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Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at off
From: |
Marc-André Lureau |
Subject: |
Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0 |
Date: |
Wed, 21 Mar 2018 15:08:40 +0100 |
Hi
On Wed, Mar 21, 2018 at 3:01 PM, Paolo Bonzini <address@hidden> wrote:
> On 21/03/2018 14:40, Marc-André Lureau wrote:
>> +/* A typecast, checking for the type of arguments */
>> +/* QObject is at offset 0, for all QObject-derived types */
>> +#define QOBJECT(x) QEMU_GENERIC(x, \
>> + (QNull *, (QObject *) x), \
>> + (const QNull *, (const QObject *) x), \
>> + (QNum *, (QObject *) x), \
>> + (const QNum *, (const QObject *) x), \
>> + (QString *, (QObject *) x), \
>> + (const QString *, (const QObject *) x), \
>> + (QDict *, (QObject *) x), \
>> + (const QDict *, (const QObject *) x), \
>> + (QList *, (QObject *) x), \
>> + (const QList *, (const QObject *) x), \
>> + (QBool *, (QObject *) x), \
>> + (const QBool *, (const QObject *) x), \
>> + (QObject *, x), \
>> + (const QObject *, x), \
>> + qobject_unknown_type(x))
>
> Why not just
>
> QEMU_GENERIC(x,
> (QObject *, x),
> (const QObject *, x),
> ({ \
> QEMU_BUILD_BUG_ON(offsetof(typeof(*x), base));
> &(x)->base;
> }))
>
> That is just an extension of what was being done before, and it is
> resilient against people putting a random "QObject base" in the middle
> of a struct.
>
Yeah, I tried a few of those approaches. Here the problem is that
QObject doesn't have base field. So you get a compile time error with
a QObject * as argument.
thanks
- [Qemu-devel] [PATCH 0/3] RFC: simplify qobject refcount, Marc-André Lureau, 2018/03/21
- [Qemu-devel] [PATCH 1/3] compiler: extend QEMU_GENERIC to handle more arguments, Marc-André Lureau, 2018/03/21
- [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Marc-André Lureau, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Eric Blake, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Paolo Bonzini, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0,
Marc-André Lureau <=
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Eric Blake, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Marc-André Lureau, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Paolo Bonzini, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Eric Blake, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Paolo Bonzini, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Marc-André Lureau, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Paolo Bonzini, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Marc-André Lureau, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Paolo Bonzini, 2018/03/21
- Re: [Qemu-devel] [PATCH 2/3] qobject: assume base of a qobject is at offset 0, Marc-André Lureau, 2018/03/21