[Info-vax] disabling a CTRL/Y ast
Tom Adams
tadamsmar at gmail.com
Fri Jan 8 10:23:54 EST 2016
On Friday, January 8, 2016 at 10:06:17 AM UTC-5, VAXman- wrote:
> In article <81b88a19-35af-4ca5-83eb-3c795c01c219 at googlegroups.com>, Tom Adams <tadamsmar at gmail.com> writes:
> >On Friday, January 8, 2016 at 9:42:40 AM UTC-5, VAXman- wrote:
> >> In article <1467ade2-ca54-4282-adf6-685268571cbd at googlegroups.com>, Tom Adams <tadamsmar at gmail.com> writes:
> >> >On Thursday, January 7, 2016 at 11:21:27 AM UTC-5, VAXman- wrote:
> >> >> In article <3a583568-e33e-446e-9805-6ea94f9ebf71 at googlegroups.com>, Tom Adams <tadamsmar at gmail.com> writes:
> >> >> >On Wednesday, January 6, 2016 at 12:22:06 PM UTC-5, Stephen Hoffman wrote:
> >> >> >> On 2016-01-06 16:46:32 +0000, Tom Adams said:
> >> >> >>
> >> >> >> > I want to turn ctrl/y into a noop in certain regions of code and turn
> >> >> >> > ctrl/y into an exit in other regions of code.
> >> >> >>
> >> >> >> Some background: I've posted more than a few replies here in the
> >> >> >> comp.os.vms newsgroup, specifically discussing the particular
> >> >> >> application in question and its general design, and an unfortunate
> >> >> >> aggregation of the UI and the more critical code paths, and your
> >> >> >> understandable preference to avoid restructuring the application code
> >> >> >> through reworking the existing design to block ^Y from arriving within
> >> >> >> the most critical sections of the code.
> >> >> >>
> >> >> >> > I do find that it is necessary to run lib$disable_ctrl at the beginning
> >> >> >> > of the program and lib$enable_ctrl at the end of the program to restore
> >> >> >> > the previous CLI state, but I need to run asts to do the rest.
> >> >> >>
> >> >> >> If you want ASTs in some parts of the code and not in others, then
> >> >> >> you're going to have to wrap those sections appropriately. That's if
> >> >> >> you don't decide to migrate those critical code sections into another
> >> >> >> process context, or related steps. Because beyond the potential for ^Y
> >> >> >> in these sections and the associated issues you're having with the
> >> >> >> image rundown processing in the absence of an EXIT command, other sorts
> >> >> >> of generic application failures ("bugs") or any arriving $forcex calls
> >> >> >> or such activities can potentially still leave the application in an
> >> >> >> indeterminate state.
> >> >> >>
> >> >> >>
> >> >> >>
> >> >> >> --
> >> >> >> Pure Personal Opinion | HoffmanLabs LLC
> >> >> >
> >> >> >Here's an example of what I am trying to do that seems to work OK.
> >> >> >I guess a forced exit from a bug could leave the CTRL\Y in
> >> >> >the disabled state at the CLI instead of the original state.
> >> >> >
> >> >> >Also, it's possible that someone could define TT to be some terminal
> >> >> >other than the login terminal. VMS leaves all the built-in process
> >> >> >logicals that refer to the login terminal vulnerable to redefinition.
> >> >> >It may be possible to roll your own safe (executive, no_alias) logical
> >> >> >name via a call in syslogin.
> >> >> >
> >> >> >Also, I still need to cover the cases where this code runs in a context
> >> >> >where TT is not defined.
> >> >>
> >> >> PROGRAM MY_TERMINAL
> >> >> IMPLICIT NONE
> >> >>
> >> >> INCLUDE '($DSCDEF)'
> >> >> INCLUDE '($JPIDEF)'
> >> >> INCLUDE '(LIB$ROUTINES)'
> >> >>
> >> >> INTEGER*4 STATUS
> >> >>
> >> >> RECORD /DSCDEF1/ TERMINAL
> >> >>
> >> >> TERMINAL.DSC$W_MAXSTRLEN = 0
> >> >> TERMINAL.DSC$B_DTYPE = DSC$K_DTYPE_T
> >> >> TERMINAL.DSC$B_CLASS = DSC$K_CLASS_D
> >> >> TERMINAL.DSC$A_POINTER = 0
> >> >>
> >> >> STATUS = LIB$GETJPI(JPI$_TERMINAL,,,,TERMINAL,)
> >> >> IF (STATUS.AND.1) THEN
> >> >> STATUS = LIB$PUT_OUTPUT(TERMINAL)
> >> >> ENDIF
> >> >>
> >> >> CALL SYS$EXIT(%VAL(STATUS))
> >> >> END
> >> >>
> >> >> --
> >> >> VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG
> >> >>
> >> >> I speak to machines with the voice of humanity.
> >> >
> >> >There is an issue.
> >> >
> >> >MY TERMINAL returns a blank string when you spawn it off the CLI:
> >> >
> >> >SPAWN RUN MY_TERMINAL
> >>
> >> No there's not. There's not terminal associated with the spawned subprocess;
> >> there's a mailbox used instead.
