Subject: Re: [PATCH] Really *do* nothing in while loop

From: Michael Tokarev <[email-masked]>
Date: Sun, 08 May 2005 15:40:40 +0400

jdow wrote:
> From: "James Purser" <[email-masked]>
> 
   while (deflate(&stream, 0) == Z_OK)
-  /* nothing */
+  /* nothing */;
  stream.next_in = buf;
> 
> You guys REALLY do not see the changed semantics here? You are
> changing:
>   while (deflate(&stream, 0) == Z_OK)
>       stream.next_in = buf;
> 
> into
> 
>   while (deflate(&stream, 0) == Z_OK)
>     ;
>   /* Then the data itself.. */
>   stream.next_in = buf;
> 
> I suspect the results of that tiny bit of code would be slightly
> different, especially if "stream.next_in" is volatile, "buf"
> is volatile, or if the assignment to next_in has an effect on
> the "deflate" operation.

As I already said, deflate() in this case does only ONE iteration.
stream.avail_in is NOT changed in the loop (except of the deflate()
itself, where it will be set to 0 - provided out buffer have enouth
room).  So the whole while loop does only ONE iteration, returning
Z_NEED_DATA or something the next one.  So no, the semantics here
(actual semantics) does NOT change.

/mjt