title: Using const char* as key for map/unordered_map
body: <p>How to create map/unordered_map that will use <code>const char*</code> as key directly?</p>
  
  <p>If I use <code>map&lt;std::string,..&gt;</code>, then on each resolving <code>map["abc"] = ...</code> a new <code>std::string</code> object will be created. That causes a big overhead for allocating memory, creating a string object and copying the string into it.  </p>
  
  <p>How do I declare a map object that uses <code>const char*</code> directly without any overhead?</p>