title: How are allocator in C++ implemented?
body: <p>I was trying to understand a bit better <code>std::allocator</code> in C++, I came across <a href="https://softwareengineering.stackexchange.com/questions/238037/why-stdallocators-are-not-that-popular">this question</a>, and it seems to me there's actually only one allocator class typically used by containers (like <code>std::vector</code>) my question is how is such allocator implemented? Is it like a stack which is periodically re-allocated? If not how is it actually implemented?</p>