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Subject: Re: Question on FIELD_PREP() for static array
From:   Johannes Berg <johannes@sipsolutions.net>
To:     John Garry <john.garry@huawei.com>, Joe Perches <joe@perches.com>,
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Date:   Thu, 11 Oct 2018 21:22:34 +0200
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On Thu, 2018-10-11 at 21:13 +0200, Johannes Berg wrote:
> 
> However, I have another trick:
> 
> #define __NLA_ENSURE(condition) (0 * sizeof(struct { unsigned int x:1 - 2*!(condition);}))
> 
> or, in this context,
> 
> #define BUILD_BUG_ON_RET_ZERO(cond) (0 * sizeof(struct { unsigned int x:1 - 2*!(condition);}))

Oops, I forgot to insert the second !, it must be

#define BUILD_BUG_ON_RET_ZERO(cond) (0 * sizeof(struct { unsigned int x:1 - 2*!!(condition);}))

johannes