[Info-vax] VAX VMS going forward

[Stephen Hoffman]

On 2020-07-24 18:51:20 +0000, John Reagan said:

> 
> I've been trying to follow this whole conversation but I might have 
> missed something.
> 
> I don't get this whole hybrid thing.  VMS has a 64-bit flat virtual 
> address layout.
> 
> It is just that only parts of it can be accessed with a 32-bit pointer. 
>  The rest requires a 64-bit pointer.  Due to things like descriptors 
> and itemlists which have a builtin assumption about only holding 32-bit 
> pointers, we go out of our way to make sure that anything that you can 
> take the address of resides in 32-bit space.   On Alpha, Itanium very 
> little S2 is used and no P2 without explicit code or linker qualifiers 
> to do so.  x86 will get code in P2 (and trampolines in 32-bit space so 
> you can still take their address).

Tried building a 64-bit app without having to contend with 32-bit 
giblets including the 32-bit APIs, the 64-bit APIs, and the either-bit 
APIs, and the switch qualifiers to get everything to 64-bit, and the 
stuff that isn't yet 64-bit?

Every time I've tried creating a 64-bit app, I get a sad and revert to 
32-bit with hunks of data up in P2 and/or S2.  At one point—haven't 
verified this limit lately—code wasn't permitted in some of the 
segments.



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