delete operator on smart pointers.

[=?iso-8859-1?q?Ernesto_Basc=F3n?=]

I am implementing my custom smart pointer:

template <typename T>
class MySmartPtr
{
public:
MySmartPtr(T* aPointer)
{
mPointer = aPointer;
}

inline T* operator->() const {return mPointer; }

private:
T* mPointer;
};
It could be used in this way:

MySmartPtr<Aobj = new A();
obj->Method1();
int value = obj->Method2();

The operator-overload allows accessing the A methods as they are
accessed via a common pointer.

I want to allow the final user call the delete operator as in a common
pointer when he wants to explicitly remove the pointer:

delete obj;
There is a way I could implement an overload of the delete pointer in
my MySmartPtr<Tor there is some workaround on this?

Thanks in advance,
ernesto

[Heinz Ozwirk]

"Ernesto Bascón" <eb******@gmail .comschrieb im Newsbeitrag
news:11******** *************@s 80g2000cwa.goog legroups.com...

>I am implementing my custom smart pointer:

template <typename T>
class MySmartPtr
{
public:
MySmartPtr(T* aPointer)
{
mPointer = aPointer;
}

inline T* operator->() const {return mPointer; }

private:
T* mPointer;
};
It could be used in this way:

MySmartPtr<Aobj = new A();
obj->Method1();
int value = obj->Method2();

The operator-overload allows accessing the A methods as they are
accessed via a common pointer.

I want to allow the final user call the delete operator as in a common
pointer when he wants to explicitly remove the pointer:

delete obj;
There is a way I could implement an overload of the delete pointer in
my MySmartPtr<Tor there is some workaround on this?

To make your smart pointer really smart, it should also implement a default
constructor, a copy constructor and an assignment operator (actually two, a
copy assignment operator and one to assign raw pointers). If they are
implemented correctly, you could just write

obj = 0; // or NULL

to free whatever the smartpointer owned before.

HTH
Heinz

[Paul Hosre]

Ernesto Bascón wrote:

I am implementing my custom smart pointer:

template <typename T>
class MySmartPtr
{
public:
MySmartPtr(T* aPointer)
{
mPointer = aPointer;
}

inline T* operator->() const {return mPointer; }

private:
T* mPointer;
};
It could be used in this way:

MySmartPtr<Aobj = new A();
obj->Method1();
int value = obj->Method2();

The operator-overload allows accessing the A methods as they are
accessed via a common pointer.

I want to allow the final user call the delete operator as in a common
pointer when he wants to explicitly remove the pointer:

delete obj;
There is a way I could implement an overload of the delete pointer in
my MySmartPtr<Tor there is some workaround on this?

Thanks in advance,
ernesto

did you try debuggig and watch what object is actually in use then
delete it directly?

[Paul Hosre]

Heinz Ozwirk wrote:

>
To make your smart pointer really smart, it should also implement a default
constructor, a copy constructor and an assignment operator (actually two, a
copy assignment operator and one to assign raw pointers). If they are
implemented correctly, you could just write

obj = 0; // or NULL

to free whatever the smartpointer owned before.

HTH
Heinz

That's an elegant point!
I watched my google search carefully with my pair of glasses and I
turned out to have the same incorrect thought with others. hehe

[Paul Hosre]

Heinz Ozwirk wrote:

>
To make your smart pointer really smart, it should also implement a default
constructor, a copy constructor and an assignment operator (actually two, a
copy assignment operator and one to assign raw pointers). If they are
implemented correctly, you could just write

obj = 0; // or NULL

to free whatever the smartpointer owned before.

HTH
Heinz

That's an elegant point!
I watched my google search carefully with my pair of glasses and I
turned out to have the same incorrect thought with others. heh

[Grizlyk]

Ernesto Bascón wrote:

MySmartPtr(T* aPointer){ mPointer = aPointer; }

Better do
MySmartPtr( T *const aPointer=0 )throw():mPoint er(aPointer){ }

MySmartPtr<Aobj = new A();

It can produce sequence

MySmartPtr<A>() + MySmartPtr<A>() + MySmartPtr<A>(c onst MySmartPtr<A>&)
or MySmartPtr<A>:: operator = (const MySmartPtr<A>&)

Better do
MySmartPtr<Aobj (new A() );

obj->Method1();

Define both
? T* operator-() ? throw(){ return mPointer; }
? T& operator* () ? throw(){ return *mPointer; }
be shure "const" instead "?" is correct for MySmartPtr behaviour

int value = obj->Method2();

