/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1992, 1993, 1994 Henry Spencer.
 * Copyright (c) 1992, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * Copyright (c) 2011 The FreeBSD Foundation
 *
 * Portions of this software were developed by David Chisnall
 * under sponsorship from the FreeBSD Foundation.
 *
 * This code is derived from software contributed to Berkeley by
 * Henry Spencer.
 *
 * 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 <stdio.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include <regex.h>
#include <stdbool.h>
#include <wchar.h>
#include <wctype.h>

#ifndef LIBREGEX
#include "collate.h"
#endif

#include "utils.h"
#include "regex2.h"

#include "cname.h"

/*
 * Branching context, used to keep track of branch state for all of the branch-
 * aware functions. In addition to keeping track of branch positions for the
 * p_branch_* functions, we use this to simplify some clumsiness in BREs for
 * detection of whether ^ is acting as an anchor or being used erroneously and
 * also for whether we're in a sub-expression or not.
 */
struct branchc {
        sopno start;
        sopno back;
        sopno fwd;

        int nbranch;
        int nchain;
        bool outer;
        bool terminate;
};

/*
 * parse structure, passed up and down to avoid global variables and
 * other clumsinesses
 */
struct parse {
        const char *next;       /* next character in RE */
        const char *end;        /* end of string (-> NUL normally) */
        int error;              /* has an error been seen? */
        int gnuext;
        sop *strip;             /* malloced strip */
        sopno ssize;            /* malloced strip size (allocated) */
        sopno slen;             /* malloced strip length (used) */
        int ncsalloc;           /* number of csets allocated */
        struct re_guts *g;
#       define  NPAREN  10      /* we need to remember () 1-9 for back refs */
        sopno pbegin[NPAREN];   /* -> ( ([0] unused) */
        sopno pend[NPAREN];     /* -> ) ([0] unused) */
        bool allowbranch;       /* can this expression branch? */
        bool bre;               /* convenience; is this a BRE? */
        int pflags;             /* other parsing flags -- legacy escapes? */
        bool (*parse_expr)(struct parse *, struct branchc *);
        void (*pre_parse)(struct parse *, struct branchc *);
        void (*post_parse)(struct parse *, struct branchc *);
};

#define PFLAG_LEGACY_ESC        0x00000001

/* ========= begin header generated by ./mkh ========= */
#ifdef __cplusplus
extern "C" {
#endif

/* === regcomp.c === */
static bool p_ere_exp(struct parse *p, struct branchc *bc);
static void p_str(struct parse *p);
static int p_branch_eat_delim(struct parse *p, struct branchc *bc);
static void p_branch_ins_offset(struct parse *p, struct branchc *bc);
static void p_branch_fix_tail(struct parse *p, struct branchc *bc);
static bool p_branch_empty(struct parse *p, struct branchc *bc);
static bool p_branch_do(struct parse *p, struct branchc *bc);
static void p_bre_pre_parse(struct parse *p, struct branchc *bc);
static void p_bre_post_parse(struct parse *p, struct branchc *bc);
static void p_re(struct parse *p, int end1, int end2);
static bool p_simp_re(struct parse *p, struct branchc *bc);
static int p_count(struct parse *p);
static void p_bracket(struct parse *p);
static int p_range_cmp(wchar_t c1, wchar_t c2);
static void p_b_term(struct parse *p, cset *cs);
static int p_b_pseudoclass(struct parse *p, char c);
static void p_b_cclass(struct parse *p, cset *cs);
static void p_b_cclass_named(struct parse *p, cset *cs, const char[]);
static void p_b_eclass(struct parse *p, cset *cs);
static wint_t p_b_symbol(struct parse *p);
static wint_t p_b_coll_elem(struct parse *p, wint_t endc);
static bool may_escape(struct parse *p, const wint_t ch);
static wint_t othercase(wint_t ch);
static void bothcases(struct parse *p, wint_t ch);
static void ordinary(struct parse *p, wint_t ch);
static void nonnewline(struct parse *p);
static void repeat(struct parse *p, sopno start, int from, int to);
static int seterr(struct parse *p, int e);
static cset *allocset(struct parse *p);
static void freeset(struct parse *p, cset *cs);
static void CHadd(struct parse *p, cset *cs, wint_t ch);
static void CHaddrange(struct parse *p, cset *cs, wint_t min, wint_t max);
static void CHaddtype(struct parse *p, cset *cs, wctype_t wct);
static wint_t singleton(cset *cs);
static sopno dupl(struct parse *p, sopno start, sopno finish);
static void doemit(struct parse *p, sop op, size_t opnd);
static void doinsert(struct parse *p, sop op, size_t opnd, sopno pos);
static void dofwd(struct parse *p, sopno pos, sop value);
static int enlarge(struct parse *p, sopno size);
static void stripsnug(struct parse *p, struct re_guts *g);
static void findmust(struct parse *p, struct re_guts *g);
static int altoffset(sop *scan, int offset);
static void computejumps(struct parse *p, struct re_guts *g);
static void computematchjumps(struct parse *p, struct re_guts *g);
static sopno pluscount(struct parse *p, struct re_guts *g);
static wint_t wgetnext(struct parse *p);

#ifdef __cplusplus
}
#endif
/* ========= end header generated by ./mkh ========= */

