Re: QNX - GNUstep and Objective C

[David Chisnall]

On 8 Jan 2010, at 18:59, bbceler wrote:

> Error: Instance variables in GSAttrDictionary overlap superclass  
> NSObject
> Offset of first instance variable, statbuf, is 8
> Last instance variable in superclass, isa, ends at offset 4
> This probably means that you are subclassing a class from a library,  
> which
> has changed in a binary-incompatible way.

This one should have been fixed - I'm now allowing for alignment.  If  
statbuf only requires alignment of 4 but is being aligned on an 8-byte  
boundary, then this is a bug in clang.  If statbuf really requires  
alignment of 8 then it's a bug in libobjc2.

I don't think clang has a QNX target, so this may be the issue, but  
usually alignment is per-CPU, not per-target.

> Error: Instance variables in GSLocalServerStream overlap superclass
> GSSocketServerStream
> Offset of first instance variable, _serverAddr, is 158
> Last instance variable in superclass, _address, ends at offset 160
> This probably means that you are subclassing a class from a library,  
> which
> has changed in a binary-incompatible way.

This one is more concerning.  The sockaddr ivar from  
GSSocketServerStream
  appears to end two bytes after the first ivar declared in  
GSLocalServerStream.


> Function __objc_compute_ivar_offsets() be called out 379 times.

Yes, it's called once per class.

> For two
> classes GSAttrDictionary and GSLocalServerStream appeared mistake.
> It can from this was infer, that mistake however appears in  
> different place
> ?

In both cases, the first instance variable is a structure, but I'm not  
sure that this makes a difference.  Unfortunately, they're both  
structures from system headers, so I can't reproduce the same  
situation on other platforms...

Do you get different behaviour if you compile these two classes with  
GCC?  I note that you're using the GCC ABI with clang, so you should  
get equivalent code from both compilers; if you don't then it's a bug.

David

-- Send from my Jacquard Loom