Q59405: Illegal DIM x AS STRING*<Variable> Can Hang QB.EXE or QBX.EXE

Article: Q59405
Product(s): See article
Version(s): 6.00 6.00b 7.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist6.00 buglist6.00b buglist7.00 fixlist7.10 B_QuickBas | mspl13_basic
Last Modified: 20-SEP-1990

Illegally defining fixed-length strings (DIM AS STRING * N%) with
integer variables (N%) can in some cases cause problems inside the
QB.EXE and QBX.EXE environments. (The length of fixed-length strings
must be defined with constants, not variables.)

Microsoft has confirmed this to be a problem in the QB.EXE environment
of Microsoft QuickBASIC versions 4.00, 4.00b, and 4.50 (buglist4.00,
buglist4.00b, buglist4.50); in the QB.EXE environment of Microsoft
BASIC Compiler versions 6.00 and 6.00b; and in the QBX.EXE environment
of Microsoft BASIC Professional Development System (PDS) version 7.00
for MS-DOS. This problem was corrected in the QBX.EXE environment of
BASIC PDS 7.10.

To find a related article on this topic, query in this Knowledge Base
on the following words:

   invalid and constant and variable and fixed and length and string

The QB.EXE environment of QuickBASIC 4.00 and 4.00b runs Examples 1
and 2 (below) without hanging; however, it fails to flag the variable
on the STRING * flen declaration as an error.

In both Examples 1 and 2, getting rid of flen and defining the string
with a constant value (x AS STRING * 82) corrects the problem. You can
also work around the problem by making flen a CONST constant, for
example:

   CONST flen = 82

Also, by changing flen to a noninteger variable, the QB.EXE or QBX.EXE
environment correctly flags the error. BC.EXE (the command-line
compiler) always correctly flags the error.

Example 1
---------

When the following program is run inside the QuickBASIC Extended
(QBX.EXE) 7.00 environment, the error message "INVALID CONSTANT" is
flagged on the line "flen = 82" instead of on the DIM line:

   DEFINT A-Z
   flen = 82
   DIM x AS STRING * flen

Example 2
---------

When the following program is run in QB.EXE 4.50 or QBX.EXE 7.00, the
computer may hang, or the error message "STRING SPACE CORRUPT" may
display and the computer may exit back to DOS:

   DEFINT A-Z
   flen = 82
   TYPE recordtype
      x AS STRING * flen
   END TYPE
   DIM datetest AS recordtype

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