/*      $OpenBSD: compile.c,v 1.53 2024/07/17 20:57:15 millert Exp $    */

/*-
 * Copyright (c) 1992 Diomidis Spinellis.
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Diomidis Spinellis of Imperial College, University of London.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <fcntl.h>
#include <limits.h>
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "defs.h"
#include "extern.h"

#define LHSZ    128
#define LHMASK  (LHSZ - 1)
static struct labhash {
        struct  labhash *lh_next;
        u_int   lh_hash;
        struct  s_command *lh_cmd;
        int     lh_ref;
} *labels[LHSZ];

static char      *compile_addr(char *, struct s_addr *);
static char      *compile_ccl(char **, char *);
static char      *compile_delimited(char *, char *);
static char      *compile_flags(char *, struct s_subst *);
static char      *compile_re(char *, regex_t **);
static char      *compile_subst(char *, struct s_subst *);
static char      *compile_text(void);
static char      *compile_tr(char *, char **);
static struct s_command
                **compile_stream(struct s_command **);
static char      *duptoeol(char *, char *, char **);
static void       enterlabel(struct s_command *);
static struct s_command
                 *findlabel(char *);
static void       fixuplabel(struct s_command *, struct s_command *);
static void       uselabel(void);

/*
 * Command specification.  This is used to drive the command parser.
 */
struct s_format {
        char code;                              /* Command code */
        int naddr;                              /* Number of address args */
        enum e_args args;                       /* Argument type */
};

static struct s_format cmd_fmts[] = {
        {'{', 2, GROUP},
        {'}', 0, ENDGROUP},
        {'a', 1, TEXT},
        {'b', 2, BRANCH},
        {'c', 2, TEXT},
        {'d', 2, EMPTY},
        {'D', 2, EMPTY},
        {'g', 2, EMPTY},
        {'G', 2, EMPTY},
        {'h', 2, EMPTY},
        {'H', 2, EMPTY},
        {'i', 1, TEXT},
        {'l', 2, EMPTY},
        {'n', 2, EMPTY},
        {'N', 2, EMPTY},
        {'p', 2, EMPTY},
        {'P', 2, EMPTY},
        {'q', 1, EMPTY},
        {'r', 1, RFILE},
        {'s', 2, SUBST},
        {'t', 2, BRANCH},
        {'w', 2, WFILE},
        {'x', 2, EMPTY},
        {'y', 2, TR},
        {'!', 2, NONSEL},
        {':', 0, LABEL},
        {'#', 0, COMMENT},
        {'=', 1, EMPTY},
        {'\0', 0, COMMENT},
};

/* The compiled program. */
struct s_command *prog;

/*
 * Compile the program into prog.
 * Initialise appends.
 */
void
compile(void)
{
        *compile_stream(&prog) = NULL;
        fixuplabel(prog, NULL);
        uselabel();
        appends = xreallocarray(NULL, appendnum, sizeof(struct s_appends));
        match = xreallocarray(NULL, maxnsub + 1, sizeof(regmatch_t));
}

#define EATSPACE() do {                                                 \
        if (p)                                                          \
                while (isascii((unsigned char)*p) &&                    \
                    isspace((unsigned char)*p))                         \
                        p++;                                            \
        } while (0)

static struct s_command **
compile_stream(struct s_command **link)
{
        char *p;
        static char *lbuf;      /* To avoid excessive malloc calls */
        static size_t bufsize;
        struct s_command *cmd, *cmd2, *stack;
        struct s_format *fp;
        int naddr;                              /* Number of addresses */

        stack = 0;
        for (;;) {
                if ((p = cu_getline(&lbuf, &bufsize)) == NULL) {
                        if (stack != 0)
                                error("unexpected EOF (pending }'s)");
                        return (link);
                }

semicolon:      EATSPACE();
                if (*p == '#' || *p == '\0')
                        continue;
                if (*p == ';') {
                        p++;
                        goto semicolon;
                }
                *link = cmd = xmalloc(sizeof(struct s_command));
                link = &cmd->next;
                cmd->nonsel = cmd->inrange = 0;
                /* First parse the addresses */
                naddr = 0;

