Patch nlohmann/json for GCC 4.8

See nlohmann#212 for details

Author: cjh1

include/nlohmann/detail/macro_scope.hpp

@@ -10,7 +10,7 @@
             #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
         #endif
     #elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
-        #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40900
+        #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40800
             #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
         #endif
     #endif

include/nlohmann/json.hpp

@@ -4943,6 +4943,23 @@ class basic_json
         return {it, res.second};
     }
 
+    /// helper for insertion of an iterator (supports GCC 4.8+)
+    template<typename... Args>
+    iterator insert_iterator(const_iterator pos, Args&& ... args)
+    {
+        iterator result(this);
+        assert(m_value.array != nullptr);
+
+        auto insert_pos = std::distance(m_value.array->begin(), pos.m_it.array_iterator);
+        m_value.array->insert(pos.m_it.array_iterator, std::forward<Args>(args)...);
+        result.m_it.array_iterator = m_value.array->begin() + insert_pos;
+
+        // For GCC 4.9+ only, this could become:
+        // result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, cnt, val);
+
+        return result;
+    }
+
     /*!
     @brief inserts element
 
@@ -4977,9 +4994,7 @@ class basic_json
             }
 
             // insert to array and return iterator
-            iterator result(this);
-            result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, val);
-            return result;
+            return insert_iterator(pos, val);
         }
 
         JSON_THROW(type_error::create(309, "cannot use insert() with " + std::string(type_name())));
@@ -5030,9 +5045,7 @@ class basic_json
             }
 
             // insert to array and return iterator
-            iterator result(this);
-            result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, cnt, val);
-            return result;
+            return insert_iterator(pos, cnt, val);
         }
 
         JSON_THROW(type_error::create(309, "cannot use insert() with " + std::string(type_name())));
@@ -5094,12 +5107,7 @@ class basic_json
         }
 
         // insert to array and return iterator
-        iterator result(this);
-        result.m_it.array_iterator = m_value.array->insert(
-                                         pos.m_it.array_iterator,
-                                         first.m_it.array_iterator,
-                                         last.m_it.array_iterator);
-        return result;
+        return insert_iterator(pos, first.m_it.array_iterator, last.m_it.array_iterator);
     }
 
     /*!
@@ -5141,9 +5149,7 @@ class basic_json
         }
 
         // insert to array and return iterator
-        iterator result(this);
-        result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, ilist.begin(), ilist.end());
-        return result;
+        return insert_iterator(pos, ilist.begin(), ilist.end());
     }
 
     /*!