string_list: call strcmp() once instead of twice

[smatch.git] / smatch_slist.c

/*
 * Copyright (C) 2008,2009 Dan Carpenter.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
 */

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

#undef CHECKORDER

ALLOCATOR(smatch_state, "smatch state");
ALLOCATOR(sm_state, "sm state");
ALLOCATOR(named_stree, "named slist");
__DO_ALLOCATOR(char, 1, 4, "state names", sname);

int sm_state_counter;

static struct stree_stack *all_pools;

const char *show_sm(struct sm_state *sm)
{
        static char buf[256];
        struct sm_state *tmp;
        int pos;
        int i;

        if (!sm)
                return "<none>";

        pos = snprintf(buf, sizeof(buf), "[%s] '%s' = '%s'",
                       check_name(sm->owner), sm->name, show_state(sm->state));
        if (pos > sizeof(buf))
                goto truncate;

        if (ptr_list_size((struct ptr_list *)sm->possible) == 1)
                return buf;

        pos += snprintf(buf + pos, sizeof(buf) - pos, " (");
        if (pos > sizeof(buf))
                goto truncate;
        i = 0;
        FOR_EACH_PTR(sm->possible, tmp) {
                if (i++)
                        pos += snprintf(buf + pos, sizeof(buf) - pos, ", ");
                if (pos > sizeof(buf))
                        goto truncate;
                pos += snprintf(buf + pos, sizeof(buf) - pos, "%s",
                               show_state(tmp->state));
                if (pos > sizeof(buf))
                        goto truncate;
        } END_FOR_EACH_PTR(tmp);
        snprintf(buf + pos, sizeof(buf) - pos, ")");

        return buf;

truncate:
        for (i = 0; i < 3; i++)
                buf[sizeof(buf) - 2 - i] = '.';
        return buf;
}

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

        printf("dumping stree at %d [%ld states]\n", get_lineno(), stree_count(stree));
        FOR_EACH_SM(stree, sm) {
                printf("%s\n", show_sm(sm));
        } END_FOR_EACH_SM(sm);
        printf("---\n");
}

/* NULL states go at the end to simplify merge_slist */
int cmp_tracker(const struct sm_state *a, const struct sm_state *b)
{
        int ret;

        if (a == b)
                return 0;
        if (!b)
                return -1;
        if (!a)
                return 1;

        if (a->owner > b->owner)
                return -1;
        if (a->owner < b->owner)
                return 1;

        ret = strcmp(a->name, b->name);
        if (ret < 0)
                return -1;
        if (ret > 0)
                return 1;

        if (!b->sym && a->sym)
                return -1;
        if (!a->sym && b->sym)
                return 1;
        if (a->sym < b->sym)
                return -1;
        if (a->sym > b->sym)
                return 1;

        return 0;
}

static int cmp_possible_sm(const struct sm_state *a, const struct sm_state *b, int preserve)
{
        int ret;

        if (a == b)
                return 0;

        ret = cmp_tracker(a, b);
        if (ret)
                return ret;

        /* todo:  add hook for smatch_extra.c */
        if (a->state > b->state)
                return -1;
        if (a->state < b->state)
                return 1;
        /* This is obviously a massive disgusting hack but we need to preserve
         * the unmerged states for smatch extra because we use them in
         * smatch_db.c.  Meanwhile if we preserve all the other unmerged states
         * then it uses a lot of memory and we don't use it.  Hence this hack.
         *
         * Also sometimes even just preserving every possible SMATCH_EXTRA state
         * takes too much resources so we have to cap that.  Capping is probably
         * not often a problem in real life.
         */
        if (a->owner == SMATCH_EXTRA && preserve) {
                if (a->merged == 1 && b->merged == 0)
                        return -1;
                if (a->merged == 0)
                        return 1;
        }

        return 0;
}

struct sm_state *alloc_sm_state(int owner, const char *name,
                                struct symbol *sym, struct smatch_state *state)
{
        struct sm_state *sm_state = __alloc_sm_state(0);

