c++ - 表达式 : string iterator not dereferencable while using boost regex

Question

我想从一个页面中恢复所有链接，同时执行我得到的代码:

Microsoft Visual C++ Debug Library

Debug Assertion Failed!

Program: C:\Users\Gandalf\Desktop\proxy\Debug\Proxy.exe File: C:\Program Files\Microsoft Visual Studio 10.0\VC\include\xstring Line: 78

Expression: string iterator not dereferencable

For information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts.

(Press Retry to debug the application)

Abort Retry Ignore

void Deltacore::Client::get_links() {
boost::smatch matches;
boost::match_flag_type flags = boost::match_default;
boost::regex URL_REGEX("^<a[^>]*(http://[^\"]*)[^>]*>([ 0-9a-zA-Z]+)</a>$");

if(!response.empty()) {

    std::string::const_iterator alfa = this->response.begin();
    std::string::const_iterator omega   = this->response.end();

    while (boost::regex_search(alfa, omega, matches, URL_REGEX))
    {
        std::cout << matches[0];
        //if(std::find(this->Links.begin(), this->Links.end(), matches[0]) != this->Links.end()) {
            this->Links.push_back(matches[0]);
        //}
        alfa = matches[0].second;
    }
}
}

有什么想法吗？

添加了更多代码:

        Deltacore::Client client;
    client.get_url(target);
    client.get_links();

            boost::property_tree::ptree props;
            for(size_t i = 0; i < client.Links.size(); i++)
                props.push_back(std::make_pair(boost::lexical_cast<std::string>(i), client.Links.at(i)));

            std::stringstream ss;
            boost::property_tree::write_json(ss, props, false);

            boost::asio::async_write(socket_,
                boost::asio::buffer(ss.str(), ss.str().length()),
                boost::bind(&session::handle_write, this,
                boost::asio::placeholders::error));

提前致谢

Answer 1

问题出在这一行:

boost::asio::buffer(ss.str(), ss.str().length())

str() 返回一个临时 std::string 对象，因此您实际上是在创建缓冲区后立即使其无效 – Vanilla UB，正如我评论的那样。 ;-]

代币 documentation citation :

The buffer is invalidated by any non-const operation called on the given string object.

当然，销毁字符串属于非常量操作。