Undefined reference to 'clock' after linking demo.elf

RE: Undefined reference to 'clock' after linking demo.elf

awneil — Wed, 16 Jan 2019 18:24:35 GMT

[quote userid="75833" url="~/f/nordic-q-a/42602/undefined-reference-to-clock-after-linking-demo-elf/166064"]it worked fine[/quote]

Excellent. Now please verify the answer:

RE: Undefined reference to 'clock' after linking demo.elf

The Boon — Wed, 16 Jan 2019 16:09:18 GMT

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,

RE: Undefined reference to 'clock' after linking demo.elf

awneil — Wed, 16 Jan 2019 14:16:04 GMT

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