使用 std::array 时的输入流问题

Question

当 struct A 中没有 bool b 时，代码有效。当 bool b 存在时，ar & mat 会给出“输入流错误”，但可以一个一个地注册 std::array 的元素。这里有什么问题？

#include <fstream>
#include <boost/serialization/array.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>

struct A
{
    std::array<int, 3> mat;
    bool b;

    template<class Archive> void serialize(Archive& ar, const unsigned int version)
    {
        //ar & mat[0];
        //ar & mat[1];
        //ar & mat[2];
        ar & mat;
        ar & b;
    }
};


int main()
{
    {
        std::string fname = "save.sr";
        std::ofstream ofs(fname);
        boost::archive::text_oarchive oa(ofs);
        A a;
        oa << a;
    }

    {
        std::string fname = "save.sr";
        std::ifstream ifs(fname);
        boost::archive::text_iarchive ia(ifs);
        A a;
        ia >> a;
    }

    return 0;
}

Answer 1

我没看出有什么问题。然后我查看 asan/ubsan 并发现域转换问题：http://coliru.stacked-crooked.com/a/edee75a22450d9ee

起初我以为特定版本的 Boost[¹] 中可能存在错误。然后我恍然大悟。

有良性警告：

g++ -std=c++17 -O2 -Wall -pedantic -pthread main.cpp -fsanitize=address,undefined -lboost_serialization && ./a.out
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct extended_type_info_typeid'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct oserializer'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct extended_type_info_typeid'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct iserializer'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct extended_type_info_typeid'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct extended_type_info_typeid'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct oserializer'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct extended_type_info_typeid'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct iserializer'
/usr/local/include/boost/serialization/singleton.hpp:181:12: runtime error: reference binding to null pointer of type 'const struct extended_type_info_typeid'

然后我们得到域错误：

/usr/local/include/boost/archive/text_oarchive.hpp:65:50: runtime error: load of value 255, which is not a valid value for type 'bool'

注意oarchive是怎么碰到他们的，确认一下：

debug: "22 serialization::archive 17 0 0 0 0 3 -2049146224 32767 -2049145920 1
"

那些是...不确定的值。对于完整的整数域来说问题不大，但对于 bool 来说是个大问题。所以，修正你的初始化：

struct A {
    std::array<int, 3> mat {};
    bool b {};

    template <class Ar> void serialize(Ar& ar, unsigned) {
        ar & mat & b;
    }
};

当然你也可以使用其他样式：

std::array<int, 3> mat = {0,0,0};
bool b = false;

或者老式的构造函数：

std::array<int, 3> mat;
bool b;

A(std::array<int, 3> mat = {}, bool b = {}) : mat(mat), b(b) {}

等只要您确保初始化您的会员数据。

Fixed On COliru

#include <boost/archive/text_iarchive.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/serialization/array.hpp>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <boost/version.hpp>

struct A {
    std::array<int, 3> mat = {0,0,0};
    bool b = false;

    template <class Ar> void serialize(Ar& ar, unsigned) {
        ar & mat & b;
    }
};

int main() {
    std::stringstream ss;
    {
        boost::archive::text_oarchive oa(ss);
        A a;
        oa << a;
    }

    std::cout << "BOOST_VERSION: " << BOOST_VERSION << "\n";
    std::cout << "debug: " << std::quoted(ss.str()) << "\n";

    {
        boost::archive::text_iarchive ia(ss);
        A a;
        ia >> a;
    }
}

版画

BOOST_VERSION: 107500
debug: "22 serialization::archive 18 0 0 0 0 3 0 0 0 0
"

[¹] 这就是徒劳无功的样子

Wandbox Boost 1.73 no problem
Wandbox Boost 1.72 no problem
Wandbox Boost 1.71 only warnings
Wandbox Boost 1.70 same warnings
Wandbox Boost 1.69 same
Wandbox Boost 1.68 no problem
Wandbox Bosot 1.67 no problem
Wanbox Boost 1.66 no problem
Wandbox Boost 1.65.1 no problem
魔杖提升 1.65 no problem
Wandbox Boost 1.64.0 no problem
Wandbox Boost 1.63.0 no problem
Wandbox Boost 1.62 no problem
Wandbox Boost 1.61 no problem
Wandbox Boost 1.60 no problem

使用 std::array 时的输入流问题

Input stream problem when using std::array

c++

serialization

boost

boost-serialization