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authorDavid Rientjes <rientjes@google.com>2007-05-09 02:35:27 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:56 -0700
commit0d7ebbbc6eaa5539f78ab20ed6ff1725a4e332ef (patch)
treeddef8183ac6440e96678fd4d1159ee86619e2a97 /include/linux/compiler.h
parentf7e4217b007d1f73e7e3cf10ba4fea4a608c603f (diff)
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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>
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r--include/linux/compiler.h21
1 files changed, 18 insertions, 3 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 3b6949b..498c359 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
/*
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