flow: clear_buffer: revert part of commit that uses too much memory

[smatch.git] / pre-process.c

/*
 * Do C preprocessing, based on a token list gathered by
 * the tokenizer.
 *
 * This may not be the smartest preprocessor on the planet.
 *
 * Copyright (C) 2003 Transmeta Corp.
 *               2003-2004 Linus Torvalds
 *
 *  Licensed under the Open Software License version 1.1
 */
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stddef.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
#include <time.h>

#include "lib.h"
#include "allocate.h"
#include "parse.h"
#include "token.h"
#include "symbol.h"
#include "expression.h"
#include "scope.h"

static int false_nesting = 0;

#define INCLUDEPATHS 300
const char *includepath[INCLUDEPATHS+1] = {
        "",
        "/usr/include",
        "/usr/local/include",
        NULL
};

static const char **quote_includepath = includepath;
static const char **angle_includepath = includepath + 1;
static const char **isys_includepath   = includepath + 1;
static const char **sys_includepath   = includepath + 1;
static const char **dirafter_includepath = includepath + 3;

#define dirty_stream(stream)                            \
        do {                                            \
                if (!stream->dirty) {                   \
                        stream->dirty = 1;              \
                        if (!stream->ifndef)            \
                                stream->protect = NULL; \
                }                                       \
        } while(0)

#define end_group(stream)                                       \
        do {                                                    \
                if (stream->ifndef == stream->top_if) {         \
                        stream->ifndef = NULL;                  \
                        if (!stream->dirty)                     \
                                stream->protect = NULL;         \
                        else if (stream->protect)               \
                                stream->dirty = 0;              \
                }                                               \
        } while(0)

#define nesting_error(stream)           \
        do {                            \
                stream->dirty = 1;      \
                stream->ifndef = NULL;  \
                stream->protect = NULL; \
        } while(0)

static struct token *alloc_token(struct position *pos)
{
        struct token *token = __alloc_token(0);

        token->pos.stream = pos->stream;
        token->pos.line = pos->line;
        token->pos.pos = pos->pos;
        token->pos.whitespace = 1;
        return token;
}

/* Expand symbol 'sym' at '*list' */
static int expand(struct token **, struct symbol *);

static void replace_with_string(struct token *token, const char *str)
{
        int size = strlen(str) + 1;
        struct string *s = __alloc_string(size);

        s->length = size;
        memcpy(s->data, str, size);
        token_type(token) = TOKEN_STRING;
        token->string = s;
}

static void replace_with_integer(struct token *token, unsigned int val)
{
        char *buf = __alloc_bytes(11);
        sprintf(buf, "%u", val);
        token_type(token) = TOKEN_NUMBER;
        token->number = buf;
}

static struct symbol *lookup_macro(struct ident *ident)
{
        struct symbol *sym = lookup_symbol(ident, NS_MACRO | NS_UNDEF);
        if (sym && sym->namespace != NS_MACRO)
                sym = NULL;
        return sym;
}

static int token_defined(struct token *token)
{
        if (token_type(token) == TOKEN_IDENT) {
                struct symbol *sym = lookup_macro(token->ident);
                if (sym) {
                        sym->used_in = file_scope;
                        return 1;
                }
                return 0;
        }

        sparse_error(token->pos, "expected preprocessor identifier");
        return 0;
}

static void replace_with_defined(struct token *token)
{
        static const char *string[] = { "0", "1" };
        int defined = token_defined(token);

        token_type(token) = TOKEN_NUMBER;
        token->number = string[defined];
}

static int expand_one_symbol(struct token **list)
{
        struct token *token = *list;
        struct symbol *sym;
        static char buffer[12]; /* __DATE__: 3 + ' ' + 2 + ' ' + 4 + '\0' */
        static time_t t = 0;

        if (token->pos.noexpand)
                return 1;

        sym = lookup_macro(token->ident);
        if (sym) {
                store_macro_pos(token);
                sym->used_in = file_scope;
                return expand(list, sym);
        }
        if (token->ident == &__LINE___ident) {
                replace_with_integer(token, token->pos.line);
        } else if (token->ident == &__FILE___ident) {
                replace_with_string(token, stream_name(token->pos.stream));
        } else if (token->ident == &__DATE___ident) {
                if (!t)
                        time(&t);
                strftime(buffer, 12, "%b %e %Y", localtime(&t));
                replace_with_string(token, buffer);
        } else if (token->ident == &__TIME___ident) {
                if (!t)
                        time(&t);
                strftime(buffer, 9, "%T", localtime(&t));
                replace_with_string(token, buffer);
        }
        return 1;
}

static inline struct token *scan_next(struct token **where)
{
        struct token *token = *where;
        if (token_type(token) != TOKEN_UNTAINT)
                return token;
        do {
                token->ident->tainted = 0;
                token = token->next;
        } while (token_type(token) == TOKEN_UNTAINT);
        *where = token;
        return token;
}

static void expand_list(struct token **list)
{
        struct token *next;
        while (!eof_token(next = scan_next(list))) {
                if (token_type(next) != TOKEN_IDENT || expand_one_symbol(list))
                        list = &next->next;
        }
}

static void preprocessor_line(struct stream *stream, struct token **line);

static struct token *collect_arg(struct token *prev, int vararg, struct position *pos)
{
        struct stream *stream = input_streams + prev->pos.stream;
        struct token **p = &prev->next;
        struct token *next;
        int nesting = 0;

        while (!eof_token(next = scan_next(p))) {
                if (next->pos.newline && match_op(next, '#')) {
                        if (!next->pos.noexpand) {
                                sparse_error(next->pos,
                                             "directive in argument list");
                                preprocessor_line(stream, p);
                                __free_token(next);     /* Free the '#' token */
                                continue;
                        }
                }
                switch (token_type(next)) {
                case TOKEN_STREAMEND:
                case TOKEN_STREAMBEGIN:
                        *p = &eof_token_entry;
                        return next;
                }
                if (false_nesting) {
                        *p = next->next;
                        __free_token(next);
                        continue;
                }
                if (match_op(next, '(')) {
                        nesting++;
                } else if (match_op(next, ')')) {
                        if (!nesting--)
                                break;
                } else if (match_op(next, ',') && !nesting && !vararg) {
                        break;
                }
                next->pos.stream = pos->stream;
                next->pos.line = pos->line;
                next->pos.pos = pos->pos;
                p = &next->next;
        }
        *p = &eof_token_entry;
        return next;
}

