Re: Another Objective-C compiler question

[Ziemowit Laski <zlaski at apple dot com>]

I do believe that we (i.e., Apple) already have a fix for this.  Stay 
tuned
for a patch.

--Zem

On Thursday, Sep 5, 2002, at 07:28 US/Pacific, Nicola Pero wrote:

> Hi Paul,
>
> > I have submitted that one to gcc's GNATS.
> Thanks
>
>
> > So I am emboldened to ask about another problem that did not affect 
> > gcc
> > 3.0.4 but does arise in 3.1 and 3.2.
> >
> > This arises when we try to compile the Swarm libraries
> > (http://www.swarm.org).
> >
> > Here is the compiler warning we see:
> >
> > ../../../swarm-2.1.140.20020514/src/analysis/Averager.m: In function
> > `-[Averager update]':
> > ../../../swarm-2.1.140.20020514/src/analysis/Averager.m:153: warning:
> > comparison of distinct pointer types lacks a cast
> > make[1]: *** [Averager.lo] Error 1
> >
> > The compiler's warning focuses on the comparison
> >
> > GETLOC (iter) == (id) Member
> I had a look at your code, and at a quick glance I think your 'Member'
> variable is of type 'id<Index>'.  When you cast it to 'id', because of 
> the
> same compiler bug we have been talking about in the other email :-), 
> the
> cast is ignored.
>
> Then, you are comparing the result of GETLOC (iter) - which is an 'id',
> with Member, which is of type 'id<Index>' (your cast for it to be an 
> 'id'
> having been ignored!) - and the compiler emits a warning because you 
> are
> comparing an 'id' with an 'id<Index>'.
>
> Incidentally, I suspect even this is wrong :-) because if you compare 
> an
> 'id' with any type of other object, no warning should be produced.  I
> think traditionally in ObjC the type 'id' precisely means 'disable any
> compile time type checking when this object is involved'.  I've already
> produced a patch to fix such warnings for type checking, but I need to
> double-check its logic and tidy it up.
>
>
> > So, if you know whether there is a way I should rewrite the Averager
> > class, let me know. If you think it is a gcc bug, let me know.
> To me it looks like your code is correct, and it's the same compiler 
> bug
> as before.
>
> Thanks for reporting!
--------------------------------------------------------------
Ziemowit Laski                 1 Infinite Loop, MS 301-2K
Mac OS X Compiler Group        Cupertino, CA USA  95014-2083
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