[avr-gcc-list] Re: sprintf

[David Brown]

David VanHorn wrote:
>      > has exactly the same effect as:
>      >
>      >       A_String[i] = 0xff;
>      >       A_String[i + 1] = 0x00;
>      >       delay_about_1000_processor_cycles();
>      >       waste_about_2000_bytes_of_code_space();
>
>     ROTF ! :-))))
>
> As was earlier, and more gently pointed out by Dave, Sprintf was pretty 
> wasteful.
> It worked though, and that's what the programmers here suggested I use.
> They are "big iron" guys, so less sensitive to the costs.
> Also, given that I had plenty of code space and cycles, the use of 
> sprintf was "good enough", in that it allowed me to demonstrate the 
> system, and show live data from my sensors.
>  
> Dropping the data into the array is unarguably more efficient, and I 
> shall use that approach in the future.
>  

Unless your "big iron" guys are similarly inexperienced (being a 
beginner is a good excuse for many mistakes), then they are incompetent. 
 There is *no* excuse for a knowledgeable programmer using an 
inefficient and unsafe function in such a horribly unclear manner.

sprintf is not a function that should be much used in real world code - 
snprintf (or asprintf on "big" systems with dynamic memory) is much 
safer for general use (you don't get buffer overflows).

Secondly, using pointer arithmetic when array access is the logically 
correct method is very bad practice.  Again, it is hard to read and 
understand, and it stops the compiler from being able to check for 
mistakes (out of bounds accesses).  If that was *your* mistake, that's 
fair enough - making mistakes is part of learning.  If that was the "big 
iron" guys' mistake, they are in the wrong job.

Having lots of memory and processor resources available is not a reason 
to write rubbish.  It *is* a good reason for prioritising development 
time over run-time (that's why I often write PC software in Python, not 
C).  If you want to go to the shop two miles away, you might take your 
car - it's faster and easier, even if it costs more than walking.  But 
you don't get your car out the garage to drive to your post box at the 
bottom of the garden - that's the equivalent of using sprintf in this case.

> I will admit to being ignorant in C, but I'm not stupid.  :)
>

Don't worry, ignorance is curable :-)