Fancy debug

fancy-debug.c

/*
 * depending on whether you use a named variadic macro or not you get either:
 *     fancy-debug.c:20:20: warning: ISO C does not permit named variadic macros
 * or
 *     fancy-debug.c:28:13: warning: ISO C99 requires rest arguments to be used
 * or sometimes both depending on your compiler.
 *
 * See also:
 *     http://gcc.gnu.org/onlinedocs/gcc-3.1/cpp/Standard-Predefined-Macros.html
 *     http://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html
 */
 
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
 
void
fancy_debug(const char *file, int line, const char *fmt, ...)
{
  va_list  ap;
 
	fprintf(stderr, "%s:%d: ", file, line);
 
	va_start(ap, fmt);
	vfprintf(stderr, fmt, ap);
	va_end(ap);
 
	fprintf(stderr, "\n");
}
 
#define fdbg(str, ...) fancy_debug(__FILE__, __LINE__, str, ##__VA_ARGS__)
 
int
main()
{
	fancy_debug("test", 42, "a%s", "b");
	fancy_debug("test", 42, "what");
	fdbg("asdf%s", " -- !");
	fdbg("blah");
	return 0;
}
 
/*
 * output is
 *     test:42: ab
 *     test:42: what
 *     fancy-debug.c:27: asdf -- !
 *     fancy-debug.c:28: blah
 */