Question

Possible Duplicate:
Proper stack and heap usage in C++?
Heap vs Stack allocation

I’m trying to understand why a Library I ported from Java to C++ (long and arduous editing work after using a converter) doesn’t free up memory and just explodes the Virtual Memory till crash.
Obviously this has to do with Java having a GC and C++ not – and the algorithms are pretty straight converted to C++.

So here’s my question. Where and how do I delete allocated memory (Free it)? When I have:

Matrix *mat = new Matrix(args);

I obviously need to end the scope with a delete mat;. Can I avoid this?
Would using Matrix mat(args); be better? in terms of Memory Allocation and freeing?
Or using Matrix mat = Matrix(args)?

Answer 1

Where and how do I delete allocated memory? (Free it)

In most cases, if you coded things properly, you don’t have to explicitly free or de-allocate any memory. Either use automatic allocation, or smart pointers. Otherwise, the answer to where is rather unsatisfying: wherever you need to, depending on your program. The answero to how is simpler: with delete (or delete[] for dynamically allocated arrays).

… I obviously need to end the scope with a delete mat;
Can I avoid this?

Yes, if you use automatic allocation:

Matrix mat(args);

As a general rule, you should only use dynamically allocated objects if you really need to. If you don’t know if you really need to, then you probably don’t.

… Or using Matrix mat = Matrix(args);

This performs a copy initialization, and in this context provides no advantages over Matrix mat(args);. The RHS of the expression is a temporary Matrix object, which gets used to copy construct the LHS mat.

Here is a recent related post.