CODEWITHSUNDEEP
c++cc-preprocessor
dragonroot
dragonroot

Reputation: 5821

Valid characters for file name in the #include directive

What are the valid characters for the file name in the #include directive?

Under Linux, for example, I can use pretty much any character except / and \0 to have a valid file name, but I would expect C preprocessor to be more restrictive about the names of files I can include.

Upvotes: 3

Views: 1894

Answers (1)

Barry
Barry

Reputation: 302817

In C++, the source character set is defined in [lex.charset]:

The basic source character set consists of 96 characters: the space character, the control characters representing horizontal tab, vertical tab, form feed, and new-line, plus the following 91 graphical characters:14

a b c d e f g h i j k l m n o p q r s t u v w x y z

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

0 1 2 3 4 5 6 7 8 9

_ { } [ ] # ( ) < > % : ; . ? * + - / ^ & | ~ ! = , \ " '

And the grammar for #includes is anything in the source character set except for characters that would mess with the #include parsing: newlines and >/" depending ([lex.header]):

header-name:
    < h-char-sequence >
    " q-char-sequence "
h-char-sequence:
    h-char
    h-char-sequence h-char
h-char:
    any member of the source character set except new-line and >
q-char-sequence:
    q-char
    q-char-sequence q-char
q-char:
    any member of the source character set except new-line and "

So something like this is perfectly† fine:

#include <hel& lo% world$@-".h>
#include ">.<>."

†For some definition of "perfectly" anyway...

Upvotes: 9

Related Questions