// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
 */

#include <sys/types.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <regex.h>

#include <hash.h>
#include <xalloc.h>
#include "internal.h"
#include "lkc.h"

struct symbol symbol_yes = {
        .name = "y",
        .type = S_TRISTATE,
        .curr = { "y", yes },
        .menus = LIST_HEAD_INIT(symbol_yes.menus),
        .flags = SYMBOL_CONST|SYMBOL_VALID,
};

struct symbol symbol_mod = {
        .name = "m",
        .type = S_TRISTATE,
        .curr = { "m", mod },
        .menus = LIST_HEAD_INIT(symbol_mod.menus),
        .flags = SYMBOL_CONST|SYMBOL_VALID,
};

struct symbol symbol_no = {
        .name = "n",
        .type = S_TRISTATE,
        .curr = { "n", no },
        .menus = LIST_HEAD_INIT(symbol_no.menus),
        .flags = SYMBOL_CONST|SYMBOL_VALID,
};

struct symbol *modules_sym;
static tristate modules_val;
static int sym_warnings;

enum symbol_type sym_get_type(const struct symbol *sym)
{
        enum symbol_type type = sym->type;

        if (type == S_TRISTATE && modules_val == no)
                type = S_BOOLEAN;
        return type;
}

const char *sym_type_name(enum symbol_type type)
{
        switch (type) {
        case S_BOOLEAN:
                return "bool";
        case S_TRISTATE:
                return "tristate";
        case S_INT:
                return "integer";
        case S_HEX:
                return "hex";
        case S_STRING:
                return "string";
        case S_UNKNOWN:
                return "unknown";
        }
        return "???";
}

/**
 * sym_get_prompt_menu - get the menu entry with a prompt
 *
 * @sym: a symbol pointer
 *
 * Return: the menu entry with a prompt.
 */
struct menu *sym_get_prompt_menu(const struct symbol *sym)
{
        struct menu *m;

        list_for_each_entry(m, &sym->menus, link)
                if (m->prompt)
                        return m;

        return NULL;
}

/**
 * sym_get_choice_menu - get the parent choice menu if present
 *
 * @sym: a symbol pointer
 *
 * Return: a choice menu if this function is called against a choice member.
 */
struct menu *sym_get_choice_menu(const struct symbol *sym)
{
        struct menu *menu = NULL;

        /*
         * Choice members must have a prompt. Find a menu entry with a prompt,
         * and assume it resides inside a choice block.
         */
        menu = sym_get_prompt_menu(sym);
        if (!menu)
                return NULL;

        do {
                menu = menu->parent;
        } while (menu && !menu->sym);

        if (menu && menu->sym && sym_is_choice(menu->sym))
                return menu;

        return NULL;
}

static struct property *sym_get_default_prop(struct symbol *sym)
{
        struct property *prop;

        for_all_defaults(sym, prop) {
                prop->visible.tri = expr_calc_value(prop->visible.expr);
                if (prop->visible.tri != no)
                        return prop;
        }
        return NULL;
}

struct property *sym_get_range_prop(struct symbol *sym)
{
        struct property *prop;

        for_all_properties(sym, prop, P_RANGE) {
                prop->visible.tri = expr_calc_value(prop->visible.expr);
                if (prop->visible.tri != no)
                        return prop;
        }
        return NULL;
}

static long long sym_get_range_val(struct symbol *sym, int base)
{
        sym_calc_value(sym);
        switch (sym->type) {
        case S_INT:
                base = 10;
                break;
        case S_HEX:
                base = 16;
                break;
        default:
                break;
        }
        return strtoll(sym->curr.val, NULL, base);
}

static void sym_validate_range(struct symbol *sym)
{
        struct property *prop;
        struct symbol *range_sym;
        int base;
        long long val, val2;

        switch (sym->type) {
        case S_INT:
                base = 10;
                break;
        case S_HEX:
                base = 16;
                break;
        default:
                return;
        }
        prop = sym_get_range_prop(sym);
        if (!prop)
                return;
        val = strtoll(sym->curr.val, NULL, base);
        range_sym = prop->expr->left.sym;
        val2 = sym_get_range_val(range_sym, base);
        if (val >= val2) {
                range_sym = prop->expr->right.sym;
                val2 = sym_get_range_val(range_sym, base);
                if (val <= val2)
                        return;
        }
        sym->curr.val = range_sym->curr.val;
}

static void sym_set_changed(struct symbol *sym)
{
        struct menu *menu;

        list_for_each_entry(menu, &sym->menus, link)
                menu->flags |= MENU_CHANGED;

        menu = sym_get_choice_menu(sym);
        if (menu)
                menu->flags |= MENU_CHANGED;
}

static void sym_set_all_changed(void)
{
        struct symbol *sym;

        for_all_symbols(sym)
                sym_set_changed(sym);
}

static void sym_calc_visibility(struct symbol *sym)
{
        struct property *prop;
        tristate tri;

        if (sym->flags & SYMBOL_TRANS) {
                sym->visible = yes;
                return;
        }

