Re: [libvirt] [PATCH] nodeinfo: Make sure we always reset errno before calling readdir

On Thu, 10 Apr 2014 15:53:57 -0600 Eric Blake <eblake(a)redhat.com&gt; wrote: > On 04/10/2014 02:52 PM, Natanael Copa wrote: > > >>> I suppose we could use helper function to make it more readable: > >>> > > >> int virReaddir(DIR *dirp, struct dirent **ent) > >> { > >> errno = 0; > >> *ent = readdir(dirp); > >> if (!*ent && errno) { > >> virReportSystemError(errno, _("unable to read directory")) > >> return -1; > >> } > >> return *ent ? 1 : 0; > > or shorter, return !!*ent; > > >> } > >> > >> and used as: > >> > >> while ((ret = virReaddir(dirp, &entry)) > 0) { > >> process entry > >> } > >> if (ret < 0) > >> goto error; > > > > This looks better yes. > > > > Should I prepare a new patch with this? And grep for more readdirs? > > Sure; and while at it, update cfg.mk to add a new syntax check to > enforce this style. We've wrapped other awkward standard functions that > require errno manipulation for correct use (such as strtol and > getpwuid_r), precisely because code is more maintainable when we can > enforce that the awkward functions are always used correctly. I found a fairly nice example of readdir used correctly in vircgroup.c. We could do it like that too. It means less intrusive changes. And we avoid changing the current error messages from "Unable to iterate over TAP/loop/NBD devices" to "unable to read directory". We could alternatively pass another option with the dirname for error messages.