From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=44876 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1PIS2f-0005VB-4E
	for qemu-devel@nongnu.org; Tue, 16 Nov 2010 15:22:14 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <peter.maydell@linaro.org>) id 1PIS2d-0003pF-Py
	for qemu-devel@nongnu.org; Tue, 16 Nov 2010 15:22:13 -0500
Received: from mail-qy0-f180.google.com ([209.85.216.180]:35898)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <peter.maydell@linaro.org>) id 1PIS2d-0003p8-NR
	for qemu-devel@nongnu.org; Tue, 16 Nov 2010 15:22:11 -0500
Received: by qyk36 with SMTP id 36so1220194qyk.4
	for <qemu-devel@nongnu.org>; Tue, 16 Nov 2010 12:22:10 -0800 (PST)
MIME-Version: 1.0
In-Reply-To: <4CE2D468.4020604@codemonkey.ws>
References: <1289244788-19961-1-git-send-email-berrange@redhat.com>
	<1289244788-19961-2-git-send-email-berrange@redhat.com>
	<4CE2A74C.6050302@codemonkey.ws>
	<AANLkTimKSU+1ayNpoRCmEhCRkUy2gf68qK1KEc35Yd4N@mail.gmail.com>
	<4CE2C92E.3030006@codemonkey.ws>
	<AANLkTik6xjnE0hmwVX5JB5hrO8ex1xXp6b-bQXMz0dmy@mail.gmail.com>
	<4CE2D468.4020604@codemonkey.ws>
Date: Tue, 16 Nov 2010 20:22:10 +0000
Message-ID: <AANLkTi=CVPsHSZp_c7zPHkj9AZ8kDBFecXAq5QjxAs8j@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH 1/2] Add a DTrace tracing backend targetted
	for SystemTAP compatability
From: Peter Maydell <peter.maydell@linaro.org>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org

On 16 November 2010 18:58, Anthony Liguori <anthony@codemonkey.ws> wrote:
> On 11/16/2010 12:54 PM, Peter Maydell wrote:
>> If I add a ".PHONY: trace" or change the "trace" target
>> name to "tracexyzzy" then this fixes the problem.
>
> Curious, care to send a patch? =C2=A0I think I'm not seeing this because =
I build
> with srcdir !=3D objdir.

Ah, yes, if I build in a different directory to the sources I can build
without having to patch the makefiles. (That feature of configure
doesn't seem to be documented anywhere, unless I've missed
something.)

Anyway, patch sent. I opted to tidy up the makefile a little to avoid
either an ugly target name or a GNU-makeism. I fiddled configure
so I could test the CONFIG_SYSTEMTAP_TRACE bit despite
not having systemtap on this machine, but it would be good if
a real systemtap user could check it.

A couple of oddities I noticed along the way:

(1) How do you get configure to enable CONFIG_SYSTEMTAP_TRACE?
The condition is:
if test "$trace_backend" =3D "dtrace" -a "$trace_backend_stap" =3D "yes" ; =
then
  echo "CONFIG_SYSTEMTAP_TRACE=3Dy" >> $config_host_mak
fi
but trace_backend_stap is only set inside code guarded by
if test "$trace_backend" =3D "ust"
...
so as far as I can tell the two halves of the -a will never
both be true.

(2) in Makefile.target, the blank line after the all: line:
> all: $(PROGS) $(STPFILES)
>
> # Dummy command so that make thinks it has done something
>         @true

is I think a bit misleading although it is valid makefile syntax.
I suspect it got added by accident.

-- PMM