        /* any prompt visible? */
        tri = no;
        for_all_prompts(sym, prop) {
                prop->visible.tri = expr_calc_value(prop->visible.expr);
                tri = EXPR_OR(tri, prop->visible.tri);
        }
        if (tri == mod && (sym->type != S_TRISTATE || modules_val == no))
                tri = yes;
        if (sym->visible != tri) {
                sym->visible = tri;
                sym_set_changed(sym);
        }
        if (sym_is_choice_value(sym))
                return;
        /* defaulting to "yes" if no explicit "depends on" are given */
        tri = yes;
        if (sym->dir_dep.expr)
                tri = expr_calc_value(sym->dir_dep.expr);
        if (tri == mod && sym_get_type(sym) == S_BOOLEAN)
                tri = yes;
        if (sym->dir_dep.tri != tri) {
                sym->dir_dep.tri = tri;
                sym_set_changed(sym);
        }
        tri = no;
        if (sym->rev_dep.expr)
                tri = expr_calc_value(sym->rev_dep.expr);
        if (tri == mod && sym_get_type(sym) == S_BOOLEAN)
                tri = yes;
        if (sym->rev_dep.tri != tri) {
                sym->rev_dep.tri = tri;
                sym_set_changed(sym);
        }
        tri = no;
        if (sym->implied.expr)
                tri = expr_calc_value(sym->implied.expr);
        if (tri == mod && sym_get_type(sym) == S_BOOLEAN)
                tri = yes;
        if (sym->implied.tri != tri) {
                sym->implied.tri = tri;
                sym_set_changed(sym);
        }
}

/*
 * Find the default symbol for a choice.
 * First try the default values for the choice symbol
 * Next locate the first visible choice value
 * Return NULL if none was found
 */
struct symbol *sym_choice_default(struct menu *choice)
{
        struct menu *menu;
        struct symbol *def_sym;
        struct property *prop;

        /* any of the defaults visible? */
        for_all_defaults(choice->sym, prop) {
                prop->visible.tri = expr_calc_value(prop->visible.expr);
                if (prop->visible.tri == no)
                        continue;
                def_sym = prop_get_symbol(prop);
                if (def_sym->visible != no)
                        return def_sym;
        }

        /* just get the first visible value */
        menu_for_each_sub_entry(menu, choice)
                if (menu->sym && menu->sym->visible != no)
                        return menu->sym;

        /* failed to locate any defaults */
        return NULL;
}

/*
 * sym_calc_choice - calculate symbol values in a choice
 *
 * @choice: a menu of the choice
 *
 * Return: a chosen symbol
 */
struct symbol *sym_calc_choice(struct menu *choice)
{
        struct symbol *res = NULL;
        struct symbol *sym;
        struct menu *menu;

        /* Traverse the list of choice members in the priority order. */
        list_for_each_entry(sym, &choice->choice_members, choice_link) {
                sym_calc_visibility(sym);
                if (sym->visible == no)
                        continue;

                /* The first visible symble with the user value 'y'. */
                if (sym_has_value(sym) && sym->def[S_DEF_USER].tri == yes) {
                        res = sym;
                        break;
                }
        }

        /*
         * If 'y' is not found in the user input, use the default, unless it is
         * explicitly set to 'n'.
         */
        if (!res) {
                res = sym_choice_default(choice);
                if (res && sym_has_value(res) && res->def[S_DEF_USER].tri == no)
                        res = NULL;
        }

        /* Still not found. Pick up the first visible, user-unspecified symbol. */
        if (!res) {
                menu_for_each_sub_entry(menu, choice) {
                        sym = menu->sym;

                        if (!sym || sym->visible == no || sym_has_value(sym))
                                continue;

                        res = sym;
                        break;
                }
        }

        /*
         * Still not found. Traverse the linked list in the _reverse_ order to
         * pick up the least prioritized 'n'.
         */
        if (!res) {
                list_for_each_entry_reverse(sym, &choice->choice_members,
                                            choice_link) {
                        if (sym->visible == no)
                                continue;

