sprintf needs to be reset every 128 characters?

[humming]

After having a problems with a function using vsnprintf, I finally boiled it down to sprintf. Every 128 characters that has been run through sprintf, it truncates the output.

Steps I used to reproduce it:

* I took the simplest example I could find which used the logging functionality (examples/peripheral/temperature)

* Changed the main function to after printing the temperature, do the following:

        NRF_LOG_INFO("Actual temperature: %d", (int) temp);
        nrf_delay_ms(500);

+        size_t rc = sprintf(buf, "01234567890123456789");
+        NRF_LOG_INFO("Result: %s (%d)", nrf_log_push(buf), rc);

        NRF_LOG_FLUSH();

* (buf is a global char array with size 32)

* Added RTT functionlity to get the logs through Segger RTT

* This resulted in the output to be as follows:

<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 0 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 0 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27
<info> app: Result: 01234567890123456789 (20)
<info> app: Actual temperature: 27

Note that it prints 128 ((20 + \0) * 6 + 1 + \0) characters before truncating, this repeats constantly. It still thinks it printed 20 characters however.

This is on SDK 15.3.0, btw.

[humming]

Thanks for your answers. The reason I don't think this is related to the logging is

a) It still prints the '(20)' text, even though the actual string is chopped off. This could be an artifact of nrf_log_push, so it's not conclusive only a sprintf problem

b) In my real code, I sprint (actually vsnprintf) some text, send that text over a serial line, and sometimes that text shows up slightly shorter than expected. This could be a problem with my code, so again, not conclusive.

When I get back to my nRF toolchain, I will try your suggestions to see if it's a problem with the logging module.

[Edvin]

What does your "buf" variable look like? I would need to know more about how you call this code. Maybe this buffer is full? But then I don't understand why it will print it later. But I still think you should remove the nrf_delay_ms(500).

BR,

Edvin