static char nuls[10];           /* place to point scanner in event of error */

/*
 * macros for use with parse structure
 * BEWARE:  these know that the parse structure is named `p' !!!
 */
#define PEEK()  (*p->next)
#define PEEK2() (*(p->next+1))
#define MORE()  (p->end - p->next > 0)
#define MORE2() (p->end - p->next > 1)
#define SEE(c)  (MORE() && PEEK() == (c))
#define SEETWO(a, b)    (MORE2() && PEEK() == (a) && PEEK2() == (b))
#define SEESPEC(a)      (p->bre ? SEETWO('\\', a) : SEE(a))
#define EAT(c)  ((SEE(c)) ? (NEXT(), 1) : 0)
#define EATTWO(a, b)    ((SEETWO(a, b)) ? (NEXT2(), 1) : 0)
#define EATSPEC(a)      (p->bre ? EATTWO('\\', a) : EAT(a))
#define NEXT()  (p->next++)
#define NEXT2() (p->next += 2)
#define NEXTn(n)        (p->next += (n))
#define GETNEXT()       (*p->next++)
#define WGETNEXT()      wgetnext(p)
#define SETERROR(e)     seterr(p, (e))
#define REQUIRE(co, e)  ((co) || SETERROR(e))
#define MUSTSEE(c, e)   (REQUIRE(MORE() && PEEK() == (c), e))
#define MUSTEAT(c, e)   (REQUIRE(MORE() && GETNEXT() == (c), e))
#define MUSTNOTSEE(c, e)        (REQUIRE(!MORE() || PEEK() != (c), e))
#define EMIT(op, sopnd) doemit(p, (sop)(op), (size_t)(sopnd))
#define INSERT(op, pos) doinsert(p, (sop)(op), HERE()-(pos)+1, pos)
#define AHEAD(pos)              dofwd(p, pos, HERE()-(pos))
#define ASTERN(sop, pos)        EMIT(sop, HERE()-pos)
#define HERE()          (p->slen)
#define THERE()         (p->slen - 1)
#define THERETHERE()    (p->slen - 2)
#define DROP(n) (p->slen -= (n))

/* Macro used by computejump()/computematchjump() */
#define MIN(a,b)        ((a)<(b)?(a):(b))

static int                              /* 0 success, otherwise REG_something */
regcomp_internal(regex_t * __restrict preg,
        const char * __restrict pattern,
        int cflags, int pflags)
{
        struct parse pa;
        struct re_guts *g;
        struct parse *p = &pa;
        int i;
        size_t len;
        size_t maxlen;
#ifdef REDEBUG
#       define  GOODFLAGS(f)    (f)
#else
#       define  GOODFLAGS(f)    ((f)&~REG_DUMP)
#endif

        cflags = GOODFLAGS(cflags);
        if ((cflags&REG_EXTENDED) && (cflags&REG_NOSPEC))
                return(REG_INVARG);

        if (cflags&REG_PEND) {
                if (preg->re_endp < pattern)
                        return(REG_INVARG);
                len = preg->re_endp - pattern;
        } else
                len = strlen(pattern);

        /* do the mallocs early so failure handling is easy */
        g = (struct re_guts *)malloc(sizeof(struct re_guts));
        if (g == NULL)
                return(REG_ESPACE);
        /*
         * Limit the pattern space to avoid a 32-bit overflow on buffer
         * extension.  Also avoid any signed overflow in case of conversion
         * so make the real limit based on a 31-bit overflow.
         *
         * Likely not applicable on 64-bit systems but handle the case
         * generically (who are we to stop people from using ~715MB+
         * patterns?).
         */
        maxlen = ((size_t)-1 >> 1) / sizeof(sop) * 2 / 3;
        if (len >= maxlen) {
                free((char *)g);
                return(REG_ESPACE);
        }
        p->ssize = len/(size_t)2*(size_t)3 + (size_t)1; /* ugh */
        assert(p->ssize >= len);

        p->strip = (sop *)malloc(p->ssize * sizeof(sop));
        p->slen = 0;
        if (p->strip == NULL) {
                free((char *)g);
                return(REG_ESPACE);
        }

        /* set things up */
        p->g = g;
        p->next = pattern;      /* convenience; we do not modify it */
        p->end = p->next + len;
        p->error = 0;
        p->ncsalloc = 0;
        p->pflags = pflags;
        for (i = 0; i < NPAREN; i++) {
                p->pbegin[i] = 0;
                p->pend[i] = 0;
        }
#ifdef LIBREGEX
        if (cflags&REG_POSIX) {
                p->gnuext = false;
                p->allowbranch = (cflags & REG_EXTENDED) != 0;
        } else
                p->gnuext = p->allowbranch = true;
#else
        p->gnuext = false;
        p->allowbranch = (cflags & REG_EXTENDED) != 0;
#endif
        if (cflags & REG_EXTENDED) {
                p->bre = false;
                p->parse_expr = p_ere_exp;
                p->pre_parse = NULL;
                p->post_parse = NULL;
        } else {
                p->bre = true;
                p->parse_expr = p_simp_re;
                p->pre_parse = p_bre_pre_parse;
                p->post_parse = p_bre_post_parse;
        }
        g->sets = NULL;
        g->ncsets = 0;
        g->cflags = cflags;
        g->iflags = 0;
        g->nbol = 0;
        g->neol = 0;
        g->must = NULL;
        g->moffset = -1;
        g->charjump = NULL;
        g->matchjump = NULL;
        g->mlen = 0;
        g->nsub = 0;
        g->backrefs = 0;

        /* do it */
        EMIT(OEND, 0);
        g->firststate = THERE();
        if (cflags & REG_NOSPEC)
                p_str(p);
        else
                p_re(p, OUT, OUT);
        EMIT(OEND, 0);
        g->laststate = THERE();

        /* tidy up loose ends and fill things in */
        stripsnug(p, g);
        findmust(p, g);
        /* only use Boyer-Moore algorithm if the pattern is bigger
         * than three characters
         */
        if(g->mlen > 3) {
                computejumps(p, g);
                computematchjumps(p, g);
                if(g->matchjump == NULL && g->charjump != NULL) {
                        free(&g->charjump[CHAR_MIN]);
                        g->charjump = NULL;
                }
        }
        g->nplus = pluscount(p, g);
        g->magic = MAGIC2;
        preg->re_nsub = g->nsub;
        preg->re_g = g;
        preg->re_magic = MAGIC1;
#ifndef REDEBUG
        /* not debugging, so can't rely on the assert() in regexec() */
        if (g->iflags&BAD)
                SETERROR(REG_ASSERT);
#endif

        /* win or lose, we're done */
        if (p->error != 0)      /* lose */
                regfree(preg);
        return(p->error);
}