                        res = sym;
                        break;
                }
        }

        menu_for_each_sub_entry(menu, choice) {
                tristate val;

                sym = menu->sym;

                if (!sym || sym->visible == no)
                        continue;

                val = sym == res ? yes : no;

                if (sym->curr.tri != val)
                        sym_set_changed(sym);

                sym->curr.tri = val;
                sym->flags |= SYMBOL_VALID | SYMBOL_WRITE;
        }

        return res;
}

static void sym_warn_unmet_dep(const struct symbol *sym)
{
        struct gstr gs = str_new();

        str_printf(&gs,
                   "\nWARNING: unmet direct dependencies detected for %s\n",
                   sym->name);
        str_printf(&gs,
                   "  Depends on [%c]: ",
                   sym->dir_dep.tri == mod ? 'm' : 'n');
        expr_gstr_print(sym->dir_dep.expr, &gs);
        str_printf(&gs, "\n");

        expr_gstr_print_revdep(sym->rev_dep.expr, &gs, yes,
                               "  Selected by [y]:\n");
        expr_gstr_print_revdep(sym->rev_dep.expr, &gs, mod,
                               "  Selected by [m]:\n");

        fputs(str_get(&gs), stderr);
        str_free(&gs);
        sym_warnings++;
}

bool sym_dep_errors(void)
{
        if (sym_warnings)
                return getenv("KCONFIG_WERROR");
        return false;
}

void sym_calc_value(struct symbol *sym)
{
        struct symbol_value newval, oldval;
        struct property *prop = NULL;
        struct menu *choice_menu;

        if (!sym)
                return;

        if (sym->flags & SYMBOL_VALID)
                return;

        sym->flags |= SYMBOL_VALID;

        oldval = sym->curr;

        newval.tri = no;

        switch (sym->type) {
        case S_INT:
                newval.val = "0";
                break;
        case S_HEX:
                newval.val = "0x0";
                break;
        case S_STRING:
                newval.val = "";
                break;
        case S_BOOLEAN:
        case S_TRISTATE:
                newval.val = "n";
                break;
        default:
                sym->curr.val = sym->name;
                sym->curr.tri = no;
                return;
        }
        sym->flags &= ~SYMBOL_WRITE;

        sym_calc_visibility(sym);

        if (sym->visible != no)
                sym->flags |= SYMBOL_WRITE;

        /* set default if recursively called */
        sym->curr = newval;

        switch (sym_get_type(sym)) {
        case S_BOOLEAN:
        case S_TRISTATE:
                choice_menu = sym_get_choice_menu(sym);

                if (choice_menu) {
                        sym_calc_choice(choice_menu);
                        newval.tri = sym->curr.tri;
                } else {
                        if (sym->visible != no) {
                                /* if the symbol is visible use the user value
                                 * if available, otherwise try the default value
                                 */
                                if (sym_has_value(sym)) {
                                        newval.tri = EXPR_AND(sym->def[S_DEF_USER].tri,
                                                              sym->visible);
                                        goto calc_newval;
                                }
                        }
                        if (sym->rev_dep.tri != no)
                                sym->flags |= SYMBOL_WRITE;
                        if (!sym_is_choice(sym)) {
                                prop = sym_get_default_prop(sym);
                                if (prop) {
                                        newval.tri = EXPR_AND(expr_calc_value(prop->expr),
                                                              prop->visible.tri);
                                        if (newval.tri != no)
                                                sym->flags |= SYMBOL_WRITE;
                                }
                                if (sym->implied.tri != no) {
                                        sym->flags |= SYMBOL_WRITE;
                                        newval.tri = EXPR_OR(newval.tri, sym->implied.tri);
                                        newval.tri = EXPR_AND(newval.tri,
                                                              sym->dir_dep.tri);
                                }
                        }
                calc_newval:
                        if (sym->dir_dep.tri < sym->rev_dep.tri)
                                sym_warn_unmet_dep(sym);
                        newval.tri = EXPR_OR(newval.tri, sym->rev_dep.tri);
                }
                if (newval.tri == mod && sym_get_type(sym) == S_BOOLEAN)
                        newval.tri = yes;
                break;
        case S_STRING:
        case S_HEX:
        case S_INT:
                if (sym->visible != no && sym_has_value(sym)) {
                        newval.val = sym->def[S_DEF_USER].val;
                        break;
                }
                prop = sym_get_default_prop(sym);
                if (prop) {
                        struct symbol *ds = prop_get_symbol(prop);
                        if (ds) {
                                sym->flags |= SYMBOL_WRITE;
                                sym_calc_value(ds);
                                newval.val = ds->curr.val;
                        }
                }
                break;
        default:
                ;
        }

