Date: Fri, 29 Dec 2017 15:17:50 -0800 From: Alfred Perlstein <bright@mu.org> To: Ian Lepore <ian@freebsd.org>, Yuri <yuri@rawbw.com>, Freebsd hackers list <freebsd-hackers@FreeBSD.org> Subject: Re: Is it considered to be ok to not check the return code of close(2) in base? Message-ID: <c9547578-fe90-3df0-253a-13c290c394df@mu.org> In-Reply-To: <1514572041.12000.7.camel@freebsd.org> References: <24acbd94-c52f-e71a-8a96-d608a10963c6@rawbw.com> <1514572041.12000.7.camel@freebsd.org>
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On 12/29/17 10:27 AM, Ian Lepore wrote: > On Fri, 2017-12-29 at 10:19 -0800, Yuri wrote: >> Some base utilities sometimes close files that they open for their >> purposes without checking the error code of close(2). >> >> Is this considered to be ok, because it's just a close call and we >> are >> done with that file descriptor, or is it considered to be more >> appropriate to check close's error code? >> >> Maybe there is some policy that covers this? >> >> IMO, every system call's return value should be checked, just in >> case. >> >> >> Yuri >> > There's really no point in checking on a close from a file opened only > for reading. You can argue it should be checked on a file open for > writing, but often isn't because you're then confronted with the > question "what should/can I do if there is an error?" If you report > the error and exit, then what about other files that were open at the > time? They're going to be closed by the kernel as part of process > cleanup, with no error checking or reporting. > > Also, with the async nature of filesystems, IO errors can still happen > after the close, unless fsync() was used. So if you're going to miss > most of the errors because of that, why bother to check at all? > A file open for writing should be tested on close for NFS and other filesystems that have "fsync on close" semantics. -Alfred
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