+/*
+ * __unused: Note that variable might be unused.
+ * Do not warn if variable is unused.
+ */
#if __GNUC_PREREQ__(2, 7)
#define __unused __attribute__((__unused__))
#else
#define __unused /* delete */
#endif
+/*
+ * __used: Note that variable is needed, even if it appears to be unused.
+ * Valid only for static variables. Do not optimise variable away.
+ * Do not warn if variable is unused.
+ */
#if __GNUC_PREREQ__(3, 1)
#define __used __attribute__((__used__))
#else
#define __used __unused
#endif
+/*
+ * __diagused: Note that variable is used in diagnostic code, but may be
+ * unused in non-diagnostic code.
+ *
+ * In the kernel, variables that are used when DIAGNOSTIC is defined,
+ * but unused when DIAGNOSTIC is not defined, may be declared with
+ * __diagused. In userland, variables that are used when NDEBUG is not
+ * defined, but unused when NDEBUG is defined, may be declared with
+ * __diagused.
+ *
+ * Variables used only in assert(3) or KASSERT(9) macros are likely
+ * candidates for being declared with __diagused.
+ */
+#if (defined(_KERNEL) && defined(DIAGNOSTIC)) \
+ || (!defined(_KERNEL) && !defined(NDEBUG))
+#define __diagused /* empty */
+#else
+#define __diagused __unused
+#endif
+
+/*
+ * __debugused: Note that variable is used in debug code, but may be
+ * unused in non-debug code.
+ *
+ * In either the kernel or userland, variables that are used when DEBUG
+ * is defined, but unused when DEBUG is not defined, may be marked with
+ * __debugused.
+ *
+ * In the kernel, variables used only in KDASSERT(9) macros are likely
+ * candidates for being declared with __debugused. There is no
+ * established convention for the use of DEBUG in userland code.
+ */
+#if defined(DEBUG)
+#define __debugused /* empty */
+#else
+#define __debugused __unused
+#endif
+
#if __GNUC_PREREQ__(3, 1)
#define __noprofile __attribute__((__no_instrument_function__))
#else