        /*
         * If the symbol lacks a user value but its value comes from a
         * single transitional symbol with an existing user value, mark
         * this symbol as having a user value to avoid prompting.
         */
        if (prop && !sym_has_value(sym)) {
                struct symbol *ds = prop_get_symbol(prop);
                if (ds && (ds->flags & SYMBOL_TRANS) && sym_has_value(ds)) {
                        sym->def[S_DEF_USER] = newval;
                        sym->flags |= SYMBOL_DEF_USER;
                }
        }

        sym->curr = newval;
        sym_validate_range(sym);

        if (memcmp(&oldval, &sym->curr, sizeof(oldval))) {
                sym_set_changed(sym);
                if (modules_sym == sym) {
                        sym_set_all_changed();
                        modules_val = modules_sym->curr.tri;
                }
        }

        if (sym_is_choice(sym) || sym->flags & SYMBOL_TRANS)
                sym->flags &= ~SYMBOL_WRITE;
}

void sym_clear_all_valid(void)
{
        struct symbol *sym;

        for_all_symbols(sym)
                sym->flags &= ~SYMBOL_VALID;
        expr_invalidate_all();
        conf_set_changed(true);
        sym_calc_value(modules_sym);
}

bool sym_tristate_within_range(const struct symbol *sym, tristate val)
{
        int type = sym_get_type(sym);

        if (sym->visible == no)
                return false;

        if (type != S_BOOLEAN && type != S_TRISTATE)
                return false;

        if (type == S_BOOLEAN && val == mod)
                return false;
        if (sym->visible <= sym->rev_dep.tri)
                return false;
        return val >= sym->rev_dep.tri && val <= sym->visible;
}

bool sym_set_tristate_value(struct symbol *sym, tristate val)
{
        tristate oldval = sym_get_tristate_value(sym);

        if (!sym_tristate_within_range(sym, val))
                return false;

        if (!(sym->flags & SYMBOL_DEF_USER) || sym->def[S_DEF_USER].tri != val) {
                sym->def[S_DEF_USER].tri = val;
                sym->flags |= SYMBOL_DEF_USER;
                sym_set_changed(sym);
        }

        if (oldval != val)
                sym_clear_all_valid();

        return true;
}

/**
 * choice_set_value - set the user input to a choice
 *
 * @choice: menu entry for the choice
 * @sym: selected symbol
 */
void choice_set_value(struct menu *choice, struct symbol *sym)
{
        struct menu *menu;
        bool changed = false;

        menu_for_each_sub_entry(menu, choice) {
                tristate val;

                if (!menu->sym)
                        continue;

                if (menu->sym->visible == no)
                        continue;

                val = menu->sym == sym ? yes : no;

                if (menu->sym->curr.tri != val)
                        changed = true;

                menu->sym->def[S_DEF_USER].tri = val;
                menu->sym->flags |= SYMBOL_DEF_USER;

                /*
                 * Now, the user has explicitly enabled or disabled this symbol,
                 * it should be given the highest priority. We are possibly
                 * setting multiple symbols to 'n', where the first symbol is
                 * given the least prioritized 'n'. This works well when the
                 * choice block ends up with selecting 'n' symbol.
                 * (see sym_calc_choice())
                 */
                list_move(&menu->sym->choice_link, &choice->choice_members);
        }

        if (changed)
                sym_clear_all_valid();
}

tristate sym_toggle_tristate_value(struct symbol *sym)
{
        struct menu *choice;
        tristate oldval, newval;

        choice = sym_get_choice_menu(sym);
        if (choice) {
                choice_set_value(choice, sym);
                return yes;
        }

        oldval = newval = sym_get_tristate_value(sym);
        do {
                switch (newval) {
                case no:
                        newval = mod;
                        break;
                case mod:
                        newval = yes;
                        break;
                case yes:
                        newval = no;
                        break;
                }
                if (sym_set_tristate_value(sym, newval))
                        break;
        } while (oldval != newval);
        return newval;
}

bool sym_string_valid(struct symbol *sym, const char *str)
{
        signed char ch;

        switch (sym->type) {
        case S_STRING:
                return true;
        case S_INT:
                ch = *str++;
                if (ch == '-')
                        ch = *str++;
                if (!isdigit(ch))
                        return false;
                if (ch == '0' && *str != 0)
                        return false;
                while ((ch = *str++)) {
                        if (!isdigit(ch))
                                return false;
                }
                return true;
        case S_HEX:
                if (str[0] == '0' && (str[1] == 'x' || str[1] == 'X'))
                        str += 2;
                ch = *str++;
                do {
                        if (!isxdigit(ch))
                                return false;
                } while ((ch = *str++));
                return true;
        case S_BOOLEAN:
        case S_TRISTATE:
                switch (str[0]) {
                case 'y': case 'Y':
                case 'm': case 'M':
                case 'n': case 'N':
                        return true;
                }
                return false;
        default:
                return false;
        }
}

bool sym_string_within_range(struct symbol *sym, const char *str)
{
        struct property *prop;
        long long val;

        switch (sym->type) {
        case S_STRING:
                return sym_string_valid(sym, str);
        case S_INT:
                if (!sym_string_valid(sym, str))
                        return false;
                prop = sym_get_range_prop(sym);
                if (!prop)
                        return true;
                val = strtoll(str, NULL, 10);
                return val >= sym_get_range_val(prop->expr->left.sym, 10) &&
                       val <= sym_get_range_val(prop->expr->right.sym, 10);
        case S_HEX:
                if (!sym_string_valid(sym, str))
                        return false;
                prop = sym_get_range_prop(sym);
                if (!prop)
                        return true;
                val = strtoll(str, NULL, 16);
                return val >= sym_get_range_val(prop->expr->left.sym, 16) &&
                       val <= sym_get_range_val(prop->expr->right.sym, 16);
        case S_BOOLEAN:
        case S_TRISTATE:
                switch (str[0]) {
                case 'y': case 'Y':
                        return sym_tristate_within_range(sym, yes);
                case 'm': case 'M':
                        return sym_tristate_within_range(sym, mod);
                case 'n': case 'N':
                        return sym_tristate_within_range(sym, no);
                }
                return false;
        default:
                return false;
        }
}

bool sym_set_string_value(struct symbol *sym, const char *newval)
{
        const char *oldval;
        char *val;
        int size;

        switch (sym->type) {
        case S_BOOLEAN:
        case S_TRISTATE:
                switch (newval[0]) {
                case 'y': case 'Y':
                        return sym_set_tristate_value(sym, yes);
                case 'm': case 'M':
                        return sym_set_tristate_value(sym, mod);
                case 'n': case 'N':
                        return sym_set_tristate_value(sym, no);
                }
                return false;
        default:
                ;
        }

        if (!sym_string_within_range(sym, newval))
                return false;

        if (!(sym->flags & SYMBOL_DEF_USER)) {
                sym->flags |= SYMBOL_DEF_USER;
                sym_set_changed(sym);
        }

        oldval = sym->def[S_DEF_USER].val;
        size = strlen(newval) + 1;
        if (sym->type == S_HEX && (newval[0] != '0' || (newval[1] != 'x' && newval[1] != 'X'))) {
                size += 2;
                sym->def[S_DEF_USER].val = val = xmalloc(size);
                *val++ = '0';
                *val++ = 'x';
        } else if (!oldval || strcmp(oldval, newval))
                sym->def[S_DEF_USER].val = val = xmalloc(size);
        else
                return true;

        strcpy(val, newval);
        free((void *)oldval);
        sym_clear_all_valid();

        return true;
}

/*
 * Find the default value associated to a symbol.
 * For tristate symbol handle the modules=n case
 * in which case "m" becomes "y".
 * If the symbol does not have any default then fallback
 * to the fixed default values.
 */
const char *sym_get_string_default(struct symbol *sym)
{
        struct property *prop;
        struct symbol *ds;
        const char *str = "";
        tristate val;

        sym_calc_visibility(sym);
        sym_calc_value(modules_sym);
        val = symbol_no.curr.tri;

        /* If symbol has a default value look it up */
        prop = sym_get_default_prop(sym);
        if (prop != NULL) {
                switch (sym->type) {
                case S_BOOLEAN:
                case S_TRISTATE:
                        /* The visibility may limit the value from yes => mod */
                        val = EXPR_AND(expr_calc_value(prop->expr), prop->visible.tri);
                        break;
                default:
                        /*
                         * The following fails to handle the situation
                         * where a default value is further limited by
                         * the valid range.
                         */
                        ds = prop_get_symbol(prop);
                        if (ds != NULL) {
                                sym_calc_value(ds);
                                str = (const char *)ds->curr.val;
                        }
                }
        }

        /* Handle select statements */
        val = EXPR_OR(val, sym->rev_dep.tri);

        /* transpose mod to yes if modules are not enabled */
        if (val == mod)
                if (!sym_is_choice_value(sym) && modules_sym->curr.tri == no)
                        val = yes;

        /* transpose mod to yes if type is bool */
        if (sym->type == S_BOOLEAN && val == mod)
                val = yes;

        /* adjust the default value if this symbol is implied by another */
        if (val < sym->implied.tri)
                val = sym->implied.tri;

        switch (sym->type) {
        case S_BOOLEAN:
        case S_TRISTATE:
                switch (val) {
                case no: return "n";
                case mod: return "m";
                case yes: return "y";
                }
        case S_INT:
                if (!str[0])
                        str = "0";
                break;
        case S_HEX:
                if (!str[0])
                        str = "0x0";
                break;
        default:
                break;
        }
        return str;
}

const char *sym_get_string_value(struct symbol *sym)
{
        tristate val;

        switch (sym->type) {
        case S_BOOLEAN:
        case S_TRISTATE:
                val = sym_get_tristate_value(sym);
                switch (val) {
                case no:
                        return "n";
                case mod:
                        return "m";
                case yes:
                        return "y";
                }
                break;
        default:
                ;
        }
        return sym->curr.val;
}

bool sym_is_changeable(const struct symbol *sym)
{
        return !sym_is_choice(sym) && sym->visible > sym->rev_dep.tri;
}

bool sym_is_choice_value(const struct symbol *sym)
{
        return !list_empty(&sym->choice_link);
}

