clear-cpp-vector.md

Clearing a C++ vector (and memory it has allocated)

I was recently having a hard time tracking down a memory leak in one of my applications. The documentation for clear is not very clear about the fact that after calling clear, the compiler is not guaranteed to cleanup the space allocated.

There are two ways to handle cleaning up the memory allocated by a vector in this case:

// Shrink method
my_vec.clear();
my_vec.shrink_to_fit(); // Capacity is now 0, memory cleared

// Swap method
vector< int >().swap( my_vec ); // Capacity is now 0