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#946 ERROR on DISPLAY STATEMENT
not-our-bug
5 - default
2024-06-15
2024-02-10
No
The following example program requires typing two fields on the screen, a name and a code.
If nothing is typed then it displays an error message requiring you to type the single field.
See screenshot.
To view the bug, proceed as follows.
a. When the program asks you to type the name, do not type anything but just press Enter see ERR10.PNG
b. The system displays the error message (using some DISPLAYS) see ERR20.PNG
c. Press Enter again to exit from the message
d. The system prompts you to enter the Name field again
e. do not type anything but just press Enter again
f. The program should display the same error message again.
g. The program executes the same DISPLAY statements again but this time the message is not displayed on the screen.
How come ?
>>SOURCE FORMAT IS FREE
REPLACE ==:BCOL:== BY ==with BACKGROUND-COLOR==
==:FCOL:== BY ==FOREGROUND-COLOR==.
IDENTIFICATION DIVISION.
program-id. TESTERROR.
ENVIRONMENT DIVISION.
Configuration Section.
SPECIAL-NAMES.
CRT STATUS IS wKeyPressed.
DATA DIVISION.
*> **************************************************************
WORKING-STORAGE SECTION.
*> **************************************************************
01 Black constant as 00.
01 Blue constant as 01.
01 Green constant as 02.
01 Cyan constant as 03.
01 Red constant as 04.
01 Magenta constant as 05.
01 Orange constant as 06.
01 Brown constant as 06. *> same color code as yellow
01 LightGrey constant as 07. *> Light Gray
01 Grey constant as 08. *> Dark Gray
01 LightBlack constant as 08. *> same color code as Grey
01 LightBlue constant as 09.
01 LightGreen constant as 10.
01 LightCyan constant as 11.
01 LightRed constant as 12.
01 LightMagenta constant as 13.
01 Pink constant as 13.
01 Yellow constant as 14.
01 White constant as 15. *> white
01 AnageRec value space.
03 AnageCodAge pic x(10) value space. *> code AGENT
03 AnageRagSoc pic x(30) value space. *> NAME
*> Values that may be returned in CRT STATUS (or COB-CRT-STATUS)
78 K-ENTER VALUE 0000.
78 K-UP VALUE 2003.
78 K-DOWN VALUE 2004.
78 K-LEFT VALUE 2009.
78 K-RIGHT VALUE 2010.
78 K-ESCAPE VALUE 2005.
78 K-TAB VALUE 2007.
78 K-BACKTAB VALUE 2008.
78 K-PAGEUP VALUE 2001.
78 K-PAGEDOWN VALUE 2002.
01 wKeyPressed PIC 9(04) VALUE 9999.
77 NumFields pic 9(02) value 2. *> number of fields on screen
01 wBox-bco pic 9(02) value cyan.
01 wBox-fco pic 9(02) value black.
01 wRetCode PIC 9999 value zero.
01 wFunc-NumVal PIC 9999 value zero.
77 Pivot pic 9(02) value 01.
77 dbc pic 9(04) value green. *> display backgr.color
77 dfc pic 9(04) value white. *> display foregr.color
77 abc pic 9(04) value 00. *> accept backgr.color
77 afc pic 9(04) value 15. *> accept backgr.color
77 Pro pic x(01) value '_'.
77 wHeader pic x(80) value space.
01 wString pic x(31) value space.
01 ER pic x.
88 NoErrors value 'N'.
88 Errors value 'Y'.
01 wCursorShow BINARY-SHORT SIGNED value 2.
01 wCursorHide BINARY-SHORT SIGNED value 0.
*> SAVE/RESTORE SCREEN VARIABLES
01 wScreenName PIC X(256) value space.
01 wiScrOk BINARY-LONG value zero.
01 Btabmess.
03 Bmess pic x(30) occurs 20 value space.
*> **************************************************************
*> P R O C E D U R E D I V I S I O N
*> **************************************************************
PROCEDURE DIVISION.
set environment 'COB_SCREEN_EXCEPTIONS' TO 'Y'.
set environment 'COB_SCREEN_ESC' TO 'Y'.
set environment 'COB_LEGACY' TO '1'
*> ************************************************************************************
*> D I S P L A Y S C R E E N
*> ************************************************************************************
string ' SAMPLE TEST APPLICATION ' delimited by size into wHeader
display wHeader at 0101 with Background-Color green Foreground-Color white highlight
display ' ESC-<Exit> '
at 2501 with Background-Color green Foreground-Color white
display ' Name ..................:' at 0501 with Background-Color dbc Foreground-Color dfc
display AnageRagSoc at 0527 with Background-Color abc Foreground-Color afc
display ' Code..:' at 0561 with Background-Color dbc Foreground-Color dfc
display AnageCodAge at 0570 with Background-Color abc Foreground-Color afc
continue.
