function_hooks: update comment explaining various function hooks

[smatch.git] / smatch_states.c

/*
 * Copyright (C) 2006 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
 */

/*
 * You have a lists of states.  kernel = locked, foo = NULL, ...
 * When you hit an if {} else {} statement then you swap the list
 * of states for a different list of states.  The lists are stored
 * on stacks.
 *
 * At the beginning of this file there are list of the stacks that
 * we use.  Each function in this file does something to one of
 * of the stacks.
 *
 * So the smatch_flow.c understands code but it doesn't understand states.
 * smatch_flow calls functions in this file.  This file calls functions
 * in smatch_slist.c which just has boring generic plumbing for handling
 * state lists.  But really it's this file where all the magic happens.
 */

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

struct smatch_state undefined = { .name = "undefined" };
struct smatch_state ghost = { .name = "ghost" };
struct smatch_state merged = { .name = "merged" };
struct smatch_state true_state = { .name = "true" };
struct smatch_state false_state = { .name = "false" };

static struct stree *cur_stree; /* current states */
static struct stree *fast_overlay;

static struct stree_stack *true_stack; /* states after a t/f branch */
static struct stree_stack *false_stack;
static struct stree_stack *pre_cond_stack; /* states before a t/f branch */

static struct stree_stack *cond_true_stack; /* states affected by a branch */
static struct stree_stack *cond_false_stack;

static struct stree_stack *fake_cur_stree_stack;
static int read_only;

static struct stree_stack *break_stack;
static struct stree_stack *fake_break_stack;
static struct stree_stack *switch_stack;
static struct range_list_stack *remaining_cases;
static struct stree_stack *default_stack;
static struct stree_stack *continue_stack;

static struct named_stree_stack *goto_stack;

static struct ptr_list *backup;

int option_debug;

void __print_cur_stree(void)
{
        __print_stree(cur_stree);
}

bool __print_states(const char *owner)
{
        struct sm_state *sm;
        bool found = false;

        if (!owner)
                return false;

        FOR_EACH_SM(__get_cur_stree(), sm) {
                if (!strstr(check_name(sm->owner), owner))
                        continue;
                sm_msg("%s", show_sm(sm));
                found = true;
        } END_FOR_EACH_SM(sm);

        return found;
}

int unreachable(void)
{
        if (!cur_stree)
                return 1;
        return 0;
}

void __set_cur_stree_readonly(void)
{
        read_only++;
}

void __set_cur_stree_writable(void)
{
        read_only--;
}

DECLARE_PTR_LIST(check_tracker_list, check_tracker_hook *);
static struct check_tracker_list **tracker_hooks;

void add_check_tracker(const char *check_name, check_tracker_hook *fn)
{
        check_tracker_hook **p;
        int owner;

        owner = id_from_name(check_name);
        if (!owner) {
                printf("check not found.  '%s'\n", check_name);
                return;
        }

        p = malloc(sizeof(check_tracker_hook *));
        *p = fn;
        add_ptr_list(&tracker_hooks[owner], p);
}

static void call_tracker_hooks(int owner, const char *name, struct symbol *sym, struct smatch_state *state)
{
        struct check_tracker_list *hooks;
        check_tracker_hook **fn;

        if ((unsigned short)owner == USHRT_MAX)
                return;

        hooks = tracker_hooks[owner];
        FOR_EACH_PTR(hooks, fn) {
                (*fn)(owner, name, sym, state);
        } END_FOR_EACH_PTR(fn);
}

void allocate_tracker_array(int num_checks)
{
        tracker_hooks = malloc(num_checks * sizeof(void *));
        memset(tracker_hooks, 0, num_checks * sizeof(void *));
}

bool debug_on(const char *check_name, const char *var)
{
        if (option_debug)
                return true;
        if (option_debug_check && strstr(check_name, option_debug_check))
                return true;
        if (option_debug_var && strcmp(var, option_debug_var) == 0)
                return true;
        return false;
}

struct sm_state *set_state(int owner, const char *name, struct symbol *sym, struct smatch_state *state)
{
        struct sm_state *ret;

        if (!name || !state)
                return NULL;

        if (read_only)
                sm_perror("cur_stree is read only.");

        if (debug_on(check_name(owner), name)) {
                struct smatch_state *s;

                s = __get_state(owner, name, sym);
                if (!s)
                        sm_msg("%s new [%s] '%s' %s", __func__,
                               check_name(owner), name, show_state(state));
                else
                        sm_msg("%s change [%s] '%s' %s => %s",
                                __func__, check_name(owner), name, show_state(s),
                                show_state(state));
        }

        call_tracker_hooks(owner, name, sym, state);

        if (owner != -1 && unreachable())
                return NULL;

        if (fake_cur_stree_stack)
                set_state_stree_stack(&fake_cur_stree_stack, owner, name, sym, state);

        ret = set_state_stree(&cur_stree, owner, name, sym, state);

        return ret;
}

struct sm_state *set_state_expr(int owner, struct expression *expr, struct smatch_state *state)
{
        char *name;
        struct symbol *sym;
        struct sm_state *ret = NULL;

        expr = strip_expr(expr);
        name = expr_to_var_sym(expr, &sym);
        if (!name || !sym)
                goto free;
        ret = set_state(owner, name, sym, state);
free:
        free_string(name);
        return ret;
}

struct stree *__swap_cur_stree(struct stree *stree)
{
        struct stree *orig = cur_stree;

        cur_stree = stree;
        return orig;
}

void __push_fake_cur_stree(void)
{
        push_stree(&fake_cur_stree_stack, NULL);
        __save_pre_cond_states();
}

struct stree *__pop_fake_cur_stree(void)
{
        if (!fake_cur_stree_stack)
                sm_perror("popping too many fake cur strees.");
        __use_pre_cond_states();
        return pop_stree(&fake_cur_stree_stack);
}

void __free_fake_cur_stree(void)
{
        struct stree *stree;

        stree = __pop_fake_cur_stree();
        free_stree(&stree);
}

void __set_fake_cur_stree_fast(struct stree *stree)
{
        if (fast_overlay) {
                sm_perror("cannot nest fast overlay");
                return;
        }
        fast_overlay = stree;
        set_fast_math_only();
}

void __pop_fake_cur_stree_fast(void)
{
        fast_overlay = NULL;
        clear_fast_math_only();
}

void __merge_stree_into_cur(struct stree *stree)
{
        struct sm_state *sm;
        struct sm_state *orig;
        struct sm_state *merged;

        FOR_EACH_SM(stree, sm) {
                orig = get_sm_state(sm->owner, sm->name, sm->sym);
                if (orig)
                        merged = merge_sm_states(orig, sm);
                else
                        merged = sm;
                __set_sm(merged);
        } END_FOR_EACH_SM(sm);
}

void __set_sm(struct sm_state *sm)
{
        if (read_only)
                sm_perror("cur_stree is read only.");

        if (debug_on(check_name(sm->owner), sm->name)) {
                struct smatch_state *s;

                s = __get_state(sm->owner, sm->name, sm->sym);
                if (!s)
                        sm_msg("%s new %s", __func__, show_sm(sm));
                else
                        sm_msg("%s change %s (was %s)", __func__, show_sm(sm),
                               show_state(s));
        }

        if (unreachable())
                return;

        if (fake_cur_stree_stack)
                overwrite_sm_state_stree_stack(&fake_cur_stree_stack, sm);

        overwrite_sm_state_stree(&cur_stree, sm);
}

void __set_sm_cur_stree(struct sm_state *sm)
{
        if (read_only)
                sm_perror("cur_stree is read only.");

        if (debug_on(check_name(sm->owner), sm->name)) {
                struct smatch_state *s;

                s = __get_state(sm->owner, sm->name, sm->sym);
                if (!s)
                        sm_msg("%s new %s", __func__, show_sm(sm));
                else
                        sm_msg("%s change %s (was %s)",
                                __func__, show_sm(sm), show_state(s));
        }

        if (unreachable())
                return;

        overwrite_sm_state_stree(&cur_stree, sm);
}

typedef void (get_state_hook)(int owner, const char *name, struct symbol *sym);
DECLARE_PTR_LIST(fn_list, get_state_hook *);
static struct fn_list *get_state_hooks;

void add_get_state_hook(get_state_hook *fn)
{
        get_state_hook **p = malloc(sizeof(get_state_hook *));
        *p = fn;
        add_ptr_list(&get_state_hooks, p);
}

static void call_get_state_hooks(int owner, const char *name, struct symbol *sym)
{
        static int recursion;
        get_state_hook **fn;

        if (recursion)
                return;
        recursion = 1;

        FOR_EACH_PTR(get_state_hooks, fn) {
                (*fn)(owner, name, sym);
        } END_FOR_EACH_PTR(fn);

        recursion = 0;
}

bool has_states(struct stree *stree, int owner)
{
        if (owner < 0 || owner > USHRT_MAX)
                return false;
        if (!stree)
                return false;
        if (owner == USHRT_MAX)
                return true;
        return stree->has_states[owner];
}

struct smatch_state *__get_state(int owner, const char *name, struct symbol *sym)
{
        struct sm_state *sm;

        sm = get_sm_state(owner, name, sym);
        if (!sm)
                return NULL;
        return sm->state;
}

struct smatch_state *get_state(int owner, const char *name, struct symbol *sym)
{
        call_get_state_hooks(owner, name, sym);

        return __get_state(owner, name, sym);
}

struct smatch_state *get_state_expr(int owner, struct expression *expr)
{
        struct expression *fake_parent;
        char *name;
        struct symbol *sym;
        struct smatch_state *ret = NULL;

        expr = strip_expr(expr);
        name = expr_to_var_sym(expr, &sym);
        if ((!name || !sym) && cur_func_sym && !cur_func_sym->parsed) {
                fake_parent = expr_get_fake_parent_expr(expr);
                if (!fake_parent)
                        goto free;
                name = expr_to_var_sym(fake_parent->left, &sym);
                if (!name || !sym)
                        goto free;
        }
        ret = get_state(owner, name, sym);
free:
        free_string(name);
        return ret;
}

bool has_possible_state(int owner, const char *name, struct symbol *sym, struct smatch_state *state)
{
        struct sm_state *sm;

        sm = get_sm_state(owner, name, sym);
        if (!sm)
                return false;

        return slist_has_state(sm->possible, state);
}

bool expr_has_possible_state(int owner, struct expression *expr, struct smatch_state *state)
{
        struct sm_state *sm;

        sm = get_sm_state_expr(owner, expr);
        if (!sm)
                return false;

        return slist_has_state(sm->possible, state);
}

struct state_list *get_possible_states(int owner, const char *name, struct symbol *sym)
{
        struct sm_state *sms;

        sms = get_sm_state_stree(cur_stree, owner, name, sym);
        if (sms)
                return sms->possible;
        return NULL;
}

struct state_list *get_possible_states_expr(int owner, struct expression *expr)
{
        char *name;
        struct symbol *sym;
        struct state_list *ret = NULL;

        expr = strip_expr(expr);
        name = expr_to_var_sym(expr, &sym);
        if (!name || !sym)
                goto free;
        ret = get_possible_states(owner, name, sym);
free:
        free_string(name);
        return ret;
}

struct sm_state *get_sm_state(int owner, const char *name, struct symbol *sym)
{
        struct sm_state *ret;

        ret = get_sm_state_stree(fast_overlay, owner, name, sym);
        if (ret)
                return ret;

        return get_sm_state_stree(cur_stree, owner, name, sym);
}

struct sm_state *get_sm_state_expr(int owner, struct expression *expr)
{
        char *name;
        struct symbol *sym;
        struct sm_state *ret = NULL;

        expr = strip_expr(expr);
        name = expr_to_var_sym(expr, &sym);
        if (!name || !sym)
                goto free;
        ret = get_sm_state(owner, name, sym);
free:
        free_string(name);
        return ret;
}

void __delete_state(int owner, const char *name, struct symbol *sym)
{
        delete_state_stree(&cur_stree, owner, name, sym);
        if (cond_true_stack) {
                delete_state_stree_stack(&pre_cond_stack, owner, name, sym);
                delete_state_stree_stack(&cond_true_stack, owner, name, sym);
                delete_state_stree_stack(&cond_false_stack, owner, name, sym);
        }
}

static void delete_all_states_stree_sym(struct stree **stree, struct symbol *sym)
{
        struct state_list *slist = NULL;
        struct sm_state *sm;

