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Q49925: CHAIN or RUN from Quick Library Can Hang QuickBASIC Editor

Article: Q49925
Product(s): See article
Version(s): 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00b buglist4.50 B_BasicCom | mspl13_basic
Last Modified: 20-SEP-1990

When executing a program within the QB.EXE or QBX.EXE (QuickBASIC
Extended) environment that CALLs a Quick library routine that executes
a RUN or CHAIN command, the system can hang under either of the
following two specific conditions:

1. If the program to be CHAINed or RUN does not exist in the current
   directory, the QuickBASIC editor will hang.

2. If the first program has been changed since being loaded, the
   QuickBASIC environment will ask if you want to save the current
   program before loading the program named in the CHAIN or RUN
   statement. An "OK" or "No" response allows QuickBASIC to load and
   execute the CHAIN or RUN program correctly. A "Cancel" response
   causes QuickBASIC to drop to DOS. Attempting to rerun QuickBASIC
   after the drop to DOS will hang the machine.

Microsoft has confirmed this to be a problem in the QB.EXE environment
of Microsoft QuickBASIC versions 4.00b and 4.50 and in the QBX.EXE
environment of Microsoft BASIC Professional Development System (PDS)
versions 7.00 and 7.10 (buglist7.00, buglist7.10). We are researching
this problem and will post new information here as it becomes
available.

These errors occur with the CHAIN or RUN statement only if it is
invoked from a Quick library routine. CHAIN and RUN work normally from
a source program in the QuickBASIC editor or from a compiled EXE
program.

For information about a separate hanging problem specific only to
QuickBASIC version 4.00 when executing ANY CHAIN or RUN from a Quick
library, query in this Knowledge Base on the following words:

   4.00 and CHAIN and Quick and library and hangs

The following set of programs reproduce the problem. QLBERR.BAS should
be compiled and made into a Quick library, while PROG1.BAS and
PROG2.BAS should be left as uncompiled source.

To reproduce the first error detailed above, do not create PROG2.BAS
at all. Instead, create and load the QLBERR.QLB Quick library and
create and save PROG1.BAS. Executing PROG1.BAS at this point will hang
QuickBASIC.

To reproduce the second error, start QuickBASIC using the QLBERR.QLB
Quick library, then load, modify, and execute PROG1. When the dialog
box asks if you want to save PROG1 before loading and running PROG2,
select Cancel. QuickBASIC will then drop to DOS.

Code Examples
-------------

   '               *** QLBERR.BAS ***
   '       ** Make this into a Quick library **
   SUB QLBErrSub
     RUN "PROG2"     'Can also be CHAIN "PROG2"
   END SUB

   '               *** PROG1.BAS ***
   '       ** Leave this as source code **
   PRINT "In program1"
   CALL QLBErrSub
   END

   '               *** PROG2.BAS ***
   '       ** Leave this as source code **
   PRINT "In Program 2"
   END

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