[PATCH v2] msvcrt: Add fallback implementations for Bessel functions

[Alex Henrie]

Signed-off-by: Alex Henrie <alexhenrie24 at gmail.com>
---
Fixes https://bugs.winehq.org/show_bug.cgi?id=37809

v2:
- Dropped inaccurate fallbacks for jn, y0, y1, and yn
- Avoided division by 0 in fallbacks for j0 and j1

 configure.ac       |  8 +++++++-
 dlls/msvcrt/math.c | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 2e99320371..e198018427 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2698,6 +2698,9 @@ AC_CHECK_FUNCS(\
 	exp2f \
 	expm1 \
 	expm1f \
+	j0 \
+	j1 \
+	jn \
 	lgamma \
 	lgammaf \
 	llrint \
@@ -2722,7 +2725,10 @@ AC_CHECK_FUNCS(\
 	round \
 	roundf \
 	trunc \
-	truncf
+	truncf \
+	y0 \
+	y1 \
+	yn
 )
 LIBS="$ac_save_LIBS"
 
diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index 9b480117fc..4fd1fc28ed 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -1412,7 +1412,12 @@ INT CDECL MSVCRT__isnan(double num)
 double CDECL MSVCRT__j0(double num)
 {
   /* FIXME: errno handling */
+#ifdef HAVE_J0
   return j0(num);
+#else
+  if (num == 0) return 1;
+  return sin(num) / num;
+#endif
 }
 
 /*********************************************************************
@@ -1421,7 +1426,12 @@ double CDECL MSVCRT__j0(double num)
 double CDECL MSVCRT__j1(double num)
 {
   /* FIXME: errno handling */
+#ifdef HAVE_J1
   return j1(num);
+#else
+  if (num == 0) return 0;
+  return sin(num) / (num * num) - cos(num) / num;
+#endif
 }
 
 /*********************************************************************
@@ -1430,7 +1440,14 @@ double CDECL MSVCRT__j1(double num)
 double CDECL MSVCRT__jn(int n, double num)
 {
   /* FIXME: errno handling */
+#ifdef HAVE_JN
   return jn(n, num);
+#else
+  if (n == 0) return MSVCRT__j0(num);
+  if (n == 1) return MSVCRT__j1(num);
+  FIXME( "not implemented\n" );
+  return 0;
+#endif
 }
 
 /*********************************************************************
@@ -1440,12 +1457,17 @@ double CDECL MSVCRT__y0(double num)
 {
   double retval;
   if (!isfinite(num)) *MSVCRT__errno() = MSVCRT_EDOM;
+#ifdef HAVE_Y0
   retval  = y0(num);
   if (MSVCRT__fpclass(retval) == MSVCRT__FPCLASS_NINF)
   {
     *MSVCRT__errno() = MSVCRT_EDOM;
     retval = sqrt(-1);
   }
+#else
+  FIXME( "not implemented\n" );
+  retval = 0;
+#endif
   return retval;
 }
 
@@ -1456,12 +1478,17 @@ double CDECL MSVCRT__y1(double num)
 {
   double retval;
   if (!isfinite(num)) *MSVCRT__errno() = MSVCRT_EDOM;
+#ifdef HAVE_Y1
   retval  = y1(num);
   if (MSVCRT__fpclass(retval) == MSVCRT__FPCLASS_NINF)
   {
     *MSVCRT__errno() = MSVCRT_EDOM;
     retval = sqrt(-1);
   }
+#else
+  FIXME( "not implemented\n" );
+  retval = 0;
+#endif
   return retval;
 }
 
@@ -1472,12 +1499,17 @@ double CDECL MSVCRT__yn(int order, double num)
 {
   double retval;
   if (!isfinite(num)) *MSVCRT__errno() = MSVCRT_EDOM;
+#ifdef HAVE_YN
   retval  = yn(order,num);
   if (MSVCRT__fpclass(retval) == MSVCRT__FPCLASS_NINF)
   {
     *MSVCRT__errno() = MSVCRT_EDOM;
     retval = sqrt(-1);
   }
+#else
+  FIXME( "not implemented\n" );
+  retval = 0;
+#endif
   return retval;
 }
 
-- 
2.16.2