        FOR_EACH_SM(*stree, sm) {
                if (sm->sym == sym)
                        add_ptr_list(&slist, sm);
        } END_FOR_EACH_SM(sm);

        FOR_EACH_PTR(slist, sm) {
                delete_state_stree(stree, sm->owner, sm->name, sm->sym);
        } END_FOR_EACH_PTR(sm);

        free_slist(&slist);
}

static void delete_all_states_stree_stack_sym(struct stree_stack **stack, struct symbol *sym)
{
        struct stree *stree;

        if (!*stack)
                return;

        stree = pop_stree(stack);
        delete_all_states_stree_sym(&stree, sym);
        push_stree(stack, stree);
}

void __delete_all_states_sym(struct symbol *sym)
{
        delete_all_states_stree_sym(&cur_stree, sym);

        delete_all_states_stree_stack_sym(&true_stack, sym);
        delete_all_states_stree_stack_sym(&true_stack, sym);
        delete_all_states_stree_stack_sym(&false_stack, sym);
        delete_all_states_stree_stack_sym(&pre_cond_stack, sym);
        delete_all_states_stree_stack_sym(&cond_true_stack, sym);
        delete_all_states_stree_stack_sym(&cond_false_stack, sym);
        delete_all_states_stree_stack_sym(&fake_cur_stree_stack, sym);
        delete_all_states_stree_stack_sym(&break_stack, sym);
        delete_all_states_stree_stack_sym(&fake_break_stack, sym);
        delete_all_states_stree_stack_sym(&switch_stack, sym);
        delete_all_states_stree_stack_sym(&continue_stack, sym);

        /*
         * deleting from the goto stack is problematic because we don't know
         * if the label is in scope and also we need the value for --two-passes.
         */
}

struct stree *get_all_states_from_stree(int owner, struct stree *source)
{
        struct stree *ret = NULL;
        struct sm_state *tmp;

        FOR_EACH_SM(source, tmp) {
                if (tmp->owner == owner)
                        avl_insert(&ret, tmp);
        } END_FOR_EACH_SM(tmp);

        return ret;
}

struct stree *get_all_states_stree(int owner)
{
        return get_all_states_from_stree(owner, cur_stree);
}

struct stree *__get_cur_stree(void)
{
        return cur_stree;
}

int is_reachable(void)
{
        if (cur_stree)
                return 1;
        return 0;
}

void set_true_false_states(int owner, const char *name, struct symbol *sym,
                           struct smatch_state *true_state,
                           struct smatch_state *false_state)
{
        if (read_only)
                sm_perror("cur_stree is read only.");

        if (debug_on(check_name(owner), name)) {
                struct smatch_state *tmp;

                tmp = __get_state(owner, name, sym);
                sm_msg("%s [%s] '%s'.  Was %s.  Now T:%s F:%s", __func__,
                       check_name(owner),  name, show_state(tmp),
                       show_state(true_state), show_state(false_state));
        }

        if (unreachable())
                return;

        if (!cond_false_stack || !cond_true_stack) {
                sm_perror("missing true/false stacks");
                return;
        }

        if (true_state)
                set_state_stree_stack(&cond_true_stack, owner, name, sym, true_state);
        if (false_state)
                set_state_stree_stack(&cond_false_stack, owner, name, sym, false_state);
}

void set_true_false_states_expr(int owner, struct expression *expr,
                           struct smatch_state *true_state,
                           struct smatch_state *false_state)
{
        char *name;
        struct symbol *sym;

        expr = strip_expr(expr);
        name = expr_to_var_sym(expr, &sym);
        if (!name || !sym)
                goto free;
        set_true_false_states(owner, name, sym, true_state, false_state);
free:
        free_string(name);
}

void __set_true_false_sm(struct sm_state *true_sm, struct sm_state *false_sm)
{
        int owner;
        const char *name;
        struct symbol *sym;

        if (!true_sm && !false_sm)
                return;

        if (unreachable())
                return;

        owner = true_sm ? true_sm->owner : false_sm->owner;
        name = true_sm ? true_sm->name : false_sm->name;
        sym = true_sm ? true_sm->sym : false_sm->sym;
        if (debug_on(check_name(owner), name)) {
                struct smatch_state *tmp;

