flow: don't call scope_guard hooks twice at the end of functions

[smatch.git] / smatch_function_hooks.c

/*
 * 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
 */

/*
 * There are several types of function hooks.
 *
 * The param_key hooks are probably the right things to use going forward.
 * They give you a name/sym pair so it means less code in the checks.
 *
 * The add_function_hook() functions are trigger for every call.  The
 * "return_implies" are triggered for specific return ranges.  The "exact"
 * variants will be triggered if it's *definitely* in the range where the
 * others will be triggered if it's *possibly* in the range.  The "late"
 * variants will be triggered after the others have run.
 *
 * There are a few miscellaneous things like add_function_assign_hook() and
 * add_macro_assign_hook() which are only triggered for assignments.  The
 * add_implied_return_hook() let's you manually adjust the return range.
 *
 * Every call:
 *     add_function_param_key_hook_early()
 *     add_function_param_key_hook()
 *     add_function_param_key_hook_late()
 *     add_param_key_expr_hook()
 *     add_function_hook_early()
 *     add_function_hook()
 *
 * Just for some return ranges:
 *     return_implies_param_key()
 *     return_implies_param_key_expr()
 *     return_implies_param_key_exact()
 *     return_implies_state()
 *     select_return_param_key()  (It's weird that this is not in smatch_db.c)
 *
 * For Assignments:
 *     add_function_assign_hook()
 *
 * For Macro Assignments:
 *     add_macro_assign_hook()
 *
 * Manipulate the return range.
 *     add_implied_return_hook()
 */

#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include "smatch.h"
#include "smatch_slist.h"
#include "smatch_extra.h"
#include "smatch_function_hashtable.h"
#include "smatch_expression_stacks.h"

struct fcall_back {
        int type;
        struct data_range *range;
        union {
                func_hook *call_back;
                implication_hook *ranged;
                implied_return_hook *implied_return;
        } u;
        void *info;
};

ALLOCATOR(fcall_back, "call backs");
DECLARE_PTR_LIST(call_back_list, struct fcall_back);

DEFINE_FUNCTION_HASHTABLE_STATIC(callback, struct fcall_back, struct call_back_list);
static struct hashtable *func_hash;

int __in_fake_parameter_assign;

enum fn_hook_type {
        REGULAR_CALL_EARLY,
        REGULAR_CALL,
        REGULAR_CALL_LATE,
        RANGED_CALL,
        RANGED_EXACT,
        ASSIGN_CALL,
        IMPLIED_RETURN,
        MACRO_ASSIGN,
        MACRO_ASSIGN_EXTRA,
};

struct param_key_data {
        param_key_hook *call_back;
        expr_func *expr_fn;
        int param;
        const char *key;
        void *info;
};

struct param_data {
        expr_func *call_back;
        int param;
        void *info;
};

struct return_implies_callback {
        int type;
        bool param_key;
        union {
                return_implies_hook *callback;
                param_key_hook *pk_callback;
        };
};
ALLOCATOR(return_implies_callback, "return_implies callbacks");
DECLARE_PTR_LIST(db_implies_list, struct return_implies_callback);
static struct db_implies_list *db_return_states_list;

static struct void_fn_list *return_states_before;
static struct void_fn_list *return_states_after;
static struct string_hook_list *return_string_hooks;

struct db_callback_info {
        int true_side;
        int comparison;
        struct expression *expr;
        struct range_list *rl;
        int left;
        struct stree *stree;
        struct stree *implied;
        struct db_implies_list *callbacks;
        struct db_implies_list *called;
        int prev_return_id;
        int cull;
        int has_states;
        bool states_merged;
        char *ret_str;
        struct smatch_state *ret_state;
        struct expression *var_expr;
        struct expression_list *fake_param_assign_stack;
        int handled;
};

static struct expression_list *fake_calls;

void add_fake_call_after_return(struct expression *call)
{
        add_ptr_list(&fake_calls, call);
}

static void parse_fake_calls(void)
{
        struct expression_list *list;
        struct expression *call;

        list = fake_calls;
        fake_calls = NULL;

        FOR_EACH_PTR(list, call) {
                __split_expr(call);
        } END_FOR_EACH_PTR(call);

        __free_ptr_list((struct ptr_list **)&list);
}

static struct fcall_back *alloc_fcall_back(int type, void *call_back,
                                           void *info)
{
        struct fcall_back *cb;

        cb = __alloc_fcall_back(0);
        cb->type = type;
        cb->u.call_back = call_back;
        cb->info = info;
        return cb;
}

static const char *get_fn_name(struct expression *fn)
{
        fn = strip_expr(fn);
        if (!fn)
                return NULL;
        if (fn->type == EXPR_SYMBOL && fn->symbol)
                return fn->symbol->ident->name;
        return get_member_name(fn);
}

static struct call_back_list *get_call_backs(const char *fn_name)
{
        if (!fn_name)
                return NULL;
        return search_callback(func_hash, (char *)fn_name);
}

void add_function_hook(const char *look_for, func_hook *call_back, void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(REGULAR_CALL, call_back, info);
        add_callback(func_hash, look_for, cb);
}

void add_function_hook_early(const char *look_for, func_hook *call_back, void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(REGULAR_CALL_EARLY, call_back, info);
        add_callback(func_hash, look_for, cb);
}

void add_function_hook_late(const char *look_for, func_hook *call_back, void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(REGULAR_CALL_LATE, call_back, info);
        add_callback(func_hash, look_for, cb);
}

void add_function_assign_hook(const char *look_for, func_hook *call_back,
                              void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(ASSIGN_CALL, call_back, info);
        add_callback(func_hash, look_for, cb);
}

static void register_funcs_from_file_helper(const char *file,
                                            func_hook *call_back, void *info,
                                            bool assign)
{
        struct token *token;
        const char *func;
        char name[64];

        snprintf(name, sizeof(name), "%s.%s", option_project_str, file);
        token = get_tokens_file(name);
        if (!token)
                return;
        if (token_type(token) != TOKEN_STREAMBEGIN)
                return;
        token = token->next;
        while (token_type(token) != TOKEN_STREAMEND) {
                if (token_type(token) != TOKEN_IDENT)
                        return;
                func = show_ident(token->ident);
                if (assign)
                        add_function_assign_hook(func, call_back, info);
                else
                        add_function_hook(func, call_back, info);
                token = token->next;
        }
        clear_token_alloc();
}

void register_func_hooks_from_file(const char *file,
                                   func_hook *call_back, void *info)
{
        register_funcs_from_file_helper(file, call_back, info, false);
}

void register_assign_hooks_from_file(const char *file,
                                     func_hook *call_back, void *info)
{
        register_funcs_from_file_helper(file, call_back, info, true);
}

