Yes, I saw that too and mention it: > As a corollary, if you include <cctype> rather than <ctype.h> (the C++ version of the C header which puts functions in th

Yes, I saw that too and mention it: > As a corollary, if you include <cctype> rather than <ctype.h> (the C++ version of the C header which puts functions in the std:: namespace) you also get the slow behavior because <cctype> ultimately includes <bits/os_defines.h>.