[Insight-developers] Vector::Get_vnl_vector() leaks

[Bill Hoffman]

1. There are two versions, one is const and one is not.  
The const one makes a copy of the itkVector, because once it is
being pointed to by a vnl_vector_ref, then the values could be changed.
So which one gets called depends on the constness of aa and not the 
lvalue of the operator=.

2. There is a leak.   I will add a copy constructor to vnl_vector_ref.
Brad checked the standard, and the parent class copy constructor is called
if one is not provided in the child.

-Bill


At 06:56 PM 7/24/2001 -0700, Lydia Ng wrote:

>FYI: There some memory leak problems with
>Vector::Get_vnl_vector.
>
>--------------------------
>Firstly there are two version of of Get_vnl_vector()
>one that returns a vnl_vector_ref and one that returns
>a vnl_vector
>
>I would expect that for:
>
>vnl_vector<double> bb = aa.Get_vnl_vector();
>
>the vnl_vector version would be called.
>But instead vnl_vector_ref version is called both
>in VC++ and gcc (Cygwin)!
>
>I don't think this is the desired effect.
>
>---------------------------
>
>In Get_vnl_vector() a vnl_vector_ref is created internally
>and returned:
>
>template<class T, unsigned int TVectorDimension>
>vnl_vector_ref< T >
>Vector<T, TVectorDimension>
>::Get_vnl_vector( void )
>{
>  vnl_vector_ref< T > vector_ref( TVectorDimension,
>this->GetDataPointer() );
>  return vector_ref;  /* <=== Copy constructor called here */
>}
>
>However, a copy constructor is called on the return statement.
>
>Since vnl_vector_ref doesn't have any copy constructors the
>vnl_vector(const vnl_vector &)constructor is called instead.
>Hence, there is allocation of new memory and element-by-element
>copying.
>
>Worst still in the vnl_vector_ref destructor, the data pointer
>is set to NULL - because it doesn't want to release memory
>it doesn't own!
>Thus, the memory allocated by the copy construction
>at the return statement is not release
>- hence a memory leak.
>
>This seems to occur both on VC++ and gcc (Cygwin).
>
>-----------------------------
>
>Lydia