[Info-vax] VMS process communication

[Arne Vajhøj]

On 3/13/2023 5:56 AM, Andreas Gruhl wrote:
> Arne Vajhøj schrieb am Freitag, 10. März 2023 um 22:01:40 UTC+1:
>> Pre-release for comments:
>>
>> https://www.vajhoej.dk/arne/articles/vms64.html

> I like to add, that you can successfully access the lower 2 GB of P2
> (%X00000000 80000000..%X00000000 FFFFFFFF) with 32 bit
> pointers and descriptors.
> You only have to treat the pointers as unsigned instead of signed
> avoiding them to be interpreted as S0/S1 addresses.
> We successfully  use this in Pascal, which is missing 64-Bit descriptors.
> The caller of a routine can then simply pass a structure in lower P2
> without any special adaptions (except having to use the compiler
> qualifier /USAGE=64BIT_TO_DESCR).
> The routine itself has to do some additional work. It must extract the
> structure's address from the descriptor and copy it to a 64-Bit Pointer
> WITHOUT sign extension.
> This makes the structure directly accessible although it resides in P2.

Is /USAGE=64BIT_TO_DESCR new for x86-64?

Arne