Q43023: Multiple Event Traps Can Malfunction in QB.EXE

Article: Q43023
Product(s): See article
Version(s): 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00b buglist4.50 SR# S890315-133 B_BasicCom | mspl13_basic
Last Modified: 26-FEB-1990

The programs below demonstrate that SETUEVENT is mistakenly remembered
in the QuickBASIC Version 4.50 environment between program
invocations. Also, any other event trap causes the UEVENT to activate.
This is incorrect behavior, since starting a new program should reset
and remove event handlers from programs previously run in the QB.EXE
environment.

Microsoft has confirmed this to be a problem with QB.EXE in QuickBASIC
Versions 4.00b and 4.50, and with QB.EXE in Microsoft BASIC Compiler
Versions 6.00 and 6.00b for MS-DOS (buglist6.00 buglist6.00b). This
problem was corrected in Microsoft BASIC Professional Development
System (PDS) Version 7.00 (fixlist7.00).

The following program is EVENT1.BAS, which sets up a user-defined
event trap but never activates it. The second program is EVENT2.BAS,
which sets up and activates another user-defined event trap.

The first time EVENT1.BAS is run in QB.EXE, the user-defined event
trap never occurs (which is correct). If it is run after EVENT2.BAS,
the EVENT1 procedure is activated. This is because the SETUEVENT is
remembered between the programs.

The steps to reproduce this are as follows:

1. Invoke QB.EXE.

2. Load EVENT1.BAS, and it runs correctly.

3. Load EVENT2.BAS and run it.

4. Load EVENT1.BAS again. User event remembers TIMER event.

The following is the program EVENT1.BAS:

CLS
ON UEVENT GOSUB event1
UEVENT ON
DO: LOOP UNTIL INKEY$ <> ""
END

event1:
 PRINT "user event"
 RETURN

The following is the program EVENT2.BAS:

'**** PROGRAM #2
CLS
ON UEVENT GOSUB event1
ON TIMER(1) GOSUB timeout
UEVENT ON
TIMER ON
CALL setuevent
DO: LOOP UNTIL INKEY$ <> ""
END

timeout:
  PRINT "timeout"
RETURN

event1:
  PRINT "user event"
RETURN

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