How to check if bool already exists

Question

I an developing a lib for use on an embedded platform. I have code in a header that is part of the lib with typdef enum bool {false, true} bool;

If the lib user has already defined a type named bool, how can I code this so that my lib does not attempt to re-declare it?

Currently I have used #defines

#ifndef _BOOL 
#define _BOOL 
typedef enum bool{...
#endif

however this depends on a user that has bool defined also defining _BOOL

Is there a way of checking if types`with specific names already exist?

(Note this is a C Question, not C++, and neither I nor my assumed lib user is using stdbool, Ta)

If the platform is embedded, you should already know if `bool` exists, shouldn't you? — WhozCraig, Apr 21 '13 at 19:46
Not if I create the lib and it is called by another author's application (on same platform) that may define bool itself?? — Toby, Apr 22 '13 at 12:47

score 5 · Accepted Answer · edited May 23 '17 at 12:18

5

You can't.

Your library probably should just define its own, distinct boolean type:

typedef enum { libname_false, libname_true } libname_bool;

Within your library implementation you could alias those to more convenient names as you desire.

Incidentally, you should not name preprocessor macros with leading underscores; those names are reserved for the compiler.

edited May 23 '17 at 12:18

Community

1
1

answered Apr 21 '13 at 19:46

jamesdlin

81,374
13
159
204

score 1 · Answer 2 · answered Apr 21 '13 at 19:42

I would go a way you going now, supplying some kind of your_lib_config.h with #defines like HAS_BOOL_DEFINED or anything similar which affects your library configuration. So user will be responsible to adjust settings in config header before using your library.

How to check if bool already exists

2 Answers2