我有一个名为 GenericMessage 的类，显示在下面的第一个代码片段中（在 GenericMessage.hxx 中定义）。
我有一个名为 TestFE.cpp 的 .cpp 文件（参见下面的第二个代码片段），它尝试通过 ZMQ 队列发送类 GenericMessage 的实例（另请参见下面的第四个代码片段 - ZmqHandler.hxx）。TesfFE.cpp 通过包含 ZmqHandler.hxx 来实现 ZMQ 推送模式。
我还有另一个名为 TestBE.cpp 的 .cpp 文件（参见下面的第三个代码片段），它通过 ZMQ 队列接收提到的 GenericMessage 实例。TestBE.cpp 在此处实现 ZMQ 拉取模式以通过 ZMQ 队列检索 GenericMessage 实例。
在 TestFE.cpp 中，我使用标准的 memcpy 函数将 GenericMessage 对象转换为 ZMQ 队列可以接受的形式。在 TestBE.cpp 的第 21 行（在注释中的第三个代码片段中标记），我得到一个分段错误，因为它看起来 memcpy 在发送方即 TestFE.cpp 上无法正常工作。执行 TestBE 时收到以下消息。我还在下面提供了 gdb 回溯。你能告诉我这里有什么问题吗？为什么你认为 memcpy 不能正确地将我的 GenericMessage 对象复制到 ZMQ message_t 格式？还是您认为问题出在其他问题上？任何意见将不胜感激。
错误信息
$ ./TestBE
Connecting to FE...
RECEIVED: 1
Segmentation fault (core dumped)
GDB 回溯
(gdb) r
Starting program: /home/holb/HOLB_DESIGN/ZMQ/WORK1/TestBE
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".
[New Thread 0xb7c84b40 (LWP 4252)]
[New Thread 0xb7483b40 (LWP 4253)]
Connecting to FE...
RECEIVED: 1
Program received signal SIGSEGV, Segmentation fault.
0xb7f371cc in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(std::string const&) ()
from /usr/lib/i386-linux-gnu/libstdc++.so.6
(gdb) bt
#0 0xb7f371cc in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(std::string const&) ()
from /usr/lib/i386-linux-gnu/libstdc++.so.6
#1 0x08049621 in GenericMessage<std::string>::getData (this=0xbffff06c)
at GenericMessage.hxx:18
#2 0x08049075 in main () at TestBE.cxx:21
(gdb)
代码片段 1 (GenericMessage.hxx) #include #include #include
template <class T>
class GenericMessage {
public:
GenericMessage(int id, T msg):
beId(id),
data(msg)
{}
~GenericMessage(){}
T getData()
{
//LINE 18 is the following line!
return data;
}
std::string toString()
{
std::ostringstream ss;
ss << getBeId();
std::string ret = ss.str();
return ret;
}
void setBeId(int id)
{
beId = id;
}
int getBeId()
{
return beId;
}
private:
int beId;
T data;
};
CODE SNIPPET 2 (TestFE.cxx ==> The sender) #include "ZmqHandler.hxx" //ZmqHandler.hxx 内容见底部的第四个片段
int main ()
{
ZmqHandler<std::string> zmqHandler;
int counter = 1;
while(1)
{
std::string data = "Hello there!\0";
GenericMessage<std::string> msg(counter, data);
zmqHandler.sendToBE(&msg);
counter++;
sleep(1);
}
return 0;
}
代码片段 3（TestBE.cxx ==> 接收器）
#include "zmq.hpp"
#include "GenericMessage.hxx"
#include <string>
#include <iostream>
int main ()
{
// Prepare our context and socket
zmq::context_t context (1);
zmq::socket_t socket (context, ZMQ_PULL);
std::cout << "Connecting to FE..." << std::endl;
socket.connect ("tcp://localhost:5555");
while(1){
zmq::message_t reply;
socket.recv (&reply);
GenericMessage<std::string> *msg = (GenericMessage<std::string>*)(reply.data());
std::cout << "RECEIVED: " << msg->toString() << std::endl;
/* ********************************* */
/* SEGMENTATION FAULT HAPPENS HERE */
/* The member "data" in class GenericMessage cannot be received while the member "id" in the previous line can be received. */
std::cout << "DATA: " << ((std::string)msg->getData()) << std::endl;
/* ********************************** */
}
return 0;
}
代码片段 4 (ZMQHandler.hxx)
#include "zmq.hpp"
#include "GenericMessage.hxx"
#include <pthread.h>
#include <unistd.h>
#include <cassert>
template <class T>
class ZmqHandler {
public:
ZmqHandler():
mContext(1),
mOutbHandlerSocket(mContext, ZMQ_PUSH)
{
mOutbHandlerSocket.bind ("tcp://*:5555");
}
~ZmqHandler() {}
void *sendToBE(GenericMessage<T> *theMsg)
{
// Place the new request to the zmq queue for BE consumption
zmq::message_t msgToSend(sizeof(*theMsg));
memcpy ( msgToSend.data(), ((GenericMessage<T>*)theMsg), sizeof(* ((GenericMessage<T>*)theMsg)));
mOutbHandlerSocket.send(msgToSend);
std::cout << "SENT request: [" << theMsg->toString() << "]" << std::endl;
return (NULL);
}
private:
zmq::context_t mContext;
zmq::socket_t mOutbHandlerSocket;
};