NRF_LOG_DEBUG with dynamic string

[joshuao]

Hello,

# Issue
I'm using a wrapper function for logging, in which you can set callbacks, which get passed the format string, and the va_list of arguments.

I'd like to use as one of my callbacks, the NRF_LOG_XXX functions.
I however notice that they do not accept va_lists.
In order to get around that, I pre-processed the format string and va_list with vsprintf, and then I attempted to pass that string to NRF_LOG_DEBUG.

Here's a little snippet to show what I mean

char formatted_log[1024];

vsnprintf(formatted_log, 1024, fmt, ap);
NRF_LOG_RAW_INFO(formatted_log)

However it ended in an infinite loop, or a HardFault.
I suspect the issue is that NRF_LOG_XXX cannot have a variable string as the first argument, is this correct?

# Workaround
As a work around, one can, as well as the vsprintf, use "%s" as the format string, and have your created format string as an argument.

Thanks,
Joshua

[Sigurd]

Hi,

As mentioned here, you can print a string with the logger module like this:

void foo(void)
{ 
    char string_on_stack[] = "stack";
    //nrf_log_push() copies the string into the logger buffer and returns address from the logger buffer
    NRF_LOG_INFO("%s",NRF_LOG_PUSH(string_on_stack));
}

[joshuao]

While I'm not using deferred logging, I take by the existence of this tip that my "workaround" way is indeed the correct way to deal with it.

Thanks!