/*
 * We store arglist as <counter> [arg1] <number of uses for arg1> ... eof
 */

struct arg {
        struct token *arg;
        struct token *expanded;
        struct token *str;
        int n_normal;
        int n_quoted;
        int n_str;
};

static int collect_arguments(struct token *start, struct token *arglist, struct arg *args, struct token *what)
{
        int wanted = arglist->count.normal;
        struct token *next = NULL;
        int count = 0;

        arglist = arglist->next;        /* skip counter */

        if (!wanted) {
                next = collect_arg(start, 0, &what->pos);
                if (eof_token(next))
                        goto Eclosing;
                if (!eof_token(start->next) || !match_op(next, ')')) {
                        count++;
                        goto Emany;
                }
        } else {
                for (count = 0; count < wanted; count++) {
                        struct argcount *p = &arglist->next->count;
                        next = collect_arg(start, p->vararg, &what->pos);
                        arglist = arglist->next->next;
                        if (eof_token(next))
                                goto Eclosing;
                        args[count].arg = start->next;
                        args[count].n_normal = p->normal;
                        args[count].n_quoted = p->quoted;
                        args[count].n_str = p->str;
                        if (match_op(next, ')')) {
                                count++;
                                break;
                        }
                        start = next;
                }
                if (count == wanted && !match_op(next, ')'))
                        goto Emany;
                if (count == wanted - 1) {
                        struct argcount *p = &arglist->next->count;
                        if (!p->vararg)
                                goto Efew;
                        args[count].arg = NULL;
                        args[count].n_normal = p->normal;
                        args[count].n_quoted = p->quoted;
                        args[count].n_str = p->str;
                }
                if (count < wanted - 1)
                        goto Efew;
        }
        what->next = next->next;
        return 1;

Efew:
        sparse_error(what->pos, "macro \"%s\" requires %d arguments, but only %d given",
                show_token(what), wanted, count);
        goto out;
Emany:
        while (match_op(next, ',')) {
                next = collect_arg(next, 0, &what->pos);
                count++;
        }
        if (eof_token(next))
                goto Eclosing;
        sparse_error(what->pos, "macro \"%s\" passed %d arguments, but takes just %d",
                show_token(what), count, wanted);
        goto out;
Eclosing:
        sparse_error(what->pos, "unterminated argument list invoking macro \"%s\"",
                show_token(what));
out:
        what->next = next->next;
        return 0;
}

static struct token *dup_list(struct token *list)
{
        struct token *res = NULL;
        struct token **p = &res;

        while (!eof_token(list)) {
                struct token *newtok = __alloc_token(0);
                *newtok = *list;
                *p = newtok;
                p = &newtok->next;
                list = list->next;
        }
        return res;
}

static const char *quote_token_sequence(struct token *token)
{
        static char buffer[1024];
        char *ptr = buffer;
        int whitespace = 0;

        while (!eof_token(token)) {
                const char *val = quote_token(token);
                int len = strlen(val);

                if (ptr + whitespace + len >= buffer + sizeof(buffer)) {
                        sparse_error(token->pos, "too long token expansion");
                        break;
                }

                if (whitespace)
                        *ptr++ = ' ';
                memcpy(ptr, val, len);
                ptr += len;
                token = token->next;
                whitespace = token->pos.whitespace;
        }
        *ptr = 0;
        return buffer;
}

static struct token *stringify(struct token *arg)
{
        const char *s = quote_token_sequence(arg);
        int size = strlen(s)+1;
        struct token *token = __alloc_token(0);
        struct string *string = __alloc_string(size);

        memcpy(string->data, s, size);
        string->length = size;
        token->pos = arg->pos;
        token_type(token) = TOKEN_STRING;
        token->string = string;
        token->next = &eof_token_entry;
        return token;
}

static void expand_arguments(int count, struct arg *args)
{
        int i;
        for (i = 0; i < count; i++) {
                struct token *arg = args[i].arg;
                if (!arg)
                        arg = &eof_token_entry;
                if (args[i].n_str)
                        args[i].str = stringify(arg);
                if (args[i].n_normal) {
                        if (!args[i].n_quoted) {
                                args[i].expanded = arg;
                                args[i].arg = NULL;
                        } else if (eof_token(arg)) {
                                args[i].expanded = arg;
                        } else {
                                args[i].expanded = dup_list(arg);
                        }
                        expand_list(&args[i].expanded);
                }
        }
}

/*
 * Possibly valid combinations:
 *  - ident + ident -> ident
 *  - ident + number -> ident unless number contains '.', '+' or '-'.
 *  - 'L' + char constant -> wide char constant
 *  - 'L' + string literal -> wide string literal
 *  - number + number -> number
 *  - number + ident -> number
 *  - number + '.' -> number
 *  - number + '+' or '-' -> number, if number used to end on [eEpP].
 *  - '.' + number -> number, if number used to start with a digit.
 *  - special + special -> either special or an error.
 */
static enum token_type combine(struct token *left, struct token *right, char *p)
{
        int len;
        enum token_type t1 = token_type(left), t2 = token_type(right);

        if (t1 != TOKEN_IDENT && t1 != TOKEN_NUMBER && t1 != TOKEN_SPECIAL)
                return TOKEN_ERROR;

        if (t1 == TOKEN_IDENT && left->ident == &L_ident) {
                if (t2 >= TOKEN_CHAR && t2 < TOKEN_WIDE_CHAR)
                        return t2 + TOKEN_WIDE_CHAR - TOKEN_CHAR;
                if (t2 == TOKEN_STRING)
                        return TOKEN_WIDE_STRING;
        }

        if (t2 != TOKEN_IDENT && t2 != TOKEN_NUMBER && t2 != TOKEN_SPECIAL)
                return TOKEN_ERROR;

        strcpy(p, show_token(left));
        strcat(p, show_token(right));
        len = strlen(p);

        if (len >= 256)
                return TOKEN_ERROR;

        if (t1 == TOKEN_IDENT) {
                if (t2 == TOKEN_SPECIAL)
                        return TOKEN_ERROR;
                if (t2 == TOKEN_NUMBER && strpbrk(p, "+-."))
                        return TOKEN_ERROR;
                return TOKEN_IDENT;
        }

        if (t1 == TOKEN_NUMBER) {
                if (t2 == TOKEN_SPECIAL) {
                        switch (right->special) {
                        case '.':
                                break;
                        case '+': case '-':
                                if (strchr("eEpP", p[len - 2]))
                                        break;
                        default:
                                return TOKEN_ERROR;
                        }
                }
                return TOKEN_NUMBER;
        }

        if (p[0] == '.' && isdigit((unsigned char)p[1]))
                return TOKEN_NUMBER;

        return TOKEN_SPECIAL;
}

static int merge(struct token *left, struct token *right)
{
        static char buffer[512];
        enum token_type res = combine(left, right, buffer);
        int n;

        switch (res) {
        case TOKEN_IDENT:
                left->ident = built_in_ident(buffer);
                left->pos.noexpand = 0;
                return 1;

        case TOKEN_NUMBER: {
                char *number = __alloc_bytes(strlen(buffer) + 1);
                memcpy(number, buffer, strlen(buffer) + 1);
                token_type(left) = TOKEN_NUMBER;        /* could be . + num */
                left->number = number;
                return 1;
        }

