Q57367: COMMON SHARED Must Be in Order in User Interface Toolbox

Article: Q57367
Product(s): See article
Version(s): 7.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S891211-54 | mspl13_basic
Last Modified: 23-FEB-1990

When using procedures from the User Interface (UI) Toolbox's MENU.BAS
or WINDOW.BAS, you must provide global-array declarations in your
program. If these declarations are in the wrong order, various errors
may occur. The proper order for COMMON SHARED declarations can be
found at the beginning of each User Interface Toolbox .BAS file.
Possible errors include "Subscript out of range in module...," "Far
Heap Corrupt," or the system may hang.

This information applies to Microsoft BASIC Professional Development
System (PDS) Version 7.00 for MS-DOS.

In most cases, switching the order of the COMMON SHARED statements for
the global-array declarations generates the error "Subscript out of
range in module..." on the first call to a procedure in MENU.BAS or
WINDOW.BAS.

Changing the order of certain COMMON SHARED statements results in a
"Far Heap Corrupt" message when the program is run from the QBX.EXE
editor. This can put the computer in an unstable memory state, which
may cause it to hang. When the same program is run from the DOS
command line, the program fails and gives a "Subscript out of range in
module..." error message.

Here is some good advice from Page 65 of the "Microsoft BASIC 7.0:
Language Reference" manual:

   Errors caused by mismatched COMMON statements are subtle and
   difficult to find. An easy way to avoid mismatched COMMON
   statements is to place COMMON declarations in a single include
   file and use the $INCLUDE metacommand in each module.

Code Example
------------

The following code exhibits the behavior of a program that has a
statement (COMMON SHARED /uitools/GloWindowStack() AS INTEGER) in the
wrong order. This program generates a "Far Heap Corrupt" message and
can hang when run from the QBX.EXE editor in either MS-DOS or in OS/2
real mode. If this program is compiled, linked, and then run from the
DOS command line, it generates a "Subscript out of range in module..."
error.

   REM $INCLUDE: 'MENU.BI'
   REM $INCLUDE: 'WINDOW.BI'
   REM $INCLUDE: 'MOUSE.BI'
   REM $INCLUDE: 'GENERAL.BI'

   COMMON SHARED /uitools/GloMenu     AS MenuMiscType
   COMMON SHARED /uitools/GloTitle()  AS MenuTitleType
   COMMON SHARED /uitools/GloItem()   AS MenuItemType

   'The next statement is out of order

   COMMON SHARED /uitools/GloWindowStack() AS INTEGER
   COMMON SHARED /uitools/GloWindow() AS WindowType
   COMMON SHARED /uitools/GloButton() AS ButtonType
   COMMON SHARED /uitools/GloEdit()   AS EditFieldType
   COMMON SHARED /uitools/Storage     AS WindowStorageType
   'This is where the statement should be
   COMMON SHARED /uitools/GloBuffer$()

   DIM GloTitle(MAXMENU)              AS MenuTitleType
   DIM GloItem(MAXMENU, MAXITEM)      AS MenuItemType
   DIM GloWindow(MAXWINDOW)           AS WindowType
   DIM GloButton(MAXBUTTON)           AS ButtonType
   DIM GloEdit(MAXEDITFIELD)          AS EditFieldType
   DIM GloWindowStack(MAXWINDOW)      AS INTEGER
   DIM GloBuffer$(MAXWINDOW +1, 2)

   MenuInit
   WindowInit

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