From patchwork Thu May 12 07:59:01 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Markus Armbruster X-Patchwork-Id: 9077501 Return-Path: X-Original-To: patchwork-qemu-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 6EC1F9F1D3 for ; Thu, 12 May 2016 08:12:53 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 86268201FA for ; Thu, 12 May 2016 08:12:52 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5D241201EC for ; Thu, 12 May 2016 08:12:51 +0000 (UTC) Received: from localhost ([::1]:55957 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b0ljm-00079x-C4 for patchwork-qemu-devel@patchwork.kernel.org; Thu, 12 May 2016 04:12:50 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54250) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b0lWn-0000xo-5b for qemu-devel@nongnu.org; Thu, 12 May 2016 03:59:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b0lWf-0006LK-Mx for qemu-devel@nongnu.org; Thu, 12 May 2016 03:59:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46719) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b0lWf-0006L6-Ba for qemu-devel@nongnu.org; Thu, 12 May 2016 03:59:17 -0400 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 C729AC05B1C9 for ; Thu, 12 May 2016 07:59:16 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-35.ams2.redhat.com [10.36.116.35]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u4C7xDaE011378 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 12 May 2016 03:59:15 -0400 Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 8C02C11421EB; Thu, 12 May 2016 09:59:10 +0200 (CEST) From: Markus Armbruster To: qemu-devel@nongnu.org Date: Thu, 12 May 2016 09:59:01 +0200 Message-Id: <1463039950-4021-15-git-send-email-armbru@redhat.com> In-Reply-To: <1463039950-4021-1-git-send-email-armbru@redhat.com> References: <1463039950-4021-1-git-send-email-armbru@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 12 May 2016 07:59:16 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 14/23] qapi: Add visit_type_null() visitor X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Blake Right now, qmp-output-visitor happens to produce a QNull result if nothing is actually visited between the creation of the visitor and the request for the resulting QObject. A stronger protocol would require that a QMP output visit MUST visit something. But to still be able to produce a JSON 'null' output, we need a new visitor function that states our intentions. Yes, we could say that such a visit must go through visit_type_any(), but that feels clunky. So this patch introduces the new visit_type_null() interface and its no-op interface in the dealloc visitor, and stubs in the qmp visitors (the next patch will finish the implementation). For the visitors that will not implement the callback, document the situation. The code in qapi-visit-core unconditionally dereferences the callback pointer, so that a segfault will inform a developer if they need to implement the callback for their choice of visitor. Note that JSON has a primitive null type, with the single value null; likewise with the QNull type for QObject; but for QAPI, we just have the 'null' value without a null type. We may eventually want to add more support in QAPI for null (most likely, we'd use it via an alternate type that permits 'null' or an object); but we'll create that usage when we need it. Signed-off-by: Eric Blake Message-Id: <1461879932-9020-15-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- include/qapi/opts-visitor.h | 3 ++- include/qapi/string-input-visitor.h | 2 +- include/qapi/string-output-visitor.h | 2 +- include/qapi/visitor-impl.h | 3 +++ include/qapi/visitor.h | 12 ++++++++++++ qapi/qapi-dealloc-visitor.c | 5 +++++ qapi/qapi-visit-core.c | 5 +++++ qapi/qmp-input-visitor.c | 6 ++++++ qapi/qmp-output-visitor.c | 6 ++++++ 9 files changed, 41 insertions(+), 3 deletions(-) diff --git a/include/qapi/opts-visitor.h b/include/qapi/opts-visitor.h index 633aa71..fe37ed9 100644 --- a/include/qapi/opts-visitor.h +++ b/include/qapi/opts-visitor.h @@ -31,7 +31,8 @@ typedef struct OptsVisitor OptsVisitor; * - values above INT64_MAX or LLONG_MAX are rejected. * * The Opts input visitor does not implement support for visiting QAPI - * alternates, numbers (other than integers), or arbitrary QTypes. + * alternates, numbers (other than integers), null, or arbitrary + * QTypes. */ OptsVisitor *opts_visitor_new(const QemuOpts *opts); void opts_visitor_cleanup(OptsVisitor *nv); diff --git a/include/qapi/string-input-visitor.h b/include/qapi/string-input-visitor.h index fdf33ae..a8d8f67 100644 --- a/include/qapi/string-input-visitor.h +++ b/include/qapi/string-input-visitor.h @@ -19,7 +19,7 @@ typedef struct StringInputVisitor StringInputVisitor; /* * The string input visitor does not implement support for visiting - * QAPI structs, alternates, or