LOOP-ACCEPT.
*> re-show the cursor
call static 'curs_set' using by value wCursorShow end-call
go to acc01 acc02 depending on Pivot.
ACC01.
*> NAME
accept AnageRagSoc at 0527 with Background-Color abc Foreground-Color afc
update prompt character is pro auto-skip reverse-video
go EVALUATE-KEY.
ACC02.
*> CODE
accept AnageCodAge at 0570 with Background-Color abc Foreground-Color afc
update prompt character is pro auto-skip reverse-video
go EVALUATE-KEY.
EVALUATE-KEY.
EVALUATE wKeyPressed
*> ******************************************************************
*> ENTER = CONTROLS ON SCREEN FIELDS
*> ******************************************************************
WHEN K-ENTER
WHEN K-TAB
WHEN K-DOWN
perform CtrFields thru CtrFieldsEx
if Errors
continue
else
*> go to next field on screen
compute Pivot = Pivot + 1
if Pivot > NumFields move 1 to Pivot end-if
end-if
WHEN K-BACKTAB
WHEN K-UP
perform CtrFields thru CtrFieldsEx
if Errors
continue
else
*> go to previous field on screen
compute Pivot = Pivot - 1
*> with following statement, when cursors is on 1st field
*> it remains there (non to go - wrap - on last filed)
if Pivot < 1 move 1 to Pivot end-if
end-if
*> ******************************************************************
*> ESCAPE = EXIT
*> ******************************************************************
when K-ESCAPE
go to END-OF-PROGRAM
END-EVALUATE
GO LOOP-ACCEPT.
*> *****************************************************************************
*> E N D O F P R O G R A M
*> *****************************************************************************
END-OF-PROGRAM.
Goback.
*> *****************************************************************************
*> C H E C K F I E L D S C O N T E N T
*> *****************************************************************************
CtrFields.
set NoErrors to true
go to ctr01 ctr02 depending on Pivot.
CTR01.
if AnageRagSoc = space
set Errors to true
move lightgreen to wbox-bco move white to wbox-fco
move '111111111111111111111111111111' to Bmess(1)
move ' >>> ERROR 1 <<< ' to Bmess(2)
move '111111111111111111111111111111' to Bmess(3)
move ' Please Type a NAME ' to Bmess(4)
move '111111111111111111111111111111' to Bmess(5)
move '111111111111111111111111111111' to Bmess(6)
move '---- enter to return ---------' to Bmess(7)
perform DisplayErrorMessage thru DisplayErrorMessageEx
end-if
go CtrFieldsEx.
CTR02.
if AnageCodAge = space
set Errors to true
move lightred to wbox-bco move yellow to wbox-fco
move '+----------------------------+' to Bmess(1)
move '| >>> ERROR 2 <<< |' to Bmess(2)
move '|2222222222222222222222222222|' to Bmess(3)
move '| Type a CODE !!! |' to Bmess(4)
move '|2222222222222222222222222222|' to Bmess(5)
move '|2222222222222222222222222222|' to Bmess(6)
move '+- Enter to return ----------+' to Bmess(7)
perform DisplayErrorMessage thru DisplayErrorMessageEx
end-if
go CtrFieldsEx.
CtrFieldsEx. exit.
DisplayErrorMessage.
move Z'DUMPSCREEN.TMP' to wScreenName
call static 'scr_dump' using by reference wScreenName returning wiScrOk end-call.
display Bmess(1) at line 04 col 10 :BCOL: wbox-bco :FCOL: wbox-fco
display Bmess(2) at line 05 col 10 :BCOL: wbox-bco :FCOL: wbox-fco
display Bmess(3) at line 06 col 10 :BCOL: wbox-bco :FCOL: wbox-fco
display Bmess(4) at line 07 col 10 :BCOL: wbox-bco :FCOL: wbox-fco
display Bmess(5) at line 08 col 10 :BCOL: wbox-bco :FCOL: wbox-fco
display Bmess(6) at line 09 col 10 :BCOL: wbox-bco :FCOL: wbox-fco
display Bmess(7) at line 10 col 10 :BCOL: wbox-bco :FCOL: wbox-fco
accept omitted
call static 'scr_restore' using by reference wScreenName returning wiScrOk end-call
call static 'refresh' returning wiScrOk end-call
*> CALL 'CBL_DELETE_FILE' USING wScreenName
continue.