        sm_state_counter++;

        sm_state->name = alloc_sname(name);
        sm_state->owner = owner;
        sm_state->sym = sym;
        sm_state->state = state;
        sm_state->line = get_lineno();
        sm_state->merged = 0;
        sm_state->pool = NULL;
        sm_state->left = NULL;
        sm_state->right = NULL;
        sm_state->nr_children = 1;
        sm_state->possible = NULL;
        add_ptr_list(&sm_state->possible, sm_state);
        return sm_state;
}

static struct sm_state *alloc_state_no_name(int owner, const char *name,
                                     struct symbol *sym,
                                     struct smatch_state *state)
{
        struct sm_state *tmp;

        tmp = alloc_sm_state(owner, NULL, sym, state);
        tmp->name = name;
        return tmp;
}

int too_many_possible(struct sm_state *sm)
{
        if (ptr_list_size((struct ptr_list *)sm->possible) >= 100)
                return 1;
        return 0;
}

void add_possible_sm(struct sm_state *to, struct sm_state *new)
{
        struct sm_state *tmp;
        int preserve = 1;
        int cmp;

        if (too_many_possible(to))
                preserve = 0;

        FOR_EACH_PTR(to->possible, tmp) {
                cmp = cmp_possible_sm(tmp, new, preserve);
                if (cmp < 0)
                        continue;
                else if (cmp == 0) {
                        return;
                } else {
                        INSERT_CURRENT(new, tmp);
                        return;
                }
        } END_FOR_EACH_PTR(tmp);
        add_ptr_list(&to->possible, new);
}

static void copy_possibles(struct sm_state *to, struct sm_state *one, struct sm_state *two)
{
        struct sm_state *large = one;
        struct sm_state *small = two;
        struct sm_state *tmp;

        /*
         * We spend a lot of time copying the possible lists.  I've tried to
         * optimize the process a bit.
         *
         */

        if (ptr_list_size((struct ptr_list *)two->possible) >
            ptr_list_size((struct ptr_list *)one->possible)) {
                large = two;
                small = one;
        }

        to->possible = clone_slist(large->possible);
        add_possible_sm(to, to);
        FOR_EACH_PTR(small->possible, tmp) {
                add_possible_sm(to, tmp);
        } END_FOR_EACH_PTR(tmp);
}

char *alloc_sname(const char *str)
{
        char *tmp;

        if (!str)
                return NULL;
        tmp = __alloc_sname(strlen(str) + 1);
        strcpy(tmp, str);
        return tmp;
}

int out_of_memory(void)
{
        /*
         * I decided to use 50M here based on trial and error.
         * It works out OK for the kernel and so it should work
         * for most other projects as well.
         */
        if (sm_state_counter * sizeof(struct sm_state) >= 100000000)
                return 1;
        return 0;
}

int low_on_memory(void)
{
        if (sm_state_counter * sizeof(struct sm_state) >= 25000000)
                return 1;
        return 0;
}

static void free_sm_state(struct sm_state *sm)
{
        free_slist(&sm->possible);
        /*
         * fixme.  Free the actual state.
         * Right now we leave it until the end of the function
         * because we don't want to double free it.
         * Use the freelist to not double free things
         */
}

static void free_all_sm_states(struct allocation_blob *blob)
{
        unsigned int size = sizeof(struct sm_state);
        unsigned int offset = 0;

        while (offset < blob->offset) {
                free_sm_state((struct sm_state *)(blob->data + offset));
                offset += size;
        }
}

