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From: Eric Blake <eblake@redhat.com>
To: Markus Armbruster <armbru@redhat.com>
Cc: qemu-devel@nongnu.org, Michael Roth <mdroth@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [PATCH v11 11/28] qapi: Check for qapi collisions of flat union branches
Date: Wed, 11 Nov 2015 08:49:42 -0700	[thread overview]
Message-ID: <56436396.60601@redhat.com> (raw)
In-Reply-To: <878u64d54n.fsf@blackfin.pond.sub.org>

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On 11/11/2015 06:42 AM, Markus Armbruster wrote:
> Eric Blake <eblake@redhat.com> writes:

> Your patch actually does two things:
> 
> 1. Extend the "object type cannot contain itself" check to cover its
>    variant types in addition to base type.  This is the two-liner change
>    to QAPISchemaObjectTypeVariants.check().
> 
> 2. Extend the "object type cannot contain members with clashing names"
>    to cover variant members.
> 
> They're related: you need the former's side effect to compute .members
> to be able to do the latter.
> 
> Doing it in two separate patches *might* make explaining it in the
> commit message easier.  See below.

Interesting observation.  I can split if you still think it is worth it;
otherwise, I think your wording makes both changes obvious:


> Let me have a stab at the commit message of the *unsplit* patch, use as
> you see fit:
> 
> qapi: Check for collisions involving variant members
> 
> Right now, our ad hoc parser ensures that we cannot have a flat union
> that introduces any members that would clash with non-variant members
> inherited from the union's base type (see flat-union-clash-member.json).
> We want QAPISchemaObjectType.check() to make the same check, so we can
> later reduce some of the ad hoc checks.
> 
> We already have a map 'seen' of all non-variant members.  We still need
> to check for collisions between each variant type's members and the
> non-variant ones.
> 
> To know the variant type's members, we need to call
> variant.type.check().  This also detects when a type contains itself in
> a variant, exactly like the existing base.check() detects when a type
> contains itself as a base.

If I split, this paragraph would go in the first patch (adding the
.check() for cycle detection).

> 
> Slight complication: an alternate's variant can have arbitrary type, but
> only an object type's check() may be called outside QAPISchema.check().
> We could either skip the call for variants of alternates, or skip it for
> non-object types.  Do the latter, because it's easier.

I actually have some churn on this; later in 22/28, I'm stuck making
Variants.check() do something for unions only, and had to reintroduce an
'if seen:' conditional, at which point I moved the v.type.check() back
to unions only.  I guess your review of that patch may determine whether
I minimize churn back here, or add a 'for now' phrase to the commit
message, or just not worry about it.

