Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix memory leak in to_json #2872

Merged
merged 9 commits into from
Jul 16, 2021
Merged

Fix memory leak in to_json #2872

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
9 commits
Select commit Hold shift + click to select a range
db98073
:white_check_mark: add regression test
nlohmann Jul 15, 2021
149ded8
:recycle: simplify destroy() function for primitive types
nlohmann Jul 15, 2021
6cbdc83
:bug: fix leak for strings
nlohmann Jul 15, 2021
c1298e6
:bug: fix leak for strings
nlohmann Jul 15, 2021
0f8666e
:bug: fix leak for strings
nlohmann Jul 15, 2021
0011cd1
:bug: fix leak for strings
nlohmann Jul 15, 2021
f6863e0
:bug: fix leak for all types
nlohmann Jul 15, 2021
ecaac22
:bulb: add comment to describe j.m_value.destroy(j.m_type) calls
nlohmann Jul 15, 2021
3e4723a
:hammer: remove noexcept annotation
nlohmann Jul 15, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
25 changes: 25 additions & 0 deletions include/nlohmann/detail/conversions/to_json.hpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,13 @@ namespace detail
// constructors //
//////////////////

/*
* Note all external_constructor<>::construct functions need to call
* j.m_value.destroy(j.m_type) to avoid a memory leak in case j contains an
* allocated value (e.g., a string). See bug issue
* https://github.com/nlohmann/json/issues/2865 for more information.
*/

template<value_t> struct external_constructor;

template<>
Expand All @@ -30,6 +37,7 @@ struct external_constructor<value_t::boolean>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::boolean_t b) noexcept
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::boolean;
j.m_value = b;
j.assert_invariant();
Expand All @@ -42,6 +50,7 @@ struct external_constructor<value_t::string>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, const typename BasicJsonType::string_t& s)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::string;
j.m_value = s;
j.assert_invariant();
Expand All @@ -50,6 +59,7 @@ struct external_constructor<value_t::string>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::string_t&& s)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::string;
j.m_value = std::move(s);
j.assert_invariant();
Expand All @@ -60,6 +70,7 @@ struct external_constructor<value_t::string>
int > = 0 >
static void construct(BasicJsonType& j, const CompatibleStringType& str)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::string;
j.m_value.string = j.template create<typename BasicJsonType::string_t>(str);
j.assert_invariant();
Expand All @@ -72,6 +83,7 @@ struct external_constructor<value_t::binary>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, const typename BasicJsonType::binary_t& b)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::binary;
j.m_value = typename BasicJsonType::binary_t(b);
j.assert_invariant();
Expand All @@ -80,6 +92,7 @@ struct external_constructor<value_t::binary>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::binary_t&& b)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::binary;
j.m_value = typename BasicJsonType::binary_t(std::move(b));;
j.assert_invariant();
Expand All @@ -92,6 +105,7 @@ struct external_constructor<value_t::number_float>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::number_float_t val) noexcept
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::number_float;
j.m_value = val;
j.assert_invariant();
Expand All @@ -104,6 +118,7 @@ struct external_constructor<value_t::number_unsigned>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::number_unsigned_t val) noexcept
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::number_unsigned;
j.m_value = val;
j.assert_invariant();
Expand All @@ -116,6 +131,7 @@ struct external_constructor<value_t::number_integer>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::number_integer_t val) noexcept
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::number_integer;
j.m_value = val;
j.assert_invariant();
Expand All @@ -128,6 +144,7 @@ struct external_constructor<value_t::array>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, const typename BasicJsonType::array_t& arr)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::array;
j.m_value = arr;
j.set_parents();
Expand All @@ -137,6 +154,7 @@ struct external_constructor<value_t::array>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::array_t&& arr)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::array;
j.m_value = std::move(arr);
j.set_parents();
Expand All @@ -150,6 +168,8 @@ struct external_constructor<value_t::array>
{
using std::begin;
using std::end;

j.m_value.destroy(j.m_type);
j.m_type = value_t::array;
j.m_value.array = j.template create<typename BasicJsonType::array_t>(begin(arr), end(arr));
j.set_parents();
Expand All @@ -159,6 +179,7 @@ struct external_constructor<value_t::array>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, const std::vector<bool>& arr)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::array;
j.m_value = value_t::array;
j.m_value.array->reserve(arr.size());
Expand All @@ -174,6 +195,7 @@ struct external_constructor<value_t::array>
enable_if_t<std::is_convertible<T, BasicJsonType>::value, int> = 0>
static void construct(BasicJsonType& j, const std::valarray<T>& arr)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::array;
j.m_value = value_t::array;
j.m_value.array->resize(arr.size());
Expand All @@ -192,6 +214,7 @@ struct external_constructor<value_t::object>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, const typename BasicJsonType::object_t& obj)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::object;
j.m_value = obj;
j.set_parents();
Expand All @@ -201,6 +224,7 @@ struct external_constructor<value_t::object>
template<typename BasicJsonType>
static void construct(BasicJsonType& j, typename BasicJsonType::object_t&& obj)
{
j.m_value.destroy(j.m_type);
j.m_type = value_t::object;
j.m_value = std::move(obj);
j.set_parents();
Expand All @@ -214,6 +238,7 @@ struct external_constructor<value_t::object>
using std::begin;
using std::end;

j.m_value.destroy(j.m_type);
j.m_type = value_t::object;
j.m_value.object = j.template create<typename BasicJsonType::object_t>(begin(obj), end(obj));
j.set_parents();
Expand Down
74 changes: 38 additions & 36 deletions include/nlohmann/json.hpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1131,53 +1131,55 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
binary = create<binary_t>(std::move(value));
}

void destroy(value_t t) noexcept
void destroy(value_t t)
{
// flatten the current json_value to a heap-allocated stack
std::vector<basic_json> stack;

// move the top-level items to stack
if (t == value_t::array)
{
stack.reserve(array->size());
std::move(array->begin(), array->end(), std::back_inserter(stack));
}
else if (t == value_t::object)
{
stack.reserve(object->size());
for (auto&& it : *object)
{
stack.push_back(std::move(it.second));
}
}

while (!stack.empty())
if (t == value_t::array || t == value_t::object)
{
// move the last item to local variable to be processed
basic_json current_item(std::move(stack.back()));
stack.pop_back();
// flatten the current json_value to a heap-allocated stack
std::vector<basic_json> stack;

// if current_item is array/object, move
// its children to the stack to be processed later
if (current_item.is_array())
// move the top-level items to stack
if (t == value_t::array)
{
std::move(current_item.m_value.array->begin(), current_item.m_value.array->end(),
std::back_inserter(stack));

current_item.m_value.array->clear();
stack.reserve(array->size());
std::move(array->begin(), array->end(), std::back_inserter(stack));
}
else if (current_item.is_object())
else
{
for (auto&& it : *current_item.m_value.object)
stack.reserve(object->size());
for (auto&& it : *object)
{
stack.push_back(std::move(it.second));
}

current_item.m_value.object->clear();
}

// it's now safe that current_item get destructed
// since it doesn't have any children
while (!stack.empty())
{
// move the last item to local variable to be processed
basic_json current_item(std::move(stack.back()));
stack.pop_back();

// if current_item is array/object, move
// its children to the stack to be processed later
if (current_item.is_array())
{
std::move(current_item.m_value.array->begin(), current_item.m_value.array->end(), std::back_inserter(stack));

current_item.m_value.array->clear();
}
else if (current_item.is_object())
{
for (auto&& it : *current_item.m_value.object)
{
stack.push_back(std::move(it.second));
}

current_item.m_value.object->clear();
}

// it's now safe that current_item get destructed
// since it doesn't have any children
}
}

switch (t)
Expand Down
Loading