        case TOKEN_SPECIAL:
                if (buffer[2] && buffer[3])
                        break;
                for (n = SPECIAL_BASE; n < SPECIAL_ARG_SEPARATOR; n++) {
                        if (!memcmp(buffer, combinations[n-SPECIAL_BASE], 3)) {
                                left->special = n;
                                return 1;
                        }
                }
                break;

        case TOKEN_WIDE_CHAR:
        case TOKEN_WIDE_STRING:
                token_type(left) = res;
                left->pos.noexpand = 0;
                left->string = right->string;
                return 1;

        case TOKEN_WIDE_CHAR_EMBEDDED_0 ... TOKEN_WIDE_CHAR_EMBEDDED_3:
                token_type(left) = res;
                left->pos.noexpand = 0;
                memcpy(left->embedded, right->embedded, 4);
                return 1;

        default:
                ;
        }
        sparse_error(left->pos, "'##' failed: concatenation is not a valid token");
        return 0;
}

static struct token *dup_token(struct token *token, struct position *streampos)
{
        struct token *alloc = alloc_token(streampos);
        token_type(alloc) = token_type(token);
        alloc->pos.newline = token->pos.newline;
        alloc->pos.whitespace = token->pos.whitespace;
        alloc->number = token->number;
        alloc->pos.noexpand = token->pos.noexpand;
        return alloc;   
}

static struct token **copy(struct token **where, struct token *list, int *count)
{
        int need_copy = --*count;
        while (!eof_token(list)) {
                struct token *token;
                if (need_copy)
                        token = dup_token(list, &list->pos);
                else
                        token = list;
                if (token_type(token) == TOKEN_IDENT && token->ident->tainted)
                        token->pos.noexpand = 1;
                *where = token;
                where = &token->next;
                list = list->next;
        }
        *where = &eof_token_entry;
        return where;
}

static int handle_kludge(struct token **p, struct arg *args)
{
        struct token *t = (*p)->next->next;
        while (1) {
                struct arg *v = &args[t->argnum];
                if (token_type(t->next) != TOKEN_CONCAT) {
                        if (v->arg) {
                                /* ignore the first ## */
                                *p = (*p)->next;
                                return 0;
                        }
                        /* skip the entire thing */
                        *p = t;
                        return 1;
                }
                if (v->arg && !eof_token(v->arg))
                        return 0; /* no magic */
                t = t->next->next;
        }
}

static struct token **substitute(struct token **list, struct token *body, struct arg *args)
{
        struct position *base_pos = &(*list)->pos;
        int *count;
        enum {Normal, Placeholder, Concat} state = Normal;

        for (; !eof_token(body); body = body->next) {
                struct token *added, *arg;
                struct token **tail;
                struct token *t;

                switch (token_type(body)) {
                case TOKEN_GNU_KLUDGE:
                        /*
                         * GNU kludge: if we had <comma>##<vararg>, behaviour
                         * depends on whether we had enough arguments to have
                         * a vararg.  If we did, ## is just ignored.  Otherwise
                         * both , and ## are ignored.  Worse, there can be
                         * an arbitrary number of ##<arg> in between; if all of
                         * those are empty, we act as if they hadn't been there,
                         * otherwise we act as if the kludge didn't exist.
                         */
                        t = body;
                        if (handle_kludge(&body, args)) {
                                if (state == Concat)
                                        state = Normal;
                                else
                                        state = Placeholder;
                                continue;
                        }
                        added = dup_token(t, base_pos);
                        token_type(added) = TOKEN_SPECIAL;
                        tail = &added->next;
                        break;

                case TOKEN_STR_ARGUMENT:
                        arg = args[body->argnum].str;
                        count = &args[body->argnum].n_str;
                        goto copy_arg;

                case TOKEN_QUOTED_ARGUMENT:
                        arg = args[body->argnum].arg;
                        count = &args[body->argnum].n_quoted;
                        if (!arg || eof_token(arg)) {
                                if (state == Concat)
                                        state = Normal;
                                else
                                        state = Placeholder;
                                continue;
                        }
                        goto copy_arg;

                case TOKEN_MACRO_ARGUMENT:
                        arg = args[body->argnum].expanded;
                        count = &args[body->argnum].n_normal;
                        if (eof_token(arg)) {
                                state = Normal;
                                continue;
                        }
                copy_arg:
                        tail = copy(&added, arg, count);
                        added->pos.newline = body->pos.newline;
                        added->pos.whitespace = body->pos.whitespace;
                        break;

                case TOKEN_CONCAT:
                        if (state == Placeholder)
                                state = Normal;
                        else
                                state = Concat;
                        continue;

                case TOKEN_IDENT:
                        added = dup_token(body, base_pos);
                        if (added->ident->tainted)
                                added->pos.noexpand = 1;
                        tail = &added->next;
                        break;

                default:
                        added = dup_token(body, base_pos);
                        tail = &added->next;
                        break;
                }

                /*
                 * if we got to doing real concatenation, we already have
                 * added something into the list, so containing_token() is OK.
                 */
                if (state == Concat && merge(containing_token(list), added)) {
                        *list = added->next;
                        if (tail != &added->next)
                                list = tail;
                } else {
                        *list = added;
                        list = tail;
                }
                state = Normal;
        }
        *list = &eof_token_entry;
        return list;
}

static int expand(struct token **list, struct symbol *sym)
{
        struct token *last;
        struct token *token = *list;
        struct ident *expanding = token->ident;
        struct token **tail;
        int nargs = sym->arglist ? sym->arglist->count.normal : 0;
        struct arg args[nargs];

        if (expanding->tainted) {
                token->pos.noexpand = 1;
                return 1;
        }

        if (sym->arglist) {
                if (!match_op(scan_next(&token->next), '('))
                        return 1;
                if (!collect_arguments(token->next, sym->arglist, args, token))
                        return 1;
                expand_arguments(nargs, args);
        }

        expanding->tainted = 1;

        last = token->next;
        tail = substitute(list, sym->expansion, args);
        /*
         * Note that it won't be eof - at least TOKEN_UNTAINT will be there.
         * We still can lose the newline flag if the sucker expands to nothing,
         * but the price of dealing with that is probably too high (we'd need
         * to collect the flags during scan_next())
         */
        (*list)->pos.newline = token->pos.newline;
        (*list)->pos.whitespace = token->pos.whitespace;
        *tail = last;

        return 0;
}

static const char *token_name_sequence(struct token *token, int endop, struct token *start)
{
        static char buffer[256];
        char *ptr = buffer;

        while (!eof_token(token) && !match_op(token, endop)) {
                int len;
                const char *val = token->string->data;
                if (token_type(token) != TOKEN_STRING)
                        val = show_token(token);
                len = strlen(val);
                memcpy(ptr, val, len);
                ptr += len;
                token = token->next;
        }
        *ptr = 0;
        if (endop && !match_op(token, endop))
                sparse_error(start->pos, "expected '>' at end of filename");
        return buffer;
}

static int already_tokenized(const char *path)
{
        int stream, next;

        for (stream = *hash_stream(path); stream >= 0 ; stream = next) {
                struct stream *s = input_streams + stream;

                next = s->next_stream;
                if (s->constant != CONSTANT_FILE_YES)
                        continue;
                if (strcmp(path, s->name))
                        continue;
                if (s->protect && !lookup_macro(s->protect))
                        continue;
                return 1;
        }
        return 0;
}