/* At the end of every function we free all the sm_states */
void free_every_single_sm_state(void)
{
        struct allocator_struct *desc = &sm_state_allocator;
        struct allocation_blob *blob = desc->blobs;

        desc->blobs = NULL;
        desc->allocations = 0;
        desc->total_bytes = 0;
        desc->useful_bytes = 0;
        desc->freelist = NULL;
        while (blob) {
                struct allocation_blob *next = blob->next;
                free_all_sm_states(blob);
                blob_free(blob, desc->chunking);
                blob = next;
        }
        clear_sname_alloc();
        clear_smatch_state_alloc();

        free_stack_and_strees(&all_pools);
        sm_state_counter = 0;
}

unsigned long get_pool_count(void)
{
        return ptr_list_size((struct ptr_list *)all_pools);
}

struct sm_state *clone_sm(struct sm_state *s)
{
        struct sm_state *ret;

        ret = alloc_state_no_name(s->owner, s->name, s->sym, s->state);
        ret->merged = s->merged;
        ret->line = s->line;
        /* clone_sm() doesn't copy the pools.  Each state needs to have
           only one pool. */
        ret->possible = clone_slist(s->possible);
        ret->left = s->left;
        ret->right = s->right;
        ret->nr_children = s->nr_children;
        return ret;
}

int is_merged(struct sm_state *sm)
{
        return sm->merged;
}

int is_leaf(struct sm_state *sm)
{
        return !sm->merged;
}

int slist_has_state(struct state_list *slist, struct smatch_state *state)
{
        struct sm_state *tmp;

        FOR_EACH_PTR(slist, tmp) {
                if (tmp->state == state)
                        return 1;
        } END_FOR_EACH_PTR(tmp);
        return 0;
}

struct state_list *clone_slist(struct state_list *from_slist)
{
        struct sm_state *sm;
        struct state_list *to_slist = NULL;

        FOR_EACH_PTR(from_slist, sm) {
                add_ptr_list(&to_slist, sm);
        } END_FOR_EACH_PTR(sm);
        return to_slist;
}

static struct smatch_state *merge_states(int owner, const char *name,
                                         struct symbol *sym,
                                         struct smatch_state *state1,
                                         struct smatch_state *state2)
{
        struct smatch_state *ret;

        if (state1 == state2)
                ret = state1;
        else if (__has_merge_function(owner))
                ret = __client_merge_function(owner, state1, state2);
        else if (state1 == &ghost)
                ret = state2;
        else if (state2 == &ghost)
                ret = state1;
        else if (!state1 || !state2)
                ret = &undefined;
        else
                ret = &merged;
        return ret;
}

struct sm_state *merge_sm_states(struct sm_state *one, struct sm_state *two)
{
        struct smatch_state *s;
        struct sm_state *result;
        static int warned;

        if (one == two)
                return one;
        if (out_of_memory()) {
                if (!warned)
                        sm_warning("Function too hairy.  No more merges.");
                warned = 1;
                return one;
        }
        warned = 0;
        s = merge_states(one->owner, one->name, one->sym, one->state, two->state);
        result = alloc_state_no_name(one->owner, one->name, one->sym, s);
        result->merged = 1;
        result->left = one;
        result->right = two;
        if (one->nr_children + two->nr_children <= MAX_CHILDREN)
                result->nr_children = one->nr_children + two->nr_children;
        else
                result->nr_children = MAX_CHILDREN;

        copy_possibles(result, one, two);

        /*
         * The ->line information is used by deref_check where we complain about
         * checking pointers that have already been dereferenced.  Let's say we
         * dereference a pointer on both the true and false paths and then merge
         * the states here.  The result state is &derefed, but the ->line number
         * is on the line where the pointer is merged not where it was
         * dereferenced..
         *
         * So in that case, let's just pick one dereference and set the ->line
         * to point at it.
         *
         */

        if (result->state == one->state)
                result->line = one->line;
        if (result->state == two->state)
                result->line = two->line;

        if (option_debug ||
            strcmp(check_name(one->owner), option_debug_check) == 0) {
                struct sm_state *tmp;
                int i = 0;

                printf("%s:%d %s() merge [%s] '%s' %s(L %d) + %s(L %d) => %s (",
                        get_filename(), get_lineno(), get_function(),
                        check_name(one->owner), one->name,
                        show_state(one->state), one->line,
                        show_state(two->state), two->line,
                        show_state(s));

