nRF9160: AWS IoT Sample Application

RE: nRF9160: AWS IoT Sample Application

Zeedel — Tue, 24 Nov 2020 16:09:54 GMT

Thanks for looking into this Didrik, and kindly informing the developers. A great debugging experience would really be helpful, and allow us to self-serve in most cases.

RE: nRF9160: AWS IoT Sample Application

Didrik Rokhaug — Tue, 24 Nov 2020 15:58:32 GMT

I can confirm that I see the crash when calling aws_topics_populate both with no optimizations and with debug optimizations. The call does not crash when optimizing for size or speed.

I haven't yet found a good reason for why the crash happens, but I have informed the developers of that library.

To me, it seems like aws_topics_populate is inlined in aws_iot_init when optimizing for speed or size. You can still step through the function, but it will look like you are inside the aws_iot_init function. This is exacerbated by the fact that aws_topics_populate is almost exclusively calls to snprintf, so most time would be spent there, rather than the few assembly instructions that "actually" come from aws_topics_populate.

I can agree that it is not be best debugging experience, but other than the crash when not optimizing the code, I can not find anything wrong.

RE: nRF9160: AWS IoT Sample Application

Didrik Rokhaug — Fri, 20 Nov 2020 17:06:39 GMT

Hi, and sorry for the late response.

It's good to hear that you found the cause of the error.

I haven't been able to look much into why you are not able to step into the aws_topics_populate function, but I will do so early next week.

Best regards,

Didrik

RE: nRF9160: AWS IoT Sample Application

Zeedel — Wed, 18 Nov 2020 15:25:17 GMT

Quick update, it appears my client-id is long, so had to adjust CONFIG_AWS_IOT_CLIENT_ID_MAX_LEN. I am no longer getting the error. However, I am yet to make sense why I was unable to step into the aws_topics_populate function. Would you be able to advise.

RE: nRF9160: AWS IoT Sample Application

Zeedel — Wed, 18 Nov 2020 14:52:45 GMT

Hi Didrik,

Thanks for picking this up, and kindly getting back to me.

I can confirm that CONFIG_AWS_IOT_CLIENT_ID_APP is not set.

The aws_iot_init implementation is as follows:

int aws_iot_init(const struct aws_iot_config *const config,
		 aws_iot_evt_handler_t event_handler)
{
	int err;

	if (IS_ENABLED(CONFIG_AWS_IOT_CLIENT_ID_APP) &&
	    config->client_id_len >= CONFIG_AWS_IOT_CLIENT_ID_MAX_LEN) {
		LOG_ERR("Client ID string too long");
		return -EMSGSIZE;
	}

	if (IS_ENABLED(CONFIG_AWS_IOT_CLIENT_ID_APP) &&
	    config->client_id == NULL) {
		LOG_ERR("Client ID not set in the application");
		return -ENODATA;
	}

	err = aws_iot_topics_populate(config->client_id, config->client_id_len);
	if (err) {
		LOG_ERR("aws_topics_populate, error: %d", err);
		return err;
	}

#if defined(CONFIG_AWS_FOTA)
	err = aws_fota_init(&client, aws_fota_cb_handler);
	if (err) {
		LOG_ERR("aws_fota_init, error: %d", err);
		return err;
	}
#endif

	module_evt_handler = event_handler;

	return err;
}

so if a NULL argument is passed for aws_iot_config*, config->client_id evaluates to garbage I would assume but as you correctly stated is not used inside aws_iot_topics_populate.

I tried debugging into aws_iot_topics_populate to see where the failure is happening but for some reason the debugger won't step into the C function. Here's a screenshot of what I get:

I thought the reason may be due to optimisations done by the compiler, so I tried the below setting in prj.conf:

CONFIG_DEBUG_OPTIMIZATIONS=y

but still couldn't step into the function. In fact, the code seems to crash... please see below:

Any suggestions / pointers?

RE: nRF9160: AWS IoT Sample Application

Didrik Rokhaug — Wed, 18 Nov 2020 13:45:14 GMT

Hi,

The sample seems to be working for me. I still get an error (when I call getaddrinfo, it does not find the hostname), but that is probably just an error on my end. Anyway, the error I get comes after the point where I should have seen your error, so the call to aws_iot_init returns successfully.

Looking at the code, the argument is not used in aws_topics_populate, unless you have set CONFIG_AWS_IOT_CLIENT_ID_APP. Do you know which call to snprintf fails in aws_topics_populate.

As for the note, I think that it is only for when CONFIG_IOT_CLIENT_ID_APP is set. But I agree that the note is confusing, and I will talk to our developers to see if it can be improved.

The socket will be created and set when you call aws_iot_connect, so you do not need to set that field yourself.

Best regards,

Didrik