From fbd1393858719c7bda7d251f742950c1bc691ea8 Mon Sep 17 00:00:00 2001
From: Kohei Takahashi <flast@flast.jp>
Date: Wed, 6 Jan 2016 19:39:55 +0900
Subject: [PATCH] Qualify std:: for isnan in some situation.

Because isnan is implemented as a macro and libstdc++ undef it within
<cmath> (at least FreeBSD 10).

Backported from fbd1393858719c7bda7d251f742950c1bc691ea8

[Jörg Krause: adjust pathes to match sourceforge release tarball]
Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>

---
 boost/math/special_functions/fpclassify.hpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/boost/math/special_functions/fpclassify.hpp b/boost/math/special_functions/fpclassify.hpp
index 58fad13..d83e111 100644
--- a/boost/math/special_functions/fpclassify.hpp
+++ b/boost/math/special_functions/fpclassify.hpp
@@ -133,6 +133,10 @@ inline bool is_nan_helper(T, const boost::false_type&)
 #if defined(BOOST_MATH_HAS_QUADMATH_H)
 inline bool is_nan_helper(__float128 f, const boost::true_type&) { return ::isnanq(f); }
 inline bool is_nan_helper(__float128 f, const boost::false_type&) { return ::isnanq(f); }
+#elif defined(BOOST_GNU_STDLIB) && BOOST_GNU_STDLIB && \
+      _GLIBCXX_USE_C99_MATH && !_GLIBCXX_USE_C99_FP_MACROS_DYNAMIC
+inline bool is_nan_helper(__float128 f, const boost::true_type&) { return std::isnan(static_cast<double>(f)); }
+inline bool is_nan_helper(__float128 f, const boost::false_type&) { return std::isnan(static_cast<double>(f)); }
 #else
 inline bool is_nan_helper(__float128 f, const boost::true_type&) { return ::isnan(static_cast<double>(f)); }
 inline bool is_nan_helper(__float128 f, const boost::false_type&) { return ::isnan(static_cast<double>(f)); }