Re: Porting from Solaris to Linux problem

[bley at wh2-19 dot st dot uni-magdeburg dot de (Claudio Bley)]

>>>>> "Frank" == Frank Schafer <frank.schafer@setuza.cz> writes:

    Frank> Frank Geck wrote:
    >> Well I have run into a little problem porting some code from
    >> Solaris to Linux.  I think I know what the problem is and I can
    >> think of a lame way to fix it but wanted to know what was the
    >> right way (maybe on Solaris I had been doing it wrong all these
    >> years).  I have 2 files each containing a function and a common
    >> header file with a global variable.  In each file I include the
    >> header file and mark the global as external.  In solaris this
    >> works fine using gcc, in Linux it gives me multi-defined.  Any
    >> thought would be appreciated.
    >> 
    >> Exmple:
    >> 
    >> file: hdr.h int i;
    >> 
    >> file: main.c #include "hdr.h" extern int i; main() { ...  }
    >> 
    >> file: func2.c #include "hdr.h" extern int i; func2() { ...  }

    Frank> Hi,

    Frank> I'd make the following changes:

    Frank> file: hdr.h #ifndef HDR_H #define HDR_H 1

    Frank> extern int i;

    Frank> #endif /* HDR_H */

    Frank> file: main.c #include "hdr.h"

    Frank> main() { ...  }

    Frank> file: func2.c #include "hdr.h"

    Frank> func2() { ...  }

    Frank> This should solve Your problem.

Not quite. `i' has to be defined somewhere, it is not sufficient to
declare it extern.

file: hdr.c
==========

#include "hdr.h"

int i; 

==========

HTH
Claudio