DisplayErrorMessageEx. exit.
second screenshot
@engboris after the other one you may want to inspect this, which will possibly lead you to do debugging on screenio.c.
Sorry for the late answer, I forgot about it.
I'm interested. You can assign it to me.
Hi, I have one more clue about the nature of the bug.
Use the following program (almost the same as the previous program, I moved the position of a field on the screen).
The program asks for two fields to be entered.
If you leave the first field blank then the program displays an error message on the screen and expects "enter" from the user.
The message appears correctly the first time you leave the field blank.
If you leave the first field blank and type "enter" more than once then the message will not appear properly from the second time onwards. The DISPLAY doesn't work !
The DISPLAY displays only the part of the message that overlaps with the first input field !
The same behavior happens on the second field.
The second error message DISPLAY displays only the part of the message that overlaps with the second input field !
I think it's a pretty serious bug!
ERR310 320 and 330 are screenshot for first field
ERR 410 420 and 430 are screenshot for second filed
Hi, this bug is very disturbing in the development of TUI interfaces.
Are there any updates and hopes for its resolution?
Hello. I will investigate it very soon.
thank you very much from me too.
Please feel free to contact me with anything I can contribute.
I am sorry for the delay although I accepted to be assigned to this bug.
I recommend to put the command line you use to compile for bug reports. I tried to execute your code but did not exactly obtain the same behaviour as you: both programs exit with
attempt to reference unallocated memory (signal SIGSEGV)after typing ENTER two times.After a first glance, it looks like it is an error related to memory and more precisely to the
call static 'scr_dump'andcall static 'src_restore'statements at the end.I will dig into it more later but what could help is to provide a minimal example where this bug occurs. Something as simple as possible.
Did you run this under Linux ?
Vince
Last edit: Simon Sobisch 2024-06-07
Yes, I did.
If this is of any importance, I'm a new contributor but I can still give this bug a try. However, if there is somebody willing to do it, it may accelerate the bug fix.
I use one of these calls on more than one program but do NOT use
STATICi.e.,Used to save a copy of current screen then restore it after completing another process that display to screen, etc.
No Idea if
STATICmight be the cause but possibly worth a try.Last edit: Simon Sobisch 2024-06-07
I have further simplified the program.
It must be compiled and executed without parameters
My compilation from OpenCobolIDE is as follows
C:\OpenCobolIDE\GC20base2\bin\cobc.exe -x -o bin\TESTERROR.exe -std=default -debug -fdebugging-line -ftrace -free -lpdcurses TESTERROR.COBAt first ACCEPT press ENTER without typing anything
The program shows an error message (asks you to type something in the field)
You type ENTER after reading the message and the program performs the ACCEPT again
Press ENTER again without typing anything in th efield at screen
The program should show the same error message but the DISPLAY statement does not work and displays nothing !!!
I have done step by step debugging of this program with COBGDB but don't see anything different.
The DISPLAY statement works well the first time, the subsequent times (after the SCREEN RESTORE) it no longer works well.
Hello @sf-mensch. After some thought, I believe it is wiser to remove my assignment to this bug as I am unfortunately being busy with other tasks and cannot guarantee I will be able to look at it soon. Sorry for the inconvenience.
Hi Simon, I have the impression that this bug, quite complex to describe, is not so simple to investigate, much less simple to solve.
This is a very bad anomaly, in my opinion.
For these reasons I believe that your direct intervention would be very desirable and important.
I think the minimal example doesn't need the curs_set() call - then drop it.
Then the error only happens when you use - outside of GnuCOBOL's
screenio - the scr_dump/scr_restore/refresh functions, right?
there is no curs_set() call in the source sample of my last post 2024-05-23.
The error happens becouse I need to save the screen, display an errore message and restore the screen previuos the error message.
There is no alternative so i have to use scr_dump to save the screen and scr_restore to restore the screen.
Last edit: Eugenio Di Lorenzo 2024-06-04
Maybe chuck can inspect this if it only happens with these calls - but
in general it seems more appropriate to create CBL functions for these
functions
Note per
https://github.com/Bill-Gray/PDCursesMod/blob/master/docs/MANUAL.md#scr_dump
the functions putwin() and getwin() would be preferable; but they do
something different as soon as we support multiple windows.
