ZeroMQ消息损坏数据

我正在通过ZeroMQ连接发送一个结构。两个字段是正确的，但其中一个已损坏。为了说明这个问题，我的代码尝试读取zmq消息的内容并创建一个新的结构。

输出：

$ ./client 
id = 100
successful = 1
data_size = 356515840
Segmentation fault

客户端.cc

#include <string>
#include <iostream>
#include "zmq.hpp"
#include "struct.h"
int main () {
    zmq::context_t context (1);
    zmq::socket_t socket (context, ZMQ_REQ);
    socket.connect ("tcp://localhost:5555");
    query q(100);
    q.data_size = 3;
    q.data = "abc";
    q.successful = true;
    zmq::message_t request = q.generate_message();
    query test_query((char *) request.data());
    return 0;
}

struct.h

#include <arpa/inet.h>
#include "zmq.hpp"
struct query {
  long id;
  bool successful;
  long data_size;
  std::string data;
  query (long id) {
    this->id = id;
    this->successful = false;
    this->data_size = 0;
    this->data = "";
  }
  query (char *start) {
    id = *((long*) start);
    start += sizeof(long);
    std::cout << "id = " << id << std::endl;
    successful = *((bool*) start);
    start += sizeof(bool);
    std::cout << "successful = " << successful << std::endl;
    data_size = *((long *) start);
    data_size = ntohl(data_size);
    start += sizeof(long);
    std::cout << "data_size = " << data_size << std::endl;
    data = std::string(start, data_size);
  }
  long get_total_size() {
    return 2 * sizeof(long) +  sizeof(bool) + data_size;
  }
  // The string is encoded by calling data.c_str()
  zmq::message_t generate_message() {
    long size = get_total_size();
    zmq::message_t msg(size);
    memcpy((void *) msg.data(), this, size);
    char *loc_of_data = (char *) msg.data() + 2 * sizeof(long) + sizeof(bool);
    memcpy((void *) loc_of_data, data.c_str(), data_size);
    return msg;
  }
};