diff --git a/amd64/bsd_ieeefp.h b/amd64/bsd_ieeefp.h
index edb0d9c..8a7ee20 100644
--- a/amd64/bsd_ieeefp.h
+++ b/amd64/bsd_ieeefp.h
@@ -38,10 +38,6 @@
 #ifndef _MACHINE_IEEEFP_H_
 #define _MACHINE_IEEEFP_H_
 
-#if !defined(_SYS_CDEFS_H) && !defined(_SYS_CDEFS_H_) && !defined(_CDEFS_H_)
-#error this file needs sys/cdefs.h as a prerequisite
-#endif
-
 /*
  * FP rounding modes
  */
diff --git a/bsdsrc/b_exp.c b/bsdsrc/b_exp.c
index 61c96eb..d71c7de 100644
--- a/bsdsrc/b_exp.c
+++ b/bsdsrc/b_exp.c
@@ -152,13 +152,13 @@ double x, c;
 			c= x - z*(p1+z*(p2+z*(p3+z*(p4+z*p5))));
 			c = (x*c)/(2.0-c);
 
-			return  scalb(1.+(hi-(lo - c)), k);
+			return  scalbn(1.+(hi-(lo - c)), k);
 		}
 		/* end of x > lntiny */
 
 		else
 		     /* exp(-big#) underflows to zero */
-		     if(finite(x))  return(scalb(1.0,-5000));
+		     if(isfinite(x))  return(scalbn(1.0,-5000));
 
 		     /* exp(-INF) is zero */
 		     else return(0.0);
@@ -167,5 +167,5 @@ double x, c;
 
 	else
 	/* exp(INF) is INF, exp(+big#) overflows to INF */
-	    return( finite(x) ?  scalb(1.0,5000)  : x);
+	    return( isfinite(x) ?  scalbn(1.0,5000)  : x);
 }
diff --git a/bsdsrc/b_tgamma.c b/bsdsrc/b_tgamma.c
index 7380b1d..a5cfb0f 100644
--- a/bsdsrc/b_tgamma.c
+++ b/bsdsrc/b_tgamma.c
@@ -140,7 +140,7 @@ tgamma(x)
 		if (x != 0.0)
 			u.a = one - tiny;	/* raise inexact */
 		return (one/x);
-	} else if (!finite(x))
+	} else if (!isfinite(x))
 		return (x - x);		/* x is NaN or -Inf */
 	else
 		return (neg_gam(x));
diff --git a/include/cdefs-compat.h b/include/cdefs-compat.h
index 173bc91..7c997c9 100644
--- a/include/cdefs-compat.h
+++ b/include/cdefs-compat.h
@@ -1,9 +1,11 @@
 #ifndef _CDEFS_COMPAT_H_
 #define	_CDEFS_COMPAT_H_
 
-#ifndef _WIN32
-#include "sys/cdefs.h"
-#else /* _WIN32 */
+/*
+ * We cannot be certain that this operating system has <sys/cdefs.h>.
+ * Instead, include a header file that is likely to pull in this header.
+ */
+#include <stdio.h>
 
 #if defined(__cplusplus)
 #define	__BEGIN_DECLS	extern "C" {
@@ -13,13 +15,6 @@
 #define	__END_DECLS
 #endif
 
-#define _SYS_CDEFS_H_
-
-#endif /* _WIN32 */
-
-
-
-
 #ifdef __GNUC__
 #ifndef __strong_reference
 #ifdef __APPLE__
diff --git a/include/fpmath.h b/include/fpmath.h
index 3b06b7e..5698b96 100644
--- a/include/fpmath.h
+++ b/include/fpmath.h
@@ -38,28 +38,37 @@
 #endif
 #endif
 
-#ifdef __linux
+#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__)
+
+/* Definitions provided directly by GCC and Clang. */
+#define _LITTLE_ENDIAN    __ORDER_LITTLE_ENDIAN__
+#define _BIG_ENDIAN       __ORDER_BIG_ENDIAN__
+#define _PDP_ENDIAN       __ORDER_PDP_ENDIAN__
+#define _BYTE_ORDER       __BYTE_ORDER__
+
+#elif defined(__linux)
+
 #include <features.h>
 #include <endian.h>
 #define _LITTLE_ENDIAN  __LITTLE_ENDIAN
 #define _BIG_ENDIAN     __BIG_ENDIAN
 #define _PDP_ENDIAN     __PDP_ENDIAN
 #define _BYTE_ORDER     __BYTE_ORDER
-#endif
 
