On Wed, 07 Mar 2012 01:34:16 -0500
KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx> wrote:
> >> And, now BUG() has renreachable() annotation. why don't it work?
> >>
> >>
> >> #define BUG() \
> >> do { \
> >> asm volatile("ud2"); \
> >> unreachable(); \
> >> } while (0)
> >>
> >
> > That's not compiled for CONFIG_BUG=n; such a config fallsback to
> > include/asm-generic/bug.h which just does
> >
> > #define BUG() do {} while (0)
> >
> > because CONFIG_BUG specifically _wants_ to bypass BUG()s and is reasonably
> > protected by CONFIG_EXPERT.
>
> So, I strongly suggest to remove CONFIG_BUG=n. It is neglected very long time and
> much plenty code assume BUG() is not no-op. I don't think we can fix all place.
>
> Just one instruction don't hurt code size nor performance.
Well yes, CONFIG_BUG=n is a crazy thing to do. a) because programmers
universally assume that BUG() doesn't return and b) given that the
kernel KNOWS that it is about to fall off a cliff, why would anyone
want to deprive themselves of information about the forthcoming crash?
So perhaps a good compromise here is to do nothing: let the
CONFIG_BUG=n build spew a pile of warnings, and let the crazy
CONFIG_BUG=n people suffer. That's if any such people exist...
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