[Info-vax] Reimplementing VMS, was: Re: HP adds OpenVMS Mature Product Support beyond the end of Standard Support
Stephen Hoffman
seaohveh at hoffmanlabs.invalid
Wed Feb 5 15:29:45 EST 2014
On 2014-02-05 18:38:30 +0000, hb said:
> On 02/05/2014 07:05 PM, John Reagan wrote:
>>>>>> Extensions and restrictions, necessary to support object file and image
>>>>>> file features that are specific to the OpenVMS operating system, will
>>>>>> be published in a future release.
>>>>
>>>> I don't recall if these extensions were ever generally published.
>> Yes. It is all in the Calling Standard Manual. There is even an
>> appendix listing the differences between the OpenVMS Calling Standard &
>> ABI vs the Intel Itanium Runtime Conventions and ABI. ...
>
> I had the impression Hoff was talking about ELF extensions: starting
> with the VMS specific note entries, the additional field in the ELF
> header for images along the OS defined values for some header fields
> and all the stuff in and appended to the dynamic segment.
What's in Appendix C is an overview. With some digging in the OpenVMS
header files (assuming all the header files for the object files are
present) and comparing that with the Itanium ABI and ELF and DWARF
documentation, a fair amount can probably be teased out from what's in
Appendix C. This would be the documentation that somebody would want
or need, if they were either implementing or modifying a compiler and a
code generator for Itanium (eg: porting llvm to OpenVMS), or that would
be useful as reference documentation when implementing ELF and
(presumably) DWARF support on x86-64.
Whether the DWARF details and any related platform-specific changes are
better documented than the semi-undocumented debugger definitions that
were occasionally available for VAX and Alpha, I'd have to check.
But then this is mostly just entertaining for now, as I don't see an
llvm port to OpenVMS in my own immediate future, nor have I seen any
administrative details nor a potential revenue models discussed that
might make an x86-64 port feasible. If any of this ever becomes
"real", then it'd be very handy to have whatever engineering specs are
available.
--
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