[OpenBIOS] patch to allow Mac OS 9 to boot

[Programmingkid]

On Feb 5, 2016, at 8:17 AM, Mark Cave-Ayland wrote:

> On 05/02/16 13:08, BALATON Zoltan wrote:
> 
>> On Fri, 5 Feb 2016, Mark Cave-Ayland wrote:
>>> The Apple 9.2 bootloader ignores the Forth specification in this respect
>>> and includes direct r-stack commands and hence the return address is
>>> corrupted once they have executed (for fun, try typing r-stack commands
>>> directly into the OpenBIOS command line).
>>> 
>>> So the solution is to find some way to preserve the r-stack in this
>>> context to ensure that execution continues back at the right location.
>> 
>> How does this work on Apple's OF implementation? How is that different
>> from OpenBIOS?
> 
> No idea, since we don't have the source code ;)  However we can assume
> that the only reason this works is due to a specific implementation
> detail of Apple's OF in this respect.
> 
> You can get fairly close by forcing the interpret word to execute in
> compile mode, however that fails as soon as you come across a : to
> define a word which is also present in the Apple bootloader. I guess the
> solution would have to involved switching to a separate r-stack context
> for words executed within the interpret string or similar.
> 
> Segher, did you have any further ideas on this?

I'm not entirely convinced that anything is broken. Mac OS 9 booting successfully in OpenBIOS doesn't translate to me as something being broken, but actually working. 

Maybe when the client interface is running, there should be two return stacks.