/* Valid characters to start an address */
#define addrchar(c)     (strchr("0123456789/\\$", (c)))
                if (addrchar(*p)) {
                        naddr++;
                        cmd->a1 = xmalloc(sizeof(struct s_addr));
                        p = compile_addr(p, cmd->a1);
                        EATSPACE();                             /* EXTENSION */
                        if (*p == ',') {
                                p++;
                                EATSPACE();                     /* EXTENSION */
                                naddr++;
                                cmd->a2 = xmalloc(sizeof(struct s_addr));
                                p = compile_addr(p, cmd->a2);
                                EATSPACE();
                        } else {
                                cmd->a2 = 0;
                        }
                } else {
                        cmd->a1 = cmd->a2 = 0;
                }

nonsel:         /* Now parse the command */
                if (!*p)
                        error("command expected");
                cmd->code = *p;
                for (fp = cmd_fmts; fp->code; fp++)
                        if (fp->code == *p)
                                break;
                if (!fp->code)
                        error("invalid command code %c", *p);
                if (naddr > fp->naddr)
                        error("command %c expects up to %d address(es),"
                            " found %d", *p, fp->naddr, naddr);
                switch (fp->args) {
                case NONSEL:                    /* ! */
                        p++;
                        EATSPACE();
                        cmd->nonsel = 1;
                        goto nonsel;
                case GROUP:                     /* { */
                        p++;
                        EATSPACE();
                        cmd->next = stack;
                        stack = cmd;
                        link = &cmd->u.c;
                        if (*p)
                                goto semicolon;
                        break;
                case ENDGROUP:
                        /*
                         * Short-circuit command processing, since end of
                         * group is really just a noop.
                         */
                        cmd->nonsel = 1;
                        if (stack == 0)
                                error("unexpected }");
                        cmd2 = stack;
                        stack = cmd2->next;
                        cmd2->next = cmd;
                        /*FALLTHROUGH*/
                case EMPTY:             /* d D g G h H l n N p P q x = \0 */
                        p++;
                        EATSPACE();
                        if (*p == ';') {
                                p++;
                                link = &cmd->next;
                                goto semicolon;
                        }
                        if (*p)
                                error("extra characters at the end of %c"
                                    " command", cmd->code);
                        break;
                case TEXT:                      /* a c i */
                        p++;
                        EATSPACE();
                        if (*p != '\\')
                                error("command %c expects \\ followed by text",
                                    cmd->code);
                        p++;
                        EATSPACE();
                        if (*p)
                                error("extra characters after \\ at the"
                                    " end of %c command", cmd->code);
                        cmd->t = compile_text();
                        break;
                case COMMENT:                   /* \0 # */
                        break;
                case WFILE:                     /* w */
                        p++;
                        EATSPACE();
                        if (*p == '\0')
                                error("filename expected");
                        cmd->t = duptoeol(p, "w command", NULL);
                        if (aflag) {
                                cmd->u.fd = -1;
                                pledge_wpath = 1;
                        }
                        else if ((cmd->u.fd = open(p,
                            O_WRONLY|O_APPEND|O_CREAT|O_TRUNC,
                            DEFFILEMODE)) == -1)
                                err(1, "%s", p);
                        break;
                case RFILE:                     /* r */
                        pledge_rpath = 1;
                        p++;
                        EATSPACE();
                        if (*p == '\0')
                                error("filename expected");
                        cmd->t = duptoeol(p, "read command", NULL);
                        break;
                case BRANCH:                    /* b t */
                        p++;
                        EATSPACE();
                        if (*p == '\0' || *p == ';')
                                cmd->t = NULL;
                        else
                                cmd->t = duptoeol(p, "branch", &p);
                        if (*p == ';') {
                                p++;
                                goto semicolon;
                        }
                        break;
                case LABEL:                     /* : */
                        p++;
                        EATSPACE();
                        cmd->t = duptoeol(p, "label", &p);
                        if (strlen(cmd->t) == 0)
                                error("empty label");
                        enterlabel(cmd);
                        if (*p == ';') {
                                p++;
                                goto semicolon;
                        }
                        break;
                case SUBST:                     /* s */
                        p++;
                        if (*p == '\0' || *p == '\\')
                                error("substitute pattern can not be"
                                    " delimited by newline or backslash");
                        cmd->u.s = xmalloc(sizeof(struct s_subst));
                        p = compile_re(p, &cmd->u.s->re);
                        if (p == NULL)
                                error("unterminated substitute pattern");
                        --p;
                        p = compile_subst(p, cmd->u.s);
                        p = compile_flags(p, cmd->u.s);
                        EATSPACE();
                        if (*p == ';') {
                                p++;
                                link = &cmd->next;
                                goto semicolon;
                        }
                        break;
                case TR:                        /* y */
                        p++;
                        p = compile_tr(p, (char **)&cmd->u.y);
                        EATSPACE();
                        if (*p == ';') {
                                p++;
                                link = &cmd->next;
                                goto semicolon;
                        }
                        if (*p)
                                error("extra text at the end of a"
                                    " transform command");
                        break;
                }
        }
}