void add_implied_return_hook(const char *look_for,
                             implied_return_hook *call_back,
                             void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(IMPLIED_RETURN, call_back, info);
        add_callback(func_hash, look_for, cb);
}

static void db_helper(struct expression *expr, param_key_hook *call_back, int param, const char *key, void *info)
{
        char *name;
        struct symbol *sym;

        if (param == -2) {
                call_back(expr, key, NULL, info);
                return;
        }

        name = get_name_sym_from_param_key(expr, param, key, &sym);
        if (!name || !sym)
                goto free;

        call_back(expr, name, sym, info);
free:
        free_string(name);
}

static struct expression *get_parent_assignment(struct expression *expr)
{
        struct expression *parent;
        int cnt = 0;

        if (expr->type == EXPR_ASSIGNMENT)
                return NULL;

        parent = expr_get_fake_parent_expr(expr);
        if (parent && parent->type == EXPR_ASSIGNMENT)
                return parent;

        parent = expr;
        while (true) {
                parent = expr_get_parent_expr(parent);
                if (!parent || ++cnt >= 5)
                        break;
                if (parent->type == EXPR_CAST)
                        continue;
                if (parent->type == EXPR_PREOP && parent->op == '(')
                        continue;
                break;
        }

        if (parent && parent->type == EXPR_ASSIGNMENT)
                return parent;
        return NULL;
}

static void param_key_function(const char *fn, struct expression *expr, void *data)
{
        struct param_key_data *pkd = data;
        struct expression *parent;

        parent = get_parent_assignment(expr);
        if (parent)
                expr = parent;

        db_helper(expr, pkd->call_back, pkd->param, pkd->key, pkd->info);
}

static void param_key_expr_function(const char *fn, struct expression *expr, void *data)
{
        struct param_key_data *pkd = data;
        struct expression *parent, *arg;

        parent = get_parent_assignment(expr);
        if (parent)
                expr = parent;

        arg = gen_expr_from_param_key(expr, pkd->param, pkd->key);
        if (!arg)
                return;
        pkd->expr_fn(arg);
}

static void param_key_implies_function(const char *fn, struct expression *call_expr,
                                       struct expression *assign_expr, void *data)
{
        struct param_key_data *pkd = data;

        db_helper(assign_expr ?: call_expr, pkd->call_back, pkd->param, pkd->key, pkd->info);
}

static void param_key_expr_implies_function(const char *fn, struct expression *call_expr,
                                            struct expression *assign_expr, void *data)
{
        struct param_key_data *pkd = data;
        struct expression *arg;

        arg = gen_expr_from_param_key(assign_expr ?: call_expr, pkd->param, pkd->key);
        if (!arg)
                return;
        pkd->expr_fn(arg);
}

static struct param_key_data *alloc_pkd(param_key_hook *call_back, int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = malloc(sizeof(*pkd));
        pkd->call_back = call_back;
        pkd->param = param;
        pkd->key = alloc_string(key);
        pkd->info = info;

        return pkd;
}

static struct param_key_data *alloc_pked(expr_func *call_back, int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = alloc_pkd(NULL, param, key, info);
        pkd->expr_fn = call_back;

        return pkd;
}

void add_function_param_key_hook_early(const char *look_for, param_key_hook *call_back,
                                       int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        if (param == -1) {
                printf("pointless early hook for '%s'", look_for);
                return;
        }

        pkd = alloc_pkd(call_back, param, key, info);
        add_function_hook_early(look_for, &param_key_function, pkd);
}

void add_function_param_key_hook(const char *look_for, param_key_hook *call_back,
                                 int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = alloc_pkd(call_back, param, key, info);
        if (param == -1)
                add_function_assign_hook(look_for, &param_key_function, pkd);
        else
                add_function_hook(look_for, &param_key_function, pkd);
}

void add_param_key_expr_hook(const char *look_for, expr_func *call_back,
                                  int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = alloc_pked(call_back, param, key, info);

        if (param == -1)
                add_function_assign_hook(look_for, &param_key_expr_function, pkd);
        else
                add_function_hook(look_for, &param_key_expr_function, pkd);
}

void add_function_param_key_hook_late(const char *look_for, param_key_hook *call_back,
                                      int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = alloc_pkd(call_back, param, key, info);
        add_function_hook_late(look_for, &param_key_function, pkd);
}

void return_implies_param_key(const char *look_for, sval_t start, sval_t end,
                              param_key_hook *call_back,
                              int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = alloc_pkd(call_back, param, key, info);
        return_implies_state_sval(look_for, start, end, &param_key_implies_function, pkd);
}

void return_implies_param_key_exact(const char *look_for, sval_t start, sval_t end,
                                    param_key_hook *call_back,
                                    int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = alloc_pkd(call_back, param, key, info);
        return_implies_exact(look_for, start, end, &param_key_implies_function, pkd);
}

void return_implies_param_key_expr(const char *look_for, sval_t start, sval_t end,
                                   expr_func *call_back,
                                   int param, const char *key, void *info)
{
        struct param_key_data *pkd;

        pkd = alloc_pked(call_back, param, key, info);
        return_implies_state_sval(look_for, start, end, &param_key_expr_implies_function, pkd);
}

void add_macro_assign_hook(const char *look_for, func_hook *call_back,
                        void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(MACRO_ASSIGN, call_back, info);
        add_callback(func_hash, look_for, cb);
}

void add_macro_assign_hook_extra(const char *look_for, func_hook *call_back,
                        void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(MACRO_ASSIGN_EXTRA, call_back, info);
        add_callback(func_hash, look_for, cb);
}

void return_implies_state(const char *look_for, long long start, long long end,
                         implication_hook *call_back, void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(RANGED_CALL, call_back, info);
        cb->range = alloc_range_perm(ll_to_sval(start), ll_to_sval(end));
        add_callback(func_hash, look_for, cb);
}

void return_implies_state_sval(const char *look_for, sval_t start, sval_t end,
                         implication_hook *call_back, void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(RANGED_CALL, call_back, info);
        cb->range = alloc_range_perm(start, end);
        add_callback(func_hash, look_for, cb);
}

void return_implies_exact(const char *look_for, sval_t start, sval_t end,
                          implication_hook *call_back, void *info)
{
        struct fcall_back *cb;

        cb = alloc_fcall_back(RANGED_EXACT, call_back, info);
        cb->range = alloc_range_perm(start, end);
        add_callback(func_hash, look_for, cb);
}

static struct return_implies_callback *alloc_db_return_callback(int type, bool param_key, void *callback)
{
        struct return_implies_callback *cb;

        cb = __alloc_return_implies_callback(0);
        cb->type = type;
        cb->param_key = param_key;
        cb->callback = callback;