                FOR_EACH_PTR(result->possible, tmp) {
                        if (i++)
                                printf(", ");
                        printf("%s", show_state(tmp->state));
                } END_FOR_EACH_PTR(tmp);
                printf(")\n");
        }

        return result;
}

struct sm_state *get_sm_state_stree(struct stree *stree, int owner, const char *name,
                                struct symbol *sym)
{
        struct tracker tracker = {
                .owner = owner,
                .name = (char *)name,
                .sym = sym,
        };

        if (!name)
                return NULL;


        return avl_lookup(stree, (struct sm_state *)&tracker);
}

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

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

/* FIXME: this is almost exactly the same as set_sm_state_slist() */
void overwrite_sm_state_stree(struct stree **stree, struct sm_state *new)
{
        avl_insert(stree, new);
}

void overwrite_sm_state_stree_stack(struct stree_stack **stack,
                        struct sm_state *sm)
{
        struct stree *stree;

        stree = pop_stree(stack);
        overwrite_sm_state_stree(&stree, sm);
        push_stree(stack, stree);
}

struct sm_state *set_state_stree(struct stree **stree, int owner, const char *name,
                     struct symbol *sym, struct smatch_state *state)
{
        struct sm_state *new = alloc_sm_state(owner, name, sym, state);

        avl_insert(stree, new);
        return new;
}

void set_state_stree_perm(struct stree **stree, int owner, const char *name,
                     struct symbol *sym, struct smatch_state *state)
{
        struct sm_state *sm;

        sm = malloc(sizeof(*sm) + strlen(name) + 1);
        memset(sm, 0, sizeof(*sm));
        sm->owner = owner;
        sm->name = (char *)(sm + 1);
        strcpy((char *)sm->name, name);
        sm->sym = sym;
        sm->state = state;

        overwrite_sm_state_stree(stree, sm);
}

void delete_state_stree(struct stree **stree, int owner, const char *name,
                        struct symbol *sym)
{
        struct tracker tracker = {
                .owner = owner,
                .name = (char *)name,
                .sym = sym,
        };

        avl_remove(stree, (struct sm_state *)&tracker);
}

void delete_state_stree_stack(struct stree_stack **stack, int owner, const char *name,
                        struct symbol *sym)
{
        struct stree *stree;

        stree = pop_stree(stack);
        delete_state_stree(&stree, owner, name, sym);
        push_stree(stack, stree);
}

void push_stree(struct stree_stack **stack, struct stree *stree)
{
        add_ptr_list(stack, stree);
}

struct stree *pop_stree(struct stree_stack **stack)
{
        struct stree *stree;

        stree = last_ptr_list((struct ptr_list *)*stack);
        delete_ptr_list_last((struct ptr_list **)stack);
        return stree;
}

struct stree *top_stree(struct stree_stack *stack)
{
        return last_ptr_list((struct ptr_list *)stack);
}

void free_slist(struct state_list **slist)
{
        __free_ptr_list((struct ptr_list **)slist);
}

void free_stree_stack(struct stree_stack **stack)
{
        __free_ptr_list((struct ptr_list **)stack);
}

void free_stack_and_strees(struct stree_stack **stree_stack)
{
        struct stree *stree;

        FOR_EACH_PTR(*stree_stack, stree) {
                free_stree(&stree);
        } END_FOR_EACH_PTR(stree);
        free_stree_stack(stree_stack);
}

struct sm_state *set_state_stree_stack(struct stree_stack **stack, int owner, const char *name,
                                struct symbol *sym, struct smatch_state *state)
{
        struct stree *stree;
        struct sm_state *sm;

        stree = pop_stree(stack);
        sm = set_state_stree(&stree, owner, name, sym, state);
        push_stree(stack, stree);

        return sm;
}

/*
 * get_sm_state_stack() gets the state for the top slist on the stack.
 */
struct sm_state *get_sm_state_stree_stack(struct stree_stack *stack,
                                int owner, const char *name,
                                struct symbol *sym)
{
        struct stree *stree;
        struct sm_state *ret;

        stree = pop_stree(&stack);
        ret = get_sm_state_stree(stree, owner, name, sym);
        push_stree(&stack, stree);
        return ret;
}

