Q62816: Passed Parameters Incorrectly PRINTed from SUB in Library

Article: Q62816
Product(s): See article
Version(s): 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S900515-50 buglist4.50 | mspl13_basic
Last Modified: 20-JUN-1990

This article demonstrates a case where PRINTing integer and
floating-point numbers from a SUBprogram that is either in a library
or in a separate module gives unpredictable results. The problem
occurs if the variables are passed to the SUB through the argument
list and if several of the variables are separated by commas when
PRINTed in one PRINT statement.

Microsoft has confirmed this to be a problem in QuickBASIC version
4.50 and in Microsoft BASIC Compiler versions 6.00 and 6.00b
(buglist6.00, buglist6.00b). This problem was corrected in Microsoft
BASIC Professional Development System (PDS) version 7.00
(fixlist7.00).

There are several ways to work around this problem. This problem does
not occur if you use the /X switch on the compile line. The problem
also does not occur if the SUB is part of the module from where it is
CALLed or if the variables are passed through COMMON SHARED
statements. The problem also does not occur if the variables are
PRINTed on separate lines, or are separated by semicolons instead of
commas.

The following code shows the problem:

From within QB.EXE 4.50, make a module or library from the following
code:

    DECLARE SUB printsub (a%, b%, c%, d%)
    SUB printsub (a%, b%, c%, d%)
    PRINT "1: ", a%, b%, c%, d%
    PRINT "2: ", a%, b%, c%, d%
    PRINT "3: ", a%, b%, c%, d%
    END SUB

If you made a Quick library from the above SUBprogram, load the
library into QuickBASIC version 4.50 as follows:

   QB /L libname

Then, from within QB.EXE 4.50, run the following main program:

' Program: TEST.BAS
    DECLARE SUB printsub (a%, b%, c%, d%)
    CLS
    CALL printsub(9, 16, 4, 70)   'the values do not matter

Output
------

   1:             9             16            4             70
   2:             9             21317         4             70
   3:             9             21317         4             70

To work around this problem, compile with the /X option, as follows:

   BC /X TEST.BAS ;

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