/* Handle include of header files.
 * The relevant options are made compatible with gcc. The only options that
 * are not supported is -withprefix and friends.
 *
 * Three set of include paths are known:
 * quote_includepath:   Path to search when using #include "file.h"
 * angle_includepath:   Paths to search when using #include <file.h>
 * isys_includepath:    Paths specified with -isystem, come before the
 *                      built-in system include paths. Gcc would suppress
 *                      warnings from system headers. Here we separate
 *                      them from the angle_ ones to keep search ordering.
 *
 * sys_includepath:     Built-in include paths.
 * dirafter_includepath Paths added with -dirafter.
 *
 * The above is implemented as one array with pointers
 *                         +--------------+
 * quote_includepath --->  |              |
 *                         +--------------+
 *                         |              |
 *                         +--------------+
 * angle_includepath --->  |              |
 *                         +--------------+
 * isys_includepath  --->  |              |
 *                         +--------------+
 * sys_includepath   --->  |              |
 *                         +--------------+
 * dirafter_includepath -> |              |
 *                         +--------------+
 *
 * -I dir insert dir just before isys_includepath and move the rest
 * -I- makes all dirs specified with -I before to quote dirs only and
 *   angle_includepath is set equal to isys_includepath.
 * -nostdinc removes all sys dirs by storing NULL in entry pointed
 *   to by * sys_includepath. Note that this will reset all dirs built-in
 *   and added before -nostdinc by -isystem and -idirafter.
 * -isystem dir adds dir where isys_includepath points adding this dir as
 *   first systemdir
 * -idirafter dir adds dir to the end of the list
 */

static void set_stream_include_path(struct stream *stream)
{
        const char *path = stream->path;
        if (!path) {
                const char *p = strrchr(stream->name, '/');
                path = "";
                if (p) {
                        int len = p - stream->name + 1;
                        char *m = malloc(len+1);
                        /* This includes the final "/" */
                        memcpy(m, stream->name, len);
                        m[len] = 0;
                        path = m;
                }
                stream->path = path;
        }
        includepath[0] = path;
}

static int try_include(const char *path, const char *filename, int flen, struct token **where, const char **next_path)
{
        int fd;
        int plen = strlen(path);
        static char fullname[PATH_MAX];

        memcpy(fullname, path, plen);
        if (plen && path[plen-1] != '/') {
                fullname[plen] = '/';
                plen++;
        }
        memcpy(fullname+plen, filename, flen);
        if (already_tokenized(fullname))
                return 1;
        fd = open(fullname, O_RDONLY);
        if (fd >= 0) {
                char * streamname = __alloc_bytes(plen + flen);
                memcpy(streamname, fullname, plen + flen);
                *where = tokenize(streamname, fd, *where, next_path);
                close(fd);
                return 1;
        }
        return 0;
}

static int do_include_path(const char **pptr, struct token **list, struct token *token, const char *filename, int flen)
{
        const char *path;

        while ((path = *pptr++) != NULL) {
                if (!try_include(path, filename, flen, list, pptr))
                        continue;
                return 1;
        }
        return 0;
}

static int free_preprocessor_line(struct token *token)
{
        while (token_type(token) != TOKEN_EOF) {
                struct token *free = token;
                token = token->next;
                __free_token(free);
        };
        return 1;
}

static int handle_include_path(struct stream *stream, struct token **list, struct token *token, int how)
{
        const char *filename;
        struct token *next;
        const char **path;
        int expect;
        int flen;

        next = token->next;
        expect = '>';
        if (!match_op(next, '<')) {
                expand_list(&token->next);
                expect = 0;
                next = token;
                if (match_op(token->next, '<')) {
                        next = token->next;
                        expect = '>';
                }
        }

        token = next->next;
        filename = token_name_sequence(token, expect, token);
        flen = strlen(filename) + 1;

        /* Absolute path? */
        if (filename[0] == '/') {
                if (try_include("", filename, flen, list, includepath))
                        return 0;
                goto out;
        }

        switch (how) {
        case 1:
                path = stream->next_path;
                break;
        case 2:
                includepath[0] = "";
                path = includepath;
                break;
        default:
                /* Dir of input file is first dir to search for quoted includes */
                set_stream_include_path(stream);
                path = expect ? angle_includepath : quote_includepath;
                break;
        }
        /* Check the standard include paths.. */
        if (do_include_path(path, list, token, filename, flen))
                return 0;
out:
        error_die(token->pos, "unable to open '%s'", filename);
}

static int handle_include(struct stream *stream, struct token **list, struct token *token)
{
        return handle_include_path(stream, list, token, 0);
}

static int handle_include_next(struct stream *stream, struct token **list, struct token *token)
{
        return handle_include_path(stream, list, token, 1);
}

static int handle_argv_include(struct stream *stream, struct token **list, struct token *token)
{
        return handle_include_path(stream, list, token, 2);
}

static int token_different(struct token *t1, struct token *t2)
{
        int different;

        if (token_type(t1) != token_type(t2))
                return 1;

        switch (token_type(t1)) {
        case TOKEN_IDENT:
                different = t1->ident != t2->ident;
                break;
        case TOKEN_ARG_COUNT:
        case TOKEN_UNTAINT:
        case TOKEN_CONCAT:
        case TOKEN_GNU_KLUDGE:
                different = 0;
                break;
        case TOKEN_NUMBER:
                different = strcmp(t1->number, t2->number);
                break;
        case TOKEN_SPECIAL:
                different = t1->special != t2->special;
                break;
        case TOKEN_MACRO_ARGUMENT:
        case TOKEN_QUOTED_ARGUMENT:
        case TOKEN_STR_ARGUMENT:
                different = t1->argnum != t2->argnum;
                break;
        case TOKEN_CHAR_EMBEDDED_0 ... TOKEN_CHAR_EMBEDDED_3:
        case TOKEN_WIDE_CHAR_EMBEDDED_0 ... TOKEN_WIDE_CHAR_EMBEDDED_3:
                different = memcmp(t1->embedded, t2->embedded, 4);
                break;
        case TOKEN_CHAR:
        case TOKEN_WIDE_CHAR:
        case TOKEN_STRING:
        case TOKEN_WIDE_STRING: {
                struct string *s1, *s2;