/*
 * Get a delimited string.  P points to the delimiter of the string; d points
 * to a buffer area.  Newline and delimiter escapes are processed; other
 * escapes are ignored.
 *
 * Returns a pointer to the first character after the final delimiter or NULL
 * in the case of a non-terminated string.  The character array d is filled
 * with the processed string.
 */
static char *
compile_delimited(char *p, char *d)
{
        char c;

        c = *p++;
        if (c == '\0')
                return (NULL);
        else if (c == '\\')
                error("\\ can not be used as a string delimiter");
        else if (c == '\n')
                error("newline can not be used as a string delimiter");

        while (p[0]) {
                /* Unescaped delimiter: We are done. */
                if (p[0] == c) {
                        *d = '\0';
                        return p + 1;
                }
                if (p[0] == '\\') {
                        /* Escaped delimiter: Skip the backslash. */
                        if (p[1] == c) {
                                p++;
                        } else {
                                /* Backslash-n: Match linefeed. */
                                if (p[1] == 'n') {
                                        *d++ = '\n';
                                        p += 2;
                                /* Other escapes remain unchanged. */
                                } else {
                                        *d++ = *p++;
                                        *d++ = *p++;
                                }
                                continue;
                        }
                }
                if (p[0] != '[')
                        *d++ = *p++;
                /*
                 * Bracket expression:
                 * It may contain the delimiter without escaping.
                 */
                else if ((d = compile_ccl(&p, d)) == NULL)
                        error("unbalanced brackets ([])");
        }
        return NULL;
}


/* compile_ccl: expand a POSIX character class */
static char *
compile_ccl(char **sp, char *t)
{
        int c, d;
        char *s = *sp;

        *t++ = *s++;
        if (*s == '^')
                *t++ = *s++;
        if (*s == ']')
                *t++ = *s++;
        for (; *s && (*t = *s) != ']'; s++, t++)
                if (*s == '[' && ((d = *(s+1)) == '.' || d == ':' || d == '=')) {
                        *++t = *++s, t++, s++;
                        for (c = *s; (*t = *s) != ']' || c != d; s++, t++)
                                if ((c = *s) == '\0')
                                        return NULL;
                } else if (*s == '\\' && s[1] == 'n') {
                        *t = '\n';
                        s++;
                }
        if (*s == ']') {
                *sp = ++s;
                return (++t);
        } else {
                return (NULL);
        }
}

