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Q167241: BUG: API Fails Passing Very Small Double Datatypes to VFP

Article: Q167241
Product(s): Microsoft FoxPro
Version(s): WINDOWS:5.0,5.0a
Operating System(s): 
Keyword(s): kbprogramming kbvfp kbvfp500aBUG kbvfp500bug
Last Modified: 11-DEC-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a 
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SYMPTOMS
========

When calling an API that returns a very small double value, Visual FoxPro
interprets this value as zero.

RESOLUTION
==========

NOTE: The file referenced in this article as Project1.dll is for example
purposes only. Project1.dll is theoretical API library not installed by any
version of Microsoft Visual FoxPro.

As a workaround, call the function through the FoxTools library.

This workaround example is based on the "Steps To Reproduce Behavior" section of
this article. The code in this example is case sensitive; therefore, it must be
typed exactly as it appears below:

     SET LIBRARY TO SYS(2004)+"FOXTOOLS"
     hh=REGFN32("getVal","C","F","Project1.dll")
     x = "0.00000000000000000000000000000000085555"
     ?CALLFN(hh,x)

This returns the correct value.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this bug and will post new
information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

Consider a custom DLL Project1.dll containing the function getVal. Function
getVal takes a number in text format and converts it to a double, which it
returns to the calling procedure.

Steps to Reproduce Behavior
---------------------------

To reproduce the problem, type the following code:

     DECLARE DOUBLE getVal IN Project1.dll STRING
     x = "0.00000000000000000000000000000000085555"
     ? getVal(x)

This returns 0.

Additional query words:

======================================================================
Keywords          : kbprogramming kbvfp kbvfp500aBUG kbvfp500bug 
Technology        : kbVFPsearch kbAudDeveloper kbVFP500 kbVFP500a
Version           : WINDOWS:5.0,5.0a
Issue type        : kbbug

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