Re: a really simple C++ abstraction around pthread_t...

From:
"Adem" <for-usenet-5c@alicewho.com>
Newsgroups:
comp.lang.c++,comp.programming.threads
Date:
Fri, 31 Oct 2008 15:40:11 +0100
Message-ID:
<gef5ep$ihk$1@aioe.org>
"Chris M. Thomasson" wrote

"Chris M. Thomasson" wrote

I use the following technique in all of my C++ projects; here is the
example code with error checking omitted for brevity:


[...]

Any suggestions on how I can improve this construct?


One addition I forgot to add would be creating an explict `guard' helper
object within the `active' helper object so that one can create objects and
intervene between its ctor and when it actually gets ran... Here is full
example code showing this moment:
_________________________________________________________________
/* Simple Thread Object
______________________________________________________________*/
#include <pthread.h>

extern "C" void* thread_entry(void*);

class thread_base {
  pthread_t m_tid;
  friend void* thread_entry(void*);
  virtual void on_active() = 0;

public:
  virtual ~thread_base() = 0;

  void active_run() {
    pthread_create(&m_tid, NULL, thread_entry, this);
  }

  void active_join() {
    pthread_join(m_tid, NULL);
  }
};

thread_base::~thread_base() {}

void* thread_entry(void* state) {
  reinterpret_cast<thread_base*>(state)->on_active();
  return 0;
}

template<typename T>
struct active : public T {
  struct guard {
    T& m_object;

    guard(T& object) : m_object(object) {
      m_object.active_run();
    }

    ~guard() {
      m_object.active_join();
    }
  };

  active() : T() {
    this->active_run();
  }

<snip>

Hmm. is it ok to stay within the ctor for the whole
duration of the lifetime of the object?
IMO the ctor should be used only for initializing the object,
but not for executing or calling the "main loop" of the object
because the object is fully created only after the ctor has finished,
isn't it?

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