From: "Matteo F. Vescovi" <mfv@debian.org>
Date: Mon, 25 Jul 2016 22:17:43 +0200
Subject: fix_gcc6_issue

---
 src/util/math.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/util/math.h b/src/util/math.h
index 018335e..85971d1 100644
--- src/util/math.h
+++ src/util/math.h
@@ -3,8 +3,20 @@
 
 // Causes MSVC to define M_PI and friends.
 // http://msdn.microsoft.com/en-us/library/4hwaceh6.aspx
+// Our SConscript defines this but check anyway.
+#ifdef __WINDOWS__
+#ifndef _USE_MATH_DEFINES
 #define _USE_MATH_DEFINES
+#endif
+#endif
+
+#include <math.h>
 #include <cmath>
+// Note: Because of our fpclassify hack, we actualy need to inlude both,
+// the c and the c++ version of the math header.
+// From GCC 6.1.1 math.h depends on cmath, which failes to compile if included
+// after our fpclassify hack
+
 #include <algorithm>
 
 #include "util/assert.h"
