1 files changed, 29 insertions, 0 deletions
diff --git a/newlib/libm/common/s_signbit.c b/newlib/libm/common/s_signbit.c
index d7d49cbb1..746ab4662 100644
--- a/newlib/libm/common/s_signbit.c
+++ b/newlib/libm/common/s_signbit.c
@@ -3,6 +3,35 @@
  * Permission to use, copy, modify, and distribute this software
  * is freely granted, provided that this notice is preserved.
  */
+/*
+FUNCTION
+<<signbit>>--Does floating-point number have negative sign?
+
+INDEX
+	signbit
+
+ANSI_SYNOPSIS
+	#include <math.h>
+	int signbit(real-floating <[x]>);
+
+DESCRIPTION
+The <<signbit>> macro determines whether the sign of its argument value is
+negative.  The macro reports the sign of all values, including infinities,
+zeros, and NaNs.  If zero is unsigned, it is treated as positive.  As shown in
+the synopsis, the argument is "real-floating," meaning that any of the real
+floating-point types (float, double, etc.) may be given to it.
+
+Note that because of the possibilities of signed 0 and NaNs, the expression
+"<[x]> < 0.0" does not give the same result as <<signbit>> in all cases.
+
+RETURNS
+The <<signbit>> macro returns a nonzero value if and only if the sign of its
+argument value is negative.
+
+PORTABILITY
+C99, POSIX.
+
+*/
 
 #include "fdlibm.h"