Q32101: No Error QB.EXE If DYNAMIC Array Wrongly DIMmed Before COMMON

Article: Q32101
Product(s): See article
Version(s): 4.00 4.00b
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00 buglist4.00b fixlist4.50 B_BasicCom | mspl13_basic
Last Modified: 8-DEC-1989

The QB.EXE Versions 4.00 and 4.00b environments fail to generate an
error if a DYNAMIC array is DIMensioned before it appears in a COMMON
statement. For dynamic arrays, a DIM statement allocates memory for
the array at run time, and is considered to be an "executable"
statement.

(Note: A STATIC array is required to be DIMensioned before it appears
in a COMMON statement. For static arrays, a DIM statement is a
"nonexecutable," as defined in Page 10 of the "Microsoft QuickBASIC
4.0: BASIC Language Reference." This is a difference between static
and dynamic arrays.)

Microsoft has confirmed this to be a problem in QuickBASIC Versions
4.00 and 4.00b, and in the version of QuickBASIC provided with the
Microsoft BASIC Compiler Versions 6.00 and 6.00b for MS-DOS and MS
OS/2 (buglist6.00, buglist6.00b). This problem has been corrected in
QuickBASIC Version 4.50 and in the QBX.EXE of the Microsoft BASIC
Compiler Version 7.00 (fixlist7.00).

BC.EXE Versions 4.00, 4.00b, and 4.50 (and QB.EXE 4.50) correctly trap
the error at compile time and display the following message:

   COMMON and DECLARE must precede executable statements

The following statement is from Page 117 of the "Microsoft QuickBASIC
4.0: BASIC Language Reference" manual and refers to $DYNAMIC arrays
that are also in COMMON:

   A dynamic array must be dimensioned in a later DIM or REDIM
   statement.

QuickBASIC Versions 2.00 and 3.00 correctly generate a "COMMON Out of
Order" error inside the QB.EXE environment for the following example:

REM This program runs correctly in the QB.EXE 4.00 environment, but
REM it should not. [Please remember that BASIC modules linked with
REM Microsoft FORTRAN modules must use STATIC arrays, not DYNAMIC.]

' $DYNAMIC
DIM x%(2048)
COMMON SHARED /xxx/ x%()
END

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