From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49895) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cilkE-0003cw-J2 for qemu-devel@nongnu.org; Tue, 28 Feb 2017 12:39:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cilkB-0005PD-DQ for qemu-devel@nongnu.org; Tue, 28 Feb 2017 12:39:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56632) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cilkB-0005Oz-73 for qemu-devel@nongnu.org; Tue, 28 Feb 2017 12:39:23 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 344374E4E5 for ; Tue, 28 Feb 2017 17:39:23 +0000 (UTC) From: Markus Armbruster Date: Tue, 28 Feb 2017 18:38:56 +0100 Message-Id: <1488303560-18803-3-git-send-email-armbru@redhat.com> In-Reply-To: <1488303560-18803-1-git-send-email-armbru@redhat.com> References: <1488303560-18803-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PATCH v3 02/26] libqtest: Work around a "QMP wants a newline" bug List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org The next commit is going to add a test that calls qmp("null"). Curiously, this hangs. Here's why. qmp_fd_sendv() doesn't send newlines. Not even when @fmt contains some. At first glance, the QMP parser seems to be fine with that. However, it turns out that it fails to react to input until it sees either a newline, an object or an array. To reproduce, feed to a QMP monitor like this: $ echo -n 'null' | socat UNIX:/work/armbru/images/test-qmp STDIO {"QMP": {"version": {"qemu": {"micro": 50, "minor": 8, "major": 2}, "package": " (v2.8.0-1195-gf84141e-dirty)"}, "capabilities": []}} No output after the greeting. Add a newline: $ echo 'null' | socat UNIX:/work/armbru/images/test-qmp STDIO {"QMP": {"version": {"qemu": {"micro": 50, "minor": 8, "major": 2}, "package": " (v2.8.0-1195-gf84141e-dirty)"}, "capabilities": []}} {"error": {"class": "GenericError", "desc": "Expected 'object' in QMP input"}} Correct output for input 'null'. Add an object instead: $ echo -n 'null { "execute": "qmp_capabilities" }' | socat UNIX:qmp-socket STDIO {"QMP": {"version": {"qemu": {"micro": 50, "minor": 8, "major": 2}, "package": " (v2.8.0-1195-gf84141e-dirty)"}, "capabilities": []}} {"error": {"class": "GenericError", "desc": "Expected 'object' in QMP input"}} {"return": {}} Also correct output. Work around this QMP bug by having qmp_fd_sendv() append a newline. Signed-off-by: Markus Armbruster Reviewed-by: Eric Blake --- tests/libqtest.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/tests/libqtest.c b/tests/libqtest.c index e54354d..ad23ce9 100644 --- a/tests/libqtest.c +++ b/tests/libqtest.c @@ -442,14 +442,20 @@ void qmp_fd_sendv(int fd, const char *fmt, va_list ap) if (qobj) { int log = getenv("QTEST_LOG") != NULL; QString *qstr = qobject_to_json(qobj); - const char *str = qstring_get_str(qstr); - size_t size = qstring_get_length(qstr); + const char *str; + + /* + * BUG: QMP doesn't react to input until it sees a newline, an + * object, or an array. Work-around: give it a newline. + */ + qstring_append_chr(qstr, '\n'); + str = qstring_get_str(qstr); if (log) { fprintf(stderr, "%s", str); } /* Send QMP request */ - socket_send(fd, str, size); + socket_send(fd, str, qstring_get_length(qstr)); QDECREF(qstr); qobject_decref(qobj); -- 2.7.4