Re: [xmlvm-users] Multiple inner classes inheriting from each other lead to a gcc error.

[Arno P. <ar...@pu...>]

Brian,

you are certainly pushing XMLVM to the limits. I do agree with you that 
a native Objective-C version would be the way to go. But one can 
certainly argue that there is a bug because we cannot handle the code 
you try to cross-compile.

Can you please do me a favor and generate a small, self-contained 
example that demonstrates the problem? That would be the easiest for me 
to investigate and (hopefully) fix the bug.

Arno


Brian Schimmel wrote:
> Hi,
> 
> I'm completely new to XMLVM, but due to the external circumstances, I'm 
> forced to do something rather advanced with it, that is, a 
> crosscompilation of the Java 6.0 Collections Framework to Objective C. 
> You might argue that it might be better to use native Objective C 
> collections and write bridges, but as I need to get the same behaviour 
> as on Java, I thought crosscompiling would be nice. To make things 
> easier for XMLVM I already used Retrotranslator to crosscompile the Java 
> 6.0 classes to Java 1.2, and checked their validity on J2ME. As far as I 
> can tell, my Java classes are 1.2 compilant and working, but 
> crosscompilation to Objective C has its quirks.
> 
> Let me first outline the class layout:
> 
> abstract class AbstractList extends AbstractCollection implements List
> {
>     class Itr implements Iterator
>     {
>         //...
>     }
> 
>     class ListItr extends Itr implements ListIterator
>     {
>         //...
>     }
> 
>     //..
> }
> 
> AbstractList has two inner classes and one of those inherits from the 
> other one. The problem is, that both AbstractList$Itr and 
> AbstractList$ListItr have the following synthetic member in their bytecode:
> 
> final synthetic AbstractList this$0;
> 
> Crosscompilation to Objective C works fine and yields two files, each 
> having the line
> 
> @public packagename_AbstractList_* this$0;
> 
> but because one class extends the other, I get this error from gcc:
> 
> error: duplicate member 'this$0';
> 
> One option would be to change my Java code, but the Collections 
> Framework has at least 4 Classes with multiple (even more than two) 
> inner classes which inherit from each other. So I guess this case should 
> somehow be handled by the XMLVM crosscompiler, but I'm completely unsure 
> how this would be done. When emitting the interface in xmlvm2objc.xsl, 
> we would need to check if there is any superclass which is also an inner 
> class, thus having a this$0 field. I think this might be beyond the 
> complexity of what should be done here, isn't it?
> 
> Im happy about any advice.
> 
> With best regards,
> Brian
> 
> 
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