From 4be5cd1f35431496edb9355a446d5960a9fdfbc0 Mon Sep 17 00:00:00 2001
From: iNaKoll <inakoll@gmail.com>
Date: Thu, 10 Nov 2016 20:54:35 +0100
Subject: [PATCH] Fixes #12599: real_generator failure

---
 .../home/karma/numeric/detail/numeric_utils.hpp    | 42 ++++++++++++++++++++++
 .../home/karma/numeric/detail/real_utils.hpp       |  2 +-
 .../boost/spirit/home/support/numeric_traits.hpp   |  3 ++
 3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/include/boost/spirit/home/karma/numeric/detail/numeric_utils.hpp b/include/boost/spirit/home/karma/numeric/detail/numeric_utils.hpp
index a36893e57e..3ecd5e3f03 100644
--- a/include/boost/spirit/home/karma/numeric/detail/numeric_utils.hpp
+++ b/include/boost/spirit/home/karma/numeric/detail/numeric_utils.hpp
@@ -237,6 +237,48 @@ namespace boost { namespace spirit { namespace traits
 
     ///////////////////////////////////////////////////////////////////////
     template <typename T, typename Enable/* = void*/>
+    struct is_subnormal
+    {
+        static bool call(T)
+        {
+            return false;
+        }
+    };
+
+    template <>
+    struct is_subnormal<float>
+    {
+        static bool call(float n)
+        {
+            return (math::fpclassify)(n) == FP_SUBNORMAL;
+        }
+    };
+
+    template <>
+    struct is_subnormal<double>
+    {
+        static bool call(double n)
+        {
+            return (math::fpclassify)(n) == FP_SUBNORMAL;
+        }
+    };
+
+    template <>
+    struct is_subnormal<long double>
+    {
+        static bool call(long double n)
+        {
+            return (math::fpclassify)(n) == FP_SUBNORMAL;
+        }
+    };
+
+    template <typename T>
+    inline bool test_subnormal(T n)
+    {
+        return is_subnormal<T>::call(n);
+    }
+    ///////////////////////////////////////////////////////////////////////
+    template <typename T, typename Enable/* = void*/>
     struct is_nan
     {
         static bool call(T n)
diff --git a/include/boost/spirit/home/karma/numeric/detail/real_utils.hpp b/include/boost/spirit/home/karma/numeric/detail/real_utils.hpp
index 526985d280..f8e263d839 100644
--- a/include/boost/spirit/home/karma/numeric/detail/real_utils.hpp
+++ b/include/boost/spirit/home/karma/numeric/detail/real_utils.hpp
@@ -95,7 +95,7 @@ namespace boost { namespace spirit { namespace karma
             using namespace std;
 
             U dim = 0;
-            if (0 == (Policies::fmtflags::fixed & flags) && !traits::test_zero(n))
+            if (0 == (Policies::fmtflags::fixed & flags) && !traits::test_zero(n) && !traits::test_subnormal(n))
             {
                 dim = log10(n);
                 if (dim > 0) 
diff --git a/include/boost/spirit/home/support/numeric_traits.hpp b/include/boost/spirit/home/support/numeric_traits.hpp
index 01771dd982..82bdfe6c4b 100644
--- a/include/boost/spirit/home/support/numeric_traits.hpp
+++ b/include/boost/spirit/home/support/numeric_traits.hpp
@@ -108,6 +108,9 @@ namespace boost { namespace spirit { namespace traits
     struct is_zero;
 
     template <typename T, typename Enable = void>
+    struct is_subnormal;
+
+    template <typename T, typename Enable = void>
     struct pow10_helper;
 
     template <typename T, typename Enable = void>