linux-next: tree build failure
hollisb at us.ibm.com
Tue Oct 20 12:29:53 EST 2009
On Tue, 2009-10-20 at 11:42 +1030, Rusty Russell wrote:
> On Tue, 20 Oct 2009 04:49:29 am Hollis Blanchard wrote:
> > On Thu, 2009-10-15 at 08:27 +0100, Jan Beulich wrote:
> > > My perspective is that it just uncovered already existing brokenness.
> > Sorry, I thought it was clear, but to be more explicit: I propose the
> > following patch, which replaces the current BUILD_BUG_ON implementation
> > with Rusty's version.
> OK, I switched my brain back on. Yeah, I agree: we may still want
> BUILD_OR_RUNTIME_BUG_ON one day, but I like this.
> It's just missing the giant comment that it needs :)
> * BUILD_BUG_ON - break compile if a condition is true.
> * @cond: the condition which the compiler should know is false.
> * If you have some code which relies on certain constants being equal, or
> * other compile-time-evaluated condition, you should use BUILD_BUG_ON to
> * detect if someone changes it.
> * The implementation uses gcc's reluctance to create a negative array, but
> * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments
> * to inline functions). So as a fallback we use the optimizer; if it can't
> * prove the condition is false, it will cause a link error on the undefined
> * "__build_bug_on_failed". This error is less neat, and can be harder to
> * track down.
Do you want to put together a signed-off patch Rusty? It's your code, so
I don't feel comfortable doing that.
Once we have that, can we remove the mysterious MAYBE_BUILD_BUG_ON
statements introduced in previous patches? (Does it BUG or doesn't it??)
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