Q46180: STATIC FUNCTION Fails to Retain Value Between Invocations

Article: Q46180
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: 20-SEP-1990

A function that has been declared with the STATIC attribute should
retain its value between calls. When a STATIC function is called and
assigned a value, subsequent calls to the function that do not assign
a new value to the function should always return the previous value,
even if you leave the function with an EXIT FUNCTION statement. This
behavior is correctly exhibited by programs compiled with BC.EXE.

However, when you attempt the same procedure in the QB.EXE or QBX.EXE
environment, a STATIC FUNCTION fails to retain its value in multiple
invocations, and incorrectly returns a 0 (zero) or null string,
depending on the type of the function.

Microsoft has confirmed this to be a problem in the QB.EXE environment
of Microsoft QuickBASIC versions 4.00, 4.00b, and 4.50; in the QB.EXE
environment of Microsoft BASIC Compiler versions 6.00 and 6.00b
(buglist6.00, buglist6.00b); and in the QBX.EXE environment of
Microsoft BASIC Professional Development System (PDS) versions 7.00
and 7.10 (buglist7.00, buglist7.10). We are researching this problem
and will post new information here as it becomes available.

The following sample program demonstrates the problem:

   x% = staticfun%(1)
   PRINT x%   ' Should print 5.
   x% = staticfun%(0)
   PRINT x%   ' Should print 5.
   END

   FUNCTION staticfun%(parm%) STATIC
     IF parm% = 0 THEN
       EXIT FUNCTION
     ELSE
       staticfun% = 5
     END IF
   END FUNCTION

When this program is compiled with BC.EXE, it correctly prints the
values 5 and 5. From inside the QuickBASIC QB.EXE or QBX.EXE
environment, it incorrectly prints 5 and 0.

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.