About C++ memory leak

Question

I want to ask some of the problems about C++ memory leak. And what is my mistake of my programme and how to rewrite the programme to prevent memory leak. Thank you

int **ptr = new int*[5];
for (int i = 0; i < 5; i++)
  ptr[i] = new int (i+1);
delete ptr;

In a toy example like this, it's easy to count the number of new and new[] statements and the number of delete and delete[] statements and see whether they match. You have 1 new[] and 5 news. You have 0 delete[]s and 1 delete. So in this case none of the new[] or new allocations you created are being cleaned up correctly. — Nathan Pierson
– Nathan Pierson, Commented Mar 31, 2022 at 13:47

MikeCAT · Accepted Answer · 2022-03-31 13:43:20Z

4

Don't use raw pointers when avoidable. Use std::vector instead.

std::vector<int> ptr(5);
for (int i = 0; i < 5; i++) {
  ptr[i] = i+1;
}

If you are forced to use raw pointers for some reason, delete whatever you allocated. Also note that you have to use delete[] to delete what is allocated via new[].

int **ptr = new int*[5];
for (int i = 0; i < 5; i++)
  ptr[i] = new int (i+1);

for (int i = 0; i < 5; i++)
  delete ptr[i];
delete[] ptr;

answered Mar 31, 2022 at 13:43

MikeCAT

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Landstalker Over a year ago

The first code follows a vector logic, the second one corresponds to a matrix logic ...

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