include: Define fpclassify().

include/msvcrt/math.h

@@ -251,11 +251,22 @@ static const union {
 #define FP_ILOGB0 (-0x7fffffff - _C2)
 #define FP_ILOGBNAN 0x7fffffff
 
+#if _MSVCR_VER >= 120
+
 _ACRTIMP short __cdecl _dclass(double);
 _ACRTIMP short __cdecl _fdclass(float);
 _ACRTIMP int   __cdecl _dsign(double);
 _ACRTIMP int   __cdecl _fdsign(float);
 
+#define fpclassify(x) (sizeof(x) == sizeof(float) ? _fdclass(x) : _dclass(x))
+#define signbit(x)    (sizeof(x) == sizeof(float) ? _fdsign(x) : _dsign(x))
+#define isinf(x)      (fpclassify(x) == FP_INFINITE)
+#define isnan(x)      (fpclassify(x) == FP_NAN)
+#define isnormal(x)   (fpclassify(x) == FP_NORMAL)
+#define isfinite(x)   (fpclassify(x) <= 0)
+
+#else
+
 static inline int __isnanf(float x)
 {
     union { float x; unsigned int i; } u = { x };
@@ -303,6 +314,8 @@ static inline int __signbit(double x)
 #define signbit(x)  (sizeof(x) == sizeof(float) ? __signbitf(x) : __signbit(x))
 #define isfinite(x) (!isinf(x) && !isnan(x))
 
+#endif
+
 #ifdef __cplusplus
 }
 #endif