From: Eric Blake <eblake@redhat.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Paolo Bonzini <pbonzini@redhat.com>,
qemu-devel@nongnu.org, Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH v3 2/4] compiler: rework BUG_ON using a struct
Date: Fri, 20 Jan 2017 08:36:08 -0600 [thread overview]
Message-ID: <7af547e6-8758-388a-17e9-9f749e927da2@redhat.com> (raw)
In-Reply-To: <20170120094124.GB2658@work-vm>
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On 01/20/2017 03:41 AM, Dr. David Alan Gilbert wrote:
>> -#define QEMU_BUILD_BUG_ON(x) \
>> - typedef char glue(qemu_build_bug_on__, __LINE__)[(x) ? -1 : 1] \
>> - __attribute__((unused))
>> +#define QEMU_BUILD_BUG_ON_STRUCT(x) \
>> + struct { \
>> + int qemu_build_bug_on : (x) ? -1 : 1; \
>> + }
>
> The problem with this is it can't be used as an expression, where as
> your previous version could.
> I've got a similar case (see previous reply) that needed an expression
> bug-on that would evaluate to zero.
Keep reading the series - the version usable in an expression is
QEMU_BUILD_BUG_ON_ZERO, introduced in 3/4. Patch 2/4 is just rewriting
the existing check, with no change in the fact that it is still a
declaration.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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next prev parent reply other threads:[~2017-01-20 14:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-19 21:07 [Qemu-devel] [PATCH v3 0/4] ARRAY_SIZE fixups Michael S. Tsirkin
2017-01-19 21:07 ` [Qemu-devel] [PATCH v3 1/4] compiler: drop ; after BUILD_BUG_ON Michael S. Tsirkin
2017-01-19 21:22 ` Eric Blake
2017-01-19 21:07 ` [Qemu-devel] [PATCH v3 2/4] compiler: rework BUG_ON using a struct Michael S. Tsirkin
2017-01-19 21:26 ` Eric Blake
2017-01-20 7:44 ` Markus Armbruster
2017-01-20 7:42 ` Markus Armbruster
2017-01-20 16:57 ` Michael S. Tsirkin
2017-01-20 17:09 ` Paolo Bonzini
2017-01-20 17:45 ` Michael S. Tsirkin
2017-01-20 18:33 ` Markus Armbruster
2017-01-20 9:41 ` Dr. David Alan Gilbert
2017-01-20 14:36 ` Eric Blake [this message]
2017-01-20 14:53 ` Dr. David Alan Gilbert
2017-01-19 21:07 ` [Qemu-devel] [PATCH v3 3/4] compiler: expression version of QEMU_BUILD_BUG_ON Michael S. Tsirkin
2017-01-19 21:28 ` Eric Blake
2017-01-19 21:07 ` [Qemu-devel] [PATCH v3 4/4] ARRAY_SIZE: check that argument is an array Michael S. Tsirkin
2017-01-19 21:59 ` Eric Blake
2017-01-19 22:11 ` Michael S. Tsirkin
2017-01-19 23:00 ` Eric Blake
2017-01-20 7:34 ` Markus Armbruster
2017-01-20 12:20 ` Paolo Bonzini
2017-01-20 7:45 ` [Qemu-devel] [PATCH v3 0/4] ARRAY_SIZE fixups Markus Armbruster
2017-01-20 14:57 ` no-reply
2017-01-20 15:15 ` no-reply
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