arbitrary QTypes. + * QAPI structs, alternates, null, or arbitrary QTypes. */ StringInputVisitor *string_input_visitor_new(const char *str); void string_input_visitor_cleanup(StringInputVisitor *v); diff --git a/include/qapi/string-output-visitor.h b/include/qapi/string-output-visitor.h index 3bb09af..89b7e4b 100644 --- a/include/qapi/string-output-visitor.h +++ b/include/qapi/string-output-visitor.h @@ -19,7 +19,7 @@ typedef struct StringOutputVisitor StringOutputVisitor; /* * The string output visitor does not implement support for visiting - * QAPI structs, alternates, or arbitrary QTypes. + * QAPI structs, alternates, null, or arbitrary QTypes. */ StringOutputVisitor *string_output_visitor_new(bool human); void string_output_visitor_cleanup(StringOutputVisitor *v); diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h index 796d180..88d27d5 100644 --- a/include/qapi/visitor-impl.h +++ b/include/qapi/visitor-impl.h @@ -90,6 +90,9 @@ struct Visitor void (*type_any)(Visitor *v, const char *name, QObject **obj, Error **errp); + /* Must be set to visit explicit null values. */ + void (*type_null)(Visitor *v, const char *name, Error **errp); + /* Must be set for input visitors, optional otherwise. The core * takes care of the return type in the public interface. */ void (*optional)(Visitor *v, const char *name, bool *present); diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h index 2211637..709cca0 100644 --- a/include/qapi/visitor.h +++ b/include/qapi/visitor.h @@ -522,4 +522,16 @@ void visit_type_number(Visitor *v, const char *name, double *obj, */ void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp); +/* + * Visit a JSON null value. + * + * @name expresses the relationship of the null value to its parent + * container; see the general description of @name above. + * + * Unlike all other visit_type_* functions, no obj parameter is + * needed; rather, this is a witness that an explicit null value is + * expected rather than any other type. + */ +void visit_type_null(Visitor *v, const char *name, Error **errp); + #endif diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c index c19a459..413d525 100644 --- a/qapi/qapi-dealloc-visitor.c +++ b/qapi/qapi-dealloc-visitor.c @@ -163,6 +163,10 @@ static void qapi_dealloc_type_anything(Visitor *v, const char *name, } } +static void qapi_dealloc_type_null(Visitor *v, const char *name, Error **errp) +{ +} + Visitor *qapi_dealloc_get_visitor(QapiDeallocVisitor *v) { return &v->visitor; @@ -193,6 +197,7 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void) v->visitor.type_str = qapi_dealloc_type_str; v->visitor.type_number = qapi_dealloc_type_number; v->visitor.type_any = qapi_dealloc_type_anything; + v->visitor.type_null = qapi_dealloc_type_null; QTAILQ_INIT(&v->stack); diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c index 0f59a1d..fe6afe8 100644 --- a/qapi/qapi-visit-core.c +++ b/qapi/qapi-visit-core.c @@ -244,6 +244,11 @@ void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp) error_propagate(errp, err); } +void visit_type_null(Visitor *v, const char *name, Error **errp) +{ + v->type_null(v, name, errp); +} + static void output_type_enum(Visitor *v, const char *name, int *obj, const char *const strings[], Error **errp) { diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c index 5159833..fa460a3 100644 --- a/qapi/qmp-input-visitor.c +++ b/qapi/qmp-input-visitor.c @@ -340,6 +340,11 @@ static void qmp_input_type_any(Visitor *v, const char *name, QObject **obj, *obj = qobj; } +static void qmp_input_type_null(Visitor *v, const char *name, Error **errp) +{ + abort(); +} + static void qmp_input_optional(Visitor *v, const char *name, bool *present) { QmpInputVisitor *qiv = to_qiv(v); @@ -383,6 +388,7 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj, bool strict) v->visitor.type_str = qmp_input_type_str; v->visitor.type_number = qmp_input_type_number; v->visitor.type_any = qmp_input_type_any; + v->visitor.type_null = qmp_input_type_null; v->visitor.optional = qmp_input_optional; v->strict = strict; diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c index 1f2a7ba..adf7731 100644 --- a/qapi/qmp-output-visitor.c +++ b/qapi/qmp-output-visitor.c @@ -196,6 +196,11 @@ static void qmp_output_type_any(Visitor *v, const char *name, QObject **obj, qmp_output_add_obj(qov, name, *obj); } +static void qmp_output_type_null(Visitor *v, const char *name, Error **errp) +{ + abort(); +} + /* Finish building, and return the root object. Will not be NULL. */ QObject *qmp_output_get_qobject(QmpOutputVisitor *qov) { @@ -246,6 +251,7 @@ QmpOutputVisitor *qmp_output_visitor_new(void) v->visitor.type_str = qmp_output_type_str; v->visitor.type_number = qmp_output_type_number; v->visitor.type_any = qmp_output_type_any; + v->visitor.type_null = qmp_output_type_null; QTAILQ_INIT(&v->stack);