                s1 = t1->string;
                s2 = t2->string;
                different = 1;
                if (s1->length != s2->length)
                        break;
                different = memcmp(s1->data, s2->data, s1->length);
                break;
        }
        default:
                different = 1;
                break;
        }
        return different;
}

static int token_list_different(struct token *list1, struct token *list2)
{
        for (;;) {
                if (list1 == list2)
                        return 0;
                if (!list1 || !list2)
                        return 1;
                if (token_different(list1, list2))
                        return 1;
                list1 = list1->next;
                list2 = list2->next;
        }
}

static inline void set_arg_count(struct token *token)
{
        token_type(token) = TOKEN_ARG_COUNT;
        token->count.normal = token->count.quoted =
        token->count.str = token->count.vararg = 0;
}

static struct token *parse_arguments(struct token *list)
{
        struct token *arg = list->next, *next = list;
        struct argcount *count = &list->count;

        set_arg_count(list);

        if (match_op(arg, ')')) {
                next = arg->next;
                list->next = &eof_token_entry;
                return next;
        }

        while (token_type(arg) == TOKEN_IDENT) {
                if (arg->ident == &__VA_ARGS___ident)
                        goto Eva_args;
                if (!++count->normal)
                        goto Eargs;
                next = arg->next;

                if (match_op(next, ',')) {
                        set_arg_count(next);
                        arg = next->next;
                        continue;
                }

                if (match_op(next, ')')) {
                        set_arg_count(next);
                        next = next->next;
                        arg->next->next = &eof_token_entry;
                        return next;
                }

                /* normal cases are finished here */

                if (match_op(next, SPECIAL_ELLIPSIS)) {
                        if (match_op(next->next, ')')) {
                                set_arg_count(next);
                                next->count.vararg = 1;
                                next = next->next;
                                arg->next->next = &eof_token_entry;
                                return next->next;
                        }

                        arg = next;
                        goto Enotclosed;
                }

                if (eof_token(next)) {
                        goto Enotclosed;
                } else {
                        arg = next;
                        goto Ebadstuff;
                }
        }

        if (match_op(arg, SPECIAL_ELLIPSIS)) {
                next = arg->next;
                token_type(arg) = TOKEN_IDENT;
                arg->ident = &__VA_ARGS___ident;
                if (!match_op(next, ')'))
                        goto Enotclosed;
                if (!++count->normal)
                        goto Eargs;
                set_arg_count(next);
                next->count.vararg = 1;
                next = next->next;
                arg->next->next = &eof_token_entry;
                return next;
        }

        if (eof_token(arg)) {
                arg = next;
                goto Enotclosed;
        }
        if (match_op(arg, ','))
                goto Emissing;
        else
                goto Ebadstuff;


Emissing:
        sparse_error(arg->pos, "parameter name missing");
        return NULL;
Ebadstuff:
        sparse_error(arg->pos, "\"%s\" may not appear in macro parameter list",
                show_token(arg));
        return NULL;
Enotclosed:
        sparse_error(arg->pos, "missing ')' in macro parameter list");
        return NULL;
Eva_args:
        sparse_error(arg->pos, "__VA_ARGS__ can only appear in the expansion of a C99 variadic macro");
        return NULL;
Eargs:
        sparse_error(arg->pos, "too many arguments in macro definition");
        return NULL;
}

static int try_arg(struct token *token, enum token_type type, struct token *arglist)
{
        struct ident *ident = token->ident;
        int nr;

        if (!arglist || token_type(token) != TOKEN_IDENT)
                return 0;

        arglist = arglist->next;

        for (nr = 0; !eof_token(arglist); nr++, arglist = arglist->next->next) {
                if (arglist->ident == ident) {
                        struct argcount *count = &arglist->next->count;
                        int n;

                        token->argnum = nr;
                        token_type(token) = type;
                        switch (type) {
                        case TOKEN_MACRO_ARGUMENT:
                                n = ++count->normal;
                                break;
                        case TOKEN_QUOTED_ARGUMENT:
                                n = ++count->quoted;
                                break;
                        default:
                                n = ++count->str;
                        }
                        if (n)
                                return count->vararg ? 2 : 1;
                        /*
                         * XXX - need saner handling of that
                         * (>= 1024 instances of argument)
                         */
                        token_type(token) = TOKEN_ERROR;
                        return -1;
                }
        }
        return 0;
}

static struct token *handle_hash(struct token **p, struct token *arglist)
{
        struct token *token = *p;
        if (arglist) {
                struct token *next = token->next;
                if (!try_arg(next, TOKEN_STR_ARGUMENT, arglist))
                        goto Equote;
                next->pos.whitespace = token->pos.whitespace;
                __free_token(token);
                token = *p = next;
        } else {
                token->pos.noexpand = 1;
        }
        return token;

Equote:
        sparse_error(token->pos, "'#' is not followed by a macro parameter");
        return NULL;
}

/* token->next is ## */
static struct token *handle_hashhash(struct token *token, struct token *arglist)
{
        struct token *last = token;
        struct token *concat;
        int state = match_op(token, ',');
        
        try_arg(token, TOKEN_QUOTED_ARGUMENT, arglist);

        while (1) {
                struct token *t;
                int is_arg;

                /* eat duplicate ## */
                concat = token->next;
                while (match_op(t = concat->next, SPECIAL_HASHHASH)) {
                        token->next = t;
                        __free_token(concat);
                        concat = t;
                }
                token_type(concat) = TOKEN_CONCAT;

                if (eof_token(t))
                        goto Econcat;

                if (match_op(t, '#')) {
                        t = handle_hash(&concat->next, arglist);
                        if (!t)
                                return NULL;
                }

                is_arg = try_arg(t, TOKEN_QUOTED_ARGUMENT, arglist);

                if (state == 1 && is_arg) {
                        state = is_arg;
                } else {
                        last = t;
                        state = match_op(t, ',');
                }

                token = t;
                if (!match_op(token->next, SPECIAL_HASHHASH))
                        break;
        }
        /* handle GNU ,##__VA_ARGS__ kludge, in all its weirdness */
        if (state == 2)
                token_type(last) = TOKEN_GNU_KLUDGE;
        return token;

Econcat:
        sparse_error(concat->pos, "'##' cannot appear at the ends of macro expansion");
        return NULL;
}

static struct token *parse_expansion(struct token *expansion, struct token *arglist, struct ident *name)
{
        struct token *token = expansion;
        struct token **p;

        if (match_op(token, SPECIAL_HASHHASH))
                goto Econcat;

        for (p = &expansion; !eof_token(token); p = &token->next, token = *p) {
                if (match_op(token, '#')) {
                        token = handle_hash(p, arglist);
                        if (!token)
                                return NULL;
                }
                if (match_op(token->next, SPECIAL_HASHHASH)) {
                        token = handle_hashhash(token, arglist);
                        if (!token)
                                return NULL;
                } else {
                        try_arg(token, TOKEN_MACRO_ARGUMENT, arglist);
                }
                if (token_type(token) == TOKEN_ERROR)
                        goto Earg;
        }
        token = alloc_token(&expansion->pos);
        token_type(token) = TOKEN_UNTAINT;
        token->ident = name;
        token->next = *p;
        *p = token;
        return expansion;

