Undefined reference to 'clock' after linking demo.elf

[The Boon]

Hi all,

I am sorry if this is a rookie question. I had researched and tried the methods shown online, including:

1. added $(ProjectDir)/flash_placement.xml to the linker section > section placement file of the project option
2. editing the sdk_config.h by correcting CLOCK_ENABLED and TIMER_ENABLED from 0 to 1
3. #include <timer.h> on the top and defined the t_latency with type clock_t

I will post my codes and the error messages in the following:

in main.c:

static void client_status_cb(const generic_on_off_client_t * p_self, generic_on_off_status_t status, uint16_t src)
{
    __LOG(LOG_SRC_APP, LOG_LEVEL_ERROR, "server status received \n");
    // Stop time for measuring latency
    t_latency_stop = clock();
    latency = t_latency_stop - t_latency_start;

... ...

... ...

void GPIOTE_IRQHandler(void)
{
    NRF_GPIOTE->EVENTS_PORT = 0;
   
        /* Check that the event was generated by a button press, and reject if it's too soon (debounce).
         * NOTE: There is a bug with this at the wrap-around for the RTC0 where the button could be
         * pressed before HAL_BUTTON_PRESS_FREQUENCY has passed a single time. It doesn't matter practically.
         */
   if( TIMER_DIFF(m_last_button_press, NRF_RTC0->COUNTER) > HAL_BUTTON_PRESS_FREQUENCY)
    {
        m_last_button_press = NRF_RTC0->COUNTER;
        // Start time for measuring latency
        t_latency_start = clock();
        button_event_handler(0);
    }
    
}

the error message:

Thank you for your time!

Best regards,

[awneil]

You make a call to the function clock():

t_latency_stop = clock();

But the linker is telling you that it cannot find any definition of that function.

Usually this happens because you've #included a header (.h) file which just declares the function - but nothing which defines it.

c-faq.com/.../decldef.html

So you need to provide that definition - either is a 'C' source file (.c), or as a prebuilt library.

This is standard 'C' stuff - not specific to Nordic.

How to properly post source code:

EDIT

Specific to the Nordic SDK, you also have to make sure that the features are enbaled in the sdk_config.h file:

https://devzone.nordicsemi.com/f/nordic-q-a/39503/undefined-reference-on-the-linker-level/153004#153004

[The Boon]

Hi awneil,

Thank you for your reply. Thank you for the tips for posting source code, that would be very helpful in the future!

I had just found out online that embedded studio used to program the firmware is a freestanding embedded environment that does not support the standard C library, as someone had the same problem using clock() for other microcontroller. So the problem will arise during linking. Clock() is incorrect for the case of an embedded controller as it measures processor time taken for CPU. I have used the time elapsed after enabling Timer 0 and it worked fine.

Best regards,

[awneil]

The Boon said:

it worked fine

Excellent. Now please verify the answer: