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

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In article <too60g$vit$1 at gioia.aioe.org>, =?UTF-8?Q?Arne_Vajh=c3=b8j?= <arne at vajhoej.dk> writes:
>On 12/30/2022 8:53 PM, Craig A. Berry wrote:
>> On 12/30/22 5:50 PM, Arne Vajhøj wrote:
>>> Where does f$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
>
>

Here's a hint:

SDA> EXAMINE @(CTL$AG_CLIDATA+PPD$L_PRC)+PRC_W_PROCLEVEL

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