#define default value

[malladisk]

Hi, If I'm using a macro
#define VAR
what would be the default value assigned to VAR?
Thanks,
Sashi

 

[Salem]

I don't think VAR is assigned any value

All you can do with it is tell whether its defined or not

#ifdef VAR
    printf( "VAR is defined\n" );
#endif

 

[malladisk]

Ok.
Thanks,
Sashi

 

[chipperMDW]

VAR expands to nothing.

That means the following:

#define VAR

VAR int VAR VAR VAR some_func VAR( VAR int VAR x VAR VAR, VAR float VAR y VAR VAR VAR ) VAR;

expands to:

int some_func( int x, float y );

Whereas if VAR hadn't been defined at all, you'd get a bunch of errors about it.


Sometimes you'll see something like:

#if CONST_WORKS_CORRECTLY
  #define CONST const
#else
  #define CONST
#endif

extern CONST int some_constant;

so that CONST can expand to "const" or expand to nothing, depending on the value of some other macro (probably set in a config header).