HASHTABLE_DEFINE(sym_hashtable, SYMBOL_HASHSIZE);

struct symbol *sym_lookup(const char *name, int flags)
{
        struct symbol *symbol;
        char *new_name;
        int hash;

        if (name) {
                if (name[0] && !name[1]) {
                        switch (name[0]) {
                        case 'y': return &symbol_yes;
                        case 'm': return &symbol_mod;
                        case 'n': return &symbol_no;
                        }
                }
                hash = hash_str(name);

                hash_for_each_possible(sym_hashtable, symbol, node, hash) {
                        if (symbol->name &&
                            !strcmp(symbol->name, name) &&
                            (flags ? symbol->flags & flags
                                   : !(symbol->flags & SYMBOL_CONST)))
                                return symbol;
                }
                new_name = xstrdup(name);
        } else {
                new_name = NULL;
                hash = 0;
        }

        symbol = xmalloc(sizeof(*symbol));
        memset(symbol, 0, sizeof(*symbol));
        symbol->name = new_name;
        symbol->type = S_UNKNOWN;
        symbol->flags = flags;
        INIT_LIST_HEAD(&symbol->menus);
        INIT_LIST_HEAD(&symbol->choice_link);

        hash_add(sym_hashtable, &symbol->node, hash);

        return symbol;
}

struct symbol *sym_find(const char *name)
{
        struct symbol *symbol = NULL;
        int hash = 0;

        if (!name)
                return NULL;

        if (name[0] && !name[1]) {
                switch (name[0]) {
                case 'y': return &symbol_yes;
                case 'm': return &symbol_mod;
                case 'n': return &symbol_no;
                }
        }
        hash = hash_str(name);

        hash_for_each_possible(sym_hashtable, symbol, node, hash) {
                if (symbol->name &&
                    !strcmp(symbol->name, name) &&
                    !(symbol->flags & SYMBOL_CONST))
                                break;
        }

        return symbol;
}

struct sym_match {
        struct symbol   *sym;
        off_t           so, eo;
};

/* Compare matched symbols as thus:
 * - first, symbols that match exactly
 * - then, alphabetical sort
 */
static int sym_rel_comp(const void *sym1, const void *sym2)
{
        const struct sym_match *s1 = sym1;
        const struct sym_match *s2 = sym2;
        int exact1, exact2;

        /* Exact match:
         * - if matched length on symbol s1 is the length of that symbol,
         *   then this symbol should come first;
         * - if matched length on symbol s2 is the length of that symbol,
         *   then this symbol should come first.
         * Note: since the search can be a regexp, both symbols may match
         * exactly; if this is the case, we can't decide which comes first,
         * and we fallback to sorting alphabetically.
         */
        exact1 = (s1->eo - s1->so) == strlen(s1->sym->name);
        exact2 = (s2->eo - s2->so) == strlen(s2->sym->name);
        if (exact1 && !exact2)
                return -1;
        if (!exact1 && exact2)
                return 1;

        /* As a fallback, sort symbols alphabetically */
        return strcmp(s1->sym->name, s2->sym->name);
}

struct symbol **sym_re_search(const char *pattern)
{
        struct symbol *sym, **sym_arr = NULL;
        struct sym_match *sym_match_arr = NULL;
        int i, cnt, size;
        regex_t re;
        regmatch_t match[1];

        cnt = size = 0;
        /* Skip if empty */
        if (strlen(pattern) == 0)
                return NULL;
        if (regcomp(&re, pattern, REG_EXTENDED|REG_ICASE))
                return NULL;

