Re: [avr-gcc-list] Should this code work? 4.1.1

[Graham Davies]

Bob Paddock wrote:
> The "falls out" is the issue with me, as I see the {} as being "contained 
> within",
> the "}" was never crossed, so to me it was still the same {} block.

Let's look at it another way.  Is there anything inside the braces that says 
"let's do all this over and over".  There isn't.  The thing that says to do 
it over is outside the braces.  So, control has to leave the sequence of 
statements inside the braces (the block) to get to the part that says do it 
again.

>  I could not find this "reinitialize" issue in my old K&R book?

I can't help you there as I don't find K&R very good is this way.  What 
you're looking for many not be in one place.  You may have to put it 
together from an understanding of control statements (such as for), blocks 
and the lifetime of automatic variables.  You should realize that if the 
lifetime of a variable ends you are supposed to infer that if it is brought 
back to life by re-entering its block it cannot be expected to have its old 
value.  Initialization of automatic variables takes place at the start of 
their lifetime (afterwards, it's assignment, not initialization.)  You may 
never find this explained as "reinitialization" because that isn't what it 
is.  The old one is gone.  The new one is initialized, not reinitialized.

> I don't see while(true){} being any different than for(;;){}
> in this context, and while(true){} causes the Lint error
> of "evaluation of constant value boolean".

There is no difference in effect.  What I'm suggesting is that when you're 
trying to puzzle out what will happen when control reaches the end of the 
block, it's easier to see that the while condition is re-evaluated to decide 
whether to repeat the block than to figure out that control goes into a for 
statement that is apparently empty of executable content.

I can't see why Lint would consider this an error and for ( ; ; ) not.  Even 
so, isn't there some markup you can add in a comment to reassure Lint that 
this is what you intend?

Graham.