#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2\*!!(condition)])) https... | Hacker News

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		DannyBee on June 16, 2015 \| parent \| context \| favorite \| on: Apple’s Bitcode Telegraphs Future CPU Plans #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) https://scaryreasoner.wordpress.com/2009/02/28/checking-size... There are many ways to make it perform different behavior at compile time (though admittedly, most are abuse). The above should compile error, but if you push sizeof evaluation, will not.

TheLoneWolfling on June 16, 2015 [–]

Better form, for certain definitions of better (works in global scope):

    #define BUILD_BUG_ON(condition) extern int build_bug_on[!!(condition)-1]

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