/*
 - regcomp - interface for parser and compilation
 = extern int regcomp(regex_t *, const char *, int);
 = #define      REG_BASIC       0000
 = #define      REG_EXTENDED    0001
 = #define      REG_ICASE       0002
 = #define      REG_NOSUB       0004
 = #define      REG_NEWLINE     0010
 = #define      REG_NOSPEC      0020
 = #define      REG_PEND        0040
 = #define      REG_DUMP        0200
 */
int                             /* 0 success, otherwise REG_something */
regcomp(regex_t * __restrict preg,
        const char * __restrict pattern,
        int cflags)
{

        return (regcomp_internal(preg, pattern, cflags, 0));
}

#ifndef LIBREGEX
/*
 * Legacy interface that requires more lax escaping behavior.
 */
int
freebsd12_regcomp(regex_t * __restrict preg,
        const char * __restrict pattern,
        int cflags, int pflags)
{

        return (regcomp_internal(preg, pattern, cflags, PFLAG_LEGACY_ESC));
}

__sym_compat(regcomp, freebsd12_regcomp, FBSD_1.0);
#endif  /* !LIBREGEX */

/*
 - p_ere_exp - parse one subERE, an atom possibly followed by a repetition op,
 - return whether we should terminate or not
 == static bool p_ere_exp(struct parse *p);
 */
static bool
p_ere_exp(struct parse *p, struct branchc *bc)
{
        char c;
        wint_t wc;
        sopno pos;
        int count;
        int count2;
#ifdef LIBREGEX
        int i;
        int handled;
#endif
        sopno subno;
        int wascaret = 0;

        (void)bc;
        assert(MORE());         /* caller should have ensured this */
        c = GETNEXT();

#ifdef LIBREGEX
        handled = 0;
#endif
        pos = HERE();
        switch (c) {
        case '(':
                (void)REQUIRE(MORE(), REG_EPAREN);
                p->g->nsub++;
                subno = p->g->nsub;
                if (subno < NPAREN)
                        p->pbegin[subno] = HERE();
                EMIT(OLPAREN, subno);
                if (!SEE(')'))
                        p_re(p, ')', IGN);
                if (subno < NPAREN) {
                        p->pend[subno] = HERE();
                        assert(p->pend[subno] != 0);
                }
                EMIT(ORPAREN, subno);
                (void)MUSTEAT(')', REG_EPAREN);
                break;
#ifndef POSIX_MISTAKE
        case ')':               /* happens only if no current unmatched ( */
                /*
                 * You may ask, why the ifndef?  Because I didn't notice
                 * this until slightly too late for 1003.2, and none of the
                 * other 1003.2 regular-expression reviewers noticed it at
                 * all.  So an unmatched ) is legal POSIX, at least until
                 * we can get it fixed.
                 */
                SETERROR(REG_EPAREN);
                break;
#endif
        case '^':
                EMIT(OBOL, 0);
                p->g->iflags |= USEBOL;
                p->g->nbol++;
                wascaret = 1;
                break;
        case '$':
                EMIT(OEOL, 0);
                p->g->iflags |= USEEOL;
                p->g->neol++;
                break;
        case '|':
                SETERROR(REG_EMPTY);
                break;
        case '*':
        case '+':
        case '?':
#ifndef NO_STRICT_REGEX
        case '{':
#endif
                SETERROR(REG_BADRPT);
                break;
        case '.':
                if (p->g->cflags&REG_NEWLINE)
                        nonnewline(p);
                else
                        EMIT(OANY, 0);
                break;
        case '[':
                p_bracket(p);
                break;
        case '\\':
                (void)REQUIRE(MORE(), REG_EESCAPE);
                wc = WGETNEXT();
#ifdef LIBREGEX
                if (p->gnuext) {
                        handled = 1;
                        switch (wc) {
                        case '`':
                                EMIT(OBOS, 0);
                                break;
                        case '\'':
                                EMIT(OEOS, 0);
                                break;
                        case 'B':
                                EMIT(ONWBND, 0);
                                break;
                        case 'b':
                                EMIT(OWBND, 0);
                                break;
                        case 'W':
                        case 'w':
                        case 'S':
                        case 's':
                                p_b_pseudoclass(p, wc);
                                break;
                        case '1':
                        case '2':
                        case '3':
                        case '4':
                        case '5':
                        case '6':
                        case '7':
                        case '8':
                        case '9':
                                i = wc - '0';
                                assert(i < NPAREN);
                                if (p->pend[i] != 0) {
                                        assert(i <= p->g->nsub);
                                        EMIT(OBACK_, i);
                                        assert(p->pbegin[i] != 0);
                                        assert(OP(p->strip[p->pbegin[i]]) == OLPAREN);
                                        assert(OP(p->strip[p->pend[i]]) == ORPAREN);
                                        (void) dupl(p, p->pbegin[i]+1, p->pend[i]);
                                        EMIT(O_BACK, i);
                                } else
                                        SETERROR(REG_ESUBREG);
                                p->g->backrefs = 1;
                                break;
                        default:
                                handled = 0;
                        }
                        /* Don't proceed to the POSIX bits if we've already handled it */
                        if (handled)
                                break;
                }
#endif
                switch (wc) {
                case '<':
                        EMIT(OBOW, 0);
                        break;
                case '>':
                        EMIT(OEOW, 0);
                        break;
                default:
                        if (may_escape(p, wc))
                                ordinary(p, wc);
                        else
                                SETERROR(REG_EESCAPE);
                        break;
                }
                break;
#ifdef NO_STRICT_REGEX
        case '{':               /* okay as ordinary except if digit follows */
            (void)REQUIRE(!MORE() || !isdigit((uch)PEEK()), REG_BADRPT);
            /* FALLTHROUGH */
#endif
        default:
                if (p->error != 0)
                        return (false);
                p->next--;
                wc = WGETNEXT();
                ordinary(p, wc);
                break;
        }

        if (!MORE())
                return (false);
        c = PEEK();
        /* we call { a repetition if followed by a digit */
        if (!( c == '*' || c == '+' || c == '?' ||
#ifdef NO_STRICT_REGEX
               (c == '{' && MORE2() && isdigit((uch)PEEK2()))
#else
               c == '{'
#endif
               ))
                return (false);         /* no repetition, we're done */
#ifndef NO_STRICT_REGEX
        else if (c == '{')
                (void)REQUIRE(MORE2() && \
                    (isdigit((uch)PEEK2()) || PEEK2() == ','), REG_BADRPT);
#endif
        NEXT();

