OS sanity watchdog hooks

The code

Embedded C for Cortex-M. It compiles. There are 3 real bugs in it: the kind that pass a bench test and fail in the field.

void vApplicationTickHook(void)
{
    IWDG->KR = 0xAAAA;
}

void vApplicationIdleHook(void)
{
    static TickType_t last;
    if (xTaskGetTickCount() - last > 1000) {
        last = xTaskGetTickCount();
        printf("idle ok\n");
        vTaskDelay(pdMS_TO_TICKS(10));
    }
}

void vApplicationStackOverflowHook(TaskHandle_t t, char *name)
{
    printf("stack overflow in %s\n", name);
}

What an interviewer expects

• Point to each line you'd stop in a code review.
• Say what actually breaks: the failure mode, not just the rule it violates.
• Fix it, then defend the fix when asked the follow-up.

The bugs, reference fixes and the follow-up question are in the practice app, after you've tried it.

Companies that test this

Matched on the skills each company's embedded roles emphasise.

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