Report task stack overflow

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.

/* FreeRTOSConfig.h */
#define configCHECK_FOR_STACK_OVERFLOW 0

/* report.c */

static int depth_of(const char *s)
{
    if (*s != '[') return 0;
    return 1 + depth_of(s + 1);
}

void report_task(void *p)
{
    char line[256];
    for (;;) {
        float t = read_temp();
        snprintf(line, sizeof line, "T=%.2f C nest=%d", (double)t, depth_of(cmd_buf));
        uart_puts(line);
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

void app_init(void)
{
    xTaskCreate(report_task, "report", 128, NULL, 2, NULL);
}

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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