                tmp = __get_state(owner, name, sym);
                sm_msg("%s [%s] '%s'.  Was %s.  Now T:%s F:%s", __func__,
                       check_name(owner),  name, show_state(tmp),
                       show_state(true_sm ? true_sm->state : NULL),
                       show_state(false_sm ? false_sm->state : NULL));
        }

        if (!cond_false_stack || !cond_true_stack) {
                sm_perror("missing true/false stacks");
                return;
        }

        if (true_sm)
                overwrite_sm_state_stree_stack(&cond_true_stack, true_sm);
        if (false_sm)
                overwrite_sm_state_stree_stack(&cond_false_stack, false_sm);
}

void nullify_path(void)
{
        if (fake_cur_stree_stack) {
                __free_fake_cur_stree();
                __push_fake_cur_stree();
        }
        free_stree(&cur_stree);
}

void __match_nullify_path_hook(const char *fn, struct expression *expr,
                               void *unused)
{
        nullify_path();
}

/*
 * At the start of every function we mark the path
 * as unnull.  That way there is always at least one state
 * in the cur_stree until nullify_path is called.  This
 * is used in merge_slist() for the first null check.
 */
void __unnullify_path(void)
{
        if (!cur_stree)
                set_state(-1, "unnull_path", NULL, &true_state);
}

int __path_is_null(void)
{
        if (cur_stree)
                return 0;
        return 1;
}

static void check_stree_stack_free(struct stree_stack **stack)
{
        if (*stack) {
                sm_perror("stack not empty");
                free_stack_and_strees(stack);
        }
}

void save_all_states(void)
{
        __add_ptr_list(&backup, cur_stree);
        cur_stree = NULL;

        __add_ptr_list(&backup, true_stack);
        true_stack = NULL;
        __add_ptr_list(&backup, false_stack);
        false_stack = NULL;
        __add_ptr_list(&backup, pre_cond_stack);
        pre_cond_stack = NULL;

        __add_ptr_list(&backup, cond_true_stack);
        cond_true_stack = NULL;
        __add_ptr_list(&backup, cond_false_stack);
        cond_false_stack = NULL;

        __add_ptr_list(&backup, fake_cur_stree_stack);
        fake_cur_stree_stack = NULL;

        __add_ptr_list(&backup, break_stack);
        break_stack = NULL;
        __add_ptr_list(&backup, fake_break_stack);
        fake_break_stack = NULL;

        __add_ptr_list(&backup, switch_stack);
        switch_stack = NULL;
        __add_ptr_list(&backup, remaining_cases);
        remaining_cases = NULL;
        __add_ptr_list(&backup, default_stack);
        default_stack = NULL;
        __add_ptr_list(&backup, continue_stack);
        continue_stack = NULL;

        __add_ptr_list(&backup, goto_stack);
        goto_stack = NULL;
}

static void *pop_backup(void)
{
        void *ret;

        ret = last_ptr_list(backup);
        delete_ptr_list_last(&backup);
        return ret;
}

void restore_all_states(void)
{
        goto_stack = pop_backup();

        continue_stack = pop_backup();
        default_stack = pop_backup();
        remaining_cases = pop_backup();
        switch_stack = pop_backup();
        fake_break_stack = pop_backup();
        break_stack = pop_backup();

        fake_cur_stree_stack = pop_backup();

        cond_false_stack = pop_backup();
        cond_true_stack = pop_backup();

        pre_cond_stack = pop_backup();
        false_stack = pop_backup();
        true_stack = pop_backup();

        cur_stree = pop_backup();
}

void free_goto_stack(void)
{
        struct named_stree *named_stree;

        FOR_EACH_PTR(goto_stack, named_stree) {
                free_stree(&named_stree->stree);
        } END_FOR_EACH_PTR(named_stree);
        __free_ptr_list((struct ptr_list **)&goto_stack);
}

void clear_all_states(void)
{
        nullify_path();
        check_stree_stack_free(&true_stack);
        check_stree_stack_free(&false_stack);
        check_stree_stack_free(&pre_cond_stack);
        check_stree_stack_free(&cond_true_stack);
        check_stree_stack_free(&cond_false_stack);
        check_stree_stack_free(&break_stack);
        check_stree_stack_free(&fake_break_stack);
        check_stree_stack_free(&switch_stack);
        check_stree_stack_free(&continue_stack);
        check_stree_stack_free(&fake_cur_stree_stack);

