clearing a vector of pointers

C++PointersMemory LeaksVector

C++ Problem Overview


Assume I have defined a class like this:

 class foo {
 private: 
    std::vector< int* > v;
 public:
    ...
    void bar1()
    {
       for (int i = 0; i < 10; i++) {
         int *a = new int;
         v.push_back( a );
       }
    };

    void bar2()
    {
       std::vector< int >::iterator it = v.begin();
       for ( ; it != v.end(); it++ )  
         std::cout << (*it);
       v.clear();
    }
 };

In short, I push back some pointers in a vector, later I clear the vector. The question is, does this code has memory leak? I mean by clearing the vector, are the pointers deleted properly?

C++ Solutions


Solution 1 - C++

Yes, the code has a memory leak unless you delete the pointers. If the foo class owns the pointers, it is its responsibility to delete them. You should do this before clearing the vector, otherwise you lose the handle to the memory you need to de-allocate.

   for (auto p : v)
   {
     delete p;
   } 
   v.clear();

You could avoid the memory management issue altogether by using a std::vector of a suitable smart pointer.

Solution 2 - C++

I think the shortest and clearest solution would be:

std::vector<Object*> container = ... ;
for (Object* obj : container)
    delete obj;
container.clear();

Solution 3 - C++

Nope you only clear the vector storage. Allocated memory with 'new' is still there.

for (int i =0; i< v.size();i++)
   {
     delete (v[i]);
   } 
   v.clear();

Solution 4 - C++

You can use for_each :

std::vector<int*> v;

template<typename T>
struct deleter : std::unary_function<const T*, void>
{
  void operator() (const T *ptr) const
  {
    delete ptr;
  }
};

// call deleter for each element , freeing them
std::for_each (v.begin (), v.end (), deleter<int> ());
v.clear ();

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Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionmahmoodView Question on Stackoverflow
Solution 1 - C++juanchopanzaView Answer on Stackoverflow
Solution 2 - C++Tim KuipersView Answer on Stackoverflow
Solution 3 - C++user349026View Answer on Stackoverflow
Solution 4 - C++tozkaView Answer on Stackoverflow