        (void)REQUIRE(!wascaret, REG_BADRPT);
        switch (c) {
        case '*':       /* implemented as +? */
                /* this case does not require the (y|) trick, noKLUDGE */
                INSERT(OPLUS_, pos);
                ASTERN(O_PLUS, pos);
                INSERT(OQUEST_, pos);
                ASTERN(O_QUEST, pos);
                break;
        case '+':
                INSERT(OPLUS_, pos);
                ASTERN(O_PLUS, pos);
                break;
        case '?':
                /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
                INSERT(OCH_, pos);              /* offset slightly wrong */
                ASTERN(OOR1, pos);              /* this one's right */
                AHEAD(pos);                     /* fix the OCH_ */
                EMIT(OOR2, 0);                  /* offset very wrong... */
                AHEAD(THERE());                 /* ...so fix it */
                ASTERN(O_CH, THERETHERE());
                break;
        case '{':
                count = p_count(p);
                if (EAT(',')) {
                        if (isdigit((uch)PEEK())) {
                                count2 = p_count(p);
                                (void)REQUIRE(count <= count2, REG_BADBR);
                        } else          /* single number with comma */
                                count2 = INFINITY;
                } else          /* just a single number */
                        count2 = count;
                repeat(p, pos, count, count2);
                if (!EAT('}')) {        /* error heuristics */
                        while (MORE() && PEEK() != '}')
                                NEXT();
                        (void)REQUIRE(MORE(), REG_EBRACE);
                        SETERROR(REG_BADBR);
                }
                break;
        }

        if (!MORE())
                return (false);
        c = PEEK();
        if (!( c == '*' || c == '+' || c == '?' ||
                                (c == '{' && MORE2() && isdigit((uch)PEEK2())) ) )
                return (false);
        SETERROR(REG_BADRPT);
        return (false);
}

/*
 - p_str - string (no metacharacters) "parser"
 == static void p_str(struct parse *p);
 */
static void
p_str(struct parse *p)
{
        (void)REQUIRE(MORE(), REG_EMPTY);
        while (MORE())
                ordinary(p, WGETNEXT());
}

/*
 * Eat consecutive branch delimiters for the kind of expression that we are
 * parsing, return the number of delimiters that we ate.
 */
static int
p_branch_eat_delim(struct parse *p, struct branchc *bc)
{
        int nskip;

        (void)bc;
        nskip = 0;
        while (EATSPEC('|'))
                ++nskip;
        return (nskip);
}

/*
 * Insert necessary branch book-keeping operations. This emits a
 * bogus 'next' offset, since we still have more to parse
 */
static void
p_branch_ins_offset(struct parse *p, struct branchc *bc)
{

        if (bc->nbranch == 0) {
                INSERT(OCH_, bc->start);        /* offset is wrong */
                bc->fwd = bc->start;
                bc->back = bc->start;
        }

        ASTERN(OOR1, bc->back);
        bc->back = THERE();
        AHEAD(bc->fwd);                 /* fix previous offset */
        bc->fwd = HERE();
        EMIT(OOR2, 0);                  /* offset is very wrong */
        ++bc->nbranch;
}

/*
 * Fix the offset of the tail branch, if we actually had any branches.
 * This is to correct the bogus placeholder offset that we use.
 */
static void
p_branch_fix_tail(struct parse *p, struct branchc *bc)
{

        /* Fix bogus offset at the tail if we actually have branches */
        if (bc->nbranch > 0) {
                AHEAD(bc->fwd);
                ASTERN(O_CH, bc->back);
        }
}

/*
 * Signal to the parser that an empty branch has been encountered; this will,
 * in the future, be used to allow for more permissive behavior with empty
 * branches. The return value should indicate whether parsing may continue
 * or not.
 */
static bool
p_branch_empty(struct parse *p, struct branchc *bc)
{

        (void)bc;
        SETERROR(REG_EMPTY);
        return (false);
}

/*
 * Take care of any branching requirements. This includes inserting the
 * appropriate branching instructions as well as eating all of the branch
 * delimiters until we either run out of pattern or need to parse more pattern.
 */
static bool
p_branch_do(struct parse *p, struct branchc *bc)
{
        int ate = 0;

        ate = p_branch_eat_delim(p, bc);
        if (ate == 0)
                return (false);
        else if ((ate > 1 || (bc->outer && !MORE())) && !p_branch_empty(p, bc))
                /*
                 * Halt parsing only if we have an empty branch and p_branch_empty
                 * indicates that we must not continue. In the future, this will not
                 * necessarily be an error.
                 */
                return (false);
        p_branch_ins_offset(p, bc);

        return (true);
}

static void
p_bre_pre_parse(struct parse *p, struct branchc *bc)
{

        (void) bc;
        /*
         * Does not move cleanly into expression parser because of
         * ordinary interpration of * at the beginning position of
         * an expression.
         */
        if (EAT('^')) {
                EMIT(OBOL, 0);
                p->g->iflags |= USEBOL;
                p->g->nbol++;
        }
}

static void
p_bre_post_parse(struct parse *p, struct branchc *bc)
{

        /* Expression is terminating due to EOL token */
        if (bc->terminate) {
                DROP(1);
                EMIT(OEOL, 0);
                p->g->iflags |= USEEOL;
                p->g->neol++;
        }
}