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

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

static void match_states_stree(struct stree **one, struct stree **two)
{
        struct smatch_state *tmp_state;
        struct sm_state *sm;
        struct state_list *add_to_one = NULL;
        struct state_list *add_to_two = NULL;
        AvlIter one_iter;
        AvlIter two_iter;

        avl_iter_begin(&one_iter, *one, FORWARD);
        avl_iter_begin(&two_iter, *two, FORWARD);

        for (;;) {
                if (!one_iter.sm && !two_iter.sm)
                        break;
                if (cmp_tracker(one_iter.sm, two_iter.sm) < 0) {
                        __set_fake_cur_stree_fast(*two);
                        tmp_state = __client_unmatched_state_function(one_iter.sm);
                        __pop_fake_cur_stree_fast();
                        sm = alloc_state_no_name(one_iter.sm->owner, one_iter.sm->name,
                                                  one_iter.sm->sym, tmp_state);
                        add_ptr_list(&add_to_two, sm);
                        avl_iter_next(&one_iter);
                } else if (cmp_tracker(one_iter.sm, two_iter.sm) == 0) {
                        avl_iter_next(&one_iter);
                        avl_iter_next(&two_iter);
                } else {
                        __set_fake_cur_stree_fast(*one);
                        tmp_state = __client_unmatched_state_function(two_iter.sm);
                        __pop_fake_cur_stree_fast();
                        sm = alloc_state_no_name(two_iter.sm->owner, two_iter.sm->name,
                                                  two_iter.sm->sym, tmp_state);
                        add_ptr_list(&add_to_one, sm);
                        avl_iter_next(&two_iter);
                }
        }

        FOR_EACH_PTR(add_to_one, sm) {
                avl_insert(one, sm);
        } END_FOR_EACH_PTR(sm);

        FOR_EACH_PTR(add_to_two, sm) {
                avl_insert(two, sm);
        } END_FOR_EACH_PTR(sm);

        free_slist(&add_to_one);
        free_slist(&add_to_two);
}

static void call_pre_merge_hooks(struct stree **one, struct stree **two)
{
        struct sm_state *sm, *other;

        save_all_states();

        __swap_cur_stree(*one);
        FOR_EACH_SM(*two, sm) {
                other = get_sm_state(sm->owner, sm->name, sm->sym);
                if (other == sm)
                        continue;
                call_pre_merge_hook(sm);
        } END_FOR_EACH_SM(sm);
        *one = clone_stree(__get_cur_stree());

        __swap_cur_stree(*two);
        FOR_EACH_SM(*one, sm) {
                other = get_sm_state(sm->owner, sm->name, sm->sym);
                if (other == sm)
                        continue;
                call_pre_merge_hook(sm);
        } END_FOR_EACH_SM(sm);
        *two = clone_stree(__get_cur_stree());

        restore_all_states();
}

static void clone_pool_havers_stree(struct stree **stree)
{
        struct sm_state *sm, *tmp;
        struct state_list *slist = NULL;

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

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

        free_slist(&slist);
}

int __stree_id;

/*
 * merge_slist() is called whenever paths merge, such as after
 * an if statement.  It takes the two slists and creates one.
 */
static void __merge_stree(struct stree **to, struct stree *stree, int add_pool)
{
        struct stree *results = NULL;
        struct stree *implied_one = NULL;
        struct stree *implied_two = NULL;
        AvlIter one_iter;
        AvlIter two_iter;
        struct sm_state *one, *two, *res;

        if (out_of_memory())
                return;