/*
 * Get a regular expression.  P points to the delimiter of the regular
 * expression; repp points to the address of a regexp pointer.  Newline
 * and delimiter escapes are processed; other escapes are ignored.
 * Returns a pointer to the first character after the final delimiter
 * or NULL in the case of a non terminated regular expression.  The regexp
 * pointer is set to the compiled regular expression.
 * Cflags are passed to regcomp.
 */
static char *
compile_re(char *p, regex_t **repp)
{
        int eval;
        char *re;

        re = xmalloc(strlen(p) + 1); /* strlen(re) <= strlen(p) */
        p = compile_delimited(p, re);
        if (p && strlen(re) == 0) {
                *repp = NULL;
                free(re);
                return (p);
        }
        *repp = xmalloc(sizeof(regex_t));
        if (p && (eval = regcomp(*repp, re, Eflag ? REG_EXTENDED : 0)) != 0)
                error("RE error: %s", strregerror(eval, *repp));
        if (maxnsub < (*repp)->re_nsub)
                maxnsub = (*repp)->re_nsub;
        free(re);
        return (p);
}

/*
 * Compile the substitution string of a regular expression and set res to
 * point to a saved copy of it.  Nsub is the number of parenthesized regular
 * expressions.
 */
static char *
compile_subst(char *p, struct s_subst *s)
{
        static char *lbuf;
        static size_t bufsize;
        size_t asize, ref, size;
        char c, *text, *op, *sp;
        int sawesc = 0;

        c = *p++;                       /* Terminator character */
        if (c == '\0')
                return (NULL);

        s->maxbref = 0;
        s->linenum = linenum;
        text = NULL;
        asize = size = 0;
        do {
                size_t len = ROUNDLEN(strlen(p) + 1);
                if (asize - size < len) {
                        do {
                                asize += len;
                        } while (asize - size < len);
                        text = xrealloc(text, asize);
                }
                op = sp = text + size;
                for (; *p; p++) {
                        if (*p == '\\' || sawesc) {
                                /*
                                 * If this is a continuation from the last
                                 * buffer, we won't have a character to
                                 * skip over.
                                 */
                                if (sawesc)
                                        sawesc = 0;
                                else
                                        p++;

                                if (*p == '\0') {
                                        /*
                                         * This escaped character is continued
                                         * in the next part of the line.  Note
                                         * this fact, then cause the loop to
                                         * exit w/ normal EOL case and reenter
                                         * above with the new buffer.
                                         */
                                        sawesc = 1;
                                        p--;
                                        continue;
                                } else if (strchr("123456789", *p) != NULL) {
                                        *sp++ = '\\';
                                        ref = *p - '0';
                                        if (s->re != NULL &&
                                            ref > s->re->re_nsub)
                                                error("\\%c not defined in the"
                                                    " RE", *p);
                                        if (s->maxbref < ref)
                                                s->maxbref = ref;
                                } else if (*p == '&' || *p == '\\')
                                        *sp++ = '\\';
                        } else if (*p == c) {
                                p++;
                                *sp++ = '\0';
                                size += sp - op;
                                s->new = xrealloc(text, size);
                                return (p);
                        } else if (*p == '\n') {
                                error("unescaped newline inside substitute"
                                    " pattern");
                        }
                        *sp++ = *p;
                }
                size += sp - op;
        } while ((p = cu_getline(&lbuf, &bufsize)));
        error("unterminated substitute in regular expression");
}

/*
 * Compile the flags of the s command
 */
static char *
compile_flags(char *p, struct s_subst *s)
{
        int gn;                 /* True if we have seen g or n */
        long l;

        s->n = 1;                               /* Default */
        s->p = 0;
        s->wfile = NULL;
        s->wfd = -1;
        for (gn = 0;;) {
                EATSPACE();                     /* EXTENSION */
                switch (*p) {
                case 'g':
                        if (gn)
                                error("more than one number or 'g' in"
                                    " substitute flags");
                        gn = 1;
                        s->n = 0;
                        break;
                case '\0':
                case '\n':
                case ';':
                        return (p);
                case 'p':
                        s->p = 1;
                        break;
                case '1': case '2': case '3':
                case '4': case '5': case '6':
                case '7': case '8': case '9':
                        if (gn)
                                error("more than one number or 'g' in"
                                    " substitute flags");
                        gn = 1;
                        l = strtol(p, &p, 10);
                        if (l <= 0 || l >= INT_MAX)
                                error("number in substitute flags out of"
                                    " range");
                        s->n = (int)l;
                        continue;
                case 'w':
                        p++;
                        EATSPACE();
                        if (*p == '\0')
                                error("filename expected");
                        s->wfile = duptoeol(p, "s command w flag", NULL);
                        *p = '\0';
                        if (aflag)
                                pledge_wpath = 1;
                        else if ((s->wfd = open(s->wfile,
                            O_WRONLY|O_APPEND|O_CREAT|O_TRUNC,
                            DEFFILEMODE)) == -1)
                                err(1, "%s", s->wfile);
                        return (p);
                default:
                        error("bad flag in substitute command: '%c'", *p);
                        break;
                }
                p++;
        }
}

