Messages in this thread | | | Date | Mon, 20 May 2013 17:31:18 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH] include/linux/posix_acl.h: need 'return NULL' when BUG(), if neither CONFIG_BUG nor HAVE_ARCH_BUG is defined. |
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On Mon, May 20, 2013 at 07:40:24AM -0700, Eric W. Biederman wrote: > Seriously? The correct fix it would seem is to give a useful default BUG > definition. Say *NULL.
Absolutely.
The real question is... how is this happening. I've seen it occasionally in the randconfig builds - though I don't have any logs to hand which show that in the build system at the moment. So, looking at the files:
arch/arm/include/asm/bug.h: #ifdef CONFIG_BUG #define BUG() _BUG(__FILE__, __LINE__, BUG_INSTR_VALUE) #define _BUG(file, line, value) __BUG(file, line, value) #ifdef CONFIG_DEBUG_BUGVERBOSE #define __BUG(__file, __line, __value) \ ... unreachable(); \ ... #else /* not CONFIG_DEBUG_BUGVERBOSE */ #define __BUG(__file, __line, __value) \ ... unreachable(); \ ... #endif /* CONFIG_DEBUG_BUGVERBOSE */
#define HAVE_ARCH_BUG #endif /* CONFIG_BUG */
#include <asm-generic/bug.h>
So here, whenever we have CONFIG_BUG enabled, we always define a non-empty BUG() macro to override the generic version. So far so good.
include/asm-generic/bug.h:
#ifdef CONFIG_BUG ... we're providing our own version ...
#else /* !CONFIG_BUG */ #ifndef HAVE_ARCH_BUG #define BUG() do {} while(0) #endif
#ifndef HAVE_ARCH_BUG_ON #define BUG_ON(condition) do { if (condition) ; } while(0) #endif
So, the generic stuff becomes no-ops which just fall through. Seriously? Is this really what we want?
So either we need to fix the generic bug.h code, or fix every site which uses BUG()/BUG_ON().
Note - I'm not saying *NULL as you did, because that isn't guaranteed to fault on all platforms. NoMMU may allow *NULL to succeed without causing an exception.
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