> 
> Then we can call each variant member's check_clash() with the
> appropriate 'seen' map.  Since members of different variants can't
> clash, We have to clone a fresh seen for each variant.  Wrap this in the
> new helper method QAPISchemaObjectTypeVariants.check_clash().
> 
> Note that cloning 'seen' inside Variants.check_clash()
> resembles the one we just removed from Variants.check(); the
> difference here is that we are now checking for clashes
> among the qapi members of the variant type, rather than for
> a single clash with the variant tag name itself.
> 
> Note that by construction collisions can't actually happen for simple
> unions: each variant's type is a wrapper with a single member 'data',
> which will never collide with the only non-variant member 'type'.
> 
> For alternates, there's nothing for a variant object type's members to
> clash with, and therefore no need to call variants.check_clash().
> 
> No change to generated code.
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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  reply	other threads:[~2015-11-11 15:53 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-11  6:51 [Qemu-devel] [PATCH v11 00/28] qapi member collision, alternate layout (post-introspection cleanups, subset D) Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 01/28] qapi: Track simple union tag in object.local_members Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 02/28] qapi-types: Consolidate gen_struct() and gen_union() Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 03/28] qapi-types: Simplify gen_struct_field[s] Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 04/28] qapi: Drop obsolete tag value collision assertions Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 05/28] qapi: Simplify QAPISchemaObjectTypeMember.check() Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 06/28] qapi: Clean up after previous commit Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 07/28] qapi: Fix up commit 7618b91's clash sanity checking change Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 08/28] qapi: Eliminate QAPISchemaObjectType.check() variable members Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 09/28] qapi: Factor out QAPISchemaObjectTypeMember.check_clash() Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 10/28] qapi: Simplify QAPISchemaObjectTypeVariants.check() Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 11/28] qapi: Check for qapi collisions of flat union branches Eric Blake
2015-11-11 13:42   ` Markus Armbruster
2015-11-11 15:49     ` Eric Blake [this message]
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 12/28] qapi: Factor out QAPISchemaObjectType.check_clash() Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 13/28] qapi: Hoist tag collision check to Variants.check() Eric Blake
2015-11-11 13:56   ` Markus Armbruster
2015-11-11 16:11     ` Eric Blake
2015-11-11 17:03       ` Markus Armbruster
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 14/28] qapi: Remove outdated tests related to QMP/branch collisions Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 15/28] qapi: Track owner of each object member Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 16/28] qapi: Detect collisions in C member names Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 17/28] cpu: Convert CpuInfo into flat union Eric Blake
2015-11-11 14:13   ` Markus Armbruster
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 18/28] qerror: more error_setg() usage Eric Blake
2015-11-11 13:26   ` Andreas Färber
2015-11-11 14:21   ` Markus Armbruster
2015-11-11 14:23     ` Andreas Färber
2015-11-11 15:51       ` Eric Blake
2015-11-11 16:19     ` Eric Blake
2015-11-11 17:31       ` Markus Armbruster
2015-11-11 17:44         ` Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 19/28] qapi: Change munging of CamelCase enum values Eric Blake
2015-11-11 13:29   ` Andreas Färber
2015-11-11 14:50   ` Markus Armbruster
2015-11-11 16:03     ` Eric Blake
2015-11-11 17:11       ` Markus Armbruster
2015-11-12  8:34         ` Gerd Hoffmann
2015-11-12 11:16           ` Markus Armbruster
2015-11-12  8:29       ` Gerd Hoffmann
2015-11-11 16:06     ` Eric Blake
2015-11-13 17:46   ` Eric Blake
2015-11-13 18:13     ` Markus Armbruster
2015-11-13 21:37       ` Eric Blake
2015-11-16 14:30         ` Markus Armbruster
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 20/28] qapi: Forbid case-insensitive clashes Eric Blake
2015-11-11 14:53   ` Markus Armbruster
2015-11-13  5:32     ` Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 21/28] qapi: Convert qtype_code into qapi enum type Eric Blake
2015-11-11 16:42   ` Markus Armbruster
2015-11-11 17:03     ` Eric Blake
2015-11-12 13:16       ` Markus Armbruster
2015-11-18  6:27         ` Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 22/28] qapi: Simplify visiting of alternate types Eric Blake
2015-11-12 14:21   ` Markus Armbruster
2015-11-12 15:54   ` Markus Armbruster
2015-11-13 23:54   ` Eric Blake
2015-11-16 14:31     ` Markus Armbruster
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 23/28] qapi: Fix alternates that accept 'number' but not 'int' Eric Blake
2015-11-12 15:01   ` Markus Armbruster
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 24/28] qapi: Add positive tests to qapi-schema-test Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 25/28] qapi: Simplify visits of optional fields Eric Blake
2015-11-12 15:11   ` Markus Armbruster
2015-11-12 15:30     ` Eric Blake
2015-11-12 16:20       ` Markus Armbruster
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 26/28] qapi: Move duplicate member checks to schema check() Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 27/28] qapi: Move duplicate enum value " Eric Blake
2015-11-12 15:46   ` Markus Armbruster
2015-11-12 16:08     ` Eric Blake
2015-11-18  6:48     ` Eric Blake
2015-11-11  6:51 ` [Qemu-devel] [PATCH v11 28/28] qapi: Detect base class loops Eric Blake
2015-11-12 16:06   ` Markus Armbruster

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