diff --git a/fdlibm.h b/fdlibm.h
index f90d5c9..d58e65f 100644
--- a/fdlibm.h
+++ b/fdlibm.h
@@ -10,14 +10,19 @@
  * ====================================================
  */
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef __LITTLE_ENDIAN
 /* Sometimes it's necessary to define __LITTLE_ENDIAN explicitly
    but these catch some common cases. */
-
 #if defined(i386) || defined(i486) || \
 	defined(intel) || defined(x86) || defined(i86pc) || \
 	defined(__alpha) || defined(__osf__)
 #define __LITTLE_ENDIAN
 #endif
+#endif
 
 #ifdef __LITTLE_ENDIAN
 #define __HI(x) *(1+(int*)&x)
@@ -31,11 +36,14 @@
 #define __LOp(x) *(1+(int*)x)
 #endif
 
+#ifndef __P
+#define __FDLIBM_P_DEFINED
 #ifdef __STDC__
 #define	__P(p)	p
 #else
 #define	__P(p)	()
 #endif
+#endif
 
 /*
  * ANSI/POSIX
@@ -214,3 +222,11 @@
 extern double __kernel_cos __P((double,double));
 extern double __kernel_tan __P((double,double,int));
 extern int    __kernel_rem_pio2 __P((double*,double*,int,int,int,const int*));
+
+#ifdef __FDLIBM_P_DEFINED
+#undef __P
+#endif
+
+#ifdef __cplusplus
+}; /* extern "C" */
+#endif