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Home » Tip Bank » C++
Language: C++
Expertise: Beginner
Dec 12, 2001

The Effects of Deleting an Array of Pointers


Suppose we have a class called A. A has a data member p which is a pointer to another object:
 
class A
{
public:
 A() {p = new B[10];}
private:
 int *p;
};

We also have an array of A objects that was allocated using new:
 
A * arr = new A[10];

The question is this: is the p member of A deleted when we delete arr? In other words, does the following statement delete the p member of each A object in arr?
 
delete [] arr;

Not necessarily. If class A doesn't have a destructor that explicitly deletes p, the delete statement above causes a memory leak. If, however, A has a destructor defined like this:
 
A::~A()
{
 delete [] p;
}

Then deleting arr will automatically invoke A's destructor, which will in turn delete the p member of each element in arr. To conclude, operator delete automatically invokes the destructor of its argument. However, it is the programmer's responsibility to make sure that that destructor releases all the dynamically allocated members of its object.
Danny Kalev
 
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