/*
 * Copyright (C) 2009 Dan Carpenter.
 *
 * 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_extra.h"

static int my_id;

STATE(derefed);

static void underef(struct sm_state *sm, struct expression *mod_expr)
{
        set_state(my_id, sm->name, sm->sym, &undefined);
}

static void match_dereference(struct expression *expr)
{
        if (__in_fake_assign)
                return;

        if (expr->type != EXPR_PREOP)
                return;
        expr = strip_expr(expr->unop);
        if (!is_pointer(expr))
                return;
        if (implied_not_equal(expr, 0))
                return;

        if (is_impossible_path())
                return;

        set_state_expr(my_id, expr, &derefed);
}

static void set_param_dereferenced(struct expression *call, struct expression *arg, char *key, char *unused)
{
        struct symbol *sym;
        char *name;

        name = get_variable_from_key(arg, key, &sym);
        if (!name || !sym)
                goto free;

        if (implied_not_equal_name_sym(name, sym, 0))
                goto free;
        set_state(my_id, name, sym, &derefed);

free:
        free_string(name);
}

static void match_condition(struct expression *expr)
{
        struct sm_state *sm;
        char *name;

        if (__in_pre_condition)
                return;

        name = get_macro_name(expr->pos);
        if (name &&
            (strcmp(name, "likely") != 0 && strcmp(name, "unlikely") != 0))
                return;

        if (!is_pointer(expr))
                return;

        sm = get_sm_state_expr(my_id, expr);
        if (!sm || sm->state != &derefed)
                return;

        sm_warning("variable dereferenced before check '%s' (see line %d)", sm->name, sm->line);
        set_state_expr(my_id, expr, &undefined);
}

void check_deref_check(int id)
{
        my_id = id;
        add_hook(&match_dereference, DEREF_HOOK);
        add_hook(&match_condition, CONDITION_HOOK);
        select_return_implies_hook(DEREFERENCE, &set_param_dereferenced);
        add_modification_hook(my_id, &underef);
}