CHAIN or RUN from Quick Library Can Hang QuickBasic Editor (49925)

SYMPTOMS

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:

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

STATUS

Microsoft has confirmed this to be a bug 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 in the Microsoft Knowledge Base 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

MORE INFORMATION

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