如何在C ++中删除指向指针的指针的内存

Question

Using Valgrind, I see that I have a problem while deleting the memory in the following function:

Obj1 Obj1::operator*(const Obj1& param) const {
int n = param.GetSize(2);
Obj2** s = new Obj2*[n];
for( int i = 0; i < n; ++i) {
    s[i] = new Obj2(*this*param.GetColumn(i+1));
}
Obj1 res = foo(s,n);
for(int i=n-1;i>-1;i--) {
    s[i]->~Obj2();
}
delete[] s;
return res;

Valgrind tells me that the leak comes from the line

s[i] = new Obj2(*this*param.GetColumn(i+1));

I'm not pretty sure if the problem is when I try to free the memory. Can anyone tell me how to fix this problem?

Answer 1

Here:

 s[i] = new Obj2(*this*param.GetColumn(i+1));

you create a dynamic object and assign s[i] to point to it.

In order to delete it, you do this:

delete s[i];

Unless you do that, the allocation will leak.

You must repeat that in a loop for every i just like you repeated the allocations. You of course have to do this before you delete s itself.

---

 s[i]->~Obj2();

Don't do that. Calling the destructor is not appropriate here. delete will call the destructor.

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PS Don't use raw owning pointers. Use containers or smart pointers instead. std::vector is a standard containers for dynamic arrays.

PPS You should avoid unnecessary dynamic allocation. Your example doesn't demonstrate any need to allocate the pointed objects dynamically. So, in this case you should probably use std::vector<Obj2> .