使用 std::array 时的输入流问题

编程问答 2022-05-28

问题描述

当 bool b 中没有 struct A 时，代码有效。当 bool b 存在时，ar & mat 给出“输入流错误”，但一一注册 std::array 的元素有效。这里有什么问题吗？

#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;
}

解决方法

我不知道有什么问题。然后我查看了 asan/ubsan 并发现了域转换问题：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。然后我就明白了。

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 是如何遇到它们的，并确认：

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不是大问题，但对于 bool 来说却是一个大问题。因此，请修复您的初始化：

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

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

当然，您可以使用其他样式：

std::array<int,3> mat = {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) {}

等等。只要你确定你初始化了你的会员数据。

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,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;
    }
}

印刷品

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

[¹] 这就是野鹅追逐的样子

boostboostboost-serializationc++serializationserialization