Econcat:
        sparse_error(token->pos, "'##' cannot appear at the ends of macro expansion");
        return NULL;
Earg:
        sparse_error(token->pos, "too many instances of argument in body");
        return NULL;
}

static int do_handle_define(struct stream *stream, struct token **line, struct token *token, int attr)
{
        struct token *arglist, *expansion;
        struct token *left = token->next;
        struct symbol *sym;
        struct ident *name;
        int ret;

        if (token_type(left) != TOKEN_IDENT) {
                sparse_error(token->pos, "expected identifier to 'define'");
                return 1;
        }

        name = left->ident;

        arglist = NULL;
        expansion = left->next;
        if (!expansion->pos.whitespace) {
                if (match_op(expansion, '(')) {
                        arglist = expansion;
                        expansion = parse_arguments(expansion);
                        if (!expansion)
                                return 1;
                } else if (!eof_token(expansion)) {
                        warning(expansion->pos,
                                "no whitespace before object-like macro body");
                }
        }

        expansion = parse_expansion(expansion, arglist, name);
        if (!expansion)
                return 1;

        ret = 1;
        sym = lookup_symbol(name, NS_MACRO | NS_UNDEF);
        if (sym) {
                int clean;

                if (attr < sym->attr)
                        goto out;

                clean = (attr == sym->attr && sym->namespace == NS_MACRO);

                if (token_list_different(sym->expansion, expansion) ||
                    token_list_different(sym->arglist, arglist)) {
                        ret = 0;
                        if ((clean && attr == SYM_ATTR_NORMAL)
                                        || sym->used_in == file_scope) {
                                warning(left->pos, "preprocessor token %.*s redefined",
                                                name->len, name->name);
                                info(sym->pos, "this was the original definition");
                        }
                } else if (clean)
                        goto out;
        }

        if (!sym || sym->scope != file_scope) {
                sym = alloc_symbol(left->pos, SYM_NODE);
                bind_symbol(sym, name, NS_MACRO);
                ret = 0;
        }

        if (!ret) {
                sym->expansion = expansion;
                sym->arglist = arglist;
                __free_token(token);    /* Free the "define" token, but not the rest of the line */
        }

        sym->namespace = NS_MACRO;
        sym->used_in = NULL;
        sym->attr = attr;
out:
        return ret;
}

static int handle_define(struct stream *stream, struct token **line, struct token *token)
{
        return do_handle_define(stream, line, token, SYM_ATTR_NORMAL);
}

static int handle_weak_define(struct stream *stream, struct token **line, struct token *token)
{
        return do_handle_define(stream, line, token, SYM_ATTR_WEAK);
}

static int handle_strong_define(struct stream *stream, struct token **line, struct token *token)
{
        return do_handle_define(stream, line, token, SYM_ATTR_STRONG);
}

static int do_handle_undef(struct stream *stream, struct token **line, struct token *token, int attr)
{
        struct token *left = token->next;
        struct symbol *sym;

        if (token_type(left) != TOKEN_IDENT) {
                sparse_error(token->pos, "expected identifier to 'undef'");
                return 1;
        }

        sym = lookup_symbol(left->ident, NS_MACRO | NS_UNDEF);
        if (sym) {
                if (attr < sym->attr)
                        return 1;
                if (attr == sym->attr && sym->namespace == NS_UNDEF)
                        return 1;
        } else if (attr <= SYM_ATTR_NORMAL)
                return 1;

        if (!sym || sym->scope != file_scope) {
                sym = alloc_symbol(left->pos, SYM_NODE);
                bind_symbol(sym, left->ident, NS_MACRO);
        }

        sym->namespace = NS_UNDEF;
        sym->used_in = NULL;
        sym->attr = attr;

        return 1;
}

static int handle_undef(struct stream *stream, struct token **line, struct token *token)
{
        return do_handle_undef(stream, line, token, SYM_ATTR_NORMAL);
}

static int handle_strong_undef(struct stream *stream, struct token **line, struct token *token)
{
        return do_handle_undef(stream, line, token, SYM_ATTR_STRONG);
}

static int preprocessor_if(struct stream *stream, struct token *token, int true)
{
        token_type(token) = false_nesting ? TOKEN_SKIP_GROUPS : TOKEN_IF;
        free_preprocessor_line(token->next);
        token->next = stream->top_if;
        stream->top_if = token;
        if (false_nesting || true != 1)
                false_nesting++;
        return 0;
}

static int handle_ifdef(struct stream *stream, struct token **line, struct token *token)
{
        struct token *next = token->next;
        int arg;
        if (token_type(next) == TOKEN_IDENT) {
                arg = token_defined(next);
        } else {
                dirty_stream(stream);
                if (!false_nesting)
                        sparse_error(token->pos, "expected preprocessor identifier");
                arg = -1;
        }
        return preprocessor_if(stream, token, arg);
}

static int handle_ifndef(struct stream *stream, struct token **line, struct token *token)
{
        struct token *next = token->next;
        int arg;
        if (token_type(next) == TOKEN_IDENT) {
                if (!stream->dirty && !stream->ifndef) {
                        if (!stream->protect) {
                                stream->ifndef = token;
                                stream->protect = next->ident;
                        } else if (stream->protect == next->ident) {
                                stream->ifndef = token;
                                stream->dirty = 1;
                        }
                }
                arg = !token_defined(next);
        } else {
                dirty_stream(stream);
                if (!false_nesting)
                        sparse_error(token->pos, "expected preprocessor identifier");
                arg = -1;
        }

        return preprocessor_if(stream, token, arg);
}

static const char *show_token_sequence(struct token *token);