        return cb;
}

void select_return_states_hook(int type, return_implies_hook *callback)
{
        struct return_implies_callback *cb;

        cb = alloc_db_return_callback(type, false, callback);
        add_ptr_list(&db_return_states_list, cb);
}

static void call_db_return_callback(struct db_callback_info *db_info,
                                    struct return_implies_callback *cb,
                                    int param, char *key, char *value)
{
        if (cb->param_key) {
                db_helper(db_info->expr, cb->pk_callback, param, key, NULL);
                add_ptr_list(&db_info->called, cb);
        } else {
                cb->callback(db_info->expr, param, key, value);
        }
}

void select_return_param_key(int type, param_key_hook *callback)
{
        struct return_implies_callback *cb;

        cb = alloc_db_return_callback(type, true, callback);
        add_ptr_list(&db_return_states_list, cb);
}

void select_return_states_before(void_fn *fn)
{
        add_ptr_list(&return_states_before, fn);
}

void select_return_states_after(void_fn *fn)
{
        add_ptr_list(&return_states_after, fn);
}

void add_return_string_hook(string_hook *fn)
{
        add_ptr_list(&return_string_hooks, fn);
}

static bool call_call_backs(struct call_back_list *list, int type,
                            const char *fn, struct expression *expr)
{
        struct fcall_back *tmp;
        bool handled = false;

        FOR_EACH_PTR(list, tmp) {
                if (tmp->type == type) {
                        (tmp->u.call_back)(fn, expr, tmp->info);
                        handled = true;
                }
        } END_FOR_EACH_PTR(tmp);

        return handled;
}

static void call_function_hooks(struct expression *expr, enum fn_hook_type type)
{
        struct call_back_list *call_backs;
        const char *fn_name;

        while (expr->type == EXPR_ASSIGNMENT)
                expr = strip_expr(expr->right);
        if (expr->type != EXPR_CALL)
                return;

        fn_name = get_fn_name(expr->fn);
        call_backs = get_call_backs(fn_name);
        if (!call_backs)
                return;

        call_call_backs(call_backs, type, fn_name, expr);
}

static void call_return_states_after_hooks(struct expression *expr)
{
        call_void_fns(return_states_after);
        __pass_to_client(expr, FUNCTION_CALL_HOOK_AFTER_DB);
        call_function_hooks(expr, REGULAR_CALL_LATE);
}

static void call_ranged_call_backs(struct call_back_list *list,
                                const char *fn, struct expression *call_expr,
                                struct expression *assign_expr)
{
        struct fcall_back *tmp;

        FOR_EACH_PTR(list, tmp) {
                (tmp->u.ranged)(fn, call_expr, assign_expr, tmp->info);
        } END_FOR_EACH_PTR(tmp);
}

static struct call_back_list *get_same_ranged_call_backs(struct call_back_list *list,
                                                struct data_range *drange)
{
        struct call_back_list *ret = NULL;
        struct fcall_back *tmp;

        FOR_EACH_PTR(list, tmp) {
                if (tmp->type != RANGED_CALL &&
                    tmp->type != RANGED_EXACT)
                        continue;
                if (ranges_equiv(tmp->range, drange))
                        add_ptr_list(&ret, tmp);
        } END_FOR_EACH_PTR(tmp);
        return ret;
}

static bool in_list_exact_sval(struct range_list *list, struct data_range *drange)
{
        struct data_range *tmp;

        FOR_EACH_PTR(list, tmp) {
                if (ranges_equiv(tmp, drange))
                        return true;
        } END_FOR_EACH_PTR(tmp);
        return false;
}

/*
 * The assign_ranged_funcs() function is called when we have no data from the DB.
 */
static bool assign_ranged_funcs(const char *fn, struct expression *expr,
                                 struct call_back_list *call_backs)
{
        struct fcall_back *tmp;
        struct sm_state *sm;
        char *var_name;
        struct symbol *sym;
        struct smatch_state *estate;
        struct stree *tmp_stree;
        struct stree *final_states = NULL;
        struct range_list *handled_ranges = NULL;
        struct range_list *unhandled_rl;
        struct call_back_list *same_range_call_backs = NULL;
        struct expression *call;
        struct range_list *rl;
        int handled = false;

        if (!call_backs)
                return false;

        var_name = expr_to_var_sym(expr->left, &sym);
        if (!var_name || !sym)
                goto free;

        call = strip_expr(expr->right);

        FOR_EACH_PTR(call_backs, tmp) {
                if (tmp->type != RANGED_CALL &&
                    tmp->type != RANGED_EXACT)
                        continue;

                if (in_list_exact_sval(handled_ranges, tmp->range))
                        continue;
                __push_fake_cur_stree();
                tack_on(&handled_ranges, tmp->range);

                same_range_call_backs = get_same_ranged_call_backs(call_backs, tmp->range);
                call_ranged_call_backs(same_range_call_backs, fn, expr->right, expr);
                __free_ptr_list((struct ptr_list **)&same_range_call_backs);

                rl = alloc_rl(tmp->range->min, tmp->range->max);
                rl = cast_rl(get_type(expr->left), rl);
                estate = alloc_estate_rl(rl);
                set_extra_mod(var_name, sym, expr->left, estate);

                tmp_stree = __pop_fake_cur_stree();
                merge_fake_stree(&final_states, tmp_stree);
                free_stree(&tmp_stree);
                handled = true;
        } END_FOR_EACH_PTR(tmp);

        unhandled_rl = rl_filter(alloc_whole_rl(get_type(call)), handled_ranges);
        if (unhandled_rl) {
                __push_fake_cur_stree();
                rl = cast_rl(get_type(expr->left), unhandled_rl);
                estate = alloc_estate_rl(rl);
                set_extra_mod(var_name, sym, expr->left, estate);
                tmp_stree = __pop_fake_cur_stree();
                merge_fake_stree(&final_states, tmp_stree);
                free_stree(&tmp_stree);
        }

        FOR_EACH_SM(final_states, sm) {
                __set_sm(sm);
        } END_FOR_EACH_SM(sm);

        free_stree(&final_states);
free:
        free_string(var_name);
        return handled;
}

static void call_implies_callbacks(int comparison, struct expression *expr, sval_t sval, int left, struct stree **implied_true, struct stree **implied_false)
{
        struct call_back_list *call_backs;
        struct fcall_back *tmp;
        const char *fn_name;
        struct data_range *value_range;
        struct stree *true_states = NULL;
        struct stree *false_states = NULL;
        struct stree *tmp_stree;

        *implied_true = NULL;
        *implied_false = NULL;
        fn_name = get_fn_name(expr->fn);
        call_backs = get_call_backs(fn_name);
        if (!call_backs)
                return;
        value_range = alloc_range(sval, sval);

