[PATCH] hesiod_end: Do not call res_nclose(&_res) [BZ #19573]

[Anders Kaseorg]

Thanks for the review!

On Sat, 23 Apr 2016, Florian Weimer wrote:
> Please use GNU style (braces on separate lines, two-space
> indentation).

hesiod/hesiod.c is not in GNU style; I preserved its existing style as per 
https://sourceware.org/glibc/wiki/Style_and_Conventions#Files_not_formatted_according_to_the_GNU_standard.

> This is one way to fix this bug.  Its correctness depends on whether we 
> export in any way the hesiod functionality.  I thought we did, but 
> libhesiod is actually a separate thing, and checking with eu-readelf, I 
> don't see any exports of the helper functions.
> 
> If there are no external users of the callback mechanism, we do not have 
> to worry about the behavioral change.
> 
> I would welcome a quick double-check on this aspect.

I agree: this file is only used in nss_hesiod, whose only exported symbols 
are the NSS interface.

Also, the test I used is the same as what __hesiod_res_set already uses 
before calling res_nclose.  This may not be strong evidence by itself, 
because it happens that __hesiod_res_set is never called in a way that 
satisfies this test, but at least it’s consistent.

Anders