I want to allow the final user call the delete operator as in a common
pointer when he wants to explicitly remove the pointer:

delete obj;

Try do
public:
operator T* ()throw(){ T *const tmp=mPointer; mPointer=0; return
tmp; }
~MySmartPtr()th row(){ delete mPointer; mPointer=0; }

Define (if you can not dynamic copy like this, else as need)
private:
MySmartPtr(cons t MySmartPtr&)thr ow():mPointer(0 ){ exit(1); }
void operator= (const MySmartPtr&)thr ow(){ exit(1); }

[Grizlyk]

Grizlyk wrote:

Define (if you can not dynamic copy like this, else as need)
private:
MySmartPtr(cons t MySmartPtr&)thr ow():mPointer(0 ){ exit(1); }
void operator= (const MySmartPtr&)thr ow(){ exit(1); }

Yes, and yet
public:
T* operator= (T *const aPointer)throw( ) { delete mPointer;
mPointer=aPoint er; }

[mlimber]

Ernesto Bascón wrote:

I am implementing my custom smart pointer:

template <typename T>
class MySmartPtr
{
public:
MySmartPtr(T* aPointer)
{
mPointer = aPointer;
}

inline T* operator->() const {return mPointer; }

private:
T* mPointer;
};
It could be used in this way:

MySmartPtr<Aobj = new A();
obj->Method1();
int value = obj->Method2();

The operator-overload allows accessing the A methods as they are
accessed via a common pointer.

I want to allow the final user call the delete operator as in a common
pointer when he wants to explicitly remove the pointer:

delete obj;
There is a way I could implement an overload of the delete pointer in
my MySmartPtr<Tor there is some workaround on this?

I presume there are other functions omitted from your code above, and
from your description, it's not clear what semantics you are intending
to give this smart pointer (though it sounds like you want shared
ownership). Generally, smart pointers (e.g., std::auto_ptr,
std::tr1::share d_ptr, boost::scoped_p tr, Loki::SmartPtr, and the smart
pointer in FAQ 16.22) are responsible for cleaning up after themselves
at the appropriate time so that the user doesn't have worry about
deleting anything. Indeed, that's often the primary point. What is your
point?

As for overloading delete, you probably don't want to do that because
it would change the semantics of delete from operating on the object
(viz. MySmartPtr<>) to operating on the contained object. In other
words, class-specific new/delete operators are for deleting the smart
pointer class itself:

MySmartPtr<T>* pT
= new MySmartPtr<T>( 0 ); // Calls MySmartPtr<T>:: operator new
delete pT; // Calls MySmartPtr<T>:: operator delete

You could accomplish your goal by supplying a cast to T*, but that
allows some other dangerous code. The preferred method is to supply a
reset function:

template<class T>
void MySmartPtr<T>:: Reset( T* const p = 0 )
{
delete mPointer;
mPointer = p;
}

It's best to use RAII and let the smart pointer do the dirty work. See
the FAQ mentioned above and those following, and see this chapter from
_Modern C++ Design_ on Loki's smart pointers:

http://www.informit.com/articles/pri...p?p=25264&rl=1

Cheers! --M

[=?iso-8859-1?q?Ernesto_Basc=F3n?=]

I presume there are other functions omitted from your code above, and
from your description, it's not clear what semantics you are intending
to give this smart pointer (though it sounds like you want shared
ownership). Generally, smart pointers (e.g., std::auto_ptr,
std::tr1::share d_ptr, boost::scoped_p tr, Loki::SmartPtr, and the smart
pointer in FAQ 16.22) are responsible for cleaning up after themselves
at the appropriate time so that the user doesn't have worry about
deleting anything. Indeed, that's often the primary point. What is your
point?

Primarily, I want to provide a hierarchy of smart pointers, providing
the basic implementation in something like AbstractPtr<T>; the basic
implementation should include null pointer checking on -and dangling
pointer avoiding.

I want to provide also a Ptr<T: public AbstractPtr<Tim plementation
that should have the same behavior that the standard pointers, but with
the null pointer checking. This smart pointer should not have any
semantics (thus, should provide mechanisms to release the pointee
object manually).

[Noah Roberts]

Ernesto Bascón wrote:

I want to allow the final user call the delete operator as in a common
pointer when he wants to explicitly remove the pointer:

delete obj;

No you don't.