[Info-vax] disabling a CTRL/Y ast

[Tom Adams]

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