[CRT:MATH] Implement _finite, _finitef

dll/win32/ucrtbase/ucrtbase.spec

@@ -371,7 +371,7 @@
 @ cdecl _findnext64(long ptr)
 @ cdecl _findnext64i32(long ptr)
 @ cdecl _finite(double)
-@ cdecl -stub -arch=!i386 _finitef(float)
+@ cdecl -arch=!i386 _finitef(float)
 @ cdecl _flushall()
 @ cdecl _fpclass(double)
 @ cdecl -stub -arch=!i386 _fpclassf(float)

sdk/lib/crt/float/isnan.c

@@ -36,19 +36,3 @@ int CDECL _isnan(double __x)
     	x.__x = &__x;
 	return ( x.x->exponent == 0x7ff  && ( x.x->mantissah != 0 || x.x->mantissal != 0 ));
 }
-
-/*
- * @implemented
- */
-int CDECL _finite(double __x)
-{
-	union
-	{
-		double*   __x;
-		double_s*   x;
-	} x;
-
-	x.__x = &__x;
-
-    return ((x.x->exponent & 0x7ff) != 0x7ff);
-}

sdk/lib/crt/math/_finite.c

@@ -0,0 +1,19 @@
+/*
+ * PROJECT:     ReactOS CRT
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of _finite.
+ * COPYRIGHT:   Copyright 2025 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#include <float.h>
+#include <stdint.h>
+
+_Check_return_
+int
+__cdecl
+_finite(_In_ double _X)
+{
+    union { double f; uint64_t ui64; } u = { _X };
+    uint64_t exp = u.ui64 & 0x7FF0000000000000;
+    return (exp != 0x7FF0000000000000);
+}

sdk/lib/crt/math/_finitef.c

@@ -0,0 +1,19 @@
+/*
+ * PROJECT:     ReactOS CRT
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of _finitef.
+ * COPYRIGHT:   Copyright 2025 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#include <float.h>
+#include <stdint.h>
+
+_Check_return_
+int
+__cdecl
+_finitef(_In_ float _X)
+{
+    union { float f; uint32_t ui32; } u = { _X };
+    uint32_t exp = u.ui32 & 0x7F800000;
+    return (exp != 0x7F800000);
+}

sdk/lib/crt/math/math.cmake

@@ -5,6 +5,8 @@ list(APPEND LIBCNTPR_MATH_SOURCE
     math/_chgsignf.c
     math/_dsign.c
     math/_fdsign.c
+    math/_finite.c
+    math/_finitef.c
     math/_invoke_matherr.c
     math/abs.c
     math/div.c