        /* set true states */
        __push_fake_cur_stree();
        FOR_EACH_PTR(call_backs, tmp) {
                if (tmp->type != RANGED_CALL &&
                    tmp->type != RANGED_EXACT)
                        continue;
                if (!true_comparison_range_LR(comparison, tmp->range, value_range, left))
                        continue;
                (tmp->u.ranged)(fn_name, expr, NULL, tmp->info);
        } END_FOR_EACH_PTR(tmp);
        tmp_stree = __pop_fake_cur_stree();
        merge_fake_stree(&true_states, tmp_stree);
        free_stree(&tmp_stree);

        /* set false states */
        __push_fake_cur_stree();
        FOR_EACH_PTR(call_backs, tmp) {
                if (tmp->type != RANGED_CALL &&
                    tmp->type != RANGED_EXACT)
                        continue;
                if (!false_comparison_range_LR(comparison, tmp->range, value_range, left))
                        continue;
                (tmp->u.ranged)(fn_name, expr, NULL, tmp->info);
        } END_FOR_EACH_PTR(tmp);
        tmp_stree = __pop_fake_cur_stree();
        merge_fake_stree(&false_states, tmp_stree);
        free_stree(&tmp_stree);

        *implied_true = true_states;
        *implied_false = false_states;
}

static void set_implied_states(struct db_callback_info *db_info)
{
        struct sm_state *sm;

        FOR_EACH_SM(db_info->implied, sm) {
                __set_sm(sm);
        } END_FOR_EACH_SM(sm);

        free_stree(&db_info->implied);
}

static void store_return_state(struct db_callback_info *db_info, const char *ret_str, struct smatch_state *state)
{
        db_info->ret_str = alloc_sname(ret_str),
        db_info->ret_state = state;
}

static struct expression_list *unfaked_calls;

struct expression *get_unfaked_call(void)
{
        return last_ptr_list((struct ptr_list *)unfaked_calls);
}

static void store_unfaked_call(struct expression *expr)
{
        push_expression(&unfaked_calls, expr);
}

static void clear_unfaked_call(void)
{
        delete_ptr_list_last((struct ptr_list **)&unfaked_calls);
}

void fake_param_assign_helper(struct expression *call, struct expression *fake_assign, bool shallow)
{
        store_unfaked_call(call);
        __in_fake_parameter_assign++;
        parse_assignment(fake_assign, true);
        __in_fake_parameter_assign--;
        clear_unfaked_call();
}

static bool fake_a_param_assignment(struct expression *expr, const char *ret_str, struct smatch_state *orig)
{
        struct expression *arg, *left, *right, *tmp, *fake_assign;
        char *p;
        int param;
        char buf[256];
        char *str;

        if (expr->type != EXPR_ASSIGNMENT || expr->op != '=')
                return false;
        left = expr->left;
        right = expr->right;

        while (right->type == EXPR_ASSIGNMENT)
                right = strip_expr(right->right);
        if (!right || right->type != EXPR_CALL)
                return false;

        p = strchr(ret_str, '[');
        if (!p)
                return false;

        p++;
        if (p[0] == '=' && p[1] == '=')
                p += 2;
        if (p[0] != '$')
                return false;

        snprintf(buf, sizeof(buf), "%s", p);

        p = buf;
        p += 1;
        param = strtol(p, &p, 10);

        p = strchr(p, ']');
        if (!p || *p != ']')
                return false;
        *p = '\0';

        arg = get_argument_from_call_expr(right->args, param);
        if (!arg)
                return false;

        /* There should be a get_other_name() function which returns an expr */
        tmp = get_assigned_expr(arg);
        if (tmp)
                arg = tmp;

        /*
         * This is a sanity check to prevent side effects from evaluating stuff
         * twice.
         */
        str = expr_to_chunk_sym_vsl(arg, NULL, NULL);
        if (!str)
                return false;
        free_string(str);

        right = gen_expression_from_key(arg, buf);
        if (!right)  /* Mostly fails for binops like [$0 + 4032] */
                return false;
        fake_assign = assign_expression(left, '=', right);
        fake_param_assign_helper(expr, fake_assign, false);

        /*
         * If the return is "0-65531[$0->nla_len - 4]" the faked expression
         * is maybe (-4)-65531 but we know it is in the 0-65531 range so both
         * parts have to be considered.  We use _nomod() because it's not really
         * another modification, it's just a clarification.
         *
         */
        if (estate_rl(orig)) {
                struct smatch_state *faked;
                struct range_list *rl;

                faked = get_extra_state(left);
                if (estate_rl(faked)) {
                        rl = rl_intersection(estate_rl(faked), estate_rl(orig));
                        if (rl)
                                set_extra_expr_nomod(left, alloc_estate_rl(rl));
                }
        }

        return true;
}

static void fake_return_assignment(struct db_callback_info *db_info, int type, int param, char *key, char *value)
{
        struct expression *call, *left, *right, *assign;
        int right_param;

        if (type != PARAM_COMPARE)
                return;

        call = db_info->expr;
        while (call && call->type == EXPR_ASSIGNMENT)
                call = strip_expr(call->right);
        if (!call || call->type != EXPR_CALL)
                return;

        // TODO: This only handles "$->foo = arg" and not "$->foo = arg->bar".
        if (param != -1)
                return;
        if (!value || strncmp(value, "== $", 4) != 0)
                return;
        if (!isdigit(value[4]) || value[5] != '\0')
                return;
        right_param = atoi(value + 4);

        left = gen_expr_from_param_key(db_info->expr, param, key);
        if (!left)
                return;
        right = get_argument_from_call_expr(call->args, right_param);

        assign = assign_expression(left, '=', right);
        push_expression(&db_info->fake_param_assign_stack, assign);
}

static void set_fresh_mtag_returns(struct db_callback_info *db_info)
{
        struct expression *expr;
        struct smatch_state *state;

        if (!db_info->ret_state)
                return;

        if (!db_info->expr ||
            db_info->expr->type != EXPR_ASSIGNMENT ||
            db_info->expr->op != '=')
                return;

        expr = db_info->expr->left;

        state = alloc_estate_rl(cast_rl(get_type(expr), clone_rl(estate_rl(db_info->ret_state))));
        state = get_mtag_return(db_info->expr, state);
        if (!state)
                return;

        set_real_absolute(expr, state);
        set_extra_expr_mod(expr, state);
}

static void set_return_assign_state(struct db_callback_info *db_info)
{
        struct expression *expr = db_info->expr->left;
        struct expression *fake_assign;
        struct smatch_state *state;

        if (!db_info->ret_state)
                return;

        state = alloc_estate_rl(cast_rl(get_type(expr), clone_rl(estate_rl(db_info->ret_state))));
        if (!fake_a_param_assignment(db_info->expr, db_info->ret_str, state))
                set_extra_expr_mod(expr, state);

        while ((fake_assign = pop_expression(&db_info->fake_param_assign_stack))) {
                struct range_list *left, *right;

