Merge pull request #122 from d-frey/patch-1

exception-safe object creation, fixes #118

src/json.hpp.re2c

@@ -584,6 +584,17 @@ class basic_json
 
 
  private:
+ /// helper for exception-safe object creation
+ template<typename T, typename... Args>
+ static T* create( Args&&... args )
+ {
+ AllocatorType<T> alloc;
+ auto deleter = [&](T* object) { alloc.deallocate(object, 1); };
+ std::unique_ptr<T, decltype(deleter)> object(alloc.allocate(1), deleter);
+ alloc.construct(object.get(), std::forward<Args>(args)...);
+ return object.release();
+ }
+
  ////////////////////////
  // JSON value storage //
  ////////////////////////
@@ -625,25 +636,19 @@ class basic_json
 
  case (value_t::object):
  {
- AllocatorType<object_t> alloc;
- object = alloc.allocate(1);
- alloc.construct(object);
+ object = create<object_t>();
  break;
  }
 
  case (value_t::array):
  {
- AllocatorType<array_t> alloc;
- array = alloc.allocate(1);
- alloc.construct(array);
+ array = create<array_t>();
  break;
  }
 
  case (value_t::string):
  {
- AllocatorType<string_t> alloc;
- string = alloc.allocate(1);
- alloc.construct(string, "");
+ string = create<string_t>("");
  break;
  }
 
@@ -670,25 +675,19 @@ class basic_json
  /// constructor for strings
  json_value(const string_t& value)
  {
- AllocatorType<string_t> alloc;
- string = alloc.allocate(1);
- alloc.construct(string, value);
+ string = create<string_t>(value);
  }
 
  /// constructor for objects
  json_value(const object_t& value)
  {
- AllocatorType<object_t> alloc;
- object = alloc.allocate(1);
- alloc.construct(object, value);
+ object = create<object_t>(value);
  }
 
  /// constructor for arrays
  json_value(const array_t& value)
  {
- AllocatorType<array_t> alloc;
- array = alloc.allocate(1);
- alloc.construct(array, value);
+ array = create<array_t>(value);
  }
  };
 
@@ -892,11 +891,9 @@ class basic_json
  basic_json(const CompatibleObjectType& value)
  : m_type(value_t::object)
  {
- AllocatorType<object_t> alloc;
- m_value.object = alloc.allocate(1);
  using std::begin;
  using std::end;
- alloc.construct(m_value.object, begin(value), end(value));
+ m_value.object = create<object_t>(begin(value), end(value));
  }
 
  /*!
@@ -953,11 +950,9 @@ class basic_json
  basic_json(const CompatibleArrayType& value)
  : m_type(value_t::array)
  {
- AllocatorType<array_t> alloc;
- m_value.array = alloc.allocate(1);
  using std::begin;
  using std::end;
- alloc.construct(m_value.array, begin(value), end(value));
+ m_value.array = create<array_t>(begin(value), end(value));
  }
 
  /*!
@@ -1315,9 +1310,7 @@ class basic_json
  {
  // the initializer list describes an array -> create array
  m_type = value_t::array;
- AllocatorType<array_t> alloc;
- m_value.array = alloc.allocate(1);
- alloc.construct(m_value.array, std::move(init));
+ m_value.array = create<array_t>(std::move(init));
  }
  }
 
@@ -1416,9 +1409,7 @@ class basic_json
  basic_json(size_type count, const basic_json& value)
  : m_type(value_t::array)
  {
- AllocatorType<array_t> alloc;
- m_value.array = alloc.allocate(1);
- alloc.construct(m_value.array, count, value);
+ m_value.array = create<array_t>(count, value);
  }
 
  /*!
@@ -1514,17 +1505,13 @@ class basic_json
 
  case value_t::object:
  {
- AllocatorType<object_t> alloc;
- m_value.object = alloc.allocate(1);
- alloc.construct(m_value.object, first.m_it.object_iterator, last.m_it.object_iterator);
+ m_value.object = create<object_t>(first.m_it.object_iterator, last.m_it.object_iterator);
  break;
  }
 
  case value_t::array:
  {
- AllocatorType<array_t> alloc;
- m_value.array = alloc.allocate(1);
- alloc.construct(m_value.array, first.m_it.array_iterator, last.m_it.array_iterator);
+ m_value.array = create<array_t>(first.m_it.array_iterator, last.m_it.array_iterator);
  break;
  }
 
@@ -2595,9 +2582,7 @@ class basic_json
  if (m_type == value_t::null)
  {
  m_type = value_t::array;
- AllocatorType<array_t> alloc;
- m_value.array = alloc.allocate(1);
- alloc.construct(m_value.array);
+ m_value.array = create<array_t>();
  }
 
  // [] only works for arrays
@@ -2667,9 +2652,7 @@ class basic_json
  if (m_type == value_t::null)
  {
  m_type = value_t::object;
- AllocatorType<object_t> alloc;
- m_value.object = alloc.allocate(1);
- alloc.construct(m_value.object);
+ m_value.object = create<object_t>();
  }
 
  // [] only works for objects