Note: from the COBOL programmer view the best would be to use DISPLAY
WINDOW and friends, but these are not implemented yet (patches welcome
and I think relative easy) and would only be portable to GnuCOBOL,
ACUCOBOL, possibly RM/COBOL and MF COBOL.
Simon
The two functions that should be implemented are the following
CBL_READ_SCR_CHATTRS
CBL_WRITE_SCR_CHATTRS
which save in the COBOL program memory and write from the COBOL program memory a rectangular portion (like a window) of the screen with the characters and attributes (color, highlight ...)
But this is another thing that has already been discussed for a long time in this forum without finding a solution.
Chuck has already created some similar functions but they are not compatible with pdcurses :-(
For now it would be useful if the bug (DISPLAY not working) could be solved.
Eugenio,
I i think that a solution would be the addition of two cbl functions to be added to libcob. one to save the screen and the other to restore.. The reason I would prefer this approach is that once you start calling curses functions directly from COBOL, the COBOL programmer would be responsible for any issues in that there is no way the screenio portion of the compiler runtime could ensure that the CURSES functionality is correct. So I think that it would be best to do this with new CBL functions within the compiler itself.
it would determine the screen size ... lines / columns / chtype size and allocate a buffer to store the screen data. Also save the screen size and cursor position. If the current screen size is not the same as the saved size the restore would fail.
i'm not sure what scr_save / scr_restore are doing under the covers and the above method would eliminate that.
I have used this technique or something very similar in my C screen painter program. it should not be too difficult to do.
l would want to get a consensus on the functionality of these before investing my time on them
so there is an agreement on the scope and deliverables.
The testing of this would be simplified as the development / testing could be done with an external C program. After approval of the testing results it could easily be incorporated into the libcob runtime.
please provide your feedback on this approach.
I am sure there must be functions in MicroFocus/ACUCOBOL to do that. For easing migrations and for pre-set of the rules and possible examples this would be preferable to create an own function.
Hi Chuck, personally I don't think your proposal of doing without the pdcurses library functions is a good solution. The entire architecture of GnuCOBOL (e.g. all ACCEPT and all DISPLAY) has been set on this library.
As I said in my previous post, the two functions that read and write characters and attributes on the screen already present in other compilers (Realia, Mricofocus ...) such as READ_SCR_CHATTRS and WRITE_SCR_CHATTRS are one of the main gaps that still remain in GnuCOBOL.
I had already raised the issue at his time (2016). please see:
https://sourceforge.net/p/gnucobol/discussion/help/thread/4a975c9b/?limit=50#32dd/5a31/df1c/3ca4/b9a9/505b/c8d9/6b10/6dbc
See also
https://sourceforge.net/p/gnucobol/discussion/contrib/thread/f5934f0f/?limit=50#fd9f
and
https://sourceforge.net/p/gnucobol/discussion/help/thread/c5345903/?limit=50#4c62/feb8/b2de/217e
The solution of using the pdcurses scr_dump and scr_restore functions is currently the only working option.
Over time, the bug I had already reported emerged. Marcos Martin Duma, the author of COBGDB, also reported the same bug in the same post.
Then I tried using calls to the pdcurses mvinch() function which reads characters and attributes from the screen. see GnuCOBOL source example in the same post.
Now we are talking about two goals.
1. Fix the bug described here. When using scr_dump and then scr_restore in the case described, the DISPLAY statement no longer works! With this solution we will also be able to do without the two functions referred to in the following point.
2. create the two new CBL functions CBL_READ_SCR_CHATTRS and CBL_WRITE_SCR_CHATTRS which would give greater compatibility with other compilers.
The bug referred to in the previous point should still be resolved.
For me at the moment it is appropriate to give priority to fixing the bug.
The DISPLAY statement does not work correctly and this bug needs to be fixed i thik ASAP.
Last edit: Eugenio Di Lorenzo 2024-06-05
The point is to call those curses functions from within
libcob/screenio.c, instead of from a COBOL program.
Eugenio,
we have confirmed that this is the result of a bug in PDCURSES_MOD. Your test program works as expected in Linux which uses NCURSES. We have communicated the issue to the author / maintainer of PDCURSES_MOD and will update this report as we learn more from Bill Gray , the maintainer of PDCURSES_MOD.
Simon may have a windows build with NCURSES. If it is urgent and you can't wait for the pdcurses fix, I could attempt to build GNUCOBOL with NCURSES on Windows. I'm busy working on restaining my deck for the next week or so depending on the weather so I may not have time for this until after that is finished.
Note: the default binaries on MSYS2 are all ncursesw based