Messages in this thread | | | Date | Tue, 28 Feb 2012 21:06:00 +0100 | From | Sam Ravnborg <> | Subject | Re: [PATCH] kernel.h: Include <linux/bug.h> to avoid build breakage with ARRAY_SIZE() |
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On Tue, Feb 28, 2012 at 11:43:36AM -0500, Paul Gortmaker wrote: > On 12-02-28 10:51 AM, Sam Ravnborg wrote: > > On Tue, Feb 28, 2012 at 10:41:39AM -0300, Fabio Estevam wrote: > >> Building imx_v6_v7_defconfig generated the following build error: > >> > >> arch/arm/mach-imx/cpu_op-mx51.c: In function 'mx51_get_cpu_op': > >> arch/arm/mach-imx/cpu_op-mx51.c:27: error: implicit declaration of function 'BUILD_BUG_ON_ZERO' > >> > >> commit 6f863554 (kernel.h: doesn't explicitly use bug.h, so don't include it.) > >> has removed asm/debug.h from linux/kernel.h. > >> > >> Quoting Russell King (http://www.spinics.net/lists/arm-kernel/msg161916.html) > >> > >> "linux/kernel.h _does_ use bug stuff - in ARRAY_SIZE(). > >> > >> ARRAY_SIZE() uses __must_be_array(), which is defined in linux/compiler-gcc.h, > >> which is obtained via linux/compiler.h and linux/linkage.h. > >> > >> linux/compiler-gcc.h defines __must_be_array() to be: > >> #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) > > > > In which case linux/compiler-gcc.h uses bug.h - so this is where you > > should add the include. > > Not in kernel.h that just happens to use __must_be_array() > > We do not want to add "#include bug.h" to all header files > > that happens to use __must_be_array. > > The approach I was taking was to consider something "used" if it was > actually in a static inline[1]. So in that sense, the kernel.h does > not "use" ARRAY_SIZE, but only defines it. This seems to be what has > been done in the past, and folks have even converted trivial static > inline functions to macros just to use this concept of "used" to > help avoid tangling includes any further than they currently are.
We have a macro which uses a macro which uses a macro from bug.h. Should we include bug.h with the first or the second macro?
I guess in this case it does not matter much.
Sam
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