CODEWITHSUNDEEP
windowswinapitimerresource-leak
Sergey Podobry
Sergey Podobry

Reputation: 7189

Is KillTimer necessary?

I use SetTimer API and I see a lot of code like this:

case WM_DESTROY: 
    // Destroy the timer. 
    KillTimer(hwnd, IDT_TIMER); 
    PostQuitMessage(0); 
    break;

Do I have to call KillTimer or the system will automatically free resources on the process exit? Does forgetting to call KillTimer lead to resource leaks?

I understand that if the timer is not needed it CAN be destroyed by KillTimer. But MUST it be destroyed manually?

Upvotes: 12

Views: 4956

Answers (3)

10100111001
10100111001

Reputation: 777

According to MSDN, one should kill timers:

Applications should use the KillTimer function to destroy timers that are no longer necessary. The following example destroys the timers identified by the constants IDT_TIMER1, IDT_TIMER2, and IDT_TIMER3.

// Destroy the timers.
KillTimer(hwnd, IDT_TIMER1);
KillTimer(hwnd, IDT_TIMER2);
KillTimer(hwnd, IDT_TIMER3);

https://msdn.microsoft.com/en-us/library/windows/desktop/ms644901(v=vs.85).aspx#creating_timer

Upvotes: 0

selbie
selbie

Reputation: 104549

Timers set from HWNDs are implicitly destroyed by the window (hwnd) being destroyed. So no, you don't have to clean up your timers when the window exits.

But it's a good practice to have all your resources related to the window cleaned up on window close.

Upvotes: 14

RichieHindle
RichieHindle

Reputation: 281505

The timer will be destroyed automatically by Windows on process exit.

But bear in mind that (so it appears) your timer belongs to the window, not the process. So if your application allows these windows to be created and destroyed within a process, you'll be leaking timers.

It's always good practice to clean things up explicitly, because otherwise the lack of cleanup can come back to bite you later on.

Upvotes: 5

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