Re: [Boost-users] HowTo Pass arguments to boost threads?

From: Gabriel Ki (gabeki_corp_at_[hidden])
Date: 2006-12-12 16:10:14

Hi,

I am just trying the boost threads example from the link.

#include <boost/thread/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/tss.hpp>
#include <iostream>

boost::mutex io_mutex;
boost::thread_specific_ptr<int> ptr;

struct count
{
  count(int id) : id(id) { }

  void operator()()
  {
    if (ptr.get() == 0)
      ptr.reset(new int(0));

    for (int i = 0; i < 10; ++i)
    {
      (*ptr)++;
      boost::mutex::scoped_lock
        lock(io_mutex);
      std::cout << id << ": "
        << *ptr << std::endl;
    }
  }

  int id;
};

int main(int argc, char* argv[])
{
  boost::thread thrd1(count(1));
  boost::thread thrd2(count(2));
  thrd1.join();
  thrd2.join();
  return 0;
}// Output 
$ ./testme
10591400: 1
10591400: 2
10591400: 3
10591400: 4
10591400: 5
10591400: 6
10591400: 7
10591400: 8
10591400: 9
10591400: 10
Segmentation fault

I have a few questions.
1)  Why is id copied incorrectly in operator()?
2)  Why does the count object get copied so many times?  (i tried to write a copy constructor into count to see the id value)
3)  I tried to add setstacksize in boost code and recompile.  Is it a better way to do it?

Thanks in advance.
Gabriel

----- Original Message ----
From: Moshe Matitya <Moshe.Matitya_at_[hidden]>
To: boost-users_at_[hidden]
Sent: Tuesday, December 12, 2006 3:40:03 AM
Subject: Re: [Boost-users] HowTo Pass arguments to boost threads?

Forever Kid wrote:
> 
> What is the method boost prefers to pass arguments to boost 
> threads?  (such as a pointer to some class
> object)
> 
> I saw the class thread_specific_ptr.  
> Is thread_specific_ptr designed for this purpose?
> 
> Is there a recommended site with boost examples to check out? 
>  Boost has good documentation, although I prefer to learn by 
> example and use strict documentation as I become more experienced.
> 
> Thanks much,
> Graham


Take a look this introductory article on Boost.Threads by Bill Kempf:
http://www.ddj.com/184401518
It addresses the question you're asking in a very clear, straightforward
manner, with examples.

Moshe
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