/*
 * Copyright (C) 2021 Oracle.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
 */

#include "smatch.h"
#include "smatch_slist.h"
#include "smatch_extra.h"

static int my_id;

static bool is_plus(struct expression *expr)
{
	if (expr->type == EXPR_BINOP && expr->op == '+')
		return true;
	/* fixme: what about dst += snprintf() */
	return false;
}

static void match_snprintf(const char *fn, struct expression *expr, void *unused)
{
	struct expression *dest, *limit;
	char *name;

	dest = get_argument_from_call_expr(expr->args, 0);
	limit = get_argument_from_call_expr(expr->args, 1);
	dest = strip_expr(dest);
	limit = strip_expr(limit);
	if (!dest || !limit)
		return;

	if (!is_plus(dest))
		return;

	if (limit->type == EXPR_BINOP && limit->op == '-')
		return;

	name = expr_to_str(limit);
	sm_warning("expected subtract in snprintf limit '%s'", name);
	free_string(name);
}

void check_snprintf_no_minus(int id)
{
	my_id = id;
	add_function_hook("snprintf", &match_snprintf, NULL);
	add_function_hook("scnprintf", &match_snprintf, NULL);
}