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Q67373: CLEAR Can Cause "Subscript out of Range" with $DYNAMIC Array

Article: Q67373
Product(s): See article
Version(s): 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 5-DEC-1990

Increasing the stack space with the CLEAR statement also reinitializes
all variables. This includes erasing the memory for any $DYNAMIC
arrays and initializing the elements of a $STATIC array to zero or
null strings. For this reason, CLEAR should normally be used only as
the very first executable statement in a program. Using it anywhere
else can cause problems. For example, once you have used CLEAR, if you
attempt to access an element of a $DYNAMIC array, the error "Subscript
out of range" will be generated. This is expected behavior because the
CLEAR statement deallocates all memory for the dynamic array. After a
CLEAR, all $DYNAMIC arrays must be re-created with the REDIM
statement.

This information applies to Microsoft QuickBASIC versions 2.00, 2.01,
3.00, 4.00, 4.00b, and 4.50 for MS-DOS; to Microsoft BASIC Compiler
versions 6.00 and 6.00b for MS-DOS and MS OS/2; to Microsoft BASIC
Professional Development System (PDS) versions 7.00 and 7.10 for
MS-DOS and MS OS/2; and to all versions of GW-BASIC (such as 3.20,
3.22, 3.23) for MS-DOS.

The following code block produces the error "Subscript out of range"
on the "x(11) = 34" assign statement:

COMMON x()
DIM x(30)
CLEAR , , 4000
x(11) = 34

Suggested Solution #1
---------------------

Create a dynamic variable and redimension the variable.

' $DYNAMIC
COMMON x()
DIM x(30)
CLEAR , , 4000
REDIM x(30)
x(11) = 34

Suggested Solution #2
---------------------

In QuickBASIC version 4.00 or later, or BASIC compiler version 6.00 or
later, use the LINK /ST[ACK]:n option, where n is the amount of bytes
to allocate to the stack space out of DGROUP (maximum allowable stack
is somewhere less than 64K).

Reference
---------

For related articles, query on the following words:

   LINK and STACK and default and size and 3.00 and 4.00 and QuickBASIC

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