/*
 * Compile a translation set of strings into a lookup table.
 */
static char *
compile_tr(char *old, char **transtab)
{
        int i;
        char delimiter, check[UCHAR_MAX + 1];
        char *new, *end;

        memset(check, 0, sizeof(check));
        delimiter = *old;
        if (delimiter == '\\')
                error("\\ can not be used as a string delimiter");
        else if (delimiter == '\n' || delimiter == '\0')
                error("newline can not be used as a string delimiter");

        new = old++;
        do {
                if ((new = strchr(new + 1, delimiter)) == NULL)
                        error("unterminated transform source string");
        } while (*(new - 1) == '\\' && *(new -2) != '\\');
        *new = '\0';
        end = new++;
        do {
                if ((end = strchr(end + 1, delimiter)) == NULL)
                        error("unterminated transform target string");
        } while (*(end -1) == '\\' && *(end -2) != '\\');
        *end = '\0';

        /* We assume characters are 8 bits */
        *transtab = xmalloc(UCHAR_MAX + 1);
        for (i = 0; i <= UCHAR_MAX; i++)
                (*transtab)[i] = (char)i;

        while (*old != '\0' && *new != '\0') {
                if (*old == '\\') {
                        old++;
                        if (*old == 'n')
                                *old = '\n';
                        else if (*old != delimiter && *old != '\\')
                                error("Unexpected character after backslash");
                }
                if (*new == '\\') {
                        new++;
                        if (*new == 'n')
                                *new = '\n';
                        else if (*new != delimiter && *new != '\\')
                                error("Unexpected character after backslash");
                }
                if (check[(u_char) *old] == 1)
                        error("Repeated character in source string");
                check[(u_char) *old] = 1;
                (*transtab)[(u_char) *old++] = *new++;
        }
        if (*old != '\0' || *new != '\0')
                error("transform strings are not the same length");
        return end + 1;
}

/*
 * Compile the text following an a, c, or i command.
 */
static char *
compile_text(void)
{
        size_t asize, size, bufsize;
        char *lbuf, *text, *p, *op, *s;
        int esc_nl;

        lbuf = text = NULL;
        asize = size = 0;
        while ((p = cu_getline(&lbuf, &bufsize))) {
                size_t len = ROUNDLEN(strlen(p) + 1);
                if (asize - size < len) {
                        do {
                                asize += len;
                        } while (asize - size < len);
                        text = xrealloc(text, asize);
                }
                op = s = text + size;
                for (esc_nl = 0; *p != '\0'; p++) {
                        if (*p == '\\' && p[1] != '\0' && *++p == '\n')
                                esc_nl = 1;
                        *s++ = *p;
                }
                size += s - op;
                if (!esc_nl) {
                        *s = '\0';
                        break;
                }
        }
        free(lbuf);
        text = xrealloc(text, size + 1);
        text[size] = '\0';
        return (text);
}

