Re: Can an object know it is dead?

From:
"Daniel T." <daniel_t@earthlink.net>
Newsgroups:
comp.lang.c++
Date:
Fri, 23 Feb 2007 16:42:56 GMT
Message-ID:
<daniel_t-0C1FA7.11425623022007@news.west.earthlink.net>
In article <1172247439.625622.103690@q2g2000cwa.googlegroups.com>,
 "Thomas Tutone" <Thomas8675309@yahoo.com> wrote:

On Feb 23, 10:54 am, "better_cs_...@yahoo.com"
<better_cs_...@yahoo.com> wrote:

Hello all,

I suspect that a threading issue is leading to an object being
destructed in one thread context while one of its member functions is
still running in another thread context. As a means of confirming
this, I would like to have the object check if it is alive in the
referenced member function and report to me if it is not. However, I
cannot think of a standards-compliant way for an object to know that
it has been destructed.

Can anybody confirm that this *cannot* be done? If it cannot, can
anybody suggest any alternatives?


Ignoring the threads aspect of this, the simplest way is to add a
private bool member and an isValid() member function:

[untested code]

class yourClass {
  private:
    bool valid_;
  protected:
    bool isValid() { return valid_; }
  public:
    yourClass() : valid_(true) {}
    ~yourClass() { valid_ = false; }
  // Rest of yourClass
};

Now have each member function check isValid() before proceeding. For
debugging purposes, you might just add an assert(isValid()); to the
beginning of each member function.

Threads make this much more complicated of course - you would need
some sort of mutex or other device to ensure that the object wasn't
destructed while in the member function.

Best regards,

Tom


The above isn't "standards-compliant" as requested. If another object is
created in the memory space vacated by the dead object, valid_ may be
true even though the object is dead.

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