operator= - code in overloaded function doesn't get called

[Tobias Langner]

I overloaded the operator= - but in the program, if the line p3=p1 gets
executed, the program doesn't jump to the method.

The class definition and the test code.

template <class T, template <class> class OwnershipPolicy >
class SmartPtr : public OwnershipPolicy <T> {
public:
explicit SmartPtr(T* pointer);
SmartPtr(const SmartPtr<T, OwnershipPolicy >& otherPointer);
SmartPtr<T, OwnershipPolicy > &operator=(cons t SmartPtr<T, OwnershipPolicy >
&);
~SmartPtr();
T& operator*() const;
T* operator->() const;

private:
void deleteObject();
void copyPtr(const SmartPtr<T, OwnershipPolicy >& otherPointer);
SmartPtr();
T* pointer_;

};

//The Testcode:

bool testSmartPtr() {
SmartPtr<LongWr apper, RefCount> *p1=new SmartPtr<LongWr apper,
RefCount>(new LongWrapper(1)) ;
SmartPtr<LongWr apper, RefCount> *p2=new SmartPtr<LongWr apper,
RefCount>(new LongWrapper(20) );
SmartPtr<LongWr apper, RefCount> *p3=new SmartPtr<LongWr apper,
RefCount>(*p2);



std::cout<<"p1= p3\n";
p3=p1;

std::cout<<"del ete p1\n";
delete p1;
std::cout<<"del ete p2\n";
delete p2;
std::cout<<"del ete p3\n";
delete p3;

return true;
}

[John Harrison]

Re: operator= - code in overloaded function doesn't get called


"Tobias Langner" <tobias.langner @t-online.de> wrote in message
news:bgal7l$16c $07$2@news.t-online.com...[color=blue]
> I overloaded the operator= - but in the program, if the line p3=p1 gets
> executed, the program doesn't jump to the method.
>
> The class definition and the test code.
>
> template <class T, template <class> class OwnershipPolicy >
> class SmartPtr : public OwnershipPolicy <T> {
> public:
> explicit SmartPtr(T* pointer);
> SmartPtr(const SmartPtr<T, OwnershipPolicy >& otherPointer);
> SmartPtr<T, OwnershipPolicy > &operator=(cons t SmartPtr<T,[/color]
OwnershipPolicy >[color=blue]
> &);
> ~SmartPtr();
> T& operator*() const;
> T* operator->() const;
>
> private:
> void deleteObject();
> void copyPtr(const SmartPtr<T, OwnershipPolicy >& otherPointer);
> SmartPtr();
> T* pointer_;
>
> };
>
> //The Testcode:
>
> bool testSmartPtr() {
> SmartPtr<LongWr apper, RefCount> *p1=new SmartPtr<LongWr apper,
> RefCount>(new LongWrapper(1)) ;
> SmartPtr<LongWr apper, RefCount> *p2=new SmartPtr<LongWr apper,
> RefCount>(new LongWrapper(20) );
> SmartPtr<LongWr apper, RefCount> *p3=new SmartPtr<LongWr apper,
> RefCount>(*p2);
>
>
>
> std::cout<<"p1= p3\n";
> p3=p1;
>
> std::cout<<"del ete p1\n";
> delete p1;
> std::cout<<"del ete p2\n";
> delete p2;
> std::cout<<"del ete p3\n";
> delete p3;
>
> return true;
> }[/color]

Well that's because p1, p2 and p3 are pointers.

I think perhaps what you meant to write is

SmartPtr<LongWr apper, RefCount> p1=SmartPtr<Lon gWrapper, RefCount>(new
LongWrapper(1)) ;
SmartPtr<LongWr apper, RefCount> p2=SmartPtr<Lon gWrapper, RefCount>(new
LongWrapper(20) );
SmartPtr<LongWr apper, RefCount> p3=p2;
std::cout<<"p1= p3\n";
p3=p1;

You seem to be getting your smart pointers and your ordinary pointers mixed
up.

john

[Jakob Bieling]

Re: operator= - code in overloaded function doesn't get called

"Tobias Langner" <tobias.langner @t-online.de> wrote in message
news:bgal7l$16c $07$2@news.t-online.com...[color=blue]
> I overloaded the operator= - but in the program, if the line p3=p1 gets
> executed, the program doesn't jump to the method.
>
> The class definition and the test code.
>
> template <class T, template <class> class OwnershipPolicy >
> class SmartPtr : public OwnershipPolicy <T> {
> public:
> explicit SmartPtr(T* pointer);
> SmartPtr(const SmartPtr<T, OwnershipPolicy >& otherPointer);
> SmartPtr<T, OwnershipPolicy > &operator=(cons t SmartPtr<T,[/color]
OwnershipPolicy >[color=blue]
> &);
> ~SmartPtr();
> T& operator*() const;
> T* operator->() const;
>
> private:
> void deleteObject();
> void copyPtr(const SmartPtr<T, OwnershipPolicy >& otherPointer);
> SmartPtr();
> T* pointer_;
>
> };
>
> //The Testcode:
>
> bool testSmartPtr() {
> SmartPtr<LongWr apper, RefCount> *p1=new SmartPtr<LongWr apper,
> RefCount>(new LongWrapper(1)) ;
> SmartPtr<LongWr apper, RefCount> *p2=new SmartPtr<LongWr apper,
> RefCount>(new LongWrapper(20) );
> SmartPtr<LongWr apper, RefCount> *p3=new SmartPtr<LongWr apper,
> RefCount>(*p2);
>
>
>
> std::cout<<"p1= p3\n";
> p3=p1;[/color]

'p3' and 'p1' are pointers, not objects. That is why the operator= for
the 'object' does not get called, but the operator= for the 'pointer'. The
original value for 'p3' is lost, meaning you also have a memory leak.
[color=blue]
> std::cout<<"del ete p1\n";
> delete p1;
> std::cout<<"del ete p2\n";
> delete p2;
> std::cout<<"del ete p3\n";
> delete p3;[/color]

You have undefined behaviour here, because above you made 'p1' and 'p3'
point to the same object, which you now try to delete a second time. Your
program might have crashed here.
[color=blue]
> return true;
> }[/color]

hth
--
jb

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