From patchwork Thu Feb 18 06:48:16 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 8346631 Return-Path: X-Original-To: patchwork-qemu-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id B5354C0553 for ; Thu, 18 Feb 2016 06:52:45 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id B25DC20386 for ; Thu, 18 Feb 2016 06:52:44 +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 8F1EF20384 for ; Thu, 18 Feb 2016 06:52:43 +0000 (UTC) Received: from localhost ([::1]:37675 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aWISB-00049q-1R for patchwork-qemu-devel@patchwork.kernel.org; Thu, 18 Feb 2016 01:52:43 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40190) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aWIOE-0005Mc-MT for qemu-devel@nongnu.org; Thu, 18 Feb 2016 01:48:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aWIOB-0001zO-Sc for qemu-devel@nongnu.org; Thu, 18 Feb 2016 01:48:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57119) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aWIOB-0001z9-GG for qemu-devel@nongnu.org; Thu, 18 Feb 2016 01:48:35 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (Postfix) with ESMTPS id 1C3D68E675; Thu, 18 Feb 2016 06:48:35 +0000 (UTC) Received: from red.redhat.com (ovpn-113-75.phx2.redhat.com [10.3.113.75]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u1I6mXAX023855; Thu, 18 Feb 2016 01:48:34 -0500 From: Eric Blake To: qemu-devel@nongnu.org Date: Wed, 17 Feb 2016 23:48:16 -0700 Message-Id: <1455778109-6278-3-git-send-email-eblake@redhat.com> In-Reply-To: <1455778109-6278-1-git-send-email-eblake@redhat.com> References: <1455778109-6278-1-git-send-email-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: armbru@redhat.com, Michael Roth Subject: [Qemu-devel] [PATCH v11 02/15] qapi: Forbid empty unions and useless alternates X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 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-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org 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 Empty unions serve no purpose, and while we compile with gcc which permits them, strict C99 forbids them. We happen to inject a dummy 'void *data' member into the C unions that represent QAPI unions and alternates, but we want to get rid of that member (it pollutes the namespace for no good reason), which would leave us with an empty union if the user didn't provide any branches. While empty structs make sense in QAPI, empty unions don't add any expressiveness to the QMP language. So prohibit them at parse time. Update the documentation and testsuite to match. Note that the documentation already mentioned that alternates should have "two or more JSON data types"; so this also fixes the code to enforce that. However, we have existing uses of a union type with only one branch, so the 2-or-more strictness is intentionally limited to alternates. Signed-off-by: Eric Blake --- v11: improve commit message v10: hoist into earlier series [no v7, v8, or v9] v6: rebase to earlier qapi.py cleanups --- scripts/qapi.py | 12 ++++++++++-- docs/qapi-code-gen.txt | 15 ++++++++------- tests/qapi-schema/alternate-empty.err | 1 + tests/qapi-schema/alternate-empty.exit | 2 +- tests/qapi-schema/alternate-empty.json | 2 +- tests/qapi-schema/alternate-empty.out | 5 ----- tests/qapi-schema/flat-union-empty.err | 1 + tests/qapi-schema/flat-union-empty.exit | 2 +- tests/qapi-schema/flat-union-empty.json | 2 +- tests/qapi-schema/flat-union-empty.out | 9 --------- tests/qapi-schema/union-empty.err | 1 + tests/qapi-schema/union-empty.exit | 2 +- tests/qapi-schema/union-empty.json | 2 +- tests/qapi-schema/union-empty.out | 6 ------ 14 files changed, 27 insertions(+), 35 deletions(-) diff --git a/scripts/qapi.py b/scripts/qapi.py index f40dc9e..f97236f 100644 --- a/scripts/qapi.py +++ b/scripts/qapi.py @@ -590,7 +590,10 @@ def check_union(expr, expr_info): "Discriminator '%s' must be of enumeration " "type" % discriminator) - # Check every branch + # Check every branch; don't allow an empty union + if len(members) == 0: + raise QAPIExprError(expr_info, + "Union '%s' cannot have empty 'data'" % name) for (key, value) in members.items(): check_name(expr_info, "Member of union '%s'" % name, key) @@ -613,7 +616,11 @@ def check_alternate(expr, expr_info): members = expr['data'] types_seen = {} - # Check every branch + # Check every branch; require at least two branches + if len(members) < 2: + raise QAPIExprError(expr_info, + "Alternate '%s' should have at least two branches " + "in 'data'" % name) for (key, value) in members.items(): check_name(expr_info, "Member of alternate '%s'" % name, key) @@ -1059,6 +1066,7 @@ class QAPISchemaObjectTypeVariants(object): assert bool(tag_member) != bool(tag_name) assert (isinstance(tag_name, str) or isinstance(tag_member, QAPISchemaObjectTypeMember)) + assert len(variants) > 0 for v in variants: assert isinstance(v, QAPISchemaObjectTypeVariant) self.tag_name = tag_name diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt index 128f074..999f3b9 100644 --- a/docs/qapi-code-gen.txt +++ b/docs/qapi-code-gen.txt @@ -187,11 +187,11 @@ prevent incomplete include files. Usage: { 'struct': STRING, 'data': DICT, '*base': STRUCT-NAME } -A struct is a dictionary containing a single 'data' key whose -value is a dictionary. This corresponds to a struct in C or an Object -in JSON. Each value of the 'data' dictionary must be the name of a -type, or a one-element array containing a type name. An example of a -struct is: +A struct is a dictionary containing a single 'data' key whose value is +a dictionary; the dictionary may be empty. This corresponds to a +struct in C or an Object in JSON. Each value of the 'data' dictionary +must be the name of a type, or a one-element array containing a type +name. An example of a struct is: { 'struct': 'MyType', 'data': { 'member1': 'str', 'member2': 'int', '*member3': 'str' } } @@ -288,9 +288,10 @@ or: { 'union': STRING, 'data': DICT, 'base': STRUCT-NAME, Union types are used to let the user choose between several different variants for an object. There are two flavors: simple (no -discriminator or base), flat (both discriminator and base). A union +discriminator or base), and flat (both discriminator and base). A union type is defined using a data dictionary as explained in the following -paragraphs. +paragraphs. The data dictionary for either type of union must not +be empty. A simple union type defines a mapping from automatic discriminator values to data types like in this example: diff --git a/tests/qapi-schema/alternate-empty.err b/tests/qapi-schema/alternate-empty.err index e69de29..bb06c5b 100644 --- a/tests/qapi-schema/alternate-empty.err +++ b/tests/qapi-schema/alternate-empty.err @@ -0,0 +1 @@ +tests/qapi-schema/alternate-empty.json:2: Alternate 'Alt' should have at least two branches in 'data' diff --git a/tests/qapi-schema/alternate-empty.exit b/tests/qapi-schema/alternate-empty.exit index 573541a..d00491f 100644 --- a/tests/qapi-schema/alternate-empty.exit +++ b/tests/qapi-schema/alternate-empty.exit @@ -1 +1 @@ -0 +1 diff --git a/tests/qapi-schema/alternate-empty.json b/tests/qapi-schema/alternate-empty.json index db3820f..fff15ba 100644 --- a/tests/qapi-schema/alternate-empty.json +++ b/tests/qapi-schema/alternate-empty.json @@ -1,2 +1,2 @@ -# FIXME - alternates should list at least two types to be useful +# alternates must list at least two types to be useful { 'alternate': 'Alt', 'data': { 'i': 'int' } } diff --git a/tests/qapi-schema/alternate-empty.out b/tests/qapi-schema/alternate-empty.out index f78f174..e69de29 100644 --- a/tests/qapi-schema/alternate-empty.out +++ b/tests/qapi-schema/alternate-empty.out @@ -1,5 +0,0 @@ -object :empty -alternate Alt - case i: int -enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool'] - prefix QTYPE diff --git a/tests/qapi-schema/flat-union-empty.err b/tests/qapi-schema/flat-union-empty.err index e69de29..15754f5 100644 --- a/tests/qapi-schema/flat-union-empty.err +++ b/tests/qapi-schema/flat-union-empty.err @@ -0,0 +1 @@ +tests/qapi-schema/flat-union-empty.json:4: Union 'Union' cannot have empty 'data' diff --git a/tests/qapi-schema/flat-union-empty.exit b/tests/qapi-schema/flat-union-empty.exit index 573541a..d00491f 100644 --- a/tests/qapi-schema/flat-union-empty.exit +++ b/tests/qapi-schema/flat-union-empty.exit @@ -1 +1 @@ -0 +1 diff --git a/tests/qapi-schema/flat-union-empty.json b/tests/qapi-schema/flat-union-empty.json index 67dd297..77f1d9a 100644 --- a/tests/qapi-schema/flat-union-empty.json +++ b/tests/qapi-schema/flat-union-empty.json @@ -1,4 +1,4 @@ -# FIXME - flat unions should not be empty +# flat unions cannot be empty { 'enum': 'Empty', 'data': [ ] } { 'struct': 'Base', 'data': { 'type': 'Empty' } } { 'union': 'Union', 'base': 'Base', 'discriminator': 'type', 'data': { } } diff --git a/tests/qapi-schema/flat-union-empty.out b/tests/qapi-schema/flat-union-empty.out index eade2d5..e69de29 100644 --- a/tests/qapi-schema/flat-union-empty.out +++ b/tests/qapi-schema/flat-union-empty.out @@ -1,9 +0,0 @@ -object :empty -object Base - member type: Empty optional=False -enum Empty [] -enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool'] - prefix QTYPE -object Union - base Base - tag type diff --git a/tests/qapi-schema/union-empty.err b/tests/qapi-schema/union-empty.err index e69de29..12c2022 100644 --- a/tests/qapi-schema/union-empty.err +++ b/tests/qapi-schema/union-empty.err @@ -0,0 +1 @@ +tests/qapi-schema/union-empty.json:2: Union 'Union' cannot have empty 'data' diff --git a/tests/qapi-schema/union-empty.exit b/tests/qapi-schema/union-empty.exit index 573541a..d00491f 100644 --- a/tests/qapi-schema/union-empty.exit +++ b/tests/qapi-schema/union-empty.exit @@ -1 +1 @@ -0 +1 diff --git a/tests/qapi-schema/union-empty.json b/tests/qapi-schema/union-empty.json index 1785007..1f0b13c 100644 --- a/tests/qapi-schema/union-empty.json +++ b/tests/qapi-schema/union-empty.json @@ -1,2 +1,2 @@ -# FIXME - unions should not be empty +# unions cannot be empty { 'union': 'Union', 'data': { } } diff --git a/tests/qapi-schema/union-empty.out b/tests/qapi-schema/union-empty.out index bdf17e5..e69de29 100644 --- a/tests/qapi-schema/union-empty.out +++ b/tests/qapi-schema/union-empty.out @@ -1,6 +0,0 @@ -object :empty -enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool'] - prefix QTYPE -object Union - member type: UnionKind optional=False -enum UnionKind []