/*
 * Expression handling for #if and #elif; it differs from normal expansion
 * due to special treatment of "defined".
 */
static int expression_value(struct token **where)
{
        struct expression *expr;
        struct token *p;
        struct token **list = where, **beginning = NULL;
        long long value;
        int state = 0;

        while (!eof_token(p = scan_next(list))) {
                switch (state) {
                case 0:
                        if (token_type(p) != TOKEN_IDENT)
                                break;
                        if (p->ident == &defined_ident) {
                                state = 1;
                                beginning = list;
                                break;
                        }
                        if (!expand_one_symbol(list))
                                continue;
                        if (token_type(p) != TOKEN_IDENT)
                                break;
                        token_type(p) = TOKEN_ZERO_IDENT;
                        break;
                case 1:
                        if (match_op(p, '(')) {
                                state = 2;
                        } else {
                                state = 0;
                                replace_with_defined(p);
                                *beginning = p;
                        }
                        break;
                case 2:
                        if (token_type(p) == TOKEN_IDENT)
                                state = 3;
                        else
                                state = 0;
                        replace_with_defined(p);
                        *beginning = p;
                        break;
                case 3:
                        state = 0;
                        if (!match_op(p, ')'))
                                sparse_error(p->pos, "missing ')' after \"defined\"");
                        *list = p->next;
                        continue;
                }
                list = &p->next;
        }

        p = constant_expression(*where, &expr);
        if (!eof_token(p))
                sparse_error(p->pos, "garbage at end: %s", show_token_sequence(p));
        value = get_expression_value(expr);
        return value != 0;
}

static int handle_if(struct stream *stream, struct token **line, struct token *token)
{
        int value = 0;
        if (!false_nesting)
                value = expression_value(&token->next);

        dirty_stream(stream);
        return preprocessor_if(stream, token, value);
}

static int handle_elif(struct stream * stream, struct token **line, struct token *token)
{
        struct token *top_if = stream->top_if;
        end_group(stream);

        if (!top_if) {
                nesting_error(stream);
                sparse_error(token->pos, "unmatched #elif within stream");
                return 1;
        }

        if (token_type(top_if) == TOKEN_ELSE) {
                nesting_error(stream);
                sparse_error(token->pos, "#elif after #else");
                if (!false_nesting)
                        false_nesting = 1;
                return 1;
        }

        dirty_stream(stream);
        if (token_type(top_if) != TOKEN_IF)
                return 1;
        if (false_nesting) {
                false_nesting = 0;
                if (!expression_value(&token->next))
                        false_nesting = 1;
        } else {
                false_nesting = 1;
                token_type(top_if) = TOKEN_SKIP_GROUPS;
        }
        return 1;
}

static int handle_else(struct stream *stream, struct token **line, struct token *token)
{
        struct token *top_if = stream->top_if;
        end_group(stream);

        if (!top_if) {
                nesting_error(stream);
                sparse_error(token->pos, "unmatched #else within stream");
                return 1;
        }

        if (token_type(top_if) == TOKEN_ELSE) {
                nesting_error(stream);
                sparse_error(token->pos, "#else after #else");
        }
        if (false_nesting) {
                if (token_type(top_if) == TOKEN_IF)
                        false_nesting = 0;
        } else {
                false_nesting = 1;
        }
        token_type(top_if) = TOKEN_ELSE;
        return 1;
}

static int handle_endif(struct stream *stream, struct token **line, struct token *token)
{
        struct token *top_if = stream->top_if;
        end_group(stream);
        if (!top_if) {
                nesting_error(stream);
                sparse_error(token->pos, "unmatched #endif in stream");
                return 1;
        }
        if (false_nesting)
                false_nesting--;
        stream->top_if = top_if->next;
        __free_token(top_if);
        return 1;
}

static const char *show_token_sequence(struct token *token)
{
        static char buffer[1024];
        char *ptr = buffer;
        int whitespace = 0;

        if (!token)
                return "<none>";
        while (!eof_token(token)) {
                const char *val = show_token(token);
                int len = strlen(val);

                if (ptr + whitespace + len >= buffer + sizeof(buffer)) {
                        sparse_error(token->pos, "too long token expansion");
                        break;
                }

                if (whitespace)
                        *ptr++ = ' ';
                memcpy(ptr, val, len);
                ptr += len;
                token = token->next;
                whitespace = token->pos.whitespace;
        }
        *ptr = 0;
        return buffer;
}

static int handle_warning(struct stream *stream, struct token **line, struct token *token)
{
        warning(token->pos, "%s", show_token_sequence(token->next));
        return 1;
}

static int handle_error(struct stream *stream, struct token **line, struct token *token)
{
        sparse_error(token->pos, "%s", show_token_sequence(token->next));
        return 1;
}

static int handle_nostdinc(struct stream *stream, struct token **line, struct token *token)
{
        /*
         * Do we have any non-system includes?
         * Clear them out if so..
         */
        *sys_includepath = NULL;
        return 1;
}

static inline void update_inc_ptrs(const char ***where)
{

        if (*where <= dirafter_includepath) {
                dirafter_includepath++;
                /* If this was the entry that we prepend, don't
                 * rise the lower entries, even if they are at
                 * the same level. */
                if (where == &dirafter_includepath)
                        return;
        }
        if (*where <= sys_includepath) {
                sys_includepath++;
                if (where == &sys_includepath)
                        return;
        }
        if (*where <= isys_includepath) {
                isys_includepath++;
                if (where == &isys_includepath)
                        return;
        }

        /* angle_includepath is actually never updated, since we
         * don't suppport -iquote rught now. May change some day. */
        if (*where <= angle_includepath) {
                angle_includepath++;
                if (where == &angle_includepath)
                        return;
        }
}

/* Add a path before 'where' and update the pointers associated with the
 * includepath array */
static void add_path_entry(struct token *token, const char *path,
        const char ***where)
{
        const char **dst;
        const char *next;

        /* Need one free entry.. */
        if (includepath[INCLUDEPATHS-2])
                error_die(token->pos, "too many include path entries");

        /* check that this is not a duplicate */
        dst = includepath;
        while (*dst) {
                if (strcmp(*dst, path) == 0)
                        return;
                dst++;
        }
        next = path;
        dst = *where;

        update_inc_ptrs(where);

        /*
         * Move them all up starting at dst,
         * insert the new entry..
         */
        do {
                const char *tmp = *dst;
                *dst = next;
                next = tmp;
                dst++;
        } while (next);
}

static int handle_add_include(struct stream *stream, struct token **line, struct token *token)
{
        for (;;) {
                token = token->next;
                if (eof_token(token))
                        return 1;
                if (token_type(token) != TOKEN_STRING) {
                        warning(token->pos, "expected path string");
                        return 1;
                }
                add_path_entry(token, token->string->data, &isys_includepath);
        }
}

static int handle_add_isystem(struct stream *stream, struct token **line, struct token *token)
{
        for (;;) {
                token = token->next;
                if (eof_token(token))
                        return 1;
                if (token_type(token) != TOKEN_STRING) {
                        sparse_error(token->pos, "expected path string");
                        return 1;
                }
                add_path_entry(token, token->string->data, &sys_includepath);
        }
}

static int handle_add_system(struct stream *stream, struct token **line, struct token *token)
{
        for (;;) {
                token = token->next;
                if (eof_token(token))
                        return 1;
                if (token_type(token) != TOKEN_STRING) {
                        sparse_error(token->pos, "expected path string");
                        return 1;
                }
                add_path_entry(token, token->string->data, &dirafter_includepath);
        }
}

/* Add to end on includepath list - no pointer updates */
static void add_dirafter_entry(struct token *token, const char *path)
{
        const char **dst = includepath;

        /* Need one free entry.. */
        if (includepath[INCLUDEPATHS-2])
                error_die(token->pos, "too many include path entries");

