compiler: introduce __used and __maybe_unused

[linux-2.6.git] / include / linux / compiler.h

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index d7378215b8514fdc0a960394a2b1b523fab9dda5..498c35920762e2e4a10ff61b1e01f9d27298e7dc 100644 (file)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -10,13 +10,13 @@
 # define __force       __attribute__((force))
 # define __nocast      __attribute__((nocast))
 # define __iomem       __attribute__((noderef, address_space(2)))
-# define __acquires(x) __attribute__((context(0,1)))
-# define __releases(x) __attribute__((context(1,0)))
-# define __acquire(x)  __context__(1)
-# define __release(x)  __context__(-1)
-# define __cond_lock(x)        ((x) ? ({ __context__(1); 1; }) : 0)
-extern void __chk_user_ptr(void __user *);
-extern void __chk_io_ptr(void __iomem *);
+# define __acquires(x) __attribute__((context(x,0,1)))
+# define __releases(x) __attribute__((context(x,1,0)))
+# define __acquire(x)  __context__(x,1)
+# define __release(x)  __context__(x,-1)
+# define __cond_lock(x,c)      ((c) ? ({ __acquire(x); 1; }) : 0)
+extern void __chk_user_ptr(const void __user *);
+extern void __chk_io_ptr(const void __iomem *);
 #else
 # define __user
 # define __kernel
@@ -31,7 +31,7 @@ extern void __chk_io_ptr(void __iomem *);
 # define __releases(x)
 # define __acquire(x) (void)0
 # define __release(x) (void)0
-# define __cond_lock(x) (x)
+# define __cond_lock(x,c) (c)
 #endif
 
 #ifdef __KERNEL__
@@ -40,10 +40,8 @@ extern void __chk_io_ptr(void __iomem *);
 #error no compiler-gcc.h file for this gcc version
 #elif __GNUC__ == 4
 # include <linux/compiler-gcc4.h>
-#elif __GNUC__ == 3
+#elif __GNUC__ == 3 && __GNUC_MINOR__ >= 2
 # include <linux/compiler-gcc3.h>
-#elif __GNUC__ == 2
-# include <linux/compiler-gcc2.h>
 #else
 # error Sorry, your compiler is too old/not recognized.
 #endif
@@ -80,6 +78,7 @@ extern void __chk_io_ptr(void __iomem *);
 
 #endif /* __ASSEMBLY__ */
 
+#ifdef __KERNEL__
 /*
  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
  * warning for each use, in hopes of speeding the functions removal.
@@ -100,19 +99,39 @@ extern void __chk_io_ptr(void __iomem *);
 #define __must_check
 #endif
 
+#ifndef CONFIG_ENABLE_MUST_CHECK
+#undef __must_check
+#define __must_check
+#endif
+
 /*
  * 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
 
 /*
@@ -129,6 +148,16 @@ extern void __chk_io_ptr(void __iomem *);
 # define __attribute_pure__    /* unimplemented */
 #endif
 
+#ifndef noinline
+#define noinline
+#endif
+
+#ifndef __always_inline
+#define __always_inline inline
+#endif
+
+#endif /* __KERNEL__ */
+
 /*
  * From the GCC manual:
  *
@@ -147,12 +176,4 @@ extern void __chk_io_ptr(void __iomem *);
 # define __attribute_const__   /* unimplemented */
 #endif
 
-#ifndef noinline
-#define noinline
-#endif
-
-#ifndef __always_inline
-#define __always_inline inline
-#endif
-
 #endif /* __LINUX_COMPILER_H */