[CRT] math.h: fix definition of NAN

- Use positive NAN by default
- add support for _UCRT_NEGATIVE_NAN to legacy CRT headers
- Use __builtin_nanf() on GCC/Clang

Author: tkreuzer

sdk/include/crt/math.h

@@ -57,7 +57,21 @@ typedef double double_t;
 #define HUGE_VALD ((double)INFINITY)
 #define HUGE_VALF ((float)INFINITY)
 #define HUGE_VALL ((long double)INFINITY)
-#define NAN       ((float)(INFINITY * 0.0F))
+#ifndef _UCRT_NEGATIVE_NAN
+// This operation creates a negative NAN adding a - to make it positive
+#ifdef _MSC_VER
+#define NAN        (-(float)(INFINITY * 0.0F))
+#else
+#define NAN        (__builtin_nanf(""))
+#endif
+#else
+// Keep this for backwards compatibility
+#ifdef _MSC_VER
+#define NAN        ((float)(INFINITY * 0.0F))
+#else
+#define NAN        (-__builtin_nanf(""))
+#endif
+#endif
 
 #define _DENORM  (-2)
 #define _FINITE  (-1)

sdk/include/ucrt/corecrt_math.h

@@ -91,10 +91,18 @@ _CRT_BEGIN_C_HEADER
 #define HUGE_VALL  ((long double)INFINITY)
 #ifndef _UCRT_NEGATIVE_NAN
 // This operation creates a negative NAN adding a - to make it positive
+#ifdef _MSC_VER
 #define NAN        (-(float)(INFINITY * 0.0F))
 #else
+#define NAN        (__builtin_nanf(""))
+#endif
+#else
 // Keep this for backwards compatibility
+#ifdef _MSC_VER
 #define NAN        ((float)(INFINITY * 0.0F))
+#else
+#define NAN        (-__builtin_nanf(""))
+#endif
 #endif
 
 #define _DENORM    (-2)