Re: QNX - GNUstep and Objective C

[David Chisnall]

Hi,

This error will appear if the first instance variable in a class  
appears before the end of the last instance variable in the  
superclass.  In this case, the first instance variable is a 'struct  
stat' and it is (apparently) overlapping with the isa pointer.

It's not clear from your post.  Are you linking against both libobjc2  
(which installs itself as libobjc.so.4) and against GCC libobjc  
(libobjc.so.3 or libobjc.so.2)?  If so, then you can expect things to  
break quite badly, because both export the same symbols.  Please use  
one or the other, not both.  If this is not the problem then...

Both NSObject and GSAttrDictionary are part of -base, so you will have  
compiled them with the same compiler.  The problem is therefore not an  
issue of mismatched compilers, but it may well be something related to  
the ABI handling in clang.  The ivar offset calculation code is not  
yet particularly well tested beyond x86 *NIX platforms.  It is  
possible that there is a bug.

I've just added a bit more debugging code to libobjc2, so it will tell  
you what the name and offsets of the offending ivars are.  Please can  
you run the new version and see what the message is?  Please can you  
also let me know what architecture you are using, so I can check that  
clang is generating the correct IR?

You can also comment out line 787 in libobjc2's init.c.  This will  
revert to the behaviour of the older versions of libobjc and see if  
things actually break.

David

On 3 Jan 2010, at 19:33, bbceler wrote:

> I finished works on porting LLVM and clang on QNX recently. I also  
> compiled
> libobjc2 from GNUstep. clang compiles without problems programs in  
> C. I make
> the tests of the compilation of programs in objc 2.0. That programs  
> do not
> use GNUstep one compiles and they work without problems.
> I have however the problem with compiling programs using GNUstep.  
> Programs
> compiles but while starting the mistake appears:
> ./autogsdoc
> Error: Instance variables in GSAttrDictionary overlap superclass
> NSObjectThis probably means that you are subclassing a class from a  
> library,
> which has changed in a binary-incompatible way.
> Abort (core dumped)
> Because I compiled gnustep-base use gcc runtime I thought that  
> should this
> gnustep-base compile also with the use of clang. I compiled the  
> library
> gnustep-base using clang and libobjc2.
> The effect is the same unfortunately. I did not have problems with  
> programs
> in objc 1.0 and GNUstep.
> Can the problem come into being because of the conflicts gcc libobjc  
> with
> the library libobjc2 from GNUstep ?
>
>
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