From: dbaum@camilla.East.Sun.COM (Derek Baum - Sun PC Distributed Systems)
Newsgroups: comp.lang.c,comp.unix.wizards,alt.sources,comp.sources.d,misc.misc
Subject: Re: #define DEBUG... (using printf for debugging)
Message-ID: <1851@east.East.Sun.COM>
Date: 8 May 90 12:29:45 GMT

In article <1104@auto-trol.UUCP> robwah@auto-trol.UUCP (Robert Wahl) writes:
>Writing "dprintf" is left as an exercise for the reader.  Using assembly
>language, it may be an easy thing to prepend stderr to the variable argument
>list and then call "fprintf".  Most likely, though, you will have to parse the
>format string for the number and type of arguments in order to set up the
>call to "fprintf".  If so, you might as well do it all in C (which at least
>is portable), and do your output in stages.
>

It is easy to write dprintf() using vfprintf() as follows:

#include <stdarg.h>

int dprintf(char *format, ...)
{
	va_list ap;

	va_start(ap, format);

	fprintf(stderr, "debug: ");
	vfprintf(stderr, format, ap);
}

--
Derek Baum consulting at:
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