Re: [Boost-users] Boost shared pointers, PThreads and void* casts

From: Andrew Holden (aholden_at_[hidden])
Date: 2007-12-19 10:34:20

STenyaK (Bruno Gonzalez) [stenyak_at_[hidden]] wrote:
> On 12/19/07, Andrew Holden <aholden_at_[hidden]> wrote:
>> typedef shared_ptr<MyClass> pMyClass;
>> void* MyClass::actionThread(void *objectPointer)
>> {
>>     MyClass * _obj = static_cast<MyClass*>(objectPointer);
>>     pMyClass obj = _obj->shared_from_this();
>>     obj->action(false);
>> }
>> 
>> void MyClass::action(bool threaded)
>> {
>>     if (threaded)
>>     {
>>         pthread_t tid;
>>         pthread_create(&tid, 0, actionThread, this)
>>     } else {
>>         //TODO: actually perform the action
>>     }
>> }
>> ----------------------------
>> 
>> This works because shared_from_this is specifically designed to allow
>> member functions of a class to recover the shared pointer to the
>> object. 
> 
> Just in case... actionThread is a static method of the class, since
> otherwise C++ won't allow me to get a pointer of it (and i dislike
> global functions). Does this fact have any implications in the last
> proposed code sample? 

Not really.  actionThread is still a member function of MyClass, which
means it has full access to MyClass's members (as long as it has access
to a MyClass object somehow), including private and protected members,
and protected members from base classes.  _obj is a valid pointer to a
MyClass, so there is nothing wrong with actionThread calling _obj's
shared_from_this function.