Subject: Re: linux-next: tree build failure

From: roel kluin <[email-masked]>
Date: Tue, 29 Sep 2009 11:51:56 +0200

On Tue, Sep 29, 2009 at 11:28 AM, Jan Beulich <[email-masked]> wrote:
>>>> Hollis Blanchard  09/29/09 2:00 AM >>>
>>First, I think there is a real bug here, and the code should read like
>>this (to match the comment):
>>    /* type has to be known at build time for optimization */
>>-    BUILD_BUG_ON(__builtin_constant_p(type));
>>+    BUILD_BUG_ON(!__builtin_constant_p(type));
>>
>>However, I get the same build error *both* ways, i.e.
>>__builtin_constant_p(type) evaluates to both 0 and 1? Either that, or
>>the new BUILD_BUG_ON() macro isn't working...
>
> No, at this point of the compilation process it's neither zero nor one,
> it's simply considered non-constant by the compiler at that stage
> (this builtin is used for optimization, not during parsing, and the
> error gets generated when the body of the function gets parsed,
> not when code gets generated from it).
>
> Jan

then maybe

if(__builtin_constant_p(type))
        BUILD_BUG_ON(1);

would work?

Roel
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