msvcrt: Import modf implementation from musl.

dlls/msvcrt/math.c

@@ -2000,10 +2000,40 @@ double CDECL frexp( double x, int *exp )
 
 /*********************************************************************
  *		modf (MSVCRT.@)
+ *
+ * Copied from musl: src/math/modf.c
  */
 double CDECL modf( double x, double *iptr )
 {
-  return unix_funcs->modf( x, iptr );
+    union {double f; UINT64 i;} u = {x};
+    UINT64 mask;
+    int e = (u.i >> 52 & 0x7ff) - 0x3ff;
+
+    /* no fractional part */
+    if (e >= 52) {
+        *iptr = x;
+        if (e == 0x400 && u.i << 12 != 0) /* nan */
+            return x;
+        u.i &= 1ULL << 63;
+        return u.f;
+    }
+
+    /* no integral part*/
+    if (e < 0) {
+        u.i &= 1ULL << 63;
+        *iptr = u.f;
+        return x;
+    }
+
+    mask = -1ULL >> 12 >> e;
+    if ((u.i & mask) == 0) {
+        *iptr = x;
+        u.i &= 1ULL << 63;
+        return u.f;
+    }
+    u.i &= ~mask;
+    *iptr = u.f;
+    return x - u.f;
 }
 
 /**********************************************************************

dlls/msvcrt/unixlib.c

@@ -460,14 +460,6 @@ static float CDECL unix_logbf( float x )
 }
 
 /*********************************************************************
- *      modf
- */
-static double CDECL unix_modf( double x, double *iptr )
-{
-    return modf( x, iptr );
-}
-
-/*********************************************************************
  *      modff
  */
 static float CDECL unix_modff( float x, float *iptr )
@@ -674,7 +666,6 @@ static const struct unix_funcs funcs =
     unix_log2f,
     unix_logb,
     unix_logbf,
-    unix_modf,
     unix_modff,
     unix_pow,
     unix_powf,

dlls/msvcrt/unixlib.h

@@ -62,7 +62,6 @@ struct unix_funcs
     float           (CDECL *log2f)(float x);
     double          (CDECL *logb)(double x);
     float           (CDECL *logbf)(float x);
-    double          (CDECL *modf)(double x, double *iptr);
     float           (CDECL *modff)(float x, float *iptr);
     double          (CDECL *pow)(double x, double y);
     float           (CDECL *powf)(float x, float y);