        /* merging a null and nonnull path gives you only the nonnull path */
        if (!stree)
                return;
        if (*to == stree)
                return;

        if (!*to) {
                *to = clone_stree(stree);
                return;
        }

        implied_one = clone_stree(*to);
        implied_two = clone_stree(stree);

        match_states_stree(&implied_one, &implied_two);
        call_pre_merge_hooks(&implied_one, &implied_two);

        if (add_pool) {
                clone_pool_havers_stree(&implied_one);
                clone_pool_havers_stree(&implied_two);

                set_stree_id(&implied_one, ++__stree_id);
                set_stree_id(&implied_two, ++__stree_id);
                if (implied_one->base_stree)
                        set_stree_id(&implied_one->base_stree, ++__stree_id);
                if (implied_two->base_stree)
                        set_stree_id(&implied_two->base_stree, ++__stree_id);
        }

        push_stree(&all_pools, implied_one);
        push_stree(&all_pools, implied_two);

        avl_iter_begin(&one_iter, implied_one, FORWARD);
        avl_iter_begin(&two_iter, implied_two, FORWARD);

        for (;;) {
                if (!one_iter.sm || !two_iter.sm)
                        break;

                one = one_iter.sm;
                two = two_iter.sm;

                if (one == two) {
                        avl_insert(&results, one);
                        goto next;
                }

                if (add_pool) {
                        one->pool = implied_one;
                        if (implied_one->base_stree)
                                one->pool = implied_one->base_stree;
                        two->pool = implied_two;
                        if (implied_two->base_stree)
                                two->pool = implied_two->base_stree;
                }
                res = merge_sm_states(one, two);
                add_possible_sm(res, one);
                add_possible_sm(res, two);
                avl_insert(&results, res);
next:
                avl_iter_next(&one_iter);
                avl_iter_next(&two_iter);
        }

        free_stree(to);
        *to = results;
}

void merge_stree(struct stree **to, struct stree *stree)
{
        __merge_stree(to, stree, 1);
}

void merge_stree_no_pools(struct stree **to, struct stree *stree)
{
        __merge_stree(to, stree, 0);
}

/*
 * This is unfortunately a bit subtle...  The problem is that if a
 * state is set on one fake stree but not the other then we should
 * look up the the original state and use that as the unset state.
 * Fortunately, after you pop your fake stree then the cur_slist should
 * reflect the original state.
 */
void merge_fake_stree(struct stree **to, struct stree *stree)
{
        struct stree *one = *to;
        struct stree *two = stree;
        struct sm_state *sm;
        struct state_list *add_to_one = NULL;
        struct state_list *add_to_two = NULL;
        AvlIter one_iter;
        AvlIter two_iter;

        if (!stree)
                return;
        if (*to == stree)
                return;
        if (!*to) {
                *to = clone_stree(stree);
                return;
        }

        avl_iter_begin(&one_iter, one, FORWARD);
        avl_iter_begin(&two_iter, two, FORWARD);

        for (;;) {
                if (!one_iter.sm && !two_iter.sm)
                        break;
                if (cmp_tracker(one_iter.sm, two_iter.sm) < 0) {
                        sm = get_sm_state(one_iter.sm->owner, one_iter.sm->name,
                                          one_iter.sm->sym);
                        if (sm)
                                add_ptr_list(&add_to_two, sm);
                        avl_iter_next(&one_iter);
                } else if (cmp_tracker(one_iter.sm, two_iter.sm) == 0) {
                        avl_iter_next(&one_iter);
                        avl_iter_next(&two_iter);
                } else {
                        sm = get_sm_state(two_iter.sm->owner, two_iter.sm->name,
                                          two_iter.sm->sym);
                        if (sm)
                                add_ptr_list(&add_to_one, sm);
                        avl_iter_next(&two_iter);
                }
        }

        FOR_EACH_PTR(add_to_one, sm) {
                avl_insert(&one, sm);
        } END_FOR_EACH_PTR(sm);