/*
 - p_re - Top level parser, concatenation and BRE anchoring
 == static void p_re(struct parse *p, int end1, int end2);
 * Giving end1 as OUT essentially eliminates the end1/end2 check.
 *
 * This implementation is a bit of a kludge, in that a trailing $ is first
 * taken as an ordinary character and then revised to be an anchor.
 * The amount of lookahead needed to avoid this kludge is excessive.
 */
static void
p_re(struct parse *p,
        int end1,       /* first terminating character */
        int end2)       /* second terminating character; ignored for EREs */
{
        struct branchc bc;

        bc.nbranch = 0;
        if (end1 == OUT && end2 == OUT)
                bc.outer = true;
        else
                bc.outer = false;
#define SEEEND()        (!p->bre ? SEE(end1) : SEETWO(end1, end2))
        for (;;) {
                bc.start = HERE();
                bc.nchain = 0;
                bc.terminate = false;
                if (p->pre_parse != NULL)
                        p->pre_parse(p, &bc);
                while (MORE() && (!p->allowbranch || !SEESPEC('|')) && !SEEEND()) {
                        bc.terminate = p->parse_expr(p, &bc);
                        ++bc.nchain;
                }
                if (p->post_parse != NULL)
                        p->post_parse(p, &bc);
                (void) REQUIRE(p->gnuext || HERE() != bc.start, REG_EMPTY);
#ifdef LIBREGEX
                if (HERE() == bc.start && !p_branch_empty(p, &bc))
                        break;
#endif
                if (!p->allowbranch)
                        break;
                /*
                 * p_branch_do's return value indicates whether we should
                 * continue parsing or not. This is both for correctness and
                 * a slight optimization, because it will check if we've
                 * encountered an empty branch or the end of the string
                 * immediately following a branch delimiter.
                 */
                if (!p_branch_do(p, &bc))
                        break;
        }
#undef SEE_END
        if (p->allowbranch)
                p_branch_fix_tail(p, &bc);
        assert(!MORE() || SEE(end1));
}

/*
 - p_simp_re - parse a simple RE, an atom possibly followed by a repetition
 == static bool p_simp_re(struct parse *p, struct branchc *bc);
 */
static bool                     /* was the simple RE an unbackslashed $? */
p_simp_re(struct parse *p, struct branchc *bc)
{
        int c;
        int cc;                 /* convenient/control character */
        int count;
        int count2;
        sopno pos;
        bool handled;
        int i;
        wint_t wc;
        sopno subno;
#       define  BACKSL  (1<<CHAR_BIT)

        pos = HERE();           /* repetition op, if any, covers from here */
        handled = false;

        assert(MORE());         /* caller should have ensured this */
        c = (uch)GETNEXT();
        if (c == '\\') {
                (void)REQUIRE(MORE(), REG_EESCAPE);
                cc = (uch)GETNEXT();
                c = BACKSL | cc;
#ifdef LIBREGEX
                if (p->gnuext) {
                        handled = true;
                        switch (c) {
                        case BACKSL|'`':
                                EMIT(OBOS, 0);
                                break;
                        case BACKSL|'\'':
                                EMIT(OEOS, 0);
                                break;
                        case BACKSL|'B':
                                EMIT(ONWBND, 0);
                                break;
                        case BACKSL|'b':
                                EMIT(OWBND, 0);
                                break;
                        case BACKSL|'W':
                        case BACKSL|'w':
                        case BACKSL|'S':
                        case BACKSL|'s':
                                p_b_pseudoclass(p, cc);
                                break;
                        default:
                                handled = false;
                        }
                }
#endif
        }
        if (!handled) {
                switch (c) {
                case '.':
                        if (p->g->cflags&REG_NEWLINE)
                                nonnewline(p);
                        else
                                EMIT(OANY, 0);
                        break;
                case '[':
                        p_bracket(p);
                        break;
                case BACKSL|'<':
                        EMIT(OBOW, 0);
                        break;
                case BACKSL|'>':
                        EMIT(OEOW, 0);
                        break;
                case BACKSL|'{':
                        SETERROR(REG_BADRPT);
                        break;
                case BACKSL|'(':
                        p->g->nsub++;
                        subno = p->g->nsub;
                        if (subno < NPAREN)
                                p->pbegin[subno] = HERE();
                        EMIT(OLPAREN, subno);
                        /* the MORE here is an error heuristic */
                        if (MORE() && !SEETWO('\\', ')'))
                                p_re(p, '\\', ')');
                        if (subno < NPAREN) {
                                p->pend[subno] = HERE();
                                assert(p->pend[subno] != 0);
                        }
                        EMIT(ORPAREN, subno);
                        (void)REQUIRE(EATTWO('\\', ')'), REG_EPAREN);
                        break;
                case BACKSL|')':        /* should not get here -- must be user */
#ifdef NO_STRICT_REGEX
                case BACKSL|'}':
#endif
                        SETERROR(REG_EPAREN);
                        break;
                case BACKSL|'1':
                case BACKSL|'2':
                case BACKSL|'3':
                case BACKSL|'4':
                case BACKSL|'5':
                case BACKSL|'6':
                case BACKSL|'7':
                case BACKSL|'8':
                case BACKSL|'9':
                        i = (c&~BACKSL) - '0';
                        assert(i < NPAREN);
                        if (p->pend[i] != 0) {
                                assert(i <= p->g->nsub);
                                EMIT(OBACK_, i);
                                assert(p->pbegin[i] != 0);
                                assert(OP(p->strip[p->pbegin[i]]) == OLPAREN);
                                assert(OP(p->strip[p->pend[i]]) == ORPAREN);
                                (void) dupl(p, p->pbegin[i]+1, p->pend[i]);
                                EMIT(O_BACK, i);
                        } else
                                SETERROR(REG_ESUBREG);
                        p->g->backrefs = 1;
                        break;
                case '*':
                        /*
                         * Ordinary if used as the first character beyond BOL anchor of
                         * a (sub-)expression, counts as a bad repetition operator if it
                         * appears otherwise.
                         */
                        (void)REQUIRE(bc->nchain == 0, REG_BADRPT);
                        /* FALLTHROUGH */
                default:
                        if (p->error != 0)
                                return (false); /* Definitely not $... */
                        p->next--;
                        wc = WGETNEXT();
                        if ((c & BACKSL) == 0 || may_escape(p, wc))
                                ordinary(p, wc);
                        else
                                SETERROR(REG_EESCAPE);
                        break;
                }
        }