                /*
                 * Originally, I tried to do this as a assignment to record that
                 * a = frob(b) implies that "a->foo == b->foo" etc.  But that
                 * caused a problem because then it was recorded that "a->foo"
                 * was modified and recorded as a PARAM_SET in the database.
                 *
                 * So now, instead of faking an assignment we use
                 * set_extra_expr_nomod() but it's still recorded as an
                 * assignment in the ->fake_param_assign_stack for legacy
                 * reasons and because it's a handy way to store a left/right
                 * pair.
                 */

                get_absolute_rl(fake_assign->left, &left);
                get_absolute_rl(fake_assign->right, &right);
                right = cast_rl(get_type(fake_assign->left), right);
                // FIXME: add some sanity checks
                // FIXME: preserve the sm state if possible
                set_extra_expr_nomod(fake_assign->left, alloc_estate_rl(right));
        }
}

static void set_other_side_state(struct db_callback_info *db_info)
{
        struct expression *expr = db_info->var_expr;
        struct smatch_state *state;

        if (!db_info->ret_state)
                return;

        // TODO: faked_assign set ==$ equiv here

        state = alloc_estate_rl(cast_rl(get_type(expr), clone_rl(estate_rl(db_info->ret_state))));
        set_extra_expr_nomod(expr, state);
        db_info->ret_state = NULL;
        db_info->ret_str = NULL;
}

static void handle_ret_equals_param(char *ret_string, struct range_list *rl, struct expression *call)
{
        char *str;
        long long param;
        struct expression *arg;
        struct range_list *orig;

        // TODO: faked_assign This needs to be handled in the assignment code

        str = strstr(ret_string, "==$");
        if (!str)
                return;
        str += 3;
        param = strtoll(str, NULL, 10);
        arg = get_argument_from_call_expr(call->args, param);
        if (!arg)
                return;
        get_absolute_rl(arg, &orig);
        rl = rl_intersection(orig, rl);
        if (!rl)
                return;
        set_extra_expr_nomod(arg, alloc_estate_rl(rl));
}

static bool impossible_limit(struct db_callback_info *db_info, int param, char *key, char *value)
{
        struct expression *expr = db_info->expr;
        struct expression *arg;
        struct smatch_state *state;
        struct range_list *passed;
        struct range_list *limit;
        struct symbol *compare_type;

        while (expr->type == EXPR_ASSIGNMENT)
                expr = strip_expr(expr->right);
        if (expr->type != EXPR_CALL)
                return false;

        arg = get_argument_from_call_expr(expr->args, param);
        if (!arg)
                return false;

        if (strcmp(key, "$") == 0) {
                if (!get_implied_rl(arg, &passed))
                        return false;

                compare_type = get_arg_type(expr->fn, param);
        } else {
                char *name;
                struct symbol *sym;

                name = get_variable_from_key(arg, key, &sym);
                if (!name || !sym)
                        return false;

                state = get_state(SMATCH_EXTRA, name, sym);
                if (!state) {
                        free_string(name);
                        return false;
                }
                passed = estate_rl(state);
                if (!passed || is_whole_rl(passed)) {
                        free_string(name);
                        return false;
                }

                compare_type = get_member_type_from_key(arg, key);
        }

        passed = cast_rl(compare_type, passed);
        call_results_to_rl(expr, compare_type, value, &limit);
        if (!limit || is_whole_rl(limit))
                return false;
        if (possibly_true_rl(passed, SPECIAL_EQUAL, limit))
                return false;
        if (option_debug || local_debug || debug_db)
                sm_msg("impossible: %d '%s' limit '%s' == '%s' return='%s'", param, key, show_rl(passed), value, db_info->ret_str);
        return true;
}

static bool is_impossible_data(int type, struct db_callback_info *db_info, int param, char *key, char *value)
{
        if (type == PARAM_LIMIT && impossible_limit(db_info, param, key, value))
                return true;
        if (type == COMPARE_LIMIT && param_compare_limit_is_impossible(db_info->expr, param, key, value)) {
                if (local_debug || debug_db)
                        sm_msg("param_compare_limit_is_impossible: %d %s %s", param, key, value);
                return true;
        }
        return false;
}

static bool func_type_mismatch(struct expression *expr, const char *value)
{
        struct symbol *type;

        /* This makes faking returns easier */
        if (!value || value[0] == '\0')
                return false;

        while (expr->type == EXPR_ASSIGNMENT)
                expr = strip_expr(expr->right);

        /*
         * Short cut:  We only care about function pointers that are struct
         * members.
         *
         */
        if (expr->fn->type == EXPR_SYMBOL)
                return false;

        type = get_type(expr->fn);
        if (!type)
                return false;
        if (type->type == SYM_PTR)
                type = get_real_base_type(type);

        if (strcmp(type_to_str(type), value) == 0)
                return false;

        return true;
}

static void process_return_states(struct db_callback_info *db_info)
{
        struct stree *stree;

        set_implied_states(db_info);
        set_fresh_mtag_returns(db_info);
        parse_fake_calls();
        free_ptr_list(&db_info->called);
        stree = __pop_fake_cur_stree();
        if (debug_db) {
                sm_msg("States from DB: %s expr='%s' ret_str='%s' rl='%s' state='%s'",
                       db_info->cull ? "Culling" : "Merging",
                       expr_to_str(db_info->expr),
                       db_info->ret_str, show_rl(db_info->rl),
                       db_info->ret_state ? db_info->ret_state->name : "<none>");
                __print_stree(stree);
        }

        if (!db_info->cull) {
                merge_fake_stree(&db_info->stree, stree);
                db_info->states_merged = true;
        }
        free_stree(&stree);

        db_info->ret_state = NULL;
        db_info->ret_str = NULL;
}

static int db_compare_callback(void *_info, int argc, char **argv, char **azColName)
{
        struct db_callback_info *db_info = _info;
        struct range_list *var_rl = db_info->rl;
        struct range_list *ret_range;
        int type, param;
        char *ret_str, *key, *value;
        struct return_implies_callback *tmp;
        int return_id;
        int comparison;

        if (argc != 6)
                return 0;

        return_id = atoi(argv[0]);
        ret_str = argv[1];
        type = atoi(argv[2]);
        param = atoi(argv[3]);
        key = argv[4];
        value = argv[5];