> >>
> >>
> >>
> >> >But (oddly enough) the TT logical name is defined in that spawned interactive process. The process has TT, SYS$COMMAND and all that but no login terminal returned by GETJPI. And, it
> >>
> >> >
> >> >This user interface program I am trying to improve gets used in all sort of processes: interactive processes, spawned interactive processes, batch jobs, detached processes, processes spawned by detached processes.
> >> >
> >> >I think the best thing to do is for the program use the special processing for CTRL/Y in all interactive processes.
> >> >
> >> >But, I cannot use the login terminal from GETJPI in a spawned interactive process.
> >> >
> >> >I can think of some options:
> >> >
> >> >1. use TT
> >> >2. use TT with a "_" added to the front
> >> >3. do not provide the special processing in detached interactive processes. Maybe just disable CTRL/Y in that case.
> >> >
> >> >BTW, when you hit CTRL/Y in an image in the spawned interactive process, it kills the process, it does not suspend the image. It acts differently from a normal interactive process.
> >> >
> >> >Is there some way to tell if you are in a spawned interactive process other than checking with GETJPI for the lack of a login terminal name?
> >>
> >> Do I need to write the whole program for you? :)
> >
> >A least the OS calls, apparently.
> >
> >>
> >> I'd first determine of the process IS a subprocess. Then, find the master PID
> >> of that process and pass it to the LIB$GETJPI as the second argument. That'll
> >> get you the terminal from the master/parent process.
> >>
> >>
> >> PROGRAM MY_TERMINAL
> >> IMPLICIT NONE
> >>
> >> INCLUDE '($DSCDEF)'
> >> INCLUDE '($JPIDEF)'
> >> INCLUDE '($STSDEF)'
> >> INCLUDE '(LIB$ROUTINES)'
> >>
> >> INTEGER*4 STATUS, MASTER_PID
> >> RECORD /DSCDEF1/ TERMINAL
> >>
> >> TERMINAL.DSC$W_MAXSTRLEN = 0
> >> TERMINAL.DSC$B_DTYPE = DSC$K_DTYPE_T
> >> TERMINAL.DSC$B_CLASS = DSC$K_CLASS_D
> >> TERMINAL.DSC$A_POINTER = 0
> >>
> >> STATUS = LIB$GETJPI(JPI$_MASTER_PID,,,MASTER_PID,,)
> >> IF (STATUS.AND.STS$M_SUCCESS) THEN
> >> STATUS = LIB$GETJPI(JPI$_TT_PHYDEVNAM,MASTER_PID,,,TERMINAL,)
> >> IF (STATUS.AND.STS$M_SUCCESS) THEN
> >> STATUS = LIB$PUT_OUTPUT(TERMINAL)
> >> ENDIF
> >> ENDIF
> >>
> >> CALL SYS$EXIT(%VAL(STATUS))
> >> END
> >>
> >> --
> >
> >That one even works for:
> >
> >SPAWN SPAWN SPAWN SPAWN RUN MY_TERMINAL
>
> Yup.
>
> For shits and giggles, I added the '_' for you too so that $ASSIGN will be
> able to assign a channel even if there's some strange logical definiiton in
> the process that looks like the terminal's name.
>
> PROGRAM MY_TERMINAL
> IMPLICIT NONE
>
> INCLUDE '($DSCDEF)'
> INCLUDE '($JPIDEF)'
> INCLUDE '($STSDEF)'
> INCLUDE '(LIB$ROUTINES)'
> INCLUDE '(STR$ROUTINES)'
>
> INTEGER*4 STATUS, MASTER_PID
> RECORD /DSCDEF1/ TERMINAL
>
> TERMINAL.DSC$W_MAXSTRLEN = 0
> TERMINAL.DSC$B_DTYPE = DSC$K_DTYPE_T
> TERMINAL.DSC$B_CLASS = DSC$K_CLASS_D
> TERMINAL.DSC$A_POINTER = 0
>
> STATUS = LIB$GETJPI(JPI$_MASTER_PID,,,MASTER_PID,,)
> IF (STATUS.AND.STS$M_SUCCESS) THEN
> STATUS = LIB$GETJPI(JPI$_TT_PHYDEVNAM,MASTER_PID,,,TERMINAL,)
> IF (STATUS.AND.STS$M_SUCCESS) THEN
> STATUS = STR$PREFIX(TERMINAL,%DESCR('_'))
> IF (STATUS.AND.STS$M_SUCCESS) THEN
> STATUS = LIB$PUT_OUTPUT(TERMINAL)
> ENDIF
> ENDIF
> ENDIF
>
> CALL SYS$EXIT(%VAL(STATUS))
> END
>
> This has been fun. I haven't written much FORTRAN since my days as the chief
> simulation guru on the Navy's HITS DATPG project at the NAEC (Naval Engineer-
> ing Center) in Lakehurst. The only other major FORTRAN was a project called
> EGRESS for the laboratory access control at the Myers Center (the HEXAGON) at
> Ft. Monmouth -- now RIF to oblivion and up for sale.
>
> --
The physical login terminal name already has a "_" at the front. So you are adding another "_".
I found that one "_" is sufficient to keep SYS$ASSIGN from trying to translate
the name.
I don't think that extra "_" adds any robustness, but maybe you know of a test case that I did not try.
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