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

[Eric Blake]

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.

Food for thought: depending on how many clients you find, it may be
worth a version of virReaddir() that takes a flag argument, for
auto-filtering '.' and '..' entries.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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