        db_info->has_states = 1;
        if (db_info->prev_return_id != -1 && type == INTERNAL) {
                set_other_side_state(db_info);
                process_return_states(db_info);
                __push_fake_cur_stree();
                db_info->cull = 0;
        }
        db_info->prev_return_id = return_id;

        if (type == INTERNAL && func_type_mismatch(db_info->expr, value))
                db_info->cull = 1;
        if (db_info->cull)
                return 0;
        if (type == CULL_PATH) {
                db_info->cull = 1;
                return 0;
        }

        if (is_impossible_data(type, db_info, param, key, value)) {
                db_info->cull = 1;
                return 0;
        }

        call_results_to_rl(db_info->expr, get_type(strip_expr(db_info->expr)), ret_str, &ret_range);
        ret_range = cast_rl(get_type(db_info->expr), ret_range);
        if (!ret_range)
                ret_range = alloc_whole_rl(get_type(db_info->expr));

        comparison = db_info->comparison;
        if (db_info->left)
                comparison = flip_comparison(comparison);

        if (db_info->true_side) {
                if (!possibly_true_rl(var_rl, comparison, ret_range))
                        return 0;
                if (type == PARAM_LIMIT)
                        param_limit_implications(db_info->expr, param, key, value, &db_info->implied);
                else if (type > PARAM_LIMIT)
                        set_implied_states(db_info);
                filter_by_comparison(&var_rl, comparison, ret_range);
                filter_by_comparison(&ret_range, flip_comparison(comparison), var_rl);
        } else {
                if (!possibly_false_rl(var_rl, comparison, ret_range))
                        return 0;
                if (type == PARAM_LIMIT)
                        param_limit_implications(db_info->expr, param, key, value, &db_info->implied);
                else if (type > PARAM_LIMIT)
                        set_implied_states(db_info);
                filter_by_comparison(&var_rl, negate_comparison(comparison), ret_range);
                filter_by_comparison(&ret_range, flip_comparison(negate_comparison(comparison)), var_rl);
        }

        handle_ret_equals_param(ret_str, ret_range, db_info->expr);

        if (type == INTERNAL) {
                set_state(-1, "unnull_path", NULL, &true_state);
                call_string_hooks(return_string_hooks, db_info->expr, ret_str);
                store_return_state(db_info, ret_str, alloc_estate_rl(clone_rl(var_rl)));
        }

        FOR_EACH_PTR(db_info->callbacks, tmp) {
                if (tmp->type == type)
                        call_db_return_callback(db_info, tmp, param, key, value);
        } END_FOR_EACH_PTR(tmp);

        fake_return_assignment(db_info, type, param, key, value);

        return 0;
}

static void compare_db_return_states_callbacks(struct expression *left, int comparison, struct expression *right, struct stree *implied_true, struct stree *implied_false)
{
        struct stree *orig_states;
        struct stree *true_states;
        struct stree *false_states;
        struct sm_state *sm;
        struct db_callback_info db_info = {};
        struct expression *var_expr;
        struct expression *call_expr;
        struct range_list *rl;
        int call_on_left;

        orig_states = clone_stree(__get_cur_stree());

        /* legacy cruft.  need to fix call_implies_callbacks(). */
        call_on_left = 1;
        call_expr = left;
        var_expr = right;
        if (left->type != EXPR_CALL) {
                call_on_left = 0;
                call_expr = right;
                var_expr = left;
        }

        get_absolute_rl(var_expr, &rl);

        db_info.comparison = comparison;
        db_info.expr = call_expr;
        db_info.rl = rl;
        db_info.left = call_on_left;
        db_info.callbacks = db_return_states_list;
        db_info.var_expr = var_expr;

        call_void_fns(return_states_before);

        db_info.true_side = 1;
        db_info.stree = NULL;
        db_info.prev_return_id = -1;
        __push_fake_cur_stree();
        sql_select_return_states("return_id, return, type, parameter, key, value",
                                 call_expr, db_compare_callback, &db_info);
        set_other_side_state(&db_info);
        process_return_states(&db_info);
        true_states = db_info.stree;
        if (!true_states && db_info.has_states) {
                __push_fake_cur_stree();
                set_path_impossible();
                true_states = __pop_fake_cur_stree();
        }

        nullify_path();
        __unnullify_path();
        FOR_EACH_SM(orig_states, sm) {
                __set_sm_cur_stree(sm);
        } END_FOR_EACH_SM(sm);

        db_info.true_side = 0;
        db_info.stree = NULL;
        db_info.prev_return_id = -1;
        db_info.cull = 0;
        __push_fake_cur_stree();
        sql_select_return_states("return_id, return, type, parameter, key, value", call_expr,
                        db_compare_callback, &db_info);
        set_other_side_state(&db_info);
        process_return_states(&db_info);
        false_states = db_info.stree;
        if (!false_states && db_info.has_states) {
                __push_fake_cur_stree();
                set_path_impossible();
                false_states = __pop_fake_cur_stree();
        }

        nullify_path();
        __unnullify_path();
        FOR_EACH_SM(orig_states, sm) {
                __set_sm_cur_stree(sm);
        } END_FOR_EACH_SM(sm);

        free_stree(&orig_states);

        FOR_EACH_SM(true_states, sm) {
                __set_true_false_sm(sm, NULL);
        } END_FOR_EACH_SM(sm);
        FOR_EACH_SM(false_states, sm) {
                __set_true_false_sm(NULL, sm);
        } END_FOR_EACH_SM(sm);

        free_stree(&true_states);
        free_stree(&false_states);

        if (!db_info.states_merged)
                mark_call_params_untracked(call_expr);

        call_return_states_after_hooks(call_expr);

        FOR_EACH_SM(implied_true, sm) {
                __set_true_false_sm(sm, NULL);
        } END_FOR_EACH_SM(sm);
        FOR_EACH_SM(implied_false, sm) {
                __set_true_false_sm(NULL, sm);
        } END_FOR_EACH_SM(sm);
}

void function_comparison(struct expression *left, int comparison, struct expression *right)
{
        struct expression *var_expr;
        struct expression *call_expr;
        struct stree *implied_true = NULL;
        struct stree *implied_false = NULL;
        struct range_list *rl;
        sval_t sval;
        int call_on_left;

        // TODO: faked_assign delete this
        // condition calls should be faked and then handled as assignments
        // this code is a lazy work around

        if (unreachable())
                return;

