Re: macros

[David Relson]

At 07:33 PM 2/22/01, ian.mondragon@bankofamerica.com wrote:
> all -
>
> a message on the dev list reminded me of this long standing question of
> mine:
>
> why do so many people use the RELEASE(foo) and AUTORELEASE(foo) macros
> instead of just typing out [foo release] or [foo autorelease] ?  they do the
> same thing, but i just fail to see the logic in using the macro.
>
> thanks.

Ian,

The macros have different definitions depending on the environment.  I 
don't recall all the particulars, but I remember seeing one set of 
definitions for garbage collection and another set of autorelease pools.

While looking at the macros and their usage, I did notice an oddity:  In 
approx 6 modules, both AUTORELEASE and RETAIN are used.  For example in 
NSTimeZone.m, the following lines appear:

        zone = AUTORELEASE(RETAIN(defaultTimeZone));
        zone = AUTORELEASE(RETAIN(systemTimeZone));

These seem really odd.  First, using both RETAIN and AUTORELEASE gives an 
expensive NOP - their effects cancel one another (in an involved, 
time-consuming manner).  Second, with NextStep it was considered a mistake 
to call autorelease twice for the same object.  Tracing through the code, I 
found 3 occurrences of the defaultTimeZone in the autorelease pool.

Looking in NSObject.h, unless the user has defined his/her own AUTORELEASE 
and RETAIN macros, the definitions will either be simple object references, 
i.e. AUTORELEASE(RETAIN(o)) is simply "o", or will be message sends of both 
retain and autorelease, i.e. "[[ o retain ] autorelease ]".  I can see no 
reason for wanting this latter construct.  Am I missing something?  Should 
I submit patches to change the modules using AUTORELEASE(RETAIN(obj))?

David
--------------------------------------------------------
David Relson                   Osage Software Systems, Inc.
relson@osagesoftware.com       Ann Arbor, MI 48103
www.osagesoftware.com          tel:  734.821.8800