        for_all_symbols(sym) {
                if (sym->flags & SYMBOL_CONST || !sym->name)
                        continue;
                if (regexec(&re, sym->name, 1, match, 0))
                        continue;
                if (cnt >= size) {
                        void *tmp;
                        size += 16;
                        tmp = realloc(sym_match_arr, size * sizeof(struct sym_match));
                        if (!tmp)
                                goto sym_re_search_free;
                        sym_match_arr = tmp;
                }
                sym_calc_value(sym);
                /* As regexec returned 0, we know we have a match, so
                 * we can use match[0].rm_[se]o without further checks
                 */
                sym_match_arr[cnt].so = match[0].rm_so;
                sym_match_arr[cnt].eo = match[0].rm_eo;
                sym_match_arr[cnt++].sym = sym;
        }
        if (sym_match_arr) {
                qsort(sym_match_arr, cnt, sizeof(struct sym_match), sym_rel_comp);
                sym_arr = malloc((cnt+1) * sizeof(struct symbol *));
                if (!sym_arr)
                        goto sym_re_search_free;
                for (i = 0; i < cnt; i++)
                        sym_arr[i] = sym_match_arr[i].sym;
                sym_arr[cnt] = NULL;
        }
sym_re_search_free:
        /* sym_match_arr can be NULL if no match, but free(NULL) is OK */
        free(sym_match_arr);
        regfree(&re);

        return sym_arr;
}

/*
 * When we check for recursive dependencies we use a stack to save
 * current state so we can print out relevant info to user.
 * The entries are located on the call stack so no need to free memory.
 * Note insert() remove() must always match to properly clear the stack.
 */
static struct dep_stack {
        struct dep_stack *prev, *next;
        struct symbol *sym;
        struct property *prop;
        struct expr **expr;
} *check_top;

static void dep_stack_insert(struct dep_stack *stack, struct symbol *sym)
{
        memset(stack, 0, sizeof(*stack));
        if (check_top)
                check_top->next = stack;
        stack->prev = check_top;
        stack->sym = sym;
        check_top = stack;
}

static void dep_stack_remove(void)
{
        check_top = check_top->prev;
        if (check_top)
                check_top->next = NULL;
}

/*
 * Called when we have detected a recursive dependency.
 * check_top point to the top of the stact so we use
 * the ->prev pointer to locate the bottom of the stack.
 */
static void sym_check_print_recursive(struct symbol *last_sym)
{
        struct dep_stack *stack;
        struct symbol *sym, *next_sym;
        struct menu *choice;
        struct dep_stack cv_stack;
        enum prop_type type;

        choice = sym_get_choice_menu(last_sym);
        if (choice) {
                dep_stack_insert(&cv_stack, last_sym);
                last_sym = choice->sym;
        }

        for (stack = check_top; stack != NULL; stack = stack->prev)
                if (stack->sym == last_sym)
                        break;
        if (!stack) {
                fprintf(stderr, "unexpected recursive dependency error\n");
                return;
        }

        for (; stack; stack = stack->next) {
                sym = stack->sym;
                next_sym = stack->next ? stack->next->sym : last_sym;
                type = stack->prop ? stack->prop->type : P_UNKNOWN;

                if (stack->sym == last_sym)
                        fprintf(stderr, "error: recursive dependency detected!\n");

                if (sym_is_choice(next_sym)) {
                        choice = list_first_entry(&next_sym->menus, struct menu, link);

                        fprintf(stderr, "\tsymbol %s is part of choice block at %s:%d\n",
                                sym->name ? sym->name : "<choice>",
                                choice->filename, choice->lineno);
                } else if (stack->expr == &sym->dir_dep.expr) {
                        fprintf(stderr, "\tsymbol %s depends on %s\n",
                                sym->name ? sym->name : "<choice>",
                                next_sym->name);
                } else if (stack->expr == &sym->rev_dep.expr) {
                        fprintf(stderr, "\tsymbol %s is selected by %s\n",
                                sym->name, next_sym->name);
                } else if (stack->expr == &sym->implied.expr) {
                        fprintf(stderr, "\tsymbol %s is implied by %s\n",
                                sym->name, next_sym->name);
                } else if (stack->expr) {
                        fprintf(stderr, "\tsymbol %s %s value contains %s\n",
                                sym->name ? sym->name : "<choice>",
                                prop_get_type_name(type),
                                next_sym->name);
                } else {
                        fprintf(stderr, "\tsymbol %s %s is visible depending on %s\n",
                                sym->name ? sym->name : "<choice>",
                                prop_get_type_name(type),
                                next_sym->name);
                }
        }

        fprintf(stderr,
                "For a resolution refer to Documentation/kbuild/kconfig-language.rst\n"
                "subsection \"Kconfig recursive dependency limitations\"\n"
                "\n");

        if (check_top == &cv_stack)
                dep_stack_remove();
}

static struct symbol *sym_check_expr_deps(const struct expr *e)
{
        struct symbol *sym;

        if (!e)
                return NULL;
        switch (e->type) {
        case E_OR:
        case E_AND:
                sym = sym_check_expr_deps(e->left.expr);
                if (sym)
                        return sym;
                return sym_check_expr_deps(e->right.expr);
        case E_NOT:
                return sym_check_expr_deps(e->left.expr);
        case E_EQUAL:
        case E_GEQ:
        case E_GTH:
        case E_LEQ:
        case E_LTH:
        case E_UNEQUAL:
                sym = sym_check_deps(e->left.sym);
                if (sym)
                        return sym;
                return sym_check_deps(e->right.sym);
        case E_SYMBOL:
                return sym_check_deps(e->left.sym);
        default:
                break;
        }
        fprintf(stderr, "Oops! How to check %d?\n", e->type);
        return NULL;
}

