Re: [avr-gcc-list] Memory Size Report

[Peter Harrison]

Ned Konz wrote:

> Look at the avr-libc manual; there are provisions for both defining  
> static constants in flash, as well as versions of the stdlib and  stdio 
> functions that deal with strings that will work with strings in  flash. 
> Look at the documentation for <avr/pgmspace.h>
>
> For instance,
>
> #include <avr/io.h>
> #include <avr/pgmspace.h>
>
> const char s1[] = "abc";  /* will take up both RAM and flash */
>
> const char PROGMEM s2[] = "def" /* will take only flash, but you have  
> to use different functions to access it */
>
> then:
>
> char myBuffer[30];    /* in RAM */
> sprintf(myBuffer, s1);
> /* but */
> sprintf_P(myBuffer, s2);

OK - got it I think.

Where I have been in the habit of just writing an explicit string 
constant in a printf or sprintf call, I should declare the string 
separately first with the PROGMEM attribute to ensure it does not get 
copied into RAM at startup...

Seems to do the job.

Bit of a shame as the printing of a message is not as self-documenting 
if the string is not there in the statement.

I had read the libc manual parts about program space strings as well as 
noticing the sprintf_P variants. Sadly, my less than nimble brain had 
not made the right connections.

Pete Harrison