From 3f71ab80ad071d837e47ec85e6ac03fe118a2812 Mon Sep 17 00:00:00 2001
From: Timo Kreuzer <timo.kreuzer@reactos.org>
Date: Fri, 15 Nov 2024 16:36:19 +0200
Subject: [PATCH] [CRT:MATH] Implement _isnan and _isnanf

---
 dll/win32/ucrtbase/ucrtbase.spec |  2 +-
 sdk/lib/crt/float/float.cmake    |  4 ----
 sdk/lib/crt/float/isnan.c        | 38 --------------------------------
 sdk/lib/crt/math/_isnan.c        | 17 ++++++++++++++
 sdk/lib/crt/math/_isnanf.c       | 17 ++++++++++++++
 sdk/lib/crt/math/math.cmake      |  2 ++
 6 files changed, 37 insertions(+), 43 deletions(-)
 delete mode 100644 sdk/lib/crt/float/isnan.c
 create mode 100644 sdk/lib/crt/math/_isnan.c
 create mode 100644 sdk/lib/crt/math/_isnanf.c

diff --git a/dll/win32/ucrtbase/ucrtbase.spec b/dll/win32/ucrtbase/ucrtbase.spec
index cb2d341f209..eba09df8d95 100644
--- a/dll/win32/ucrtbase/ucrtbase.spec
+++ b/dll/win32/ucrtbase/ucrtbase.spec
@@ -560,7 +560,7 @@
 @ cdecl _ismbstrail(ptr ptr)
 @ cdecl _ismbstrail_l(ptr ptr ptr)
 @ cdecl _isnan(double)
-@ cdecl -stub -arch=x86_64 _isnanf(float)
+@ cdecl -arch=x86_64 _isnanf(float)
 @ cdecl _isprint_l(long ptr)
 @ cdecl _ispunct_l(long ptr)
 @ cdecl _isspace_l(long ptr)
diff --git a/sdk/lib/crt/float/float.cmake b/sdk/lib/crt/float/float.cmake
index 86568dcb7d1..036dfa3e3f9 100644
--- a/sdk/lib/crt/float/float.cmake
+++ b/sdk/lib/crt/float/float.cmake
@@ -1,8 +1,4 @@
 
-list(APPEND LIBCNTPR_FLOAT_SOURCE
-    float/isnan.c
-)
-
 list(APPEND CRT_FLOAT_SOURCE
     ${LIBCNTPR_FLOAT_SOURCE}
     float/chgsign.c
diff --git a/sdk/lib/crt/float/isnan.c b/sdk/lib/crt/float/isnan.c
deleted file mode 100644
index 580639f3e76..00000000000
--- a/sdk/lib/crt/float/isnan.c
+++ /dev/null
@@ -1,38 +0,0 @@
-/* Copyright (C) 1991, 1992, 1995 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, write to the Free
-   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
-   Boston, MA 02110-1301, USA.
-*/
-
-#include <precomp.h>
-
-#if defined(_MSC_VER) && defined(_M_ARM)
-#pragma function(_isnan)
-#endif /* _MSC_VER */
-
-/*
- * @implemented
- */
-int CDECL _isnan(double __x)
-{
-	union
-	{
-		double*   __x;
-		double_s*   x;
-	} x;
-    	x.__x = &__x;
-	return ( x.x->exponent == 0x7ff  && ( x.x->mantissah != 0 || x.x->mantissal != 0 ));
-}
diff --git a/sdk/lib/crt/math/_isnan.c b/sdk/lib/crt/math/_isnan.c
new file mode 100644
index 00000000000..ca8ce2a1a12
--- /dev/null
+++ b/sdk/lib/crt/math/_isnan.c
@@ -0,0 +1,17 @@
+/*
+ * PROJECT:     ReactOS CRT
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of _isnan.
+ * COPYRIGHT:   Copyright 2025 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#include <float.h>
+#include <stdint.h>
+
+int
+__cdecl
+_isnan(_In_ double _X)
+{
+    union { double f; uint64_t ui64; } u = { _X };
+    return (u.ui64 & ~0x8000000000000000ull) > 0x7FF0000000000000ull;
+}
diff --git a/sdk/lib/crt/math/_isnanf.c b/sdk/lib/crt/math/_isnanf.c
new file mode 100644
index 00000000000..36a36a778a1
--- /dev/null
+++ b/sdk/lib/crt/math/_isnanf.c
@@ -0,0 +1,17 @@
+/*
+ * PROJECT:     ReactOS CRT
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of _isnanf.
+ * COPYRIGHT:   Copyright 2025 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#include <math.h>
+#include <stdint.h>
+
+int
+__cdecl
+_isnanf(_In_ float _X)
+{
+    union { float f; uint32_t ui32; } u = { _X };
+    return (u.ui32 & ~0x80000000) > 0x7F800000;
+}
diff --git a/sdk/lib/crt/math/math.cmake b/sdk/lib/crt/math/math.cmake
index d1f8a1fa4a6..30c054eed40 100644
--- a/sdk/lib/crt/math/math.cmake
+++ b/sdk/lib/crt/math/math.cmake
@@ -7,6 +7,8 @@ list(APPEND LIBCNTPR_MATH_SOURCE
     math/_fdsign.c
     math/_finite.c
     math/_finitef.c
+    math/_isnan.c
+    math/_isnanf.c
     math/_invoke_matherr.c
     math/abs.c
     math/div.c