/* return NULL when dependencies are OK */
static struct symbol *sym_check_sym_deps(struct symbol *sym)
{
        struct symbol *sym2;
        struct property *prop;
        struct dep_stack stack;

        dep_stack_insert(&stack, sym);

        stack.expr = &sym->dir_dep.expr;
        sym2 = sym_check_expr_deps(sym->dir_dep.expr);
        if (sym2)
                goto out;

        stack.expr = &sym->rev_dep.expr;
        sym2 = sym_check_expr_deps(sym->rev_dep.expr);
        if (sym2)
                goto out;

        stack.expr = &sym->implied.expr;
        sym2 = sym_check_expr_deps(sym->implied.expr);
        if (sym2)
                goto out;

        stack.expr = NULL;

        for (prop = sym->prop; prop; prop = prop->next) {
                if (prop->type == P_SELECT || prop->type == P_IMPLY)
                        continue;
                stack.prop = prop;
                sym2 = sym_check_expr_deps(prop->visible.expr);
                if (sym2)
                        break;
                if (prop->type != P_DEFAULT || sym_is_choice(sym))
                        continue;
                stack.expr = &prop->expr;
                sym2 = sym_check_expr_deps(prop->expr);
                if (sym2)
                        break;
                stack.expr = NULL;
        }

out:
        dep_stack_remove();

        return sym2;
}

static struct symbol *sym_check_choice_deps(struct symbol *choice)
{
        struct menu *choice_menu, *menu;
        struct symbol *sym2;
        struct dep_stack stack;

        dep_stack_insert(&stack, choice);

        choice_menu = list_first_entry(&choice->menus, struct menu, link);

        menu_for_each_sub_entry(menu, choice_menu) {
                if (menu->sym)
                        menu->sym->flags |= SYMBOL_CHECK | SYMBOL_CHECKED;
        }

        choice->flags |= (SYMBOL_CHECK | SYMBOL_CHECKED);
        sym2 = sym_check_sym_deps(choice);
        choice->flags &= ~SYMBOL_CHECK;
        if (sym2)
                goto out;

        menu_for_each_sub_entry(menu, choice_menu) {
                if (!menu->sym)
                        continue;
                sym2 = sym_check_sym_deps(menu->sym);
                if (sym2)
                        break;
        }
out:
        menu_for_each_sub_entry(menu, choice_menu)
                if (menu->sym)
                        menu->sym->flags &= ~SYMBOL_CHECK;

        if (sym2) {
                struct menu *choice_menu2;

                choice_menu2 = sym_get_choice_menu(sym2);
                if (choice_menu2 == choice_menu)
                        sym2 = choice;
        }

        dep_stack_remove();

        return sym2;
}

struct symbol *sym_check_deps(struct symbol *sym)
{
        struct menu *choice;
        struct symbol *sym2;

        if (sym->flags & SYMBOL_CHECK) {
                sym_check_print_recursive(sym);
                return sym;
        }
        if (sym->flags & SYMBOL_CHECKED)
                return NULL;

        choice = sym_get_choice_menu(sym);
        if (choice) {
                struct dep_stack stack;

                /* for choice groups start the check with main choice symbol */
                dep_stack_insert(&stack, sym);
                sym2 = sym_check_deps(choice->sym);
                dep_stack_remove();
        } else if (sym_is_choice(sym)) {
                sym2 = sym_check_choice_deps(sym);
        } else {
                sym->flags |= (SYMBOL_CHECK | SYMBOL_CHECKED);
                sym2 = sym_check_sym_deps(sym);
                sym->flags &= ~SYMBOL_CHECK;
        }

        return sym2;
}

struct symbol *prop_get_symbol(const struct property *prop)
{
        if (prop->expr && prop->expr->type == E_SYMBOL)
                return prop->expr->left.sym;
        return NULL;
}

const char *prop_get_type_name(enum prop_type type)
{
        switch (type) {
        case P_PROMPT:
                return "prompt";
        case P_COMMENT:
                return "comment";
        case P_MENU:
                return "menu";
        case P_DEFAULT:
                return "default";
        case P_SELECT:
                return "select";
        case P_IMPLY:
                return "imply";
        case P_RANGE:
                return "range";
        case P_UNKNOWN:
                break;
        }
        return "unknown";
}