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Date: Mon, 24 Aug 2020 23:26:00 -0400
From: Rich Felker <>
Subject: Re: Incompatible behaviour of res_query(3) w.r.t. NXDOMAIN

On Mon, Aug 24, 2020 at 06:09:23PM -0400, Rich Felker wrote:
> On Mon, Aug 24, 2020 at 11:51:52PM +0200, Daniel Neri wrote:
> > On 24 Aug 2020, at 23:32, Rich Felker <> wrote:
> > > 
> > > Does such a distinction exist? I thought res_query was just equivalent
> > > to res_mkquery+res_send and that calling res_send directly would get
> > > you the same errors.
> > 
> > I thought so too, but I’ve been reading the musl implementation. ;-)
> > 
> > After looking more at the other implementations, I think Florian is
> > correct though: it’s more like res_mkquery+res_send+setting h_errno
> > and the return value based on the RCODE of the response.
> If this is indeed the case and the right behavior can be obtained
> reliably by ignoring res_query and using res_mkquery+res_send, I have
> no fundamental objection to changing this. However we should have a
> plan for moving h_errno to be thread-local and figuring out what
> breakage if any there could be for apps built with it global.
> Thankfully, it looks like we're already using (*__h_errno_location())
> even though it was not thread-local, so existing apps built against
> current musl headers should be immediately compatible with changing it
> to be thread-local.

I have the attached patches queued now.


View attachment "0001-make-h_errno-thread-local.patch" of type "text/plain" (1414 bytes)

View attachment "0002-report-res_query-failures-including-nxdomain-nodata-.patch" of type "text/plain" (1556 bytes)

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