DOCUMENT:Q253938 13-JUN-2000 [foxpro] TITLE :BUG: Application Error When Accessing Cursors/Tables in Loop PRODUCT :Microsoft FoxPro PROD/VER:WINDOWS:3.0b,5.0a,6.0 OPER/SYS: KEYWORDS:kbDatabase kbvfp300 kbvfp300bBUG kbvfp500 kbvfp500a kbvfp500aBUG kbvfp600 kbvfp600bug K ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual FoxPro for Windows, versions 3.0b, 5.0a, 6.0 ------------------------------------------------------------------------------- SYMPTOMS ======== When you are creating cursors and changing the cursor names in a loop, after about 32,160 cursor name changes, Visual FoxPro generates an error message and shuts down. The error message can be: Fatal Error: Exception code=C00000005 -or- Alias '' is not found. This is followed by the error message: Fatal Error. CAUSE ===== The use of macro expansion/variable substitution, in conjunction with the use of macro expansion/variable substitution to access the table, causes this problem. For example: lcAlias = "A" + ALLTRIM(STR(x)) CREATE CURSOR (lcAlias) (fld1 c(10)) cValue = &lcAlias..fld1 -or- lcAlias = SYS(2015) USE Table1 ALIAS &lcAlias cValue = &lcAlias..fld1 The more instances of macro expansion/variable substitution, the sooner the problem occurs. However, the problem only occurs when a table/cursor is USEd/CREATEd with macro substitution/variable substitution. RESOLUTION ========== Use constant alias names. Do not change the name of the alias each time it is created. For example, when you create a cursor in a loop, use the same name each time instead of using a unique name. LOCAL lcAlias, x CLEAR @ 2,1 SAY "Starting User Object Memory Use" @ 3,1 SAY SYS(1016) && User Object Memory Use @ 4,1 SAY "Current User Object Memory Use" FOR x = 1 TO 100000 lcAlias = "ABCDEF" CREATE CURSOR (lcAlias) (fld1 c(10)) cValue = &lcAlias..fld1 USE IN (lcAlias) @ 1,1 SAY lcAlias @ 5,1 SAY SYS(1016) && User Object Memory Use ENDFOR RETURN STATUS ====== Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. MORE INFORMATION ================ The sample program fails at approximately 32,160 iterations. The problem is exacerbated when you use additional variables, arrays, cursors, and tables created in this manner. Then the error occurs at a fraction of the 32,160 iterations. If you modify the reproduction code to have three different aliases, then the problem occurs at one third (1/3) of 32,160 iterations. So, this problem may occur sooner or later in an application depending on how many macro expansion/variable substitutions variables are used. Steps to Reproduce Behavior --------------------------- 1. Copy the following code to a program (.prg) file and save it as "MemTest" (without the quotation marks): LOCAL lcAlias, x CLEAR @ 2,1 SAY "Starting User Object Memory Use" @ 3,1 SAY SYS(1016) && User Object Memory Use @ 4,1 SAY "Current User Object Memory Use" FOR x = 1 TO 100000 lcAlias = "A" + ALLTRIM(STR(x)) CREATE CURSOR (lcAlias) (fld1 c(10)) cValue = &lcAlias..fld1 USE IN (lcAlias) @ 1,1 SAY lcAlias @ 5,1 SAY SYS(1016) && User Object Memory Use ENDFOR RETURN 2. Exit FoxPro. 3. Start Visual FoxPro. 4. Run the .prg file MemTest. 5. Watch the User Object Memory Use climb. It should cause an error at approximately 32,160 iterations through the loop. Additional query words: ====================================================================== Keywords : kbDatabase kbvfp300 kbvfp300bBUG kbvfp500 kbvfp500a kbvfp500aBUG kbvfp600 kbvfp600bug KbDBFDBC kbGrpDSFox kbDSupport Technology : kbVFPsearch kbAudDeveloper kbVFP300b kbVFP600 kbVFP500a Version : WINDOWS:3.0b,5.0a,6.0 Issue type : kbbug Solution Type : kbpending ============================================================================= 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 2000.