From patchwork Thu Sep 10 04:06:18 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 516098 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id EEA2D14030C for ; Thu, 10 Sep 2015 14:12:16 +1000 (AEST) Received: from localhost ([::1]:46782 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZtDY-0004H0-CY for incoming@patchwork.ozlabs.org; Thu, 10 Sep 2015 00:12:12 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34133) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZt8Q-00037c-N2 for qemu-devel@nongnu.org; Thu, 10 Sep 2015 00:06:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZt8O-00052q-3L for qemu-devel@nongnu.org; Thu, 10 Sep 2015 00:06:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54739) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZt8N-00052E-Qk for qemu-devel@nongnu.org; Thu, 10 Sep 2015 00:06:52 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 581F691DD5; Thu, 10 Sep 2015 04:06:51 +0000 (UTC) Received: from red.redhat.com ([10.3.113.15]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t8A46Zhd031165; Thu, 10 Sep 2015 00:06:50 -0400 From: Eric Blake To: qemu-devel@nongnu.org Date: Wed, 9 Sep 2015 22:06:18 -0600 Message-Id: <1441857991-7309-17-git-send-email-eblake@redhat.com> In-Reply-To: <1441857991-7309-1-git-send-email-eblake@redhat.com> References: <1441857991-7309-1-git-send-email-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Michael Roth , marcandre.lureau@redhat.com, armbru@redhat.com, DirtY.iCE.hu@gmail.com Subject: [Qemu-devel] [PATCH RFC v4 16/29] 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+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Empty unions serve no purpose, and while we compile with gcc which permits them, strict C99 forbids them. We could inject a dummy member (and in fact, we do for empty structs), but 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. Signed-off-by: Eric Blake --- docs/qapi-code-gen.txt | 13 +++++++------ scripts/qapi.py | 12 ++++++++++-- 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 | 3 --- 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 | 7 ------- 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 | 4 ---- 14 files changed, 26 insertions(+), 28 deletions(-) diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt index 3272b24..ff57010 100644 --- a/docs/qapi-code-gen.txt +++ b/docs/qapi-code-gen.txt @@ -182,11 +182,11 @@ 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' } } @@ -277,7 +277,8 @@ 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 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/scripts/qapi.py b/scripts/qapi.py index a0eca74..475d2c2 100644 --- a/scripts/qapi.py +++ b/scripts/qapi.py @@ -563,7 +563,10 @@ 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) @@ -601,7 +604,11 @@ def check_alternate(expr, expr_info): values = { 'MAX': '(automatic)' } 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) @@ -964,6 +971,7 @@ class QAPISchemaObjectTypeVariants(object): def __init__(self, tag_name, tag_enum, variants): assert tag_name is None or isinstance(tag_name, str) assert tag_enum is None or isinstance(tag_enum, str) + assert len(variants) > 0 for v in variants: assert isinstance(v, QAPISchemaObjectTypeVariant) self._tag_name = tag_name 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 9b010d8..e69de29 100644 --- a/tests/qapi-schema/alternate-empty.out +++ b/tests/qapi-schema/alternate-empty.out @@ -1,3 +0,0 @@ -object :empty -alternate Alt - case i: int 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 0e0665a..e69de29 100644 --- a/tests/qapi-schema/flat-union-empty.out +++ b/tests/qapi-schema/flat-union-empty.out @@ -1,7 +0,0 @@ -object :empty -object Base - member type: Empty optional=False -enum Empty [] -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 c5500da..e69de29 100644 --- a/tests/qapi-schema/union-empty.out +++ b/tests/qapi-schema/union-empty.out @@ -1,4 +0,0 @@ -object :empty -object Union - tag type -enum UnionKind []