan 2014 11:49:39 -0600 From: Bryan Drewery <bryan@shatow.net> To: Konstantin Belousov <kostikbel@gmail.com> Cc: bapt@FreeBSD.org, freebsd-standards@FreeBSD.org, Jilles Tjoelker <jilles@stack.nl> Subject: Re: closedir(3) handling NULL Message-ID: <20140124174938.GB73838@admin.xzibition.com> In-Reply-To: <20140124172123.GK24664@kib.kiev.ua> References: <20140124014105.GC37334@admin.xzibition.com> <20140124132435.GA90996@stack.nl> <20140124165509.GA73838@admin.xzibition.com> <20140124172123.GK24664@kib.kiev.ua>
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--7iMSBzlTiPOCCT2k Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jan 24, 2014 at 07:21:23PM +0200, Konstantin Belousov wrote: > On Fri, Jan 24, 2014 at 10:55:09AM -0600, Bryan Drewery wrote: > > On Fri, Jan 24, 2014 at 02:24:35PM +0100, Jilles Tjoelker wrote: > > > On Thu, Jan 23, 2014 at 07:41:05PM -0600, Bryan Drewery wrote: > > > > I found that Linux handles closedir(NULL) fine and returns EINVAL. = POSIX > > > > [1] specifies that EBADF should be returned if "The dirp argument d= oes > > > > not refer to an open directory stream" > > >=20 > > > > [1] http://pubs.opengroup.org/onlinepubs/009696799/functions/closed= ir.html > > >=20 > > > > I've updated fdclosedir(3) as well to behave the same. > > >=20 > > > > I'll also update the manpage if there is no objection. > > >=20 > > > If you do this, it is to improve compatibility with poorly written > > > software and not for POSIX compliance. POSIX only permits passing null > > > pointers where explicitly specified (e.g. time()); otherwise, passing= a > > > null pointer is undefined behaviour like passing any argument outside > > > the required domain. > >=20 > > I do think that improving portability is important. Even against sloppy > > coding. Applications developed for Linux are fine passing NULL to close= dir(3), > > which leads to a style of coding that does not reveal itself to be a > > problem on FreeBSD until an edge case comes up. > >=20 > > This is the situation to led to me find this. A mountpoint disappeared > > and some code written for Linux, that ported to FreeBSD without changes, > > segfaulted in closedir(3). > This is somewhat strange description of events, it definitely misses > some intermediate steps. The mere fact of unmounting does not change > anonymous memory content of some application. Even if the DIR * was > assotiated with the directory descriptor belonging to the disappeared > mount point, the DIR * and file descriptors are still valid, although > not that functional. The code constructed a path, called opendir(3), received NULL, skipped over code that uses the entry since it was NULL, then called closedir(3). Also, I don't find this very different than free(3) with a NULL. It's considered bad practice to check for NULL before calling it, why is closedir(3) any different? Regards, Bryan Drewery --7iMSBzlTiPOCCT2k Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (FreeBSD) iQJ8BAEBCgBmBQJS4qeyXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQzNkZFQkU5OTJGNTI4MERGNDgxMTM2MkE2 RTc4MkFDMDNDOUIwQ0Y5AAoJEG54KsA8mwz5pnEQAJnXxJWcElWv/ZRvwPyldug2 PDVrabYk6w5aaFPkINHm8GrNveQJMa7w6zvZGNpMpGhJgvNwSPjNxHVckrv6fN8M duKHGMfgun9VuoSYwzxX9fBIu0UNDywFm7BIbiRnwFotRY6BxE35K9/8EW29bU3Q V6Zy/LQv4uVFpkMafFX0OAnPS7TRRcGRNRoHlJPfRXu8Qd7IjcE2uEqyOmQ0KPlA BVL936xfAFuNfQJR4vdSsoOyRpSyLC1Cf8ewtlJHJkgnppX4IB/M1x6wd4mjHJvL 7sMBNmdEyu/Wjdr8m8+aX4WQdW756ZR2+MAKJWlUGvPqprDKnDg1cM5Tuh5iXLjX ilZ8RLLrYt5BJU+0e+LUCDGEoiNh7lYkC5Gu1d2d7MF/axqMHR4OYFfbBrMq4pzj SEa5y4QNzxEoIth9yRCxB321XQZ+9LkiYM90FS+Frc+GH+Jx57hVbB4FWEDNkxxJ YqKr7Ka1Ij+DDHJmeAiLHSxXRPQ4RCnjR+llI8zKr5d8wmed/h+ADdDqv3zmHXk/ oMOEiG9F/89472r0jG27rOM9IXcoxNapW/H8OMoH2NsNNuoC4hnZK6YHATuXeCGx XluC4L7BRllInPL/iI0IFy0i7peTjioNyocQ+Bh6o0fPTV82DKgGpjEaJKi99tJF aOP2s6dN2AJVKV+rnfZC =xlaf -----END PGP SIGNATURE----- --7iMSBzlTiPOCCT2k--
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