BUG: API Fails Passing Very Small Double Datatypes to VFP

• Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a

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)

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)