Question--EXTERN: good or bad (or neutral)?

Question--EXTERN: good or bad (or neutral)?

[Elena Zannoni]

How do people feel about this thing in buildsym.h?

/* [...]
   Variables declared in this file can be defined by #define-ing the
   name EXTERN to null.  It is used to declare variables that are
   normally extern, but which get defined in a single module using
   this technique.  */

#ifndef EXTERN
#define	EXTERN extern 
#endif


buildsym.c does this:


/* Ask buildsym.h to define the vars it normally declares `extern'.  */
#define	EXTERN
/**/
#include "buildsym.h"		/* Our own declarations */
#undef	EXTERN


while the other files that need those variables, simply include
buildsym.h w/o redefining EXTERN.


Same thing occurs with stabsread.h and stabsread.c.


Is there any reason for not moving the definitions into the .c files?

Elena

Re: Question--EXTERN: good or bad (or neutral)?

[Kevin Buettner]

On Aug 1,  6:45pm, Elena Zannoni wrote:

> How do people feel about this thing in buildsym.h?
> 
> /* [...]
>    Variables declared in this file can be defined by #define-ing the
>    name EXTERN to null.  It is used to declare variables that are
>    normally extern, but which get defined in a single module using
>    this technique.  */
> 
> #ifndef EXTERN
> #define	EXTERN extern 
> #endif
> 
> 
> buildsym.c does this:
> 
> 
> /* Ask buildsym.h to define the vars it normally declares `extern'.  */
> #define	EXTERN
> /**/
> #include "buildsym.h"		/* Our own declarations */
> #undef	EXTERN
> 
> 
> while the other files that need those variables, simply include
> buildsym.h w/o redefining EXTERN.
> 
> 
> Same thing occurs with stabsread.h and stabsread.c.
> 
> 
> Is there any reason for not moving the definitions into the .c files?

If you *really* need lots of global variables, the EXTERN trickery
could be a good thing because it could make maintenance easier.  I.e,
when you want to change one of the types, it would only need to be
changed in one spot and you don't have diverging comments, etc.

However, I think we're taking the viewpoint these days that macro
trickery like the above is bad style.  In addition, we shouldn't be
defining that many global variables anyway.  In fact, we *should* be
attempting to eliminate as many of these globals as we can.  So, I see
nothing wrong with making these globals more painful to use and
maintain.  That way, when one of us wants to change one of these,
perhaps we'll take a look at the code and find a way to do the same
job without the global.

(So, yes, I think moving the definitions into a .c file is a good idea.)

Kevin

Re: Question--EXTERN: good or bad (or neutral)?

[Elena Zannoni]

Kevin Buettner writes:
 > On Aug 1,  6:45pm, Elena Zannoni wrote:
 > 
 > > How do people feel about this thing in buildsym.h?

 > > Is there any reason for not moving the definitions into the .c files?
 > 
 > If you *really* need lots of global variables, the EXTERN trickery
 > could be a good thing because it could make maintenance easier.  I.e,
 > when you want to change one of the types, it would only need to be
 > changed in one spot and you don't have diverging comments, etc.
 > 
 > However, I think we're taking the viewpoint these days that macro
 > trickery like the above is bad style.  In addition, we shouldn't be
 > defining that many global variables anyway.  In fact, we *should* be
 > attempting to eliminate as many of these globals as we can.  So, I see
 > nothing wrong with making these globals more painful to use and
 > maintain.  That way, when one of us wants to change one of these,
 > perhaps we'll take a look at the code and find a way to do the same
 > job without the global.

Yes, I haven't actually even looked at how many of these globals need
to be exported. Maybe it is the case that only a few are actually
necessary in the .h file. 

 > 
 > (So, yes, I think moving the definitions into a .c file is a good idea.)
 > 

Yeah. Lots of low hanging fruits in those files.


 > Kevin

Elena

Re: Question--EXTERN: good or bad (or neutral)?

[Elena Zannoni]

Andrew Cagney writes:
 > > How do people feel about this thing in buildsym.h?
 > 
 > 
 > I think you've just found use 438 for a partial-stab.h printout .....
 > 

No comment! :-)

 > 
 > > Is there any reason for not moving the definitions into the .c files?
 > 
 > 
 > Per Kevin's comments, it was a good idea at the time.
 > I can't think of a good reason for hanging on to it.
 > 

Yeah. I 'suspected' we all would think this way. I posted that for
amusement value, more than anything else. The stuff has been there
since October of 91.

 > 	Andrew

Elena