        /* legacy cruft.  need to fix call_implies_callbacks(). */
        call_on_left = 1;
        call_expr = left;
        var_expr = right;
        if (left->type != EXPR_CALL) {
                call_on_left = 0;
                call_expr = right;
                var_expr = left;
        }

        get_absolute_rl(var_expr, &rl);

        if (rl_to_sval(rl, &sval))
                call_implies_callbacks(comparison, call_expr, sval, call_on_left, &implied_true, &implied_false);

        compare_db_return_states_callbacks(left, comparison, right, implied_true, implied_false);
        free_stree(&implied_true);
        free_stree(&implied_false);
}

static void call_ranged_return_hooks(struct db_callback_info *db_info)
{
        struct call_back_list *call_backs;
        struct range_list *range_rl;
        struct expression *expr;
        struct fcall_back *tmp;
        const char *fn_name;

        expr = strip_expr(db_info->expr);
        while (expr->type == EXPR_ASSIGNMENT)
                expr = strip_expr(expr->right);
        if (expr->type != EXPR_CALL)
                return;

        fn_name = get_fn_name(expr->fn);
        call_backs = get_call_backs(fn_name);
        FOR_EACH_PTR(call_backs, tmp) {
                if (tmp->type != RANGED_CALL)
                        continue;
                range_rl = alloc_rl(tmp->range->min, tmp->range->max);
                range_rl = cast_rl(estate_type(db_info->ret_state), range_rl);
                if (possibly_true_rl(range_rl, SPECIAL_EQUAL, estate_rl(db_info->ret_state)))
                        (tmp->u.ranged)(fn_name, expr, db_info->expr, tmp->info);
        } END_FOR_EACH_PTR(tmp);

        FOR_EACH_PTR(call_backs, tmp) {
                if (tmp->type != RANGED_EXACT)
                        continue;
                if (!estate_rl(db_info->ret_state))
                        continue;

                range_rl = alloc_rl(tmp->range->min, tmp->range->max);
                range_rl = cast_rl(estate_type(db_info->ret_state), range_rl);

                /*
                 * If there is an returned value out of range then this is not
                 * an exact match.  In other words, "0,4096-ptr_max" is not
                 * necessarily a valid match.
                 *
                 */
                if (remove_range(estate_rl(db_info->ret_state),
                                 rl_min(range_rl), rl_max(range_rl)))
                        continue;
                (tmp->u.ranged)(fn_name, expr, db_info->expr, tmp->info);
        } END_FOR_EACH_PTR(tmp);
}

static int db_assign_return_states_callback(void *_info, int argc, char **argv, char **azColName)
{
        struct db_callback_info *db_info = _info;
        struct range_list *ret_range;
        int type, param;
        char *ret_str, *key, *value;
        struct return_implies_callback *tmp;
        int return_id;

        if (argc != 6)
                return 0;

        return_id = atoi(argv[0]);
        ret_str = argv[1];
        type = atoi(argv[2]);
        param = atoi(argv[3]);
        key = argv[4];
        value = argv[5];

        if (db_info->prev_return_id != -1 && type == INTERNAL) {
                call_ranged_return_hooks(db_info);
                set_return_assign_state(db_info);
                process_return_states(db_info);
                __push_fake_cur_stree();
                db_info->cull = 0;
        }
        db_info->prev_return_id = return_id;

        if (type == INTERNAL && func_type_mismatch(db_info->expr, value))
                db_info->cull = 1;
        if (db_info->cull)
                return 0;
        if (type == CULL_PATH) {
                db_info->cull = 1;
                return 0;
        }
        if (is_impossible_data(type, db_info, param, key, value)) {
                db_info->cull = 1;
                return 0;
        }

        if (type == PARAM_LIMIT)
                param_limit_implications(db_info->expr, param, key, value, &db_info->implied);
        else if (type > PARAM_LIMIT)
                set_implied_states(db_info);

        db_info->handled = 1;
        call_results_to_rl(db_info->expr->right, get_type(strip_expr(db_info->expr->right)), ret_str, &ret_range);
        if (!ret_range)
                ret_range = alloc_whole_rl(get_type(strip_expr(db_info->expr->right)));
        ret_range = cast_rl(get_type(db_info->expr->right), ret_range);

        if (type == INTERNAL) {
                set_state(-1, "unnull_path", NULL, &true_state);
                __add_comparison_info(db_info->expr->left, strip_expr(db_info->expr->right), ret_str);
                call_string_hooks(return_string_hooks, db_info->expr, ret_str);
                store_return_state(db_info, ret_str, alloc_estate_rl(ret_range));
        }

        FOR_EACH_PTR(db_return_states_list, tmp) {
                if (tmp->type == type)
                        call_db_return_callback(db_info, tmp, param, key, value);
        } END_FOR_EACH_PTR(tmp);

        fake_return_assignment(db_info, type, param, key, value);

        return 0;
}

static int db_return_states_assign(struct expression *expr)
{
        struct expression *right;
        struct sm_state *sm;
        struct db_callback_info db_info = {};

        right = strip_expr(expr->right);

        db_info.prev_return_id = -1;
        db_info.expr = expr;
        db_info.stree = NULL;
        db_info.handled = 0;

        call_void_fns(return_states_before);

        __push_fake_cur_stree();
        sql_select_return_states("return_id, return, type, parameter, key, value",
                        right, db_assign_return_states_callback, &db_info);
        if (option_debug) {
                sm_msg("%s return_id %d return_ranges %s",
                        db_info.cull ? "culled" : "merging",
                        db_info.prev_return_id,
                        db_info.ret_state ? db_info.ret_state->name : "'<empty>'");
        }
        if (db_info.handled)
                call_ranged_return_hooks(&db_info);
        set_return_assign_state(&db_info);
        process_return_states(&db_info);

        if (!db_info.stree && db_info.cull) { /* this means we culled everything */
                set_extra_expr_mod(expr->left, alloc_estate_whole(get_type(expr->left)));
                set_path_impossible();
        }
        FOR_EACH_SM(db_info.stree, sm) {
                __set_sm(sm);
        } END_FOR_EACH_SM(sm);

        free_stree(&db_info.stree);

        if (!db_info.states_merged)
                mark_call_params_untracked(right);

        call_return_states_after_hooks(right);

        return db_info.handled;
}

static bool handle_implied_return(struct expression *expr)
{
        struct range_list *rl;

        if (!get_implied_return(expr->right, &rl))
                return false;
        rl = cast_rl(get_type(expr->left), rl);
        set_extra_expr_mod(expr->left, alloc_estate_rl(rl));
        return true;
}

static void match_assign_call(struct expression *expr)
{
        struct call_back_list *call_backs;
        const char *fn_name;
        struct expression *right;
        int handled = 0;
        struct range_list *rl;

        if (expr->op != '=')
                return;

        right = strip_expr(expr->right);
        if (is_fake_call(right))
                return;

        fn_name = get_fn_name(right->fn);
        call_backs = get_call_backs(fn_name);

