Re: [libobjc] Shouldn't "version" take a long?

[Jose Quinteiro <gentoo at quinteiro dot org>]

Please forgive me if I'm being dense, I'm very new to Objective-C.

The problem was that a class in GNUMail (PGPController) implemented a 
method thusly:

- (NSString *) version
{
  return @"v0.9.1";
}

That method is declared in the GNUMailBundle protocol.  GNUMail would 
segfault when the pointer returned by that method was accessed in any 
way.  I looked at it in gdb and figured out that the pointer was being 
truncated to 4 bytes (I have an LP64 system.)  Renaming the method made 
the truncation and crash go away.

Object.m declares a "version" class method that returns an int. 
NSObject in the GNUStep base library also has a "version" class method 
that returns an int.   I don't know what the rules are in Objective-C 
for overloading by return type, but gcc did not complain when it 
compiled PGPController. (The output from gcc 4.1.2 for that class is at 
the end of this message.)

Incidentally, what are the rules for overloading by return type?  I 
looked around and all I found was this:

"Although identically named class methods and instance methods are 
represented by the same selector, they can have different argument and 
return types."
http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/Articles/chapter_4_section_6.html

Which makes me think that what GNUMail does should be allowed.  I don't 
know where the confusion between pointer and int is coming in.

Thanks,
Jose.




x86_64-pc-linux-gnu-gcc PGPController.m -c \
              -MMD -MP -DGNUSTEP -DGNUSTEP_BASE_LIBRARY=1 
-DGNU_GUI_LIBRARY=1 -DGNU_RUNTIME=1 -DGNUSTEP_BASE_LIBRARY=1 
-D_REENTRANT -fPIC -g -Wall -DDEBUG -fno-omit-frame-pointer -DGSWARN 
-DGSDIAGNOSE -Wno-import -march=nocona -pipe -fno-strict-aliasing 
-fexceptions -fobjc-exceptions -D_NATIVE_OBJC_EXCEPTIONS -fgnu-runtime 
-Wall -Wno-import -fconstant-string-class=NSConstantString 
-I../../Framework/GNUMail -I. 
-I/var/tmp/portage/gnustep-apps/gnumail-1.2.0_pre3/temp/GNUstep/Library/Headers 
-I/usr/GNUstep/Local/Library/Headers -I/usr/GNUstep/System/Library/Headers \
               -o obj/PGPController.o
PGPController.m:743: warning: incomplete implementation of class 
'PGPController'
PGPController.m:743: warning: method definition for 
'-bodyWasDecoded:forMessage:' not found
PGPController.m:743: warning: method definition for 
'-bodyWillBeDecoded:forMessage:' not found
PGPController.m:743: warning: method definition for 
'-bodyWasEncoded:forMessage:' not found
PGPController.m:743: warning: method definition for 
'-bodyWillBeEncoded:forMessage:' not found
PGPController.m:743: warning: method definition for 
'-composeViewAccessoryWillBeRemovedFromSuperview:' not found
PGPController.m:743: warning: class 'PGPController' does not fully 
implement the 'GNUMailBundle' protocol


Andrew Pinski wrote:
> On 9/26/07, Jose Quinteiro <gentoo@quinteiro.org> wrote:
> > Hello,
> >
> > The getter/setter for version in Object.M gets/takes an int, and they
> > eventually get/set the "version" field in struct objc_class.   This
> > field is declared as a long in objc/objc.h.
>
> Why?  Any change here will change the ABI so it incorrect thing to do.
> So the GNUMail issue seems like people are ignoring warnings that GCC
> generates about methods are not declared in the class.
>
> -- Pinski