Q179140: BUG: "Too Many Local, Nonstatic Variables" Error Message
Article: Q179140
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0;
Operating System(s):
Keyword(s): kbnokeyword kbVBp500bug kbVBp600bug kbGrpDSVB
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
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SYMPTOMS
========
When compiling an application that calls functions or subroutines in a DLL and
that passes large User Defined Types to the DLL, you may receive the following
error message:
Too many local, nonstatic variables
CAUSE
=====
The above error is the result of a bug in the Visual Basic compiler when
allocating memory for passing User Defined Types (UDTs) to functions or
subroutines in DLLs. The error may occur when this amount exceeds approximately
64KB.
RESOLUTION
==========
You can work around this problem by changing the way that such UDTs are passed
to the DLL. When you pass a UDT to a DLL, you are actually passing a pointer to
the first memory location of the UDT. Another way to pass this pointer is by
copying the UDT to a Byte array and passing the first element of the Byte array
by reference.
NOTE: You will need to calculate the size of this Byte array manually, taking
into consideration the issues relating to byte-alignment.
For more information regarding byte-alignment, refer to Section 6 of the
VB5DLL.DOC document located in the Tools\Docs folder of the Visual Basic
CD-ROM.
Because the Visual Basic run-time library converts the strings from UNICODE to
ANSI when using the CopyMemory function below, you should only allocate 1 byte
for each character in your fixed-length strings.
Assuming you have the following UDT and Declare statement for your DLL:
Type LargeUDT
nAge as Integer
sName As String * 4000
lMiles as Long
End Type
Dim aLargeUDT As LargeUDT
Declare Sub MySub Lib "MYDLL.DLL" (x As LargeUDT)
Follow these steps to implement a workaround to the problem:
1. Manually calculate the size necessary for the UDT:
Const UDT_SIZE = 4008
2. Create the following Declare within your application (a Windows A function to
copy memory from one location to another):
Declare Sub CopyMemory Lib "KERNEL32" Alias "RtlMoveMemory" ( _
lpvDest as Any, lpvSource as Any, ByVal cbCopy as Long)
3. Change the declaration of the subroutine within the DLL to accept 1 byte by
reference in place of the UDT argument:
Declare Sub MySub Lib "MYDLL.DLL" (x As Byte)
4. Create a Byte Array to store the User Defined Type. Re-dimension the UDT
using the manually-calculated constant UDT_SIZE in step 1:
Dim ab() as byte
Redim ab(UDT_SIZE)
5. When calling the subroutine in the DLL, you must first call CopyMemory to
copy the UDT into the Byte array. Next, call the subroutine, passing it the
first element of the Byte array. Finally, call CopyMemory again to copy the
Byte array back into the UDT:
CopyMemory ab(0), aLargeUDT, UDT_SIZE
MySub ab(0)
CopyMemory aLargeUDT, ab(0), UDT_SIZE
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
================
Steps to Reproduce Behavior
---------------------------
1. Start a new Standard EXE project. Form1 is created by default.
2. Paste the following code into the code window of the form. Note that there
are nine calls to MySub and the ninth one is commented out:
Option Explicit
Private Type LargeUDT
a As String * 4000
End Type
Dim aLargeUDT As LargeUDT
Private Declare Sub MySub Lib "MYDLL.DLL" (x As LargeUDT)
Private Sub Form_Load()
MySub aLargeUDT
MySub aLargeUDT
MySub aLargeUDT
MySub aLargeUDT
MySub aLargeUDT
MySub aLargeUDT
MySub aLargeUDT
MySub aLargeUDT
'MySub aLargeUDT
End Sub
3. Compile the application by selecting "Make Project1.exe" from the File Menu.
It should compile as expected, and create the Project1.exe file.
4. Uncomment the last call to MySub by removing the apostrophe at the start of
the line.
5. Compile the application again and note that it now fails with the error, "Too
many local, nonstatic variables."
REFERENCES
==========
For additional information on calling subroutines and functions in DLLs, please
see the following document:
VB5DLL.DOC, Visual Basic 5 CD-ROM (Professional and Enterprise Editions Only), in
the following folder ...\TOOLS\DOCS\.
Additional query words: UDT
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Keywords : kbnokeyword kbVBp500bug kbVBp600bug kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Version : WINDOWS:5.0,6.0;
Issue type : kbbug
Solution Type : kbpending
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