Does std::vector.clear() do delete (free memory) on each element?

c++ std
Ignas Limanauskas picture Ignas Limanauskas · Feb 27, 2009 · Viewed 87.4k times · Source

Consider this code:

#include <vector>

void Example()
{
    std::vector<TCHAR*> list;
    TCHAR* pLine = new TCHAR[20];
    list.push_back(pLine);
    list.clear();    // is delete called here?
    // is delete pLine; necessary?
}

Does list.clear() call delete on each element? I.e. do I have to free the memory before / after list.clear()?

Answer

Beno&#238;t picture Benoît · Feb 27, 2009

std::vector does call the destructor of every element it contains when clear() is called. In your particular case, it destroys the pointer but the objects remain.

Smart pointers are the right way to go, but be careful. auto_ptr cannot be used in std containers. boost::scoped_ptr can't either. boost::shared_ptr can, but it won't work in your case because you don't have a pointer to an object, you are actually using an array. So the solution to your problem is to use boost::shared_array.

But I suggest you use std::basic_string<TCHAR> instead, where you won't have to deal with memory management, while still getting the benefits of working with a string.

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