        if (EAT('*')) {         /* implemented as +? */
                /* this case does not require the (y|) trick, noKLUDGE */
                INSERT(OPLUS_, pos);
                ASTERN(O_PLUS, pos);
                INSERT(OQUEST_, pos);
                ASTERN(O_QUEST, pos);
#ifdef LIBREGEX
        } else if (p->gnuext && EATTWO('\\', '?')) {
                INSERT(OQUEST_, pos);
                ASTERN(O_QUEST, pos);
        } else if (p->gnuext && EATTWO('\\', '+')) {
                INSERT(OPLUS_, pos);
                ASTERN(O_PLUS, pos);
#endif
        } else if (EATTWO('\\', '{')) {
                count = p_count(p);
                if (EAT(',')) {
                        if (MORE() && isdigit((uch)PEEK())) {
                                count2 = p_count(p);
                                (void)REQUIRE(count <= count2, REG_BADBR);
                        } else          /* single number with comma */
                                count2 = INFINITY;
                } else          /* just a single number */
                        count2 = count;
                repeat(p, pos, count, count2);
                if (!EATTWO('\\', '}')) {       /* error heuristics */
                        while (MORE() && !SEETWO('\\', '}'))
                                NEXT();
                        (void)REQUIRE(MORE(), REG_EBRACE);
                        SETERROR(REG_BADBR);
                }
        } else if (c == '$')     /* $ (but not \$) ends it */
                return (true);

        return (false);
}

/*
 - p_count - parse a repetition count
 == static int p_count(struct parse *p);
 */
static int                      /* the value */
p_count(struct parse *p)
{
        int count = 0;
        int ndigits = 0;

        while (MORE() && isdigit((uch)PEEK()) && count <= DUPMAX) {
                count = count*10 + ((uch)GETNEXT() - '0');
                ndigits++;
        }

        (void)REQUIRE(ndigits > 0 && count <= DUPMAX, REG_BADBR);
        return(count);
}

/*
 - p_bracket - parse a bracketed character list
 == static void p_bracket(struct parse *p);
 */
static void
p_bracket(struct parse *p)
{
        cset *cs;
        wint_t ch;

        /* Dept of Truly Sickening Special-Case Kludges */
        if (p->end - p->next > 5) {
                if (strncmp(p->next, "[:<:]]", 6) == 0) {
                        EMIT(OBOW, 0);
                        NEXTn(6);
                        return;
                }
                if (strncmp(p->next, "[:>:]]", 6) == 0) {
                        EMIT(OEOW, 0);
                        NEXTn(6);
                        return;
                }
        }

        if ((cs = allocset(p)) == NULL)
                return;

        if (p->g->cflags&REG_ICASE)
                cs->icase = 1;
        if (EAT('^'))
                cs->invert = 1;
        if (EAT(']'))
                CHadd(p, cs, ']');
        else if (EAT('-'))
                CHadd(p, cs, '-');
        while (MORE() && PEEK() != ']' && !SEETWO('-', ']'))
                p_b_term(p, cs);
        if (EAT('-'))
                CHadd(p, cs, '-');
        (void)MUSTEAT(']', REG_EBRACK);

        if (p->error != 0)      /* don't mess things up further */
                return;

        if (cs->invert && p->g->cflags&REG_NEWLINE)
                cs->bmp['\n' >> 3] |= 1 << ('\n' & 7);

        if ((ch = singleton(cs)) != OUT) {      /* optimize singleton sets */
                ordinary(p, ch);
                freeset(p, cs);
        } else
                EMIT(OANYOF, (int)(cs - p->g->sets));
}

static int
p_range_cmp(wchar_t c1, wchar_t c2)
{
#ifndef LIBREGEX
        return __wcollate_range_cmp(c1, c2);
#else
        /* Copied from libc/collate __wcollate_range_cmp */
        wchar_t s1[2], s2[2];

        s1[0] = c1;
        s1[1] = L'\0';
        s2[0] = c2;
        s2[1] = L'\0';
        return (wcscoll(s1, s2));
#endif
}

/*
 - p_b_term - parse one term of a bracketed character list
 == static void p_b_term(struct parse *p, cset *cs);
 */
static void
p_b_term(struct parse *p, cset *cs)
{
        char c;
        wint_t start, finish;
        wint_t i;
#ifndef LIBREGEX
        struct xlocale_collate *table =
                (struct xlocale_collate*)__get_locale()->components[XLC_COLLATE];
#endif
        /* classify what we've got */
        switch ((MORE()) ? PEEK() : '\0') {
        case '[':
                c = (MORE2()) ? PEEK2() : '\0';
                break;
        case '-':
                SETERROR(REG_ERANGE);
                return;                 /* NOTE RETURN */
        default:
                c = '\0';
                break;
        }

        switch (c) {
        case ':':               /* character class */
                NEXT2();
                (void)REQUIRE(MORE(), REG_EBRACK);
                c = PEEK();
                (void)REQUIRE(c != '-' && c != ']', REG_ECTYPE);
                p_b_cclass(p, cs);
                (void)REQUIRE(MORE(), REG_EBRACK);
                (void)REQUIRE(EATTWO(':', ']'), REG_ECTYPE);
                break;
        case '=':               /* equivalence class */
                NEXT2();
                (void)REQUIRE(MORE(), REG_EBRACK);
                c = PEEK();
                (void)REQUIRE(c != '-' && c != ']', REG_ECOLLATE);
                p_b_eclass(p, cs);
                (void)REQUIRE(MORE(), REG_EBRACK);
                (void)REQUIRE(EATTWO('=', ']'), REG_ECOLLATE);
                break;
        default:                /* symbol, ordinary character, or range */
                start = p_b_symbol(p);
                if (SEE('-') && MORE2() && PEEK2() != ']') {
                        /* range */
                        NEXT();
                        if (EAT('-'))
                                finish = '-';
                        else
                                finish = p_b_symbol(p);
                } else
                        finish = start;
                if (start == finish)
                        CHadd(p, cs, start);
                else {
#ifndef LIBREGEX
                        if (table->__collate_load_error || MB_CUR_MAX > 1) {
#else
                        if (MB_CUR_MAX > 1) {
#endif
                                (void)REQUIRE(start <= finish, REG_ERANGE);
                                CHaddrange(p, cs, start, finish);
                        } else {
                                (void)REQUIRE(p_range_cmp(start, finish) <= 0, REG_ERANGE);
                                for (i = 0; i <= UCHAR_MAX; i++) {
                                        if (p_range_cmp(start, i) <= 0 &&
                                            p_range_cmp(i, finish) <= 0 )
                                                CHadd(p, cs, i);
                                }
                        }
                }
                break;
        }
}

