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Q43530: QB.EXE 4.50 Hangs If File Unloaded While Watch Is Set

Article: Q43530
Product(s): See article
Version(s): 4.50
Operating System(s): OS/2
Keyword(s): ENDUSER | SR# S890410-127 buglist4.50 B_BasicCom | mspl13_basic
Last Modified: 21-FEB-1991

Choosing to UNLOAD a file while a Watch on a variable is set hangs the
QB.EXE editor, requiring a warm or cold reboot if operating under
MS-DOS. If you are running under OS/2, this choice hangs the DOS
compatibility box. This problem does not occur when UNLOADing a file
if a Watchpoint is set to watch an expression.

Microsoft has confirmed this to be a problem with QB.EXE in QuickBASIC
version 4.50. This problem was corrected in QBX.EXE in Microsoft BASIC
Professional Development System (PDS) version 7.00 (fixlist7.00).

Example 1
---------

To demonstrate this problem do the following:

1. Type the following two lines in the QuickBASIC editor:

      B$ = "Hello"
      END

2. Save the file by choosing Save As from the File menu.

3. Choose Add Watch from the Debug menu by pressing ALT+D and then
   pressing "A".

4. Enter B$ as the expression to watch. Press ENTER.

5. Choose Unload from the File menu by pressing ALT+F and then
   pressing "U". Press ENTER to UNLOAD the program. The editor will
   then display a menu prompting you to choose a new main module. If
   the editor does not hang, press ENTER again to choose "Untitled" as
   the main module. At this point the editor will hang, requiring a
   cold or warm reboot.

Example 2
---------

The following exact steps also cause QB.EXE version 4.50 to hang under
similar circumstances:

 1. Start QuickBASIC and load any Quick library:

       QB /L QB.QLB

 2. Type the following and press ENTER:

       PRINT "any text"

 3. Press the UP ARROW cursor key, thus placing the cursor under the
    "P" in PRINT.

 4. Press F9, thus placing a breakpoint on that line.

 5. Run the program by pressing SHIFT+F5.

 6. Select the Debug menu with ALT+D and press ENTER, thus choosing to
    set a watch variable.

 7. Type FRE("") as the watch variable and press ENTER.

 8. Press ALT+F+L (to select the Load File command), and press ESC.

10. Press ALT+F+U (to select the Unload File command), and press
    ENTER.

11. Press TAB, then the SPACE key, then ENTER, and the editor will
    be hung.

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