printf() and _write() in newlib-nano

printf() and _write() in newlib-nano

[massimiliano cialdi]

I use newlib-nano in an embedded project.
I have implemented my version of _write() to make printf() output chars 
to UART.

I wonder if a single call of printf() results in a single call of 
_write(), or, otherwise _write() can be called more than once by printf().

best regards

Max

Re: printf() and _write() in newlib-nano

[Craig Howland]

On 04/19/2017 04:55 AM, massimiliano cialdi wrote:
> I use newlib-nano in an embedded project.
> I have implemented my version of _write() to make printf() output chars to UART.
>
> I wonder if a single call of printf() results in a single call of _write(), 
> or, otherwise _write() can be called more than once by printf().
>
> best regards
>
> Max 
It depends on many factors (the actual print string, buffered, line buffered, 
text mode, etc.), but either alternative can happen--either one _write per print 
or more than one.  It can range from one write per print to one per character.  
If it is important to you, it probably would be best to instrument it to find 
out directly, and you could observe how it varies.