Re: [TCLUG:10678] Simple C Question

["Eric M. Hopper" <hopper@omnifarious.mn.org>]

On Wed, Dec 01, 1999 at 10:36:54AM -0600, Brian Ackermann wrote:
> Ok, simple question for all you C programmers out there...
> 
> Here's the line of code in question...
> 
> printf("%s\n", (char *)(FO_Offset+=16));
> 
> Assuming FO_Offset=0 at start and this code runs in a loop we should
> see:
> 
> 16
> 32
> 48
> 64
> 80
> 96
> 
> and so on...
> 
> I'm assuming that (FO_Offset+=16) evaluates to an integer value, say,
> 16, in
> the first instance,
> and then casting it to a (char *) will let the printf() do what it
> does.
> 
> The program compiles without errors or warnings, but the text is just
> garbage...
> 
> What am I missing?

	*puzzled look*

	The approach you're taking to the problem shows a distinct lack
of understanding of what a C string is.  To explain your misconception
would require talking to you a lot to find out exactly what it was, and
then a lengthy explanation.  I suggest you find a programmer to talk to
in person.

	The answer is this...  You code _should_ read:

print("%d\n", FO_Offset += 16);

	It's bad style to increment FO_Offset in the same statement like
that.  It makes your code much harder to read.  I would suggest:

FO_Offset += 16;
print("%d\n", FO_Offset);

	instead.

	Like I said, please go find someone to explain C strings and how
they work to you.

Have fun (if at all possible),
-- 
Its name is Public Opinion.  It is held in reverence. It settles everything.
Some think it is the voice of God.  Loyalty to petrified opinion never yet
broke a chain or freed a human soul.     ---Mark Twain
-- Eric Hopper (hopper@omnifarious.mn.org
                http://ehopper-host105.dsl.visi.com/~hopper) --

PGP signature