[Info-vax] CRTL and RMS vs SSIO

[Simon Clubley]

On 2021-10-12, Arne Vajhøj <arne at vajhoej.dk> wrote:
> On 10/12/2021 1:57 PM, Simon Clubley wrote:
>> BTW, I wonder, with the required changes for the new filesystems
>> for disks >2TB, if VSI will still support Macro-32 with the new
>> filesystems or if we are moving to data structures with abstracted
>> pointer sizes (and subroutine interfaces) just as in Unix and elsewhere.
>
> I think your view of *nix is a bit too rosy.
>
> Try read about lseek vs llseek vs lseek64, off_t vs off64_t vs loff_t
> and how they behave depending on whether #define _FILE_OFFSET_BITS 64
> is used or not.
>

Not really. Those are all about maximum supported file sizes.

VMS has a major additional problem that no other operating systems do
in that the size of an address is directly visible in program-visible
system call structures instead of being abstracted away by the compiler.

This is because the lowest supported application language on VMS is
Macro-32 but the lowest supported application language on those
other operating systems is C which has a pointer data type that
programs don't generally care about the size of.

About the only place I can immediately think it where does matter
elsewhere is in bounce buffers and there are supported interfaces
for those.

VMS is still a really good operating system for some things (such as
clustering) but design decisions make it much harder to port than with
other operating systems.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.