/*
 - p_b_pseudoclass - parse a pseudo-class (\w, \W, \s, \S)
 == static int p_b_pseudoclass(struct parse *p, char c)
 */
static int
p_b_pseudoclass(struct parse *p, char c) {
        cset *cs;

        if ((cs = allocset(p)) == NULL)
                return(0);

        if (p->g->cflags&REG_ICASE)
                cs->icase = 1;

        switch (c) {
        case 'W':
                cs->invert = 1;
                /* PASSTHROUGH */
        case 'w':
                p_b_cclass_named(p, cs, "alnum");
                CHadd(p, cs, '_');
                break;
        case 'S':
                cs->invert = 1;
                /* PASSTHROUGH */
        case 's':
                p_b_cclass_named(p, cs, "space");
                break;
        default:
                return(0);
        }

        EMIT(OANYOF, (int)(cs - p->g->sets));
        return(1);
}

/*
 - p_b_cclass - parse a character-class name and deal with it
 == static void p_b_cclass(struct parse *p, cset *cs);
 */
static void
p_b_cclass(struct parse *p, cset *cs)
{
        const char *sp = p->next;
        size_t len;
        char clname[16];

        while (MORE() && isalpha((uch)PEEK()))
                NEXT();
        len = p->next - sp;
        if (len >= sizeof(clname) - 1) {
                SETERROR(REG_ECTYPE);
                return;
        }
        memcpy(clname, sp, len);
        clname[len] = '\0';

        p_b_cclass_named(p, cs, clname);
}
/*
 - p_b_cclass_named - deal with a named character class
 == static void p_b_cclass_named(struct parse *p, cset *cs, const char []);
 */
static void
p_b_cclass_named(struct parse *p, cset *cs, const char clname[]) {
        wctype_t wct;

        if ((wct = wctype(clname)) == 0) {
                SETERROR(REG_ECTYPE);
                return;
        }
        CHaddtype(p, cs, wct);
}

/*
 - p_b_eclass - parse an equivalence-class name and deal with it
 == static void p_b_eclass(struct parse *p, cset *cs);
 *
 * This implementation is incomplete. xxx
 */
static void
p_b_eclass(struct parse *p, cset *cs)
{
        wint_t c;

        c = p_b_coll_elem(p, '=');
        CHadd(p, cs, c);
}

/*
 - p_b_symbol - parse a character or [..]ed multicharacter collating symbol
 == static wint_t p_b_symbol(struct parse *p);
 */
static wint_t                   /* value of symbol */
p_b_symbol(struct parse *p)
{
        wint_t value;

        (void)REQUIRE(MORE(), REG_EBRACK);
        if (!EATTWO('[', '.'))
                return(WGETNEXT());

        /* collating symbol */
        value = p_b_coll_elem(p, '.');
        (void)REQUIRE(EATTWO('.', ']'), REG_ECOLLATE);
        return(value);
}

/*
 - p_b_coll_elem - parse a collating-element name and look it up
 == static wint_t p_b_coll_elem(struct parse *p, wint_t endc);
 */
static wint_t                   /* value of collating element */
p_b_coll_elem(struct parse *p,
        wint_t endc)            /* name ended by endc,']' */
{
        const char *sp = p->next;
        struct cname *cp;
        mbstate_t mbs;
        wchar_t wc;
        size_t clen, len;

        while (MORE() && !SEETWO(endc, ']'))
                NEXT();
        if (!MORE()) {
                SETERROR(REG_EBRACK);
                return(0);
        }
        len = p->next - sp;
        for (cp = cnames; cp->name != NULL; cp++)
                if (strncmp(cp->name, sp, len) == 0 && strlen(cp->name) == len)
                        return(cp->code);       /* known name */
        memset(&mbs, 0, sizeof(mbs));
        if ((clen = mbrtowc(&wc, sp, len, &mbs)) == len)
                return (wc);                    /* single character */
        else if (clen == (size_t)-1 || clen == (size_t)-2)
                SETERROR(REG_ILLSEQ);
        else
                SETERROR(REG_ECOLLATE);         /* neither */
        return(0);
}

/*
 - may_escape - determine whether 'ch' is escape-able in the current context
 == static int may_escape(struct parse *p, const wint_t ch)
 */
static bool
may_escape(struct parse *p, const wint_t ch)
{

        if ((p->pflags & PFLAG_LEGACY_ESC) != 0)
                return (true);
        if (iswalpha(ch) || ch == '\'' || ch == '`')
                return (false);
        return (true);
#ifdef NOTYET
        /*
         * Build a whitelist of characters that may be escaped to produce an
         * ordinary in the current context. This assumes that these have not
         * been otherwise interpreted as a special character. Escaping an
         * ordinary character yields undefined results according to
         * IEEE 1003.1-2008. Some extensions (notably, some GNU extensions) take
         * advantage of this and use escaped ordinary characters to provide
         * special meaning, e.g. \b, \B, \w, \W, \s, \S.
         */
        switch(ch) {
        case '|':
        case '+':
        case '?':
                /* The above characters may not be escaped in BREs */
                if (!(p->g->cflags&REG_EXTENDED))
                        return (false);
                /* Fallthrough */
        case '(':
        case ')':
        case '{':
        case '}':
        case '.':
        case '[':
        case ']':
        case '\\':
        case '*':
        case '^':
        case '$':
                return (true);
        default:
                return (false);
        }
#endif
}

/*
 - othercase - return the case counterpart of an alphabetic
 == static wint_t othercase(wint_t ch);
 */
static wint_t                   /* if no counterpart, return ch */
othercase(wint_t ch)
{
        assert(iswalpha(ch));
        if (iswupper(ch))
                return(towlower(ch));
        else if (iswlower(ch))
                return(towupper(ch));
        else                    /* peculiar, but could happen */
                return(ch);
}

