FIX: Placing Icons in Picture Object Causes Memory Leak

ID: Q176765

The information in this article applies to:

SYMPTOMS

A program that loads a series of icon files into the Picture property of a FoxPro image object causes a memory leak in Visual FoxPro 3.0b and 5.0x. Eventually, the operating system becomes unstable and the computer locks.


CAUSE

Loading the icon files may create a leak in process memory. As the program runs, increasing amounts of RAM are consumed. When the program starts using virtual memory, performance suffers and the computer may lock.


RESOLUTION

Here are two workarounds:


STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This has been corrected in Visual FoxPro 6.0.


MORE INFORMATION

Steps to Reproduce Behavior

WARNING: Running the code below causes a low memory situation on the computer. This condition may cause the operating system to become unstable. Close all open applications and save your data before using this procedure. In Windows 95 and Windows NT, press the CTRL+ALT+DEL keys simultaneously to invoke the Close Dialog window or the Task Manager, respectively.

Create and run a program that contains the following code: 

   LOCAL ARRAY laIcons[1,1]
   LOCAL loForm, lnI, lnFile, lnFiles

   loForm = CREATEOBJECT('Form')
   loForm.HEIGHT = 600
   loForm.WIDTH = 200

   FOR lnI = 1 TO 10
   loForm.ADDOBJECT('imgObject' + ALLTRIM(STR(lnI)), 'Image')
   WITH loForm.CONTROLS[lnI]
   .LEFT    = 10
   .TOP     = 10 + (lnI ) * 50
   .WIDTH   = 25
   .HEIGHT  = 25
   .VISIBLE = .T.
   ENDWITH
   ENDFOR

   loForm.ADDOBJECT('lblCounter', 'Label')
   loForm.lblCounter.TOP      = 1
   loForm.lblCounter.LEFT     = 1
   loForm.lblCounter.AUTOSIZE = .T.
   loForm.lblCounter.VISIBLE  = .T.
   loForm.SHOW()
   lnFiles = ADIR(laIcons, HOME() ;
   + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\*.ICO')

   FOR lnI = 1 TO 1000
   loForm.lblCounter.CAPTION = 'Loop :' + PADL(lnI, 4)
   FOR lnFile = 1 TO lnFiles - 10
   loForm.CONTROLS[ 1].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile , 1]
   loForm.CONTROLS[ 2].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile+1, 1]
   loForm.CONTROLS[ 3].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+ laIcons[lnFile+2, 1]
   loForm.CONTROLS[ 4].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 3, 1]
   loForm.CONTROLS[ 5].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 4, 1]
   loForm.CONTROLS[ 6].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 5, 1]
   loForm.CONTROLS[ 7].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 6, 1]
   loForm.CONTROLS[ 8].PICTURE = ;
   HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile+7, 1]
   loForm.CONTROLS[ 9].PICTURE = ;
   HOME()+'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile + 8, 1]
   loForm.CONTROLS[10].PICTURE = ;
   HOME()+'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile + 9, 1]
   IF INKEY(0.001, 'HM') = 27
   CANCEL
   ENDIF
   ENDFOR
   ENDFOR
The first indication of a memory problem appears when the icons no longer appear in the individual image objects. The number of iterations before this symptom appears depends on the amount of physical RAM installed on the computer. Once the memory leak consumes all the physical RAM, Visual FoxPro begins using virtual memory. At this point, performance suffers greatly and the operating system may lock.


REFERENCES

Visual FoxPro Help 3.0b, 5.0, 5.0a; search on: Visual FoxPro HWND Control

Additional query words: kbvfp600fix 


Keywords          : kbVFp FxenvMemory 
Version           : WINDOWS:3.0b,5.0,5.0a
Platform          : WINDOWS 
Issue type        : kbbug

Last Reviewed: August 12, 1999