Yes, this happens inside a single translation unit (.cpp file). However if you have multiple .cpp files which include the same header file you have to reparse i

Yes, this happens inside a single translation unit (.cpp file). However if you have multiple .cpp files which include the same header file you have to reparse it each time. This is because before the inclusion of that header different #defines might have been set (e.g. through other headers), and therefore the content of the header file might be different.