/*
 - bothcases - emit a dualcase version of a two-case character
 == static void bothcases(struct parse *p, wint_t ch);
 *
 * Boy, is this implementation ever a kludge...
 */
static void
bothcases(struct parse *p, wint_t ch)
{
        const char *oldnext = p->next;
        const char *oldend = p->end;
        char bracket[3 + MB_LEN_MAX];
        size_t n;
        mbstate_t mbs;

        assert(othercase(ch) != ch);    /* p_bracket() would recurse */
        p->next = bracket;
        memset(&mbs, 0, sizeof(mbs));
        n = wcrtomb(bracket, ch, &mbs);
        assert(n != (size_t)-1);
        bracket[n] = ']';
        bracket[n + 1] = '\0';
        p->end = bracket+n+1;
        p_bracket(p);
        assert(p->next == p->end);
        p->next = oldnext;
        p->end = oldend;
}

/*
 - ordinary - emit an ordinary character
 == static void ordinary(struct parse *p, wint_t ch);
 */
static void
ordinary(struct parse *p, wint_t ch)
{
        cset *cs;

        if ((p->g->cflags&REG_ICASE) && iswalpha(ch) && othercase(ch) != ch)
                bothcases(p, ch);
        else if ((ch & OPDMASK) == ch)
                EMIT(OCHAR, ch);
        else {
                /*
                 * Kludge: character is too big to fit into an OCHAR operand.
                 * Emit a singleton set.
                 */
                if ((cs = allocset(p)) == NULL)
                        return;
                CHadd(p, cs, ch);
                EMIT(OANYOF, (int)(cs - p->g->sets));
        }
}

/*
 - nonnewline - emit REG_NEWLINE version of OANY
 == static void nonnewline(struct parse *p);
 *
 * Boy, is this implementation ever a kludge...
 */
static void
nonnewline(struct parse *p)
{
        const char *oldnext = p->next;
        const char *oldend = p->end;
        char bracket[4];

        p->next = bracket;
        p->end = bracket+3;
        bracket[0] = '^';
        bracket[1] = '\n';
        bracket[2] = ']';
        bracket[3] = '\0';
        p_bracket(p);
        assert(p->next == bracket+3);
        p->next = oldnext;
        p->end = oldend;
}

/*
 - repeat - generate code for a bounded repetition, recursively if needed
 == static void repeat(struct parse *p, sopno start, int from, int to);
 */
static void
repeat(struct parse *p,
        sopno start,            /* operand from here to end of strip */
        int from,               /* repeated from this number */
        int to)                 /* to this number of times (maybe INFINITY) */
{
        sopno finish = HERE();
#       define  N       2
#       define  INF     3
#       define  REP(f, t)       ((f)*8 + (t))
#       define  MAP(n)  (((n) <= 1) ? (n) : ((n) == INFINITY) ? INF : N)
        sopno copy;

        if (p->error != 0)      /* head off possible runaway recursion */
                return;

        assert(from <= to);

        switch (REP(MAP(from), MAP(to))) {
        case REP(0, 0):                 /* must be user doing this */
                DROP(finish-start);     /* drop the operand */
                break;
        case REP(0, 1):                 /* as x{1,1}? */
        case REP(0, N):                 /* as x{1,n}? */
        case REP(0, INF):               /* as x{1,}? */
                /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
                INSERT(OCH_, start);            /* offset is wrong... */
                repeat(p, start+1, 1, to);
                ASTERN(OOR1, start);
                AHEAD(start);                   /* ... fix it */
                EMIT(OOR2, 0);
                AHEAD(THERE());
                ASTERN(O_CH, THERETHERE());
                break;
        case REP(1, 1):                 /* trivial case */
                /* done */
                break;
        case REP(1, N):                 /* as x?x{1,n-1} */
                /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
                INSERT(OCH_, start);
                ASTERN(OOR1, start);
                AHEAD(start);
                EMIT(OOR2, 0);                  /* offset very wrong... */
                AHEAD(THERE());                 /* ...so fix it */
                ASTERN(O_CH, THERETHERE());
                copy = dupl(p, start+1, finish+1);
                assert(copy == finish+4);
                repeat(p, copy, 1, to-1);
                break;
        case REP(1, INF):               /* as x+ */
                INSERT(OPLUS_, start);
                ASTERN(O_PLUS, start);
                break;
        case REP(N, N):                 /* as xx{m-1,n-1} */
                copy = dupl(p, start, finish);
                repeat(p, copy, from-1, to-1);
                break;
        case REP(N, INF):               /* as xx{n-1,INF} */
                copy = dupl(p, start, finish);
                repeat(p, copy, from-1, to);
                break;
        default:                        /* "can't happen" */
                SETERROR(REG_ASSERT);   /* just in case */
                break;
        }
}

/*
 - wgetnext - helper function for WGETNEXT() macro. Gets the next wide
 - character from the parse struct, signals a REG_ILLSEQ error if the
 - character can't be converted. Returns the number of bytes consumed.
 */
static wint_t
wgetnext(struct parse *p)
{
        mbstate_t mbs;
        wchar_t wc;
        size_t n;

        memset(&mbs, 0, sizeof(mbs));
        n = mbrtowc(&wc, p->next, p->end - p->next, &mbs);
        if (n == (size_t)-1 || n == (size_t)-2) {
                SETERROR(REG_ILLSEQ);
                return (0);
        }
        if (n == 0)
                n = 1;
        p->next += n;
        return (wc);
}

/*
 - seterr - set an error condition
 == static int seterr(struct parse *p, int e);
 */
static int                      /* useless but makes type checking happy */
seterr(struct parse *p, int e)
{
        if (p->error == 0)      /* keep earliest error condition */
                p->error = e;
        p->next = nuls;         /* try to bring things to a halt */
        p->end = nuls;
        return(0);              /* make the return value well-defined */
}

/*
 - allocset - allocate a set of characters for []
 == static cset *allocset(struct parse *p);
 */
static cset *
allocset(struct parse *p)
{
        cset *cs, *ncs;

        ncs = reallocarray(p->g->sets, p->g->ncsets + 1, sizeof(*ncs));
        if