Message-ID:	<01BB4FB0.9776BC00@vessers.mpce.mq.edu.au>
From:	"Victor R. Essers" <vessers AT mpce DOT mq DOT edu DOT au>
To:	"'Vincenzo Morello'" <morellov AT mbox DOT vol DOT it>
Cc:	"'djgpp AT delorie DOT com'" <djgpp AT delorie DOT com>
Subject:	RE: printf("%s",0) - Segmentation fault
Date:	Sat, 1 Jun 1996 11:50:54 +1000
MIME-Version:	1.0

Oh, come on! Why not:

(pp ? "" : pp)

I've never seen any C implementation that treats NULL as something other than 0, so the above code is much more elegant.

- Victor R. Essers.

----------
From: 	Vincenzo Morello
Sent: 	Wednesday, May 29, 1996 3:16 PM
To: 	djgpp AT delorie DOT com
Subject: 	Re: printf("%s",0) - Segmentation fault

Rikard Thunberg wrote:
> 
> The following line will produce a "Segmentation fault" -error on some platforms/compilers:
> printf("%s",0);
> 
> However, some platforms/compilers will produce a string like "(Null)" or similar.
> 
> Is it possible to tell the compiler what to do in this situation?
> 
> /Rikard Thunberg, thunberg AT algonet DOT se

You cannot expect a compiler to act as an interpreter!
The C compiler simply puts in the stack the pointer to
the constant string "%s" and the integer value and then
calls a function. (Note that 0 could be a 16 bit value
in some environment!). The compiler knows nothing about
the use of such parameters in the called function.
When you get the output (null) from the printf function,
it means your program has a BUG. If you need to treat
a NULL string pointer as an empty string, you could
substitute the pointer pp with the expression:
(pp == NULL ? "" : pp)

- Raw text -