Re: noob question - destructors - freeing memory...

From:
Nick Keighley <nick_keighley_nospam@hotmail.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 31 Dec 2011 01:52:51 -0800 (PST)
Message-ID:
<9a8fd0c3-1f5f-4df6-8a62-c6bb94226969@v24g2000yqk.googlegroups.com>
On Dec 31, 4:37 am, someone <newsbo...@gmail.com> wrote:

On 12/31/2011 04:50 AM, Garrett Hartshaw wrote:

On Sat, 31 Dec 2011 02:43:28 +0100, someone <newsbo...@gmail.com> wrote=

:

Hi
Please advice, thank you!


A statically constructed object will be destroyed when the scope is lef=

t.

e.g destructors will be called in:
int main()
{
Derived d;
return 0;
}


Ah, stupid me. I thought I had tried the above, and that it didn't work
- thank you very much. My mistake, maybe also in reply to MikeWhy...

A dynamically constructed object (created using new) is destroyed when
delete is called.

e.g destructors called in this:
int main()
{
Base * b = new Derived();
delete b;
return 0;
}

but not this:
int main()
{
Base * b = new Derived();
return 0;
}


Yes, this is clear now, the static thing was a brain-something that hit
me...

When exit(int) is called, the program is terminated *without unwinding
the stack* so no destructors are called.


Yes, clear.

When a execption is thrown and not caught, the program is terminated
*with stack unwinding*, so static objects are destroyed.


Aah, only static objects... DAMN...

Note: int main()
{
Base * b = new Derived();
throw std::exception();
delete b;
return 0;
}

In the above, the delete expression is never reached, so destructors ar=

e

not called.


That is a big problem/issue in my program, I think...

So if I allocate memory in my constructor, and I never call the
destructor and I keep running and exiting, running and exiting the
program, then I end up using all my memory because I never free'd it?

If this is an issue, a smart pointer (boost::shared_ptr,
boost::scoped_ptr, etc:) should be used.


Ooh, damn...

I hoped, I could avoid having to learn something new and timeconsuming
like boost...

Isn't there an easier solution without including more libraries?


std::auto_ptr

though I believe this is now deprecated. Hasn't been removed though
and does the job.

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