        free_goto_stack();

        free_every_single_sm_state();
        free_tmp_expressions();
}

void __push_cond_stacks(void)
{
        push_stree(&cond_true_stack, NULL);
        push_stree(&cond_false_stack, NULL);
        __push_fake_cur_stree();
}

void __fold_in_set_states(void)
{
        struct stree *new_states;
        struct sm_state *sm;

        new_states = __pop_fake_cur_stree();
        FOR_EACH_SM(new_states, sm) {
                __set_sm(sm);
                __set_true_false_sm(sm, sm);
        } END_FOR_EACH_SM(sm);
        free_stree(&new_states);
}

void __free_set_states(void)
{
        struct stree *new_states;

        new_states = __pop_fake_cur_stree();
        free_stree(&new_states);
}

struct stree *__copy_cond_true_states(void)
{
        struct stree *ret;

        ret = pop_stree(&cond_true_stack);
        push_stree(&cond_true_stack, clone_stree(ret));
        return ret;
}

struct stree *__copy_cond_false_states(void)
{
        struct stree *ret;

        ret = pop_stree(&cond_false_stack);
        push_stree(&cond_false_stack, clone_stree(ret));
        return ret;
}

struct stree *__pop_cond_true_stack(void)
{
        return pop_stree(&cond_true_stack);
}

struct stree *__pop_cond_false_stack(void)
{
        return pop_stree(&cond_false_stack);
}

/*
 * This combines the pre cond states with either the true or false states.
 * For example:
 * a = kmalloc() ; if (a !! foo(a)
 * In the pre state a is possibly null.  In the true state it is non null.
 * In the false state it is null.  Combine the pre and the false to get
 * that when we call 'foo', 'a' is null.
 */
static void __use_cond_stack(struct stree_stack **stack)
{
        struct stree *stree;

        free_stree(&cur_stree);

        cur_stree = pop_stree(&pre_cond_stack);
        push_stree(&pre_cond_stack, clone_stree(cur_stree));

        stree = pop_stree(stack);
        overwrite_stree(stree, &cur_stree);
        push_stree(stack, stree);
}

void __use_pre_cond_states(void)
{
        free_stree(&cur_stree);
        cur_stree = pop_stree(&pre_cond_stack);
}

void __use_cond_true_states(void)
{
        __use_cond_stack(&cond_true_stack);
}

void __use_cond_false_states(void)
{
        __use_cond_stack(&cond_false_stack);
}

void __negate_cond_stacks(void)
{
        struct stree *old_false, *old_true;

        old_false = pop_stree(&cond_false_stack);
        old_true = pop_stree(&cond_true_stack);
        push_stree(&cond_false_stack, old_true);
        push_stree(&cond_true_stack, old_false);
}

void __and_cond_states(void)
{
        and_stree_stack(&cond_true_stack);
        or_stree_stack(&pre_cond_stack, cur_stree, &cond_false_stack);
}

void __or_cond_states(void)
{
        or_stree_stack(&pre_cond_stack, cur_stree, &cond_true_stack);
        and_stree_stack(&cond_false_stack);
}

void __save_pre_cond_states(void)
{
        push_stree(&pre_cond_stack, clone_stree(cur_stree));
}

void __discard_pre_cond_states(void)
{
        struct stree *tmp;

        tmp = pop_stree(&pre_cond_stack);
        free_stree(&tmp);
}

struct stree *__get_true_states(void)
{
        return clone_stree(top_stree(cond_true_stack));
}

struct stree *__get_false_states(void)
{
        return clone_stree(top_stree(cond_false_stack));
}

void __use_cond_states(void)
{
        struct stree *pre, *pre_clone, *true_states, *false_states;

        pre = pop_stree(&pre_cond_stack);
        pre_clone = clone_stree(pre);

        true_states = pop_stree(&cond_true_stack);
        overwrite_stree(true_states, &pre);
        free_stree(&true_states);
        /* we use the true states right away */
        free_stree(&cur_stree);
        cur_stree = pre;

        false_states = pop_stree(&cond_false_stack);
        overwrite_stree(false_states, &pre_clone);
        free_stree(&false_states);
        push_stree(&false_stack, pre_clone);
}

void __push_true_states(void)
{
        push_stree(&true_stack, clone_stree(cur_stree));
}

void __use_false_states(void)
{
        free_stree(&cur_stree);
        cur_stree = pop_stree(&false_stack);
}

void __discard_false_states(void)
{
        struct stree *stree;

        stree = pop_stree(&false_stack);
        free_stree(&stree);
}

void __merge_false_states(void)
{
        struct stree *stree;

        stree = pop_stree(&false_stack);
        merge_stree(&cur_stree, stree);
        free_stree(&stree);
}