-#ifdef __APPLE__
+#elif defined(__APPLE__)
+
 #include <machine/endian.h>
 #define _LITTLE_ENDIAN  LITTLE_ENDIAN
 #define _BIG_ENDIAN     BIG_ENDIAN
 #define _PDP_ENDIAN     PDP_ENDIAN
 #define _BYTE_ORDER     BYTE_ORDER
-#endif
 
-#ifdef __FreeBSD__
+#elif defined(__FreeBSD__)
+
 #include <machine/endian.h>
-#endif
 
-#ifdef _WIN32
+#elif defined(_WIN32)
+
 #define _LITTLE_ENDIAN 1234
 #define _BIG_ENDIAN    4321
 #define _PDP_ENDIAN    3412
@@ -69,6 +78,7 @@
 #define BIG_ENDIAN     _BIG_ENDIAN
 #define PDP_ENDIAN     _PDP_ENDIAN
 #define BYTE_ORDER     _BYTE_ORDER
+
 #endif
 
 #ifndef _IEEE_WORD_ORDER
diff --git a/src/e_scalb.c b/src/e_scalb.c
index d575100..e0c9165 100644
--- a/src/e_scalb.c
+++ b/src/e_scalb.c
@@ -35,7 +35,7 @@ __ieee754_scalb(double x, double fn)
 	return scalbn(x,fn);
 #else
 	if (isnan(x)||isnan(fn)) return x*fn;
-	if (!finite(fn)) {
+	if (!isfinite(fn)) {
 	    if(fn>0.0) return x*fn;
 	    else       return x/(-fn);
 	}
diff --git a/src/e_scalbf.c b/src/e_scalbf.c
index d506719..7472d37 100644
--- a/src/e_scalbf.c
+++ b/src/e_scalbf.c
@@ -30,8 +30,8 @@ __ieee754_scalbf(float x, float fn)
 #ifdef _SCALB_INT
 	return scalbnf(x,fn);
 #else
-	if ((__isnanf)(x)||(__isnanf)(fn)) return x*fn;
-	if (!finitef(fn)) {
+	if (isnan(x)||isnan(fn)) return x*fn;
+	if (!isfinite(fn)) {
 	    if(fn>(float)0.0) return x*fn;
 	    else       return x/(-fn);
 	}
diff --git a/src/math_private.h b/src/math_private.h
index a8c0595..05d95c3 100644
--- a/src/math_private.h
+++ b/src/math_private.h
@@ -333,9 +333,7 @@ double	__kernel_sin(double,double,int);
 double	__kernel_cos(double,double);
 double	__kernel_tan(double,double,int);
 double	__ldexp_exp(double,int);
-#ifdef _COMPLEX_H
 double complex __ldexp_cexp(double complex,int);
-#endif
 
 /* float precision kernel functions */
 #ifdef INLINE_REM_PIO2F
@@ -355,9 +353,7 @@ __inline
 #endif
 float	__kernel_tandf(double,int);
 float	__ldexp_expf(float,int);
-#ifdef _COMPLEX_H
 float complex __ldexp_cexpf(float complex,int);
-#endif
 
 /* long double precision kernel functions */
 long double __kernel_sinl(long double, long double, int);
diff --git a/src/openlibm.h b/src/openlibm.h
index 5bfd0af..5635612 100644
--- a/src/openlibm.h
+++ b/src/openlibm.h
@@ -57,7 +57,9 @@ extern const union __nan_un {
 //VBS begin
 #define __MATH_BUILTIN_CONSTANTS
 #define	__MATH_BUILTIN_RELOPS
+#ifndef __ISO_C_VISIBLE
 #define __ISO_C_VISIBLE 1999
+#endif
 //VBS end
 
 #ifdef __MATH_BUILTIN_CONSTANTS