On Thursday 23 May 2013, Geert Uytterhoeven wrote:
> > The problem is: trying to fix that will mean the result is a larger
> > kernel than if you just do the usual arch-implemented thing of placing
> > an defined faulting instruction at the BUG() site - which defeats the
> > purpose of turning off CONFIG_BUG.
>
> Is __builtin_unreachable() working well these days?
>
Hmm, I just tried the trivial patch below, which seemed to do the right thing.
Needs a little more investigation, but that might actually be the correct
solution. I thought that at some point __builtin_unreachable() was the same
as "do {} while (1)", but this is not the case with the gcc I was using --
it just tells gcc that we don't expect to ever get here.
Signed-off-by: Arnd Bergmann <a...@arndb.de>
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 7d10f96..9afff7d 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -108,11 +108,11 @@ extern void warn_slowpath_null(const char *file, const
int line);
#else /* !CONFIG_BUG */
#ifndef HAVE_ARCH_BUG
-#define BUG() do {} while(0)
+#define BUG() __builtin_unreachable ()
#endif
#ifndef HAVE_ARCH_BUG_ON
-#define BUG_ON(condition) do { if (condition) ; } while(0)
+#define BUG_ON(condition) do { if (condition) __builtin_unreachable(); }
while(0)
#endif
#ifndef HAVE_ARCH_WARN_ON
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