        /* Add to the end */
        while (*dst)
                dst++;
        *dst = path;
        dst++;
        *dst = NULL;
}

static int handle_add_dirafter(struct stream *stream, struct token **line, struct token *token)
{
        for (;;) {
                token = token->next;
                if (eof_token(token))
                        return 1;
                if (token_type(token) != TOKEN_STRING) {
                        sparse_error(token->pos, "expected path string");
                        return 1;
                }
                add_dirafter_entry(token, token->string->data);
        }
}

static int handle_split_include(struct stream *stream, struct token **line, struct token *token)
{
        /*
         * -I-
         *  From info gcc:
         *  Split the include path.  Any directories specified with `-I'
         *  options before `-I-' are searched only for headers requested with
         *  `#include "FILE"'; they are not searched for `#include <FILE>'.
         *  If additional directories are specified with `-I' options after
         *  the `-I-', those directories are searched for all `#include'
         *  directives.
         *  In addition, `-I-' inhibits the use of the directory of the current
         *  file directory as the first search directory for `#include "FILE"'.
         */
        quote_includepath = includepath+1;
        angle_includepath = sys_includepath;
        return 1;
}

/*
 * We replace "#pragma xxx" with "__pragma__" in the token
 * stream. Just as an example.
 *
 * We'll just #define that away for now, but the theory here
 * is that we can use this to insert arbitrary token sequences
 * to turn the pragmas into internal front-end sequences for
 * when we actually start caring about them.
 *
 * So eventually this will turn into some kind of extended
 * __attribute__() like thing, except called __pragma__(xxx).
 */
static int handle_pragma(struct stream *stream, struct token **line, struct token *token)
{
        struct token *next = *line;

        token->ident = &pragma_ident;
        token->pos.newline = 1;
        token->pos.whitespace = 1;
        token->pos.pos = 1;
        *line = token;
        token->next = next;
        return 0;
}

/*
 * We ignore #line for now.
 */
static int handle_line(struct stream *stream, struct token **line, struct token *token)
{
        return 1;
}

static int handle_nondirective(struct stream *stream, struct token **line, struct token *token)
{
        sparse_error(token->pos, "unrecognized preprocessor line '%s'", show_token_sequence(token));
        return 1;
}


static void init_preprocessor(void)
{
        int i;
        int stream = init_stream("preprocessor", -1, includepath);
        static struct {
                const char *name;
                int (*handler)(struct stream *, struct token **, struct token *);
        } normal[] = {
                { "define",             handle_define },
                { "weak_define",        handle_weak_define },
                { "strong_define",      handle_strong_define },
                { "undef",              handle_undef },
                { "strong_undef",       handle_strong_undef },
                { "warning",            handle_warning },
                { "error",              handle_error },
                { "include",            handle_include },
                { "include_next",       handle_include_next },
                { "pragma",             handle_pragma },
                { "line",               handle_line },

                // our internal preprocessor tokens
                { "nostdinc",      handle_nostdinc },
                { "add_include",   handle_add_include },
                { "add_isystem",   handle_add_isystem },
                { "add_system",    handle_add_system },
                { "add_dirafter",  handle_add_dirafter },
                { "split_include", handle_split_include },
                { "argv_include",  handle_argv_include },
        }, special[] = {
                { "ifdef",      handle_ifdef },
                { "ifndef",     handle_ifndef },
                { "else",       handle_else },
                { "endif",      handle_endif },
                { "if",         handle_if },
                { "elif",       handle_elif },
        };

        for (i = 0; i < ARRAY_SIZE(normal); i++) {
                struct symbol *sym;
                sym = create_symbol(stream, normal[i].name, SYM_PREPROCESSOR, NS_PREPROCESSOR);
                sym->handler = normal[i].handler;
                sym->normal = 1;
        }
        for (i = 0; i < ARRAY_SIZE(special); i++) {
                struct symbol *sym;
                sym = create_symbol(stream, special[i].name, SYM_PREPROCESSOR, NS_PREPROCESSOR);
                sym->handler = special[i].handler;
                sym->normal = 0;
        }

}

static void handle_preprocessor_line(struct stream *stream, struct token **line, struct token *start)
{
        int (*handler)(struct stream *, struct token **, struct token *);
        struct token *token = start->next;
        int is_normal = 1;

        if (eof_token(token))
                return;

        if (token_type(token) == TOKEN_IDENT) {
                struct symbol *sym = lookup_symbol(token->ident, NS_PREPROCESSOR);
                if (sym) {
                        handler = sym->handler;
                        is_normal = sym->normal;
                } else {
                        handler = handle_nondirective;
                }
        } else if (token_type(token) == TOKEN_NUMBER) {
                handler = handle_line;
        } else {
                handler = handle_nondirective;
        }

        if (is_normal) {
                dirty_stream(stream);
                if (false_nesting)
                        goto out;
        }
        if (!handler(stream, line, token))      /* all set */
                return;

out:
        free_preprocessor_line(token);
}

static void preprocessor_line(struct stream *stream, struct token **line)
{
        struct token *start = *line, *next;
        struct token **tp = &start->next;

        for (;;) {
                next = *tp;
                if (next->pos.newline)
                        break;
                tp = &next->next;
        }
        *line = next;
        *tp = &eof_token_entry;
        handle_preprocessor_line(stream, line, start);
}

static void do_preprocess(struct token **list)
{
        struct token *next;

        while (!eof_token(next = scan_next(list))) {
                struct stream *stream = input_streams + next->pos.stream;

                if (next->pos.newline && match_op(next, '#')) {
                        if (!next->pos.noexpand) {
                                preprocessor_line(stream, list);
                                __free_token(next);     /* Free the '#' token */
                                continue;
                        }
                }

                switch (token_type(next)) {
                case TOKEN_STREAMEND:
                        if (stream->top_if) {
                                nesting_error(stream);
                                sparse_error(stream->top_if->pos, "unterminated preprocessor conditional");
                                stream->top_if = NULL;
                                false_nesting = 0;
                        }
                        if (!stream->dirty)
                                stream->constant = CONSTANT_FILE_YES;
                        *list = next->next;
                        continue;
                case TOKEN_STREAMBEGIN:
                        *list = next->next;
                        continue;

                default:
                        dirty_stream(stream);
                        if (false_nesting) {
                                *list = next->next;
                                __free_token(next);
                                continue;
                        }

                        if (token_type(next) != TOKEN_IDENT ||
                            expand_one_symbol(list))
                                list = &next->next;
                }
        }
}

struct token * preprocess(struct token *token)
{
        preprocessing = 1;
        init_preprocessor();
        do_preprocess(&token);

        // Drop all expressions from preprocessing, they're not used any more.
        // This is not true when we have multiple files, though ;/
        // clear_expression_alloc();
        preprocessing = 0;

        return token;
}