#ifndef DIRECTORY HEADERFILE not found

Question

How can I use directory in preprecessor command ifndef

EXAMPLE

#ifndef DIR/HEADERFILE_H 
#include "dir/headerfile.h"
#endif

Use a character the preprocessor allows? `#ifndef DIR_HEADERFILE_H` — Simon Kraemer, Nov 07 '16 at 13:43
What are you trying to achieve? The preprocessor understands text - not directory structures? Once a file has been `#included`d it doesn't then have the filename/directory #defined. — doctorlove, Nov 07 '16 at 13:50
IT IS VERY INTERESTING, WHY I AM GETTING -2? SOME COMMENTS FIRST? — Dušan Tichý, Nov 07 '16 at 14:07

score 1 · Answer 1 · edited May 23 '17 at 10:33

1

As explained in this question, only alphanumeric characters and underscores (a-z, A-Z, 0-9, and _) are allowed for macro and constants names. You can define your own constant replacing / with _:

#ifndef DIR_HEADERFILE_H

edited May 23 '17 at 10:33

Community

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answered Nov 07 '16 at 13:46

SimoV8

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score 1 · Accepted Answer · edited May 23 '17 at 12:10

To answer the specicif question, you cannot use a directory in a preprocessor command like #ifndef.

The include guards in the header file often take the form

#ifndef DIRECTORY_HEADERFILE_INCLUDED
#define DIRECTORY_HEADERFILE_INCLUDED

//.... contents

#endif

To include the header, then simple use

#include "dir/headerfile.h"

A long while ago some people suugested a double include guard, or redundant include guard, wherein you checked before the #include line to speed things up, as mentioned in this question. The c2 wiki has some further information esp.

"Good compilers make this idiom unnecessary. "

In either case the tendacny is to use _ instead of /, to form a valid macro.

#ifndef DIRECTORY HEADERFILE not found

2 Answers2