/*
 * Get an address and return a pointer to the first character after
 * it.  Fill the structure pointed to according to the address.
 */
static char *
compile_addr(char *p, struct s_addr *a)
{
        char *end;

        switch (*p) {
        case '\\':                              /* Context address */
                ++p;
                /* FALLTHROUGH */
        case '/':                               /* Context address */
                p = compile_re(p, &a->u.r);
                if (p == NULL)
                        error("unterminated regular expression");
                a->type = AT_RE;
                return (p);

        case '$':                               /* Last line */
                a->type = AT_LAST;
                return (p + 1);
                                                /* Line number */
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
                a->type = AT_LINE;
                a->u.l = strtoul(p, &end, 10);
                return (end);
        default:
                error("expected context address");
                return (NULL);
        }
}

/*
 * duptoeol --
 *      Return a copy of all the characters up to \n or \0.
 */
static char *
duptoeol(char *s, char *ctype, char **semi)
{
        size_t len;
        int ws;
        char *start;

        ws = 0;
        if (semi) {
                for (start = s; *s != '\0' && *s != '\n' && *s != ';'; ++s)
                        ws = isspace((unsigned char)*s);
        } else {
                for (start = s; *s != '\0' && *s != '\n'; ++s)
                        ws = isspace((unsigned char)*s);
                *s = '\0';
        }
        if (ws)
                warning("whitespace after %s", ctype);
        len = s - start + 1;
        if (semi)
                *semi = s;
        s = xmalloc(len);
        strlcpy(s, start, len);
        return (s);
}

/*
 * Convert goto label names to addresses, and count a and r commands, in
 * the given subset of the script.  Free the memory used by labels in b
 * and t commands (but not by :).
 *
 * TODO: Remove } nodes
 */
static void
fixuplabel(struct s_command *cp, struct s_command *end)
{

        for (; cp != end; cp = cp->next)
                switch (cp->code) {
                case 'a':
                case 'r':
                        appendnum++;
                        break;
                case 'b':
                case 't':
                        /* Resolve branch target. */
                        if (cp->t == NULL) {
                                cp->u.c = NULL;
                                break;
                        }
                        if ((cp->u.c = findlabel(cp->t)) == NULL)
                                error("undefined label '%s'", cp->t);
                        free(cp->t);
                        break;
                case '{':
                        /* Do interior commands. */
                        fixuplabel(cp->u.c, cp->next);
                        break;
                }
}

/*
 * Associate the given command label for later lookup.
 */
static void
enterlabel(struct s_command *cp)
{
        struct labhash **lhp, *lh;
        u_char *p;
        u_int h, c;

        for (h = 0, p = (u_char *)cp->t; (c = *p) != 0; p++)
                h = (h << 5) + h + c;
        lhp = &labels[h & LHMASK];
        for (lh = *lhp; lh != NULL; lh = lh->lh_next)
                if (lh->lh_hash == h && strcmp(cp->t, lh->lh_cmd->t) == 0)
                        error("duplicate label '%s'", cp->t);
        lh = xmalloc(sizeof *lh);
        lh->lh_next = *lhp;
        lh->lh_hash = h;
        lh->lh_cmd = cp;
        lh->lh_ref = 0;
        *lhp = lh;
}

/*
 * Find the label contained in the command l in the command linked
 * list cp.  L is excluded from the search.  Return NULL if not found.
 */
static struct s_command *
findlabel(char *name)
{
        struct labhash *lh;
        u_char *p;
        u_int h, c;

        for (h = 0, p = (u_char *)name; (c = *p) != 0; p++)
                h = (h << 5) + h + c;
        for (lh = labels[h & LHMASK]; lh != NULL; lh = lh->lh_next) {
                if (lh->lh_hash == h && strcmp(name, lh->lh_cmd->t) == 0) {
                        lh->lh_ref = 1;
                        return (lh->lh_cmd);
                }
        }
        return (NULL);
}

/*
 * Warn about any unused labels.  As a side effect, release the label hash
 * table space.
 */
static void
uselabel(void)
{
        struct labhash *lh, *next;
        int i;

        for (i = 0; i < LHSZ; i++) {
                for (lh = labels[i]; lh != NULL; lh = next) {
                        next = lh->lh_next;
                        if (!lh->lh_ref)
                                warning("unused label '%s'",
                                    lh->lh_cmd->t);
                        free(lh);
                }
        }
}