src/lib9/fmt/sprint.c

/*
 * The authors of this software are Rob Pike and Ken Thompson,
 * with contributions from Mike Burrows and Sean Dorward.
 *
 *     Copyright (c) 2002-2006 by Lucent Technologies.
 *     Portions Copyright (c) 2004 Google Inc.
 * 
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES 
 * NOR GOOGLE INC MAKE ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING 
 * THE MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 */

#include <u.h>
#include <libc.h>
#include "fmtdef.h"

int
sprint(char *buf, char *fmt, ...)
{
	int n;
	uint len;
	va_list args;

	len = 1<<30;  /* big number, but sprint is deprecated anyway */
	/*
	 * on PowerPC, the stack is near the top of memory, so
	 * we must be sure not to overflow a 32-bit pointer.
	 *
	 * careful!  gcc-4.2 assumes buf+len < buf can never be true and
	 * optimizes the test away.  casting to uintptr works around this bug.
	 */
	if((uintptr)buf+len < (uintptr)buf)
		len = (uint)-(uintptr)buf-1;

	va_start(args, fmt);
	n = (int)vsnprint(buf, (int)len, fmt, args);
	va_end(args);
	return n;
}