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Message-ID: <Pine.LNX.4.64.0705031734520.21416@chino.kir.corp.google.com> Date: Thu, 3 May 2007 17:35:57 -0700 (PDT) From: David Rientjes <rientjes@...gle.com> To: Andrew Morton <akpm@...ux-foundation.org> cc: Rusty Russell <rusty@...tcorp.com.au>, Adrian Bunk <bunk@...sta.de>, linux-kernel@...r.kernel.org Subject: [patch] compiler: introduce __used and __maybe_unused __used is defined to be __attribute__((unused)) for all pre-3.4 gcc compilers to suppress warnings for unused functions because perhaps they are referenced only in inline assembly. It is defined to be __attribute__((used)) for gcc 3.4 and later so that the code is still emitted for such functions. There was a mistake in the current implementation of __attribute_used__ whereas it would be defined to be __attribute__((used)) incorrectly for gcc 3.3 and later. The unit-at-a-time compilation scheme was only introduced in gcc 3.4 and later versions as specified in http://www.gnu.org/software/gcc/gcc-3.4/changes.html. __maybe_unused is defined to be __attribute__((unused)) for both function and variable use if it could possibly be unreferenced due to the evaluation of preprocessor macros. Function prototypes shall be marked with __maybe_unused if the actual definition of the function is dependant on preprocessor macros. No update to compiler-intel.h is necessary because ICC supports both __attribute__((used)) and __attribute__((unused)) as specified by the gcc manual. __attribute_used__ is deprecated and will be removed once all current code is converted to using __used. Cc: Rusty Russell <rusty@...tcorp.com.au> Cc: Andrian Bunk <bunk@...sta.de> Signed-off-by: David Rientjes <rientjes@...gle.com> --- include/linux/compiler-gcc.h | 1 + include/linux/compiler-gcc3.h | 13 ++++++------- include/linux/compiler-gcc4.h | 3 ++- include/linux/compiler.h | 17 ++++++++++++++--- 4 files changed, 23 insertions(+), 11 deletions(-) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -37,3 +37,4 @@ #define noinline __attribute__((noinline)) #define __attribute_pure__ __attribute__((pure)) #define __attribute_const__ __attribute__((__const__)) +#define __maybe_unused __attribute__((unused)) diff --git a/include/linux/compiler-gcc3.h b/include/linux/compiler-gcc3.h --- a/include/linux/compiler-gcc3.h +++ b/include/linux/compiler-gcc3.h @@ -3,14 +3,13 @@ /* These definitions are for GCC v3.x. */ #include <linux/compiler-gcc.h> -#if __GNUC_MINOR__ >= 3 -# define __attribute_used__ __attribute__((__used__)) -#else -# define __attribute_used__ __attribute__((__unused__)) -#endif - #if __GNUC_MINOR__ >= 4 -#define __must_check __attribute__((warn_unused_result)) +# define __used __attribute__((__used__)) +# define __attribute_used__ __used /* deprecated */ +# define __must_check __attribute__((warn_unused_result)) +#else +# define __used __attribute__((__unused__)) +# define __attribute_used__ __used /* deprecated */ #endif #define __always_inline inline __attribute__((always_inline)) diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h --- a/include/linux/compiler-gcc4.h +++ b/include/linux/compiler-gcc4.h @@ -12,7 +12,8 @@ # define __inline __inline __attribute__((always_inline)) #endif -#define __attribute_used__ __attribute__((__used__)) +#define __used __attribute__((__used__)) +#define __attribute_used__ __used /* deprecated */ #define __must_check __attribute__((warn_unused_result)) #define __compiler_offsetof(a,b) __builtin_offsetof(a,b) #define __always_inline inline __attribute__((always_inline)) diff --git a/include/linux/compiler.h b/include/linux/compiler.h --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -108,15 +108,26 @@ extern void __chk_io_ptr(const void __iomem *); * Allow us to avoid 'defined but not used' warnings on functions and data, * as well as force them to be emitted to the assembly file. * - * As of gcc 3.3, static functions that are not marked with attribute((used)) - * may be elided from the assembly file. As of gcc 3.3, static data not so + * As of gcc 3.4, static functions that are not marked with attribute((used)) + * may be elided from the assembly file. As of gcc 3.4, static data not so * marked will not be elided, but this may change in a future gcc version. * * In prior versions of gcc, such functions and data would be emitted, but * would be warned about except with attribute((unused)). + * + * Mark functions that are referenced only in inline assembly as __used so + * the code is emitted even though it appears to be unreferenced. */ #ifndef __attribute_used__ -# define __attribute_used__ /* unimplemented */ +# define __attribute_used__ /* deprecated */ +#endif + +#ifndef __used +# define __used /* unimplemented */ +#endif + +#ifndef __maybe_unused +# define __maybe_unused /* unimplemented */ #endif /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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