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Q39245: BC.EXE "Internal Error" Using Passed Integers in Expression

Article: Q39245
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00 buglist4.00b buglist4.50 B_BasicCom | mspl13_basic
Last Modified: 27-FEB-1990

An "internal error" is produced when compiling the sample code
fragment (below) with BC.EXE. The problem relates to a compiler
code-optimization problem in a particular case of passing integer
variables as parameters to a subprogram and using them in certain
expressions.

Microsoft has confirmed this to be a problem in BC.EXE in Microsoft
QuickBASIC Versions 4.00, 4.00b, and 4.50, and in the BASIC Compiler
Versions 6.00 and 6.00b for MS-DOS and MS OS/2 (buglist6.00,
buglist6.00b). This problem was corrected in Microsoft BASIC
Professional Development System (PDS) Version 7.00 (fixlist7.00)

To work around this problem, assign a temporary value to one of the
integer parameters before doing arithmetic (see below).

The following code example causes an "internal error":

DECLARE SUB XSCROLL (BarLen%, LCol%, BRow%, Rcol%)
SUB XSCROLL (BarLen%, LCol%, BRow%, Rcol%)
   LCol% = LCol% + 3
   NumCol# = ((Rcol% - LCol%) + 1) \ BarLen%
END SUB

The following code example works around the problem:

DECLARE SUB XSCROLL (BarLen%, LCol%, BRow%, Rcol%)
SUB XSCROLL (BarLen%, LCol%, BRow%, Rcol%)
   temp1% = LCol%
   temp1% = temp1% + 3
   LCol% = temp1%
   NumCol# = ((Rcol% - LCol%) + 1) \ BarLen%
END SUB

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