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

Prevent stackoverflow caused by recursive deconstruction

Author: nlohmann

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));
+    }
+}
+