Boost.Asio 段错误，不知道为什么

2022-01-12 00:00:00 segmentation-fault c++ boost-asio

这是我的 Boost.Asio 项目基于示例的 SSCCE.我花了大约一个小时来跟踪这个错误:

This is a SSCCE from my Boost.Asio project based on the examples. It took me about an hour to track the bug down to this:

#include <boost/bind.hpp>
#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>

class Connection  {
public:
    Connection(boost::asio::io_service& io_service) : socket(io_service) {}

private:
    boost::asio::ip::tcp::socket socket;
};

class Server {
public:
    Server() : signal_monitor(io_service) {
        signal_monitor.add(SIGINT);
        signal_monitor.add(SIGTERM);

        signal_monitor.async_wait(
            boost::bind(&Server::handle_signal_caught, this)
        );
    }

    void run() {
        // comment out the next line and there's no segfault
        connection.reset(new Connection(io_service));

        io_service.run();
    }

private:
    void handle_signal_caught() {
        io_service.stop();
    }

    boost::shared_ptr<Connection> connection;
    boost::asio::io_service io_service;
    boost::asio::signal_set signal_monitor;
};

int main(int argc, char **argv) {
    Server server;
    server.run();

    return 0;
}

当我发送信号 (ctrl+C) 时，程序会出现段错误，而不是很好地关闭.我已经花了最后半个小时看这个，但我根本不明白为什么这会出现段错误，你们中的任何人都可以发现这个问题吗?

When I send a signal (ctrl+C) the program segfaults instead of shutting down nicely. I've spent the last half hour looking at this, but I simply do not see why this would segfault, can any of you guys spot the issue?

推荐答案

我想我找到了问题所在.注意Server成员的声明顺序:

I think I found out the issue. Note the declaration order of the members of Server:

boost::shared_ptr<Connection> connection;
boost::asio::io_service io_service;
boost::asio::signal_set signal_monitor;

销毁顺序与声明顺序相反.这意味着首先 signal_monitor，然后是 io_service，最后是 connection 被破坏.但是 connection 包含一个 boost::asio::ip::tcp::socket 包含对 io_service 的引用，该引用已被破坏.

Destruction order is done in the opposite order of declaration. This means that first signal_monitor, then io_service and finally connection get destroyed. But connection contains a boost::asio::ip::tcp::socket containing a reference to io_service, which got destroyed.

事实上，这几乎就是正在发生的事情，并且也会导致段错误:

And indeed, this is pretty much what happening, and causes a segfault too:

int main(int argc, char **argv) {
    auto io_service = new boost::asio::io_service();
    auto socket = new boost::asio::ip::tcp::socket(*io_service);

    delete io_service;
    delete socket;

    return 0;
}

在 io_service 解决问题后声明 connection.

Declaring connection after io_service solves the issue.

该死的

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