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| John |
 Posted: Mon Jun 07, 2004 10:15 pm |
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Hi all:
Just learn to use smart pointer. I get a question. In the following
code:
void foo()
{
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
}
By the end of function foo(), the memory that is allocated to p will
be automatically deallocated. But if I have other functions that need
to access the memory allocated to p, and eventually that memory will
be deallocated by one function. So I do not want the memory allocated
to p to be deallocated by the end of function foo(). What should I do?
Thanks a lot.
John
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| Xiaobin Yang |
| Posted: Mon Jun 07, 2004 10:23 pm |
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can you give the declaration/implementation of "template <class T> class
auot_ptr {.....}"?
On Mon, 7 Jun 2004, John wrote:
Quote: Hi all:
Just learn to use smart pointer. I get a question. In the following
code:
void foo()
{
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
}
By the end of function foo(), the memory that is allocated to p will
be automatically deallocated. But if I have other functions that need
to access the memory allocated to p, and eventually that memory will
be deallocated by one function. So I do not want the memory allocated
to p to be deallocated by the end of function foo(). What should I do?
Thanks a lot.
John
-- xiaobin
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| Jeff Flinn |
| Posted: Mon Jun 07, 2004 10:28 pm |
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"John" <johnw822003@yahoo.com> wrote in message
news:c30e885a.0406071015.6f9aa158@posting.google.com...
Quote: Hi all:
Just learn to use smart pointer. I get a question. In the following
code:
[see below]
Quote: By the end of function foo(), the memory that is allocated to p will
be automatically deallocated. But if I have other functions that need
to access the memory allocated to p, and eventually that memory will
be deallocated by one function. So I do not want the memory allocated
to p to be deallocated by the end of function foo(). What should I do?
void foo()
auto_ptr<MyClass> foo()
Quote: {
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
return p;
> }
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| Alan Johnson |
| Posted: Mon Jun 07, 2004 10:45 pm |
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John wrote:
Quote: Hi all:
Just learn to use smart pointer. I get a question. In the following
code:
void foo()
{
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
}
By the end of function foo(), the memory that is allocated to p will
be automatically deallocated. But if I have other functions that need
to access the memory allocated to p, and eventually that memory will
be deallocated by one function. So I do not want the memory allocated
to p to be deallocated by the end of function foo(). What should I do?
Thanks a lot.
John
The release() method will cause the auto_ptr to give up ownership of the
memory. For example:
void foo()
{
auto_ptr<MyClass> p(new MyClass);
MyClass *t;
p->DoSomething();
// Other stuff.
t = p.release();
// Now we must manually delete the memory.
delete t;
}
Alan
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| Alan Johnson |
| Posted: Mon Jun 07, 2004 10:45 pm |
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Xiaobin Yang wrote:
Quote: can you give the declaration/implementation of "template <class T> class
auot_ptr {.....}"?
On Mon, 7 Jun 2004, John wrote:
Hi all:
Just learn to use smart pointer. I get a question. In the following
code:
void foo()
{
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
}
By the end of function foo(), the memory that is allocated to p will
be automatically deallocated. But if I have other functions that need
to access the memory allocated to p, and eventually that memory will
be deallocated by one function. So I do not want the memory allocated
to p to be deallocated by the end of function foo(). What should I do?
Thanks a lot.
John
-- xiaobin
std::auto_ptr<T> is in <memory>.
Alan
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| John |
| Posted: Tue Jun 08, 2004 2:03 am |
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"Jeff Flinn" <NONONE@nowhere.com> wrote in message news:<ca2c4m$909$1@bluegill.adi.com>...
Quote: "John" <johnw822003@yahoo.com> wrote in message
news:c30e885a.0406071015.6f9aa158@posting.google.com...
Hi all:
Just learn to use smart pointer. I get a question. In the following
code:
[see below]
By the end of function foo(), the memory that is allocated to p will
be automatically deallocated. But if I have other functions that need
to access the memory allocated to p, and eventually that memory will
be deallocated by one function. So I do not want the memory allocated
to p to be deallocated by the end of function foo(). What should I do?
void foo()
auto_ptr<MyClass> foo()
{
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
return p;
}
But that allocated memory will still be deallocated by the end of foo(), right?
Thanks.
JOhn
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| Jeff Flinn |
| Posted: Tue Jun 08, 2004 2:15 am |
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"John" <johnw822003@yahoo.com> wrote in message
news:c30e885a.0406071403.311202df@posting.google.com...
Quote: "Jeff Flinn" <NONONE@nowhere.com> wrote in message
news:<ca2c4m$909$1@bluegill.adi.com>...
"John" <johnw822003@yahoo.com> wrote in message
news:c30e885a.0406071015.6f9aa158@posting.google.com...
Hi all:
Just learn to use smart pointer. I get a question. In the following
code:
[see below]
By the end of function foo(), the memory that is allocated to p will
be automatically deallocated. But if I have other functions that need
to access the memory allocated to p, and eventually that memory will
be deallocated by one function. So I do not want the memory allocated
to p to be deallocated by the end of function foo(). What should I do?
void foo()
auto_ptr<MyClass> foo()
{
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
return p;
}
But that allocated memory will still be deallocated by the end of foo(),
right?
Wrong.
Jeff F
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| Dietmar Kuehl |
| Posted: Tue Jun 08, 2004 5:13 pm |
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"Jeff Flinn" <NONONE@nowhere.com> wrote:
Quote: "John" <johnw822003@yahoo.com> wrote:
"Jeff Flinn" <NONONE@nowhere.com> wrote:
"John" <johnw822003@yahoo.com> wrot:
auto_ptr<MyClass> foo()
{
auto_ptr<MyClass> p(new MyClass);
p->DoSomething();
return p;
}
But that allocated memory will still be deallocated by the end of foo(),
right?
Wrong.
To elaborate a little bit: 'std::auto_ptr' transfers ownership of the
pointer when it is assigned or copied. That is, the pointer owned by 'p'
is returned to 'std::auto_ptr' returned from 'foo' and will be deleted
when this auto pointer is destructed - unless, of course, it is
transfered to yet another pointer.
The utility of 'std::auto_ptr' is relatively limited. In situations where
the ownership of a pointer is less clear, it is probably advisable to use
a reference counted pointer like eg. 'boost::shared_ptr' which is coming
up in the library TR as 'std::tr1::shared_ptr'.
--
<mailto:dietmar_kuehl@yahoo.com> <http://www.dietmar-kuehl.de/>
<http://www.contendix.com> - Software Development & Consulting
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