/*
 * This function probably seemed common sensical when I wrote it but, oh wow,
 * does it look subtle in retrospect.  Say we set a state on one side of the if
 * else path but not on the other, then what we should record in the fake stree
 * is the merged state.
 *
 * This function relies on the fact that the we always set the cur_stree as well
 * and we already have the infrastructure to merge things correctly into the
 * cur_stree.
 *
 * So instead of merging fake strees together which is probably a lot of work,
 * we just use it as a list of set states and look up the actual current values
 * in the cur_stree.
 *
 */
static void update_stree_with_merged(struct stree **stree)
{
        struct state_list *slist = NULL;
        struct sm_state *sm, *new;

        FOR_EACH_SM(*stree, sm) {
                new = get_sm_state(sm->owner, sm->name, sm->sym);
                if (!new)  /* This can happen if we go out of scope */
                        continue;
                add_ptr_list(&slist, new);
        } END_FOR_EACH_SM(sm);

        FOR_EACH_PTR(slist, sm) {
                overwrite_sm_state_stree(stree, sm);
        } END_FOR_EACH_PTR(sm);

        free_slist(&slist);
}

static void update_fake_stree_with_merged(void)
{
        struct stree *stree;

        if (!fake_cur_stree_stack)
                return;
        stree = pop_stree(&fake_cur_stree_stack);
        update_stree_with_merged(&stree);
        push_stree(&fake_cur_stree_stack, stree);
}

void __merge_true_states(void)
{
        struct stree *stree;

        stree = pop_stree(&true_stack);
        merge_stree(&cur_stree, stree);
        update_fake_stree_with_merged();
        free_stree(&stree);
}

void __push_continues(void)
{
        push_stree(&continue_stack, NULL);
}

void __discard_continues(void)
{
        struct stree *stree;

        stree = pop_stree(&continue_stack);
        free_stree(&stree);
}

void __process_continues(void)
{
        struct stree *stree;

        stree = pop_stree(&continue_stack);
        if (!stree)
                stree = clone_stree(cur_stree);
        else
                merge_stree(&stree, cur_stree);

        push_stree(&continue_stack, stree);
}

void __merge_continues(void)
{
        struct stree *stree;

        stree = pop_stree(&continue_stack);
        merge_stree(&cur_stree, stree);
        free_stree(&stree);
}

void __push_breaks(void)
{
        push_stree(&break_stack, NULL);
        if (fake_cur_stree_stack)
                push_stree(&fake_break_stack, NULL);
}

void __process_breaks(void)
{
        struct stree *stree;

        stree = pop_stree(&break_stack);
        if (!stree)
                stree = clone_stree(cur_stree);
        else
                merge_stree(&stree, cur_stree);
        push_stree(&break_stack, stree);

        if (!fake_cur_stree_stack)
                return;

        stree = pop_stree(&fake_break_stack);
        if (!stree)
                stree = clone_stree(top_stree(fake_cur_stree_stack));
        else
                merge_stree(&stree, top_stree(fake_cur_stree_stack));
        push_stree(&fake_break_stack, stree);
}

int __has_breaks(void)
{
        struct stree *stree;
        int ret;

        stree = pop_stree(&break_stack);
        ret = !!stree;
        push_stree(&break_stack, stree);
        return ret;
}

void __merge_breaks(void)
{
        struct stree *stree;
        struct sm_state *sm;

        stree = pop_stree(&break_stack);
        merge_stree(&cur_stree, stree);
        free_stree(&stree);

        if (!fake_cur_stree_stack)
                return;

