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authorDavid Rientjes <rientjes@google.com>2007-05-09 13:35:27 +0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 23:30:56 +0400
commit0d7ebbbc6eaa5539f78ab20ed6ff1725a4e332ef (patch)
treeddef8183ac6440e96678fd4d1159ee86619e2a97
parentf7e4217b007d1f73e7e3cf10ba4fea4a608c603f (diff)
downloadlinux-0d7ebbbc6eaa5539f78ab20ed6ff1725a4e332ef.tar.xz
compiler: introduce __used and __maybe_unused
__used is defined to be __attribute__((unused)) for all pre-3.3 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 3.3 and later so that the code is still emitted for such functions. __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@rustcorp.com.au> Cc: Adrian Bunk <bunk@stusta.de> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/compiler-gcc.h1
-rw-r--r--include/linux/compiler-gcc3.h6
-rw-r--r--include/linux/compiler-gcc4.h3
-rw-r--r--include/linux/compiler.h21
4 files changed, 25 insertions, 6 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index a9f794716a81..03ec2311fb29 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -40,3 +40,4 @@
#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
index ecd621fd27d2..a9e2863c2dbf 100644
--- a/include/linux/compiler-gcc3.h
+++ b/include/linux/compiler-gcc3.h
@@ -4,9 +4,11 @@
#include <linux/compiler-gcc.h>
#if __GNUC_MINOR__ >= 3
-# define __attribute_used__ __attribute__((__used__))
+# define __used __attribute__((__used__))
+# define __attribute_used__ __used /* deprecated */
#else
-# define __attribute_used__ __attribute__((__unused__))
+# define __used __attribute__((__unused__))
+# define __attribute_used__ __used /* deprecated */
#endif
#if __GNUC_MINOR__ >= 4
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index fd0cc7c4a636..a03e9398a6c2 100644
--- 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
index 3b6949b41745..498c35920762 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -108,15 +108,30 @@ 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.
*
+ * NOTE: Because distributions shipped with a backported unit-at-a-time
+ * compiler in gcc 3.3, we must define __used to be __attribute__((used))
+ * for gcc >=3.3 instead of 3.4.
+ *
* 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
/*