| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"Tobias Langner" |
| Date: |
31 Jul 2003 03:49:11 AM |
| Object: |
operator= - code in overloaded function doesn't get called |
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=(const 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<LongWrapper, RefCount> *p1=new SmartPtr<LongWrapper,
RefCount>(new LongWrapper(1));
SmartPtr<LongWrapper, RefCount> *p2=new SmartPtr<LongWrapper,
RefCount>(new LongWrapper(20));
SmartPtr<LongWrapper, RefCount> *p3=new SmartPtr<LongWrapper,
RefCount>(*p2);
std::cout<<"p1=p3\n";
p3=p1;
std::cout<<"delete p1\n";
delete p1;
std::cout<<"delete p2\n";
delete p2;
std::cout<<"delete p3\n";
delete p3;
return true;
}
.
|
|
| User: "John Harrison" |
|
| Title: Re: operator= - code in overloaded function doesn't get called |
31 Jul 2003 04:22:19 AM |
|
|
"Tobias Langner" <tobias.langner@t-online.de> wrote in message
news:bgal7l$16c$07$2@news.t-online.com...
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=(const 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<LongWrapper, RefCount> *p1=new SmartPtr<LongWrapper,
RefCount>(new LongWrapper(1));
SmartPtr<LongWrapper, RefCount> *p2=new SmartPtr<LongWrapper,
RefCount>(new LongWrapper(20));
SmartPtr<LongWrapper, RefCount> *p3=new SmartPtr<LongWrapper,
RefCount>(*p2);
std::cout<<"p1=p3\n";
p3=p1;
std::cout<<"delete p1\n";
delete p1;
std::cout<<"delete p2\n";
delete p2;
std::cout<<"delete p3\n";
delete p3;
return true;
}
Well that's because p1, p2 and p3 are pointers.
I think perhaps what you meant to write is
SmartPtr<LongWrapper, RefCount> p1=SmartPtr<LongWrapper, RefCount>(new
LongWrapper(1));
SmartPtr<LongWrapper, RefCount> p2=SmartPtr<LongWrapper, RefCount>(new
LongWrapper(20));
SmartPtr<LongWrapper, 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
.
|
|
|
|
| User: "Jakob Bieling" |
|
| Title: Re: operator= - code in overloaded function doesn't get called |
31 Jul 2003 04:22:26 AM |
|
|
"Tobias Langner" <tobias.langner@t-online.de> wrote in message
news:bgal7l$16c$07$2@news.t-online.com...
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=(const 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<LongWrapper, RefCount> *p1=new SmartPtr<LongWrapper,
RefCount>(new LongWrapper(1));
SmartPtr<LongWrapper, RefCount> *p2=new SmartPtr<LongWrapper,
RefCount>(new LongWrapper(20));
SmartPtr<LongWrapper, RefCount> *p3=new SmartPtr<LongWrapper,
RefCount>(*p2);
std::cout<<"p1=p3\n";
p3=p1;
'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.
std::cout<<"delete p1\n";
delete p1;
std::cout<<"delete p2\n";
delete p2;
std::cout<<"delete p3\n";
delete p3;
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.
return true;
}
hth
--
jb
(replace y with x if you want to reply by e-mail)
.
|
|
|
|
|
Related Articles |
|
|
