functor for boost::thread_group threads: which one is correct?
Hi there, 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(); } }; 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 }; int main() { group_helper gh; boost::thread thrd(gh); thrd.join(); }
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
Hi Steven and other guys,
Thanks for Steven's input. Is the following code correct?
class FileThread
{
public:
void find() { std::cout << "FileThread::find() called" << std::endl;}
void print() { std::cout << "FileThread::print() called" << std::endl;}
};
class group_helper
{
private:
boost::shared_ptr<FileThread> m_object;
public:
group_helper() : m_object(boost::shared_ptr<FileThread>(new FileThread))
{ std::cout << "group_helper::ctor called" << std::endl;}
void operator()() { m_object->find(); m_object->print(); }
~group_helper() { std::cout << "group_helper::***dtor called" <<
std::endl; }
};
int main()
{
group_helper gp;
boost::thread_group threads;
for (int i = 0; i < 1; ++i)
threads.create_thread(gp);
threads.join_all();
return 0;
}
===========
Output: 1 call to "group_helper::ctor called"
6 calls to "group_helper::***dtor called"
===========
If the code is correct, does this mean that with thread_group we can no
longer expect the # of ctors matches that of the dtors in threaded code?
Thanks in advance,
Robert
On Sun, Aug 23, 2009 at 3:06 PM, Steven Watanabe
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
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
Boost lzw wrote:
class group_helper { private: boost::shared_ptr<FileThread> m_object; public: group_helper() : m_object(boost::shared_ptr<FileThread>(new FileThread)) { std::cout << "group_helper::ctor called" << std::endl;} void operator()() { m_object->find(); m_object->print(); } ~group_helper() { std::cout << "group_helper::***dtor called" << std::endl; } };
int main() { group_helper gp; boost::thread_group threads; for (int i = 0; i < 1; ++i) threads.create_thread(gp); threads.join_all();
return 0; } =========== Output: 1 call to "group_helper::ctor called" 6 calls to "group_helper::***dtor called" =========== If the code is correct, does this mean that with thread_group we can no longer expect the # of ctors matches that of the dtors in threaded code?
It has nothing to do with threads, it's because you're not displaying calls to the copy constructor.
Hi Guys, Steven is correct. After adding the following copy contructor to group_helper class: group_helper(const group_helper& gp) { std::cout << "group_helper::copy ctor called" << std::endl; } The number of ctors matches that of the dtors. So the threaded code is correct thanks to boost::shared_ptr. Cheers, Robert On Sun, Aug 23, 2009 at 10:05 PM, Mathias Gaunard < mathias.gaunard@ens-lyon.org> wrote:
Boost lzw wrote:
class group_helper { private:
boost::shared_ptr<FileThread> m_object; public: group_helper() : m_object(boost::shared_ptr<FileThread>(new FileThread)) { std::cout << "group_helper::ctor called" << std::endl;} void operator()() { m_object->find(); m_object->print(); } ~group_helper() { std::cout << "group_helper::***dtor called" << std::endl; } };
int main() { group_helper gp; boost::thread_group threads; for (int i = 0; i < 1; ++i) threads.create_thread(gp); threads.join_all();
return 0; } =========== Output: 1 call to "group_helper::ctor called" 6 calls to "group_helper::***dtor called" =========== If the code is correct, does this mean that with thread_group we can no longer expect the # of ctors matches that of the dtors in threaded code?
It has nothing to do with threads, it's because you're not displaying calls to the copy constructor.
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
Hi Guys,
Sorry for Mathias. Mathias is correct concerning the copy contructor. So my
completed code looks like this:
-----------------------------------------------
// Invoke several functions from multiple threads
#include <iostream>
#include "boost/thread/thread.hpp"
#include "boost/shared_ptr.hpp"
class FileThread
{
public:
void find() { }
void print() { }
};
class group_helper
{
private:
boost::shared_ptr<FileThread> m_object;
public:
group_helper() : m_object(boost::shared_ptr<FileThread>(new FileThread)) {
}
void operator()() { m_object->find(); m_object->print(); }
};
int main()
{
group_helper gp;
boost::thread_group threads;
for (int i = 0; i < 2; ++i)
threads.create_thread(gp);
threads.join_all();
return 0;
}
-----------------------------------------------
On Sun, Aug 23, 2009 at 10:23 PM, Boost lzw
Hi Guys,
Steven is correct. After adding the following copy contructor to group_helper class: group_helper(const group_helper& gp) { std::cout << "group_helper::copy ctor called" << std::endl; }
The number of ctors matches that of the dtors. So the threaded code is correct thanks to boost::shared_ptr.
Cheers, Robert
On Sun, Aug 23, 2009 at 10:05 PM, Mathias Gaunard < mathias.gaunard@ens-lyon.org> wrote:
Boost lzw wrote:
class group_helper { private:
boost::shared_ptr<FileThread> m_object; public: group_helper() : m_object(boost::shared_ptr<FileThread>(new FileThread)) { std::cout << "group_helper::ctor called" << std::endl;} void operator()() { m_object->find(); m_object->print(); } ~group_helper() { std::cout << "group_helper::***dtor called" << std::endl; } };
int main() { group_helper gp; boost::thread_group threads; for (int i = 0; i < 1; ++i) threads.create_thread(gp); threads.join_all();
return 0; } =========== Output: 1 call to "group_helper::ctor called" 6 calls to "group_helper::***dtor called" =========== If the code is correct, does this mean that with thread_group we can no longer expect the # of ctors matches that of the dtors in threaded code?
It has nothing to do with threads, it's because you're not displaying calls to the copy constructor.
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
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participants (3)
-
Boost lzw -
Mathias Gaunard -
Steven Watanabe