10 years, 1 month ago.

Thread Local Objects Persist after Termination

I'm encountering a strange problem with local objects in a thread persisting even after the threads destruction. In this case, I have a USB thread that owns a USBHID object like so:

void USB_Thread(void const *args)
{
    USBHID hid;

    while (true) {
        //Do USB stuff!!
    }
}

Now, one would expect that after terminating that thread or destroying it's Thread class wrapper (which deletes it's stack as well), USBHID would go out of scope and be similarly destroyed. Not so. The USBHID object is persisting somehow and the USB peripheral is continuing to enumerate and work. The only thing that has stopped is the actual communication logic that was in the thread loop.

I thought maybe the USB peripheral could continue to run after being setup, so I did some experiments with the following code snippets:

Automatic Version

if (true) {
    USBHID hid(8, 8);
    led1 = 1;
    wait(5.0);
}
led1 = 0;
while(1);

Heap Version

USBHID* hid = new USBHID(8, 8);
led1 = 1;
wait(5.0);
delete hid;
led1 = 0;
while(1);

In both cases, the USB peripheral disconnects from the host as soon as the USBHID object is destroyed. So why is it persisting in a thread?