Question

If I have the following code,

Foo *f = new Foo(); vector<Foo*> vect; vect.push_back(f); // do stuff vect.erase(f); 

Did I create a memory leak? I guess so, but the word erase gives the feeling that it is deleting it.

Writing this, I am wondering if it is not a mistake to put a pointer in a STL vector. What do you think?

Answer 1

Yes, you created a memory leak by that. std::vector and other containers will just remove the pointer, they won’t free the memory the pointer points to.

It’s not unusual to put a pointer into a standard library container. The problem, however, is that you have to keep track of deleting it when removing it from the container. A better, yet simple, way to do the above, is to use boost::shared_ptr:

{      boost::shared_ptr<foo> f(new foo);      std::vector< boost::shared_ptr<foo> > v;     v.push_back(f);     v.erase(v.begin()); } /* if the last copy of foo goes out of scope, the memory is automatically freed */ 

The next C++ standard (called C++1x and C++0x commonly) will include std::shared_ptr. There, you will also be able to use std::unique_ptr<T> which is faster, as it doesn’t allow copying. Using std::unique_ptr with containers in c++0x is similar to the ptr_container library in boost.