BUG: CDK: VBSetVariantValue Return Value Changed in 4.0 (142465)
The information in this article applies to:
- Microsoft Visual Basic Professional Edition, 16-bit, for Windows 4.0
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows 4.0
This article was previously published under Q142465 SYMPTOMS
The return value of the VBSetVariantValue function in the VBAPI library has
changed in the 16-bit version of Microsoft Visual Basic version 4.0. This
change in behavior affects 16-bit DLLs and custom controls (VBXs) that
previously worked with Microsoft Visual Basic version 3.0.
MORE INFORMATION
The documentation for the VBSetVariantValue function in the Control
Development Guide in the Professional Edition of Microsoft Visual Basic
states that when this function is used with the documented VB_<type> types,
a -1 value is returned for errors, and 0 is returned for success. This
statement is no longer true for DLLs and custom controls (VBXs) used with
Visual Basic 4.0. The VBSetVariantValue function returns -1 for errors, 0
or greater for success.
STATUS
Microsoft has confirmed this to be a issue in the 16-bit version of Visual
Basic for Windows version 4.0. We are researching this issue and will post
new information here in the Microsoft Knowledge Base as it becomes
available.
RESOLUTION
To indicate success, change the DLL or VBX source code to handle return
values of 0 or greater, instead of equivalence to 0. For example, if you
have code that resembles the following:
#include <vbapi.h>
#define SUCCESS 0
#define FAIL -1
int VBAPI SetMyVariant (LPVAR pVariant)
{
short NewValue = 0x1234;
ERR nResult;
nResult = VBSetVariantValue (pVariant, VT_I2, (LPVOID) &NewValue);
if (0 == nResult)
return SUCCESS;
else
return FAIL;
}
A DLL or VBX that contains this function correctly returns SUCCESS when
used from a Visual Basic version 3.0 program. When the same DLL or VBX is
used from a Visual Basic version 4.0 program, it incorrectly returns
FAIL.
You can avoid this problem by changing the line:
if (0 == nResult)
to
if (0 <= nResult)
-OR-
you can test for a failure only. For example:
if (-1 == nResult)
return FAIL;
else
return SUCCESS;
| Modification Type: | Minor | Last Reviewed: | 1/8/2003 |
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| Keywords: | kbbug KB142465 |
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