        /*
         * The ordering here is sort of important.
         * One example, of how this matters is that when we do:
         *
         *      len = strlen(str);
         *
         * That is handled by smatch_common_functions.c and smatch_strlen.c.
         * They use implied_return and function_assign_hook respectively.
         * We want to get the implied return first before we do the function
         * assignment hook otherwise we end up writing the wrong thing for len
         * in smatch_extra.c because we assume that it already holds the
         * strlen() when we haven't set it yet.
         */

        if (db_return_states_assign(expr))
                handled = 1;
        else
                handled = assign_ranged_funcs(fn_name, expr, call_backs);
        handled |= handle_implied_return(expr);


        call_call_backs(call_backs, ASSIGN_CALL, fn_name, expr);

        if (handled)
                return;

        /* assignment wasn't handled at all */
        get_absolute_rl(expr->right, &rl);
        rl = cast_rl(get_type(expr->left), rl);
        set_extra_expr_mod(expr->left, alloc_estate_rl(rl));
}

static int db_return_states_callback(void *_info, int argc, char **argv, char **azColName)
{
        struct db_callback_info *db_info = _info;
        struct range_list *ret_range;
        int type, param;
        char *ret_str, *key, *value;
        struct return_implies_callback *tmp;
        int return_id;

        if (argc != 6)
                return 0;

        return_id = atoi(argv[0]);
        ret_str = argv[1];
        type = atoi(argv[2]);
        param = atoi(argv[3]);
        key = argv[4];
        value = argv[5];

        if (db_info->prev_return_id != -1 && type == INTERNAL) {
                call_ranged_return_hooks(db_info);
                process_return_states(db_info);
                __push_fake_cur_stree();
                __unnullify_path();
                db_info->cull = 0;
        }
        db_info->prev_return_id = return_id;

        if (type == INTERNAL && func_type_mismatch(db_info->expr, value))
                db_info->cull = 1;
        if (db_info->cull)
                return 0;
        if (type == CULL_PATH) {
                db_info->cull = 1;
                return 0;
        }
        if (is_impossible_data(type, db_info, param, key, value)) {
                db_info->cull = 1;
                return 0;
        }

        if (type == PARAM_LIMIT)
                param_limit_implications(db_info->expr, param, key, value, &db_info->implied);
        else if (type > PARAM_LIMIT)
                set_implied_states(db_info);

        call_results_to_rl(db_info->expr, get_type(strip_expr(db_info->expr)), ret_str, &ret_range);
        ret_range = cast_rl(get_type(db_info->expr), ret_range);

        if (type == INTERNAL) {
                struct smatch_state *state;

                set_state(-1, "unnull_path", NULL, &true_state);
                call_string_hooks(return_string_hooks, db_info->expr, ret_str);
                state = alloc_estate_rl(ret_range);
                store_return_state(db_info, ret_str, state);
        }

        FOR_EACH_PTR(db_return_states_list, tmp) {
                if (tmp->type == type)
                        call_db_return_callback(db_info, tmp, param, key, value);
        } END_FOR_EACH_PTR(tmp);

        fake_return_assignment(db_info, type, param, key, value);

        return 0;
}

static void db_return_states(struct expression *expr)
{
        struct sm_state *sm;
        struct db_callback_info db_info = {};

        if (!__get_cur_stree())  /* no return functions */
                return;

        db_info.prev_return_id = -1;
        db_info.expr = expr;
        db_info.stree = NULL;

        call_void_fns(return_states_before);

        __push_fake_cur_stree();
        __unnullify_path();
        sql_select_return_states("return_id, return, type, parameter, key, value",
                        expr, db_return_states_callback, &db_info);
        call_ranged_return_hooks(&db_info);
        process_return_states(&db_info);

        FOR_EACH_SM(db_info.stree, sm) {
                __set_sm(sm);
        } END_FOR_EACH_SM(sm);

        free_stree(&db_info.stree);

        if (!db_info.states_merged)
                mark_call_params_untracked(expr);

        call_return_states_after_hooks(expr);
}

static void db_return_states_call(struct expression *expr)
{
        if (unreachable())
                return;

        if (is_assigned_call(expr) || is_fake_assigned_call(expr))
                return;
        if (is_condition_call(expr))
                return;
        db_return_states(expr);
}

static void match_function_call_early(struct expression *expr)
{
        call_function_hooks(expr, REGULAR_CALL_EARLY);
}

static void match_function_call(struct expression *expr)
{
        call_function_hooks(expr, REGULAR_CALL);
        db_return_states_call(expr);
        /* If we have no database there could be unprocessed fake calls */
        parse_fake_calls();
}

static void match_macro_assign(struct expression *expr)
{
        struct call_back_list *call_backs;
        const char *macro;
        struct expression *right;

        right = strip_expr(expr->right);
        macro = get_macro_name(right->pos);
        call_backs = search_callback(func_hash, (char *)macro);
        if (!call_backs)
                return;
        call_call_backs(call_backs, MACRO_ASSIGN, macro, expr);
        call_call_backs(call_backs, MACRO_ASSIGN_EXTRA, macro, expr);
}

bool get_implied_return(struct expression *expr, struct range_list **rl)
{
        struct call_back_list *call_backs;
        struct fcall_back *tmp;
        bool handled = false;
        char *fn;

        *rl = NULL;

        expr = strip_expr(expr);
        fn = expr_to_var(expr->fn);
        if (!fn)
                goto out;

        call_backs = search_callback(func_hash, fn);

        FOR_EACH_PTR(call_backs, tmp) {
                if (tmp->type == IMPLIED_RETURN)
                        handled |= (tmp->u.implied_return)(expr, tmp->info, rl);
        } END_FOR_EACH_PTR(tmp);

out:
        free_string(fn);
        return handled;
}

struct range_list *get_range_implications(const char *fn)
{
        struct call_back_list *call_backs;
        struct range_list *ret = NULL;
        struct fcall_back *tmp;

        call_backs = search_callback(func_hash, (char *)fn);

        FOR_EACH_PTR(call_backs, tmp) {
                if (tmp->type != RANGED_CALL &&
                    tmp->type != RANGED_EXACT)
                        continue;
                add_ptr_list(&ret, tmp->range);
        } END_FOR_EACH_PTR(tmp);

        return ret;
}

void create_function_hook_hash(void)
{
        func_hash = create_function_hashtable(5000);
}

void register_function_hooks_early(int id)
{
        add_hook(&match_function_call_early, FUNCTION_CALL_HOOK_BEFORE);
}

void register_function_hooks(int id)
{
        add_function_data((unsigned long *)&fake_calls);
        add_hook(&match_function_call, CALL_HOOK_AFTER_INLINE);
        add_hook(&match_assign_call, CALL_ASSIGNMENT_HOOK);
        add_hook(&match_macro_assign, MACRO_ASSIGNMENT_HOOK);
}