Copy Constructor and memory allocation

[Michael]

Hi,
I'm writing a vector class:

//mv3.h

class mv3Impl;

class mv3
{
public:
mv3();
mv3(mv3&);
mv3& operator= ( const mv3& RHS);

private:
mv3Impl* pImpl;
};



//mv3.cpp

class mv3Impl
{
public:
float x,y,z;
};

mv3::mv3()
{
pImpl = new mv3Impl;
pImpl->x = pImpl->y = pImpl->z = 1.0f;
}

mv3::mv3(mv3& v)
{
pImpl = new mv3Impl;
*pImpl = *(v->pImpl);
}

mv3& mv3:perator= ( const mv3& RHS)
{
pImpl = new mv3Impl; /* <----------------Do I need this line??
*/
*pImpl = *(RHS->pImpl);

}

Do i need the line that allocates memory or will this create a memory leak?
What functions are called in:

mv3 a;
mv3 b = a;

??
Thanks

Mike

 

[John Harrison]

Hi,
I'm writing a vector class:

//mv3.h

class mv3Impl;

class mv3
{
public:
mv3();
mv3(mv3&);

Should be

mv3(const mv3&);

mv3& operator= ( const mv3& RHS);

private:
mv3Impl* pImpl;
};



//mv3.cpp

class mv3Impl
{
public:
float x,y,z;
};

mv3::mv3()
{
pImpl = new mv3Impl;
pImpl->x = pImpl->y = pImpl->z = 1.0f;
}

mv3::mv3(mv3& v)
{
pImpl = new mv3Impl;
*pImpl = *(v->pImpl);
}

mv3& mv3:perator= ( const mv3& RHS)
{
pImpl = new mv3Impl; /* <----------------Do I need this line??
*/

No. You are assigning to an already existing object, so it will already have
allocated some memory.

*pImpl = *(RHS->pImpl);

}

Do i need the line that allocates memory or will this create a memory
leak?

A memory leak.

What functions are called in:

mv3 a;
mv3 b = a;

First line - default constructor
Second line - copy constructor

John

 

[Jeff Flinn]

Hi,
I'm writing a vector class:

//mv3.h

class mv3Impl;

class mv3
{
public:
mv3();
mv3(mv3&);
mv3& operator= ( const mv3& RHS);

private:
mv3Impl* pImpl;
};



//mv3.cpp

class mv3Impl
{
public:
float x,y,z;
};

mv3::mv3()
{
pImpl = new mv3Impl;
pImpl->x = pImpl->y = pImpl->z = 1.0f;
}

mv3::mv3(mv3& v)
{
pImpl = new mv3Impl;
*pImpl = *(v->pImpl);
}

mv3& mv3:perator= ( const mv3& RHS)
{
pImpl = new mv3Impl; /* <----------------Do I need this line??
*/
*pImpl = *(RHS->pImpl);

}

Do i need the line that allocates memory or will this create a memory

leak?

Yes, In addition to the already existing memory leak(s). Think about it.

Jeff F

 

[Jeff Flinn]

Should be

mv3(const mv3&);

Also here:

 

[E. Robert Tisdale]

Michael wrote:

[snip]

Take a look at
The C++ Scalar, Vector, Matrix and Tensor class library

http://www.netwood.net/~edwin/svmtl/

 

[Michael]

delete pImpl;

in the destructor

Cheers guys

 

[Michael]

Sorry But I can't see the relevance, please explain further.
Fanks
Mike

 

[John Harrison]

Sorry But I can't see the relevance, please explain further.
Fanks
Mike

More or less any post that is about vectors and the like, Robert advertises
his vector library.

john