#include header guard format?

Question

I know it makes little difference to a project but, assuming you use #defined header guards for your C++ code, what format do you use? e.g. assuming a header called f

Answer 1

Personally, i just use the filename FOO_HPP. Google uses the whole path like SRC_ENGINE_FAST_HPP.

Certain sets of names and function signatures are always reserved to the implementation:

• Each name that contains a double underscore (_ _) or begins with an underscore followed by an uppercase letter (2.11) is reserved to the implementation for any use.
• Each name that begins with an underscore is reserved to the implementation for use as a name in the global namespace.

(17.4.3.1.2/1)