Re: [Boost-users] functor for boost::thread_group threads: which one is correct?

23 Aug 2009


      AMDG

Boost lzw wrote:
...
I have two versions (VERSION1 and VERSION2) of a group_helper functor to be
called from boost::thread_group, which one of them is correct?
class FileThread
{
public:
void print() {...}
void find() {...}
};
class group_helper
{
private:
    boost::shared_ptr<FileThread> m_object;
public:
   //VISION1
    group_helper(boost::shared_ptr<FileThread>& object) : m_object(object) {
}
//VISION2
    group_helper() : m_object(boost::shared_ptr<FileThread>(new FileThread))
{ }
void operator()() { m_object->find(); m_object->print(); }
};
Both are correct depending on whether you want to pass an external 
FileThread
or create a new FileThread in the constructor.
...
On another matter, why the following code results in a runtime exception
from the group_helper's dtor?
#include <iostream>
#include "boost/thread/thread.hpp"
class FileThread
{
public:
  void find() { }
  void print() { }
};
class group_helper			
{							
private:
  FileThread* m_object;	
public:			
  group_helper() : m_object(new FileThread) {}
  void operator()() { m_object->find(); m_object->print(); }
  ~group_helper() { if (m_object) delete m_object; }// EXCEPTION from dtor
};
group_helper is copied and both copies try to
delete m_object.
...
int main()
{
  group_helper gh;
  boost::thread thrd(gh);						
  thrd.join();
}
In Christ,
Steven Watanabe