FIX: Memory Leak Using CLEAR ALL on Subclass with Array

• Microsoft Visual FoxPro for Windows, version 5.0

SYMPTOMS

The CLEAR ALL command does not recover memory after altering the array property of a class from a subclass. Because the CLEAR ALL command does not recover the memory, running the program numerous times may cause the Visual FoxPro application to exhaust system memory resources.

This problem does not occur in Visual FoxPro for Windows 3.0b.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem was corrected in Visual FoxPro 5.0a for Windows.

MORE INFORMATION

Steps to Reproduce Behavior

Create a program file, add the following code, and execute it.

   * This program illustrates a memory leak in Visual FoxPro 5.0:
   * If an array property of a class is altered in a subclass
   * then there is a memory leak with each instantiation of the
   * subclass.
   * The loop demonstrates the memory leak: Every instantiation of
   * a test1 class will use memory not recoverable by CLEAR ALL.

   FOR lncounter=1 TO 500
      oa=CREATEOBJ("test1")
      _PAGENO=lncounter
      CLEAR ALL
      WAIT WINDOW NOWAIT "Test "+ALLT(STR(_PAGENO,6))+": ;
      Memory used"+ALLTRIM(SYS(1016))
      lncounter=_PAGENO
   ENDFOR
   CLEAR ALL
   RETURN

   *   DO-NOTHING CLASSES which demonstrate the memory leak.
   DEFINE CLASS objectWithArray AS LINE
      DIMENSION atest[1]
      atest[1]=""
      p1="base value for p1"
   ENDDEFINE

   DEFINE CLASS Test1 AS objectWithArray
      DIMENSION atest[4]
      atest[1]="p1"
      atest[2]="p2"
      atest[3]="a1"
      atest[4]="a2"

      p1="default for p1"
      p2="default for p2"
   ENDDEFINE
   *   End of test loop program