Compilation error when using pthread in C++

Question

I'm writing a sniffer class with c++ as following code.

#include "Capture.h"
#include <sys/socket.h>
#include <cstring>
#include <linux/if_ether.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <pthread.h>

Capture::Capture(int sniff_socket): sniff_socket_(sniff_socket), sniff_threadID_(0)
{
}

bool Capture::endCapture()
{
  if(!sniff_threadID_)
    return false;
  cout << "Asking capture thread to stop\n" <<endl;
  return !pthread_cancel(sniff_threadID_);
}

bool Capture::startCapture()
{
  if(pthread_create(&sniff_threadID_, NULL, Capture::sniffer_thread, NULL)) {
    cerr << "Unable to create capture thread"<<endl;
    return false;
  }
  return true;
}

void *Capture::sniffer_thread(void *)
{
  int MTU = 2048;
  char buffer[MTU];
  ssize_t msg_len;
  struct iphdr *ip_header;
  struct ethhdr *eth_header;
  struct tcphdr *tcp_header;
  void *packet;

  pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);
  while (1) {
    msg_len = recvfrom(sniff_socket_, buffer, MTU, 0, NULL, NULL);
    eth_header = (struct ethhdr*)buffer;
    ip_header = (iphdr*)(buffer + sizeof(ethhdr));
    tcp_header = (struct tcphdr*)(buffer + sizeof(struct ethhdr) + sizeof(struct iphdr));

    if(msg_len != -1){
      packet = malloc(msg_len);
      memcpy(packet, buffer, msg_len);
      pthread_testcancel();
      //queue add should be here
    } else {
      cerr<<"Error capture thread recvfrom"<<endl;
      pthread_exit(NULL);
    }
  }
  return NULL;
}

Capture::~Capture()
{
  // TODO Auto-generated destructor stub
}

However, when I compiled the code, g++ said that

../Capture.cpp: In member function ‘bool Capture::startCapture()’:
../Capture.cpp:30: error: argument of type ‘void* (Capture::)(void*)’ does not match ‘void* (*)(void*)’

Could somebody help me out of this problem?

possible duplicate of [Attaching Member function of a class in pthread](http://stackoverflow.com/questions/2460219/attaching-member-function-of-a-class-in-pthread) — Mat, May 01 '11 at 08:26
see also http://stackoverflow.com/questions/1151582/pthread-function-from-a-class, and http://stackoverflow.com/questions/86046/best-way-to-start-a-thread-as-a-member-of-a-c-class — Mat, May 01 '11 at 08:27

Alok Save · Accepted Answer · 2011-05-01T09:01:01.620

3

A member function in C++ class passes this as hidden parameter, the C function pthread_create cannot understand what this is, Since static member functions dont pass this you can use a static function like this:

class Capture
{
    public:
        static void *sniffer_thread(void*);
};



pthread_create(..., Capture::sniffer_thread, NULL);

edited May 01 '11 at 09:01

answered May 01 '11 at 08:33

Alok Save

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score 1 · Answer 2 · answered May 01 '11 at 08:29

1

First of all: is Capture::sniffer_thread static? cause a member function pointer is not a function pointer! These two kinds of pointers are incompatible!

answered May 01 '11 at 08:29

MFH

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Compilation error when using pthread in C++

2 Answers2