No type checking in ctype builtins

[Andrea Monaco]

  > Try -Wsystem-headers.

You're right.  That showed a warning.


  > You need to suppress the macro to get the builtin.

That means a macro expansion takes precedence over a builtin function
substitution, if I understand correctly.  It makes sense, because
preprocessing happens before compilation.

Maybe we could mention that in the manual, for example in "6.59 Other
Built-in Functions Provided by GCC"
(https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html).



Andrea Monaco