        stree = pop_stree(&fake_break_stack);
        update_stree_with_merged(&stree);
        FOR_EACH_SM(stree, sm) {
                overwrite_sm_state_stree_stack(&fake_cur_stree_stack, sm);
        } END_FOR_EACH_SM(sm);
        free_stree(&stree);
}

void __use_breaks(void)
{
        struct stree *stree;
        struct sm_state *sm;

        free_stree(&cur_stree);
        cur_stree = pop_stree(&break_stack);

        if (!fake_cur_stree_stack)
                return;
        stree = pop_stree(&fake_break_stack);
        FOR_EACH_SM(stree, sm) {
                overwrite_sm_state_stree_stack(&fake_cur_stree_stack, sm);
        } END_FOR_EACH_SM(sm);
        free_stree(&stree);


}

void __save_switch_states(struct expression *switch_expr)
{
        struct range_list *rl;

        get_absolute_rl(switch_expr, &rl);

        push_rl(&remaining_cases, rl);
        push_stree(&switch_stack, clone_stree(cur_stree));
}

int have_remaining_cases(void)
{
        return !!top_rl(remaining_cases);
}

void __merge_switches(struct expression *switch_expr, struct range_list *case_rl)
{
        struct stree *stree;
        struct stree *implied_stree;

        stree = pop_stree(&switch_stack);
        if (!stree) {
                /*
                 * If the cur_stree was NULL before the start of the switch
                 * statement then we don't want to unnullify it.
                 *
                 */
                push_stree(&switch_stack, stree);
                return;
        }
        implied_stree = __implied_case_stree(switch_expr, case_rl, &remaining_cases, &stree);
        merge_stree(&cur_stree, implied_stree);
        free_stree(&implied_stree);
        push_stree(&switch_stack, stree);
}

void __discard_switches(void)
{
        struct stree *stree;

        pop_rl(&remaining_cases);
        stree = pop_stree(&switch_stack);
        free_stree(&stree);
}

void __push_default(void)
{
        push_stree(&default_stack, NULL);
}

void __set_default(void)
{
        set_state_stree_stack(&default_stack, 0, "has_default", NULL, &true_state);
}

int __pop_default(void)
{
        struct stree *stree;

        stree = pop_stree(&default_stack);
        if (stree) {
                free_stree(&stree);
                return 1;
        }
        return 0;
}

static struct named_stree *alloc_named_stree(const char *name, struct symbol *sym, struct stree *stree)
{
        struct named_stree *named_stree = __alloc_named_stree(0);

        named_stree->name = (char *)name;
        named_stree->stree = stree;
        named_stree->sym = sym;
        return named_stree;
}

void __save_gotos(const char *name, struct symbol *sym)
{
        struct stree **stree;
        struct stree *clone;

        stree = get_named_stree(goto_stack, name, sym);
        if (stree) {
                merge_stree(stree, cur_stree);
                return;
        } else {
                struct named_stree *named_stree;

                clone = clone_stree(cur_stree);
                named_stree = alloc_named_stree(name, sym, clone);
                add_ptr_list(&goto_stack, named_stree);
        }
}

void __merge_gotos(const char *name, struct symbol *sym)
{
        struct stree **stree;

        stree = get_named_stree(goto_stack, name, sym);
        if (stree)
                merge_stree(&cur_stree, *stree);
}

void __discard_fake_states(struct expression *call)
{
        struct stree *new = NULL;
        struct sm_state *sm;
        char buf[64];
        int len;

        if (__fake_state_cnt == 0)
                return;

        /*
         * This is just a best effort type of thing.  There could be
         * fake states in the true/false trees already.  They might
         * eventually get cleared out too because we call after probably
         * 50% of function calls.  But the point is that I don't want to
         * waste resources tracking them.
         */
        FOR_EACH_SM(cur_stree, sm) {
                if (call) {
                        len = snprintf(buf, sizeof(buf), "__fake_param_%p_", call);
                        if (strncmp(sm->name, buf, len) != 0)
                                avl_insert(&new, sm);
                        continue;
                }
                if (strncmp(sm->name, "__fake_param_", 13) != 0)
                        avl_insert(&new, sm);
        } END_FOR_EACH_SM(sm);

        free_stree(&cur_stree);
        cur_stree = new;
        __fake_state_cnt = 0;
}