[Info-vax] disabling a CTRL/Y ast

[Tom Adams]

On Friday, January 8, 2016 at 9:11:47 AM UTC-5, Tom Adams wrote:
> 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
> 
> 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

I mean translate TT and add a "_" on the front, but now I am thinking I might
as well use TT.

> 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?