Add __only_inline, for use in headers like <ctype.h> for defining copies

of functions that can only by used by the compiler for inlining.
Also, document __returns_twice, a particularly black piece of magic.

ok deraadt@, kettenis@, millert@

1 files changed, 24 insertions, 1 deletions

diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
index 1c672893947..6325402b619 100644
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cdefs.h,v 1.30 2010/07/01 03:22:12 jsg Exp $	*/
+/*	$OpenBSD: cdefs.h,v 1.31 2010/10/01 04:51:49 guenther Exp $	*/
 /*	$NetBSD: cdefs.h,v 1.16 1996/04/03 20:46:39 christos Exp $	*/
 
 /*
@@ -141,6 +141,12 @@
 #define	__used		__unused	/* suppress -Wunused warnings */
 #endif
 
+/*
+ * __returns_twice makes the compiler not assume the function
+ * only returns once.  This affects registerisation of variables:
+ * even local variables need to be in memory across such a call.
+ * Example: setjmp()
+ */
 #if __GNUC_PREREQ__(4, 1)
 #define __returns_twice	__attribute__((returns_twice))
 #else
@@ -148,6 +154,23 @@
 #endif
 
 /*
+ * __only_inline makes the compiler only use this function definition
+ * for inlining; references that can't be inlined will be left as
+ * external references instead of generating a local copy.  The
+ * matching library should include a simple extern definition for
+ * the function to handle those references.  c.f. ctype.h
+ */
+#ifdef __GNUC__
+#  if __GNUC_PREREQ__(4, 2)
+#define __only_inline	extern __inline __attribute__((__gnu_inline__))
+#  else
+#define __only_inline	extern __inline
+#  endif
+#else
+#define __only_inline	static __inline
+#endif
+
+/*
  * GNU C version 2.96 adds explicit branch prediction so that
  * the CPU back-end can hint the processor and also so that
  * code blocks can be reordered such that the predicted path