[Info-vax] f$env("depth") from where?

[Arne Vajhøj]

On 12/30/2022 8:53 PM, Craig A. Berry wrote:
> On 12/30/22 5:50 PM, Arne Vajhøj wrote:
>> Where does f$env("depth") get the value from?
>>
>> Or how does one get that value from a program?
> 
> As far as I know there is only one program where that value has any
> meaning and that program's name is DCL.  I wouldn't expect other
> programs to have the ability to peek into the context of the procedure
> from which they were invoked, if any.

There are a couple of different questions.

Are there any use for getting that info from a program?

In most cases it does not make any sense, but I actually have a
case where it would make sense. Weird code requiring weird
information. Evils tongues may add: due to weird programmer.  :-)

Does the program (user mode) have access to that
part of memory?

I don't know. If the answer is no, then no luck.

If there is access to that memory then how does
one find it?

Which is basically what I am asking.

As an example of something slightly similar, the
code below gets verify status:

         .entry  sys2_verify,^m<>
         movl    #CTL$AG_CLIDATA,r0
         movl    W^PPD$L_PRC(r0),r0
         moval   W^PRC_W_FLAGS(r0),r0
         movzwl  (r0),r0
         bbs     #PRC_V_VERIFY,r0,100$
         movl    #FALSE, at B^4(ap)
         ret
100$:   movl    #TRUE, at B^4(ap)
         ret

Arne