        FOR_EACH_PTR(add_to_two, sm) {
                avl_insert(&two, sm);
        } END_FOR_EACH_PTR(sm);

        one->base_stree = clone_stree(__get_cur_stree());
        FOR_EACH_SM(one, sm) {
                avl_insert(&one->base_stree, sm);
        } END_FOR_EACH_SM(sm);

        two->base_stree = clone_stree(__get_cur_stree());
        FOR_EACH_SM(two, sm) {
                avl_insert(&two->base_stree, sm);
        } END_FOR_EACH_SM(sm);

        free_slist(&add_to_one);
        free_slist(&add_to_two);

        __merge_stree(&one, two, 1);

        *to = one;
}

/*
 * filter_slist() removes any sm states "slist" holds in common with "filter"
 */
void filter_stree(struct stree **stree, struct stree *filter)
{
        struct stree *results = NULL;
        AvlIter one_iter;
        AvlIter two_iter;

        avl_iter_begin(&one_iter, *stree, FORWARD);
        avl_iter_begin(&two_iter, filter, FORWARD);

        /* FIXME: This should probably be re-written with trees in mind */

        for (;;) {
                if (!one_iter.sm && !two_iter.sm)
                        break;
                if (cmp_tracker(one_iter.sm, two_iter.sm) < 0) {
                        avl_insert(&results, one_iter.sm);
                        avl_iter_next(&one_iter);
                } else if (cmp_tracker(one_iter.sm, two_iter.sm) == 0) {
                        if (one_iter.sm != two_iter.sm)
                                avl_insert(&results, one_iter.sm);
                        avl_iter_next(&one_iter);
                        avl_iter_next(&two_iter);
                } else {
                        avl_iter_next(&two_iter);
                }
        }

        free_stree(stree);
        *stree = results;
}


/*
 * and_slist_stack() pops the top two slists, overwriting the one with
 * the other and pushing it back on the stack.
 */
void and_stree_stack(struct stree_stack **stack)
{
        struct sm_state *tmp;
        struct stree *right_stree = pop_stree(stack);

        FOR_EACH_SM(right_stree, tmp) {
                overwrite_sm_state_stree_stack(stack, tmp);
        } END_FOR_EACH_SM(tmp);
        free_stree(&right_stree);
}

/*
 * or_slist_stack() is for if we have:  if (foo || bar) { foo->baz;
 * It pops the two slists from the top of the stack and merges them
 * together in a way that preserves the things they have in common
 * but creates a merged state for most of the rest.
 * You could have code that had:  if (foo || foo) { foo->baz;
 * It's this function which ensures smatch does the right thing.
 */
void or_stree_stack(struct stree_stack **pre_conds,
                    struct stree *cur_stree,
                    struct stree_stack **stack)
{
        struct stree *new;
        struct stree *old;
        struct stree *pre_stree;
        struct stree *res;
        struct stree *tmp_stree;

        new = pop_stree(stack);
        old = pop_stree(stack);

        pre_stree = pop_stree(pre_conds);
        push_stree(pre_conds, clone_stree(pre_stree));

        res = clone_stree(pre_stree);
        overwrite_stree(old, &res);

        tmp_stree = clone_stree(cur_stree);
        overwrite_stree(new, &tmp_stree);

        merge_stree(&res, tmp_stree);
        filter_stree(&res, pre_stree);

        push_stree(stack, res);
        free_stree(&tmp_stree);
        free_stree(&pre_stree);
        free_stree(&new);
        free_stree(&old);
}

/*
 * get_named_stree() is only used for gotos.
 */
struct stree **get_named_stree(struct named_stree_stack *stack,
                               const char *name,
                               struct symbol *sym)
{
        struct named_stree *tmp;

        FOR_EACH_PTR(stack, tmp) {
                if (tmp->sym == sym &&
                    strcmp(tmp->name, name) == 0)
                        return &tmp->stree;
        } END_FOR_EACH_PTR(tmp);
        return NULL;
}

/* FIXME:  These parameters are in a different order from expected */
void overwrite_stree(struct stree *from, struct stree **to)
{
        struct sm_state *tmp;

        FOR_EACH_SM(from, tmp) {
                overwrite_sm_state_stree(to, tmp);
        } END_FOR_EACH_SM(tmp);
}