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Subject: [bug#27704] [PATCH] daemon: Show actual rather than collateral error
	when export fails.
Resent-Message-ID: <handler.27704.B27704.150028484221775@debbugs.gnu.org>
From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=)
References: <20170715105851.24979-1-janneke@gnu.org>
Date: Mon, 17 Jul 2017 11:47:04 +0200
In-Reply-To: <20170715105851.24979-1-janneke@gnu.org> (Jan Nieuwenhuizen's
	message of "Sat, 15 Jul 2017 12:58:51 +0200")
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To: Jan Nieuwenhuizen <janneke@gnu.org>
Cc: 27704@debbugs.gnu.org

Hello,

Jan Nieuwenhuizen <janneke@gnu.org> skribis:

> Having the wrong permissions on /etc/guix/signing-key.sec gives
>
>     guix-daemon: nix/libutil/serialise.cc:15: virtual nix::BufferedSink::=
~BufferedSink(): Assertion `!bufPos' failed.
>
> this patch changes that to
>
>     guix-daemon: error: file `/etc/guix/signing-key.sec' should be secret=
 (inaccessible to everybody else)!
>
> * nix/nix-daemon/nix-daemon.cc (performOp): Catch any exportPath exceptio=
n,
> report and exit on that.  Fixes failing later with uninformative collater=
al error.

Good catch!

> --- a/nix/nix-daemon/nix-daemon.cc
> +++ b/nix/nix-daemon/nix-daemon.cc
> @@ -436,7 +436,13 @@ static void performOp(bool trusted, unsigned int cli=
entVersion,
>          bool sign =3D readInt(from) =3D=3D 1;
>          startWork();
>          TunnelSink sink(to);
> -        store->exportPath(path, sign, sink);
> +        try {
> +            store->exportPath(path, sign, sink);
> +        }
> +        catch (std::exception &e) {
> +            fprintf (stderr, "guix-daemon: error: %s\n", e.what ());
> +            exit (EXIT_FAILURE);

I think we should simply do:

  sink.flush();
  throw e;

in the =E2=80=98catch=E2=80=99 handler.

That way, we won=E2=80=99t have the assertion failure, and yet the error wi=
ll
correctly propagate to the client without forcing a disconnect.

Could you check if that works as expected?

Thank you!

Ludo=E2=80=99.