Merge pull request #1436 from nickaein/iterate-on-destruction

Prevent stackoverflow caused by recursive deconstruction

include/nlohmann/json.hpp

@@ -998,6 +998,55 @@ class basic_json
 
  void destroy(value_t t) noexcept
  {
+ // 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())
+ {
+ // 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())
+ {
+ stack.reserve(stack.size() + current_item.m_value.array->size());
+
+ 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())
+ {
+ stack.reserve(stack.size() + current_item.m_value.object->size());
+
+ for (auto&& it : *current_item.m_value.object)
+ {
+ stack.push_back(std::move(it.second));
+ }
+ }
+
+ // current_item is destroyed here
+ }
+
  switch (t)
  {
  case value_t::object:

single_include/nlohmann/json.hpp

@@ -15541,6 +15541,55 @@ class basic_json
 
  void destroy(value_t t) noexcept
  {
+ // 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())
+ {
+ // 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())
+ {
+ stack.reserve(stack.size() + current_item.m_value.array->size());
+
+ 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())
+ {
+ stack.reserve(stack.size() + current_item.m_value.object->size());
+
+ for (auto&& it : *current_item.m_value.object)
+ {
+ stack.push_back(std::move(it.second));
+ }
+ }
+
+ // current_item is destroyed here
+ }
+
  switch (t)
  {
  case value_t::object:

test/CMakeLists.txt

@@ -127,6 +127,7 @@ set(files
  src/unit-iterators2.cpp
  src/unit-json_patch.cpp
  src/unit-json_pointer.cpp
+ src/unit-large_json.cpp
  src/unit-merge_patch.cpp
  src/unit-meta.cpp
  src/unit-modifiers.cpp

test/src/unit-large_json.cpp

@@ -0,0 +1,49 @@
+/*
+ __ _____ _____ _____
+ __| | __| | | | JSON for Modern C++ (test suite)
+| | |__ | | | | | | version 3.7.1
+|_____|_____|_____|_|___| https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
+Copyright (c) 2013-2019 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "doctest_compatibility.h"
+
+#include <nlohmann/json.hpp>
+using nlohmann::json;
+
+#include <algorithm>
+
+TEST_CASE("tests on very large JSONs")
+{
+ SECTION("issue #1419 - Segmentation fault (stack overflow) due to unbounded recursion")
+ {
+ const auto depth = 5000000;
+
+ std::string s(2 * depth, '[');
+ std::fill(s.begin() + depth, s.end(), ']');
+
+ CHECK_NOTHROW(nlohmann::json::parse(s));
+ }
+}
+