The use of double include guards in C++

I am pretty sure that it is a bad practice to add another include guard like:

#ifndef __HEADER_A_HPP__
#include "header_a.hpp"
#endif

Here are some reasons why:

1. To avoid double inclusion it is enough to add a usual include guard inside the header file itself. It does the job well. Another include guard in the place of inclusion just messes the code and reduces readability.

2. It adds unnecessary dependencies. If you change include guard inside the header file you have to change it in all places where the header is included.

3. It is definitely not the most expensive operation comparing the whole compilation/linkage process so it can hardly reduce the total build time.

4. Any compiler worth anything already optimizes file-wide include-guards.