global declarations

[jsdy at SEISMO.ARPA]

> i have done both of what lauren & yao suggested. have a file called global.h
> which contains:
> 
> 	#ifndef	GLOBAL
> 	#define	GLOBAL	extern
> 	#endif
> 	GLOBAL	int	foo;
> 	GLOBAL	char	bar;
> 
> all files include global.h. from here there are two ways to go about things.
> 1) a file global.c contains:
> 	#define	GLOBAL
> 	#include "global.h"	/* optional */
> 	int	foo = 1;
> 	char	bar;
> ...
> 2) other files just declare a var where they need to, probably only if
>    they desire initialization.

This is almost exactly what I'd rather  n o t  be done.  (Notice, by
the way, that (2) will always conflict with the identical declaration
in (1) if the "extern" storage class is not considered default.)

The C Reference Manual states that a missing storage class defaults
to "extern" outside a function (sec. 8.1, K&R p. 193, last para).
I'd rather leave it at that.  However, many C compilers ignore this.
To be compatible with them, I'd prefer to use an explicit "extern"
in all header (include) files.  Definition and initialisation of a
variable should occur in that module in which that variable is most
used.  (This could be the main module, if the data is (*shudder*)
used everywhere.)  Side benefits:  we don't have to keep travelling
to data.c/global.c to see what something  r e a l l y  is; we may
find that some extern's can become static's; localisation of data
becomes easier; and probably some others.

Joe Yao		(UUCP!seismo!hadron!jsdy / hadron!jsdy at seismo.ARPA)