Re: GCJ on arm-linux

[Casey Marshall <csm at gnu dot org>]

Andrew Haley wrote:
> Casey Marshall writes:
>  > 
>  > I'm looking into running GCJ on an arm-linux system, and from some
>  > searching it looks as though we do not yet have full support for this
>  > platform. Is this right?
>  > 
>  > My understanding is that some of the hairy bits for handling null
>  > dereferences, and libffi, are currently missing. Is there anything else
>  > missing?
>  > 
>  > How should I go about determining what's missing, and what is
>  > necessary to implement proper arm-linux support? This stuff feels
>  > under-documented.
> 
> Yeah, we haven't documented what we haven't done.  :-)
> 

Or, uh, what you have.

> I think we're missing the signal handler and libffi invocation
> interface.  
> 
> Signal handlers are simpler than they used to be, for sure.  We'd need
> MD_FALLBACK_FRAME_STATE_FOR.
> 

This I was aware of (and the replies confirmed it). What does this do? I
understand what FFI needs to do, but this is really opaque.

> Where this starts to get rather weird is ARM using non-DWARF unwinder
> data.  I don't know if the ARM unwinder data on your system is DWARF
> or not; I don't know if ARM unwinder data is suitable for the things
> we need to do in Java.
> 

That's a good thing to look out for, thanks for mentioning that.

> But it's easy enought to find out all the answers we need by asking
> the right people.
> 

I'll try to get someone with a deeper understanding of ARM to look at
this on my side.