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Date: Fri, 25 Feb 2000 19:17:08 -0800
From: Alfred Perlstein <bright@wintelcom.net>
To: Marco Molteni <molter@csl.sri.com>
Cc: freebsd-chat@FreeBSD.ORG
Subject: Re: how to do this C preprocessor trick?
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* Marco Molteni <molter@csl.sri.com> [000225 18:54] wrote:
> Hi all,
> 
> I have a function that takes a variable number of arguments:
> 
>     void d_printf(const char *format, ...)
> 
> I would like to make it print automatically the function name 
> from which it is called, eg instead of doing
> 
>     f() { d_printf("f: blabla", x, y, z); }
> 
> doing simply
> 
>     f() { d_printf("blabla", x, y, z); }
> 
> To do that, I though of wrapping d_printf() around a macro like
> 
>     #define dprintf(x) d_printf(__FUNCTION__, x)
> 
> but whatever combination I use (also with #), the thing is not going to work:
> 
>     main.c:231: macro `d_printf' used with too many (4) args
> 
> Is it possible to trick the C preprocessor to do what I want?

It's kinda ugly but:

#define panic(A)	\
	do {	\
		panic_set_location(__FILE__, __LINE__);	\
		panic_print_and_die A ;	\
	} while (0)

you'll need to use your macro like this:

 panic(("foo! %s", msg));

there is a way to use varargs macros, but i don't think it's portable.

good luck,
-Alfred


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