From 158c112e03dcd064327688576f00d1d8150d2932 Mon Sep 17 00:00:00 2001
From: fvogel <fvogelnew1@free.fr>
Date: Thu, 2 Jan 2020 20:56:20 +0000
Subject: Restore the build by providing a copysign replacement for old MSVC
 versions.

---
 generic/tclStrToD.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/generic/tclStrToD.c b/generic/tclStrToD.c
index a535aed..60429c4 100644
--- a/generic/tclStrToD.c
+++ b/generic/tclStrToD.c
@@ -21,6 +21,18 @@
 #include <math.h>
 
 /*
+ * Older MSVC has no copysign function, but it's available at least since
+ * MSVC++ 12.0 (that is Visual Studio 2013).
+ */
+
+#if (defined(_MSC_VER) && (_MSC_VER < 1800))
+inline static double
+copysign(double a, double b) {
+    return _copysign(a, b);
+}
+#endif
+
+/*
  * Define KILL_OCTAL to suppress interpretation of numbers with leading zero
  * as octal. (Ceterum censeo: numeros octonarios delendos esse.)
  */
-- 
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