GetWindowLong, hEdit, GWL_WNDPROC

[dedndave]

yah - you write a program that doesn't "balance" the GDI stuff and run it 100 times   

[jj2007]

yah - you write a program that doesn't "balance" the GDI stuff and run it 100 times   

Here is one that launches 1,000 times a Win GUI app that creates 1,000 brushes and exits without deleting them. That's a Million "unreleased" GDI handles ;-)

Read the disclaimer. On Win XP SP3 it seems to work fine :icon_mrgreen:

[dedndave]

select them into a DC   

[jj2007]

select them into a DC   

   CASE WM_PAINT
      invoke BeginPaint, hWnd, addr ps
      xchg eax, edi
      .While ctGDI<1000
         invoke CreateSolidBrush, ctGDI
         invoke SelectObject, edi, eax
         inc ctGDI
         SetWin$ hEdit=Str$("brush #%i", ctGDI)
      .endw
      invoke EndPaint, hWnd, addr ps
      invoke SendMessage, hWnd, WM_CLOSE, 0, 0
   ENDSW

[dedndave]

let me sign out and test it - lol

[dedndave]

before and after
oops, i lost 3 mb RAM   :redface:

[jj2007]

before and after
oops, i lost 3 mb RAM   :redface:

3 bytes for a brush? Hmmm...
Probably one of your svchost processes had a hiccup. Or Firefox loaded a page more.
Try again a hundred times ;-)

[dedndave]

3 mb

[jj2007]

3 mb

Divided by one Million unreleased undeleted brushes = 3 bytes per brush :P

[dedndave]

i thought we did 1000

[jj2007]

1000 brushes per launch * 1000 launches = 1Mio

[dedndave]

maybe brush objects is a bad example
i know i have seen problems related to GDI in some newbie programs - lol
i don't recall the exact circumstances, perhaps it was a DIB section or a DC
you run the program several times, then you have to reboot (or maybe log out/in)

[jj2007]

I guess you have to distinguish between
1. a memory leak because of repeated GDI object creations without DeleteObject inside the same app
2. creation of GDI objects once during WM_CREATE, no DeleteObject before ExitProcess.

Case 1 may play havoc with your system, of course. Case 2 depends on whether the object had any "global" implications (atoms, for example). If the object was in the memory that was allocated to the process, then it's gone for good when ExitProcess has done its work.

There is a lot of confusion on this issue - google for memory leak exitprocess to see some of it.

Here is a horribly confused thread: "Should I delete these memory before exit process", here a more solid page: "Does an Application memory leak cause an Operating System memory leak?"

See also M$ support DDEML: Memory Leak in Global Shared Memory - but even GlobalAlloc with the GMEM_DDESHARE flag does not use globally shared memory.