json/test/src/unit-allocator.cpp

/*
    __ _____ _____ _____
 __|  |   __|     |   | |  JSON for Modern C++ (test suite)
|  |  |__   |  |  | | | |  version 3.10.5
|_____|_____|_____|_|___|  https://github.com/nlohmann/json

Licensed under the MIT License <http://opensource.org/licenses/MIT>.
SPDX-License-Identifier: MIT
Copyright (c) 2013-2022 Niels Lohmann <http://nlohmann.me>.

Permission is hereby  granted, free of charge, to any  person obtaining a copy
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in the Software  without restriction, including without  limitation the rights
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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
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LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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*/

#include "doctest_compatibility.h"

#define JSON_TESTS_PRIVATE
#include <nlohmann/json.hpp>
using nlohmann::json;

namespace
{
// special test case to check if memory is leaked if constructor throws
template<class T>
struct bad_allocator : std::allocator<T>
{
    template<class... Args>
    void construct(T* /*unused*/, Args&& ... /*unused*/)
    {
        throw std::bad_alloc();
    }
};
} // namespace

TEST_CASE("bad_alloc")
{
    SECTION("bad_alloc")
    {
        // create JSON type using the throwing allocator
        using bad_json = nlohmann::basic_json<std::map,
              std::vector,
              std::string,
              bool,
              std::int64_t,
              std::uint64_t,
              double,
              bad_allocator>;

        // creating an object should throw
        CHECK_THROWS_AS(bad_json(bad_json::value_t::object), std::bad_alloc&);
    }
}

namespace
{
bool next_construct_fails = false;
bool next_destroy_fails = false;
bool next_deallocate_fails = false;

template<class T>
struct my_allocator : std::allocator<T>
{
    using std::allocator<T>::allocator;

    template<class... Args>
    void construct(T* p, Args&& ... args)
    {
        if (next_construct_fails)
        {
            next_construct_fails = false;
            throw std::bad_alloc();
        }

        ::new (reinterpret_cast<void*>(p)) T(std::forward<Args>(args)...);
    }

    void deallocate(T* p, std::size_t n)
    {
        if (next_deallocate_fails)
        {
            next_deallocate_fails = false;
            throw std::bad_alloc();
        }

        std::allocator<T>::deallocate(p, n);
    }

    void destroy(T* p)
    {
        if (next_destroy_fails)
        {
            next_destroy_fails = false;
            throw std::bad_alloc();
        }

        static_cast<void>(p); // fix MSVC's C4100 warning
        p->~T();
    }

    template <class U>
    struct rebind
    {
        using other = my_allocator<U>;
    };
};

// allows deletion of raw pointer, usually hold by json_value
template<class T>
void my_allocator_clean_up(T* p)
{
    assert(p != nullptr);
    my_allocator<T> alloc;
    alloc.destroy(p);
    alloc.deallocate(p, 1);
}
} // namespace

TEST_CASE("controlled bad_alloc")
{
    // create JSON type using the throwing allocator
    using my_json = nlohmann::basic_json<std::map,
          std::vector,
          std::string,
          bool,
          std::int64_t,
          std::uint64_t,
          double,
          my_allocator>;

    SECTION("class json_value")
    {
        SECTION("json_value(value_t)")
        {
            SECTION("object")
            {
                next_construct_fails = false;
                auto t = my_json::value_t::object;
                CHECK_NOTHROW(my_allocator_clean_up(my_json::json_value(t).object));
                next_construct_fails = true;
                CHECK_THROWS_AS(my_json::json_value(t), std::bad_alloc&);
                next_construct_fails = false;
            }
            SECTION("array")
            {
                next_construct_fails = false;
                auto t = my_json::value_t::array;
                CHECK_NOTHROW(my_allocator_clean_up(my_json::json_value(t).array));
                next_construct_fails = true;
                CHECK_THROWS_AS(my_json::json_value(t), std::bad_alloc&);
                next_construct_fails = false;
            }
            SECTION("string")
            {
                next_construct_fails = false;
                auto t = my_json::value_t::string;
                CHECK_NOTHROW(my_allocator_clean_up(my_json::json_value(t).string));
                next_construct_fails = true;
                CHECK_THROWS_AS(my_json::json_value(t), std::bad_alloc&);
                next_construct_fails = false;
            }
        }

        SECTION("json_value(const string_t&)")
        {
            next_construct_fails = false;
            my_json::string_t v("foo");
            CHECK_NOTHROW(my_allocator_clean_up(my_json::json_value(v).string));
            next_construct_fails = true;
            CHECK_THROWS_AS(my_json::json_value(v), std::bad_alloc&);
            next_construct_fails = false;
        }
    }

    SECTION("class basic_json")
    {
        SECTION("basic_json(const CompatibleObjectType&)")
        {
            next_construct_fails = false;
            std::map<std::string, std::string> v {{"foo", "bar"}};
            CHECK_NOTHROW(my_json(v));
            next_construct_fails = true;
            CHECK_THROWS_AS(my_json(v), std::bad_alloc&);
            next_construct_fails = false;
        }

        SECTION("basic_json(const CompatibleArrayType&)")
        {
            next_construct_fails = false;
            std::vector<std::string> v {"foo", "bar", "baz"};
            CHECK_NOTHROW(my_json(v));
            next_construct_fails = true;
            CHECK_THROWS_AS(my_json(v), std::bad_alloc&);
            next_construct_fails = false;
        }

        SECTION("basic_json(const typename string_t::value_type*)")
        {
            next_construct_fails = false;
            CHECK_NOTHROW(my_json("foo"));
            next_construct_fails = true;
            CHECK_THROWS_AS(my_json("foo"), std::bad_alloc&);
            next_construct_fails = false;
        }

        SECTION("basic_json(const typename string_t::value_type*)")
        {
            next_construct_fails = false;
            std::string s("foo");
            CHECK_NOTHROW(my_json(s));
            next_construct_fails = true;
            CHECK_THROWS_AS(my_json(s), std::bad_alloc&);
            next_construct_fails = false;
        }
    }
}

namespace
{
template<class T>
struct allocator_no_forward : std::allocator<T>
{
    allocator_no_forward() = default;
    template <class U>
    allocator_no_forward(allocator_no_forward<U> /*unused*/) {}

    template <class U>
    struct rebind
    {
        using other =  allocator_no_forward<U>;
    };

    template <class... Args>
    void construct(T* p, const Args& ... args) noexcept(noexcept(::new (static_cast<void*>(p)) T(args...)))
    {
        // force copy even if move is available
        ::new (static_cast<void*>(p)) T(args...);
    }
};
} // namespace

TEST_CASE("bad my_allocator::construct")
{
    SECTION("my_allocator::construct doesn't forward")
    {
        using bad_alloc_json = nlohmann::basic_json<std::map,
              std::vector,
              std::string,
              bool,
              std::int64_t,
              std::uint64_t,
              double,
              allocator_no_forward>;

        bad_alloc_json j;
        j["test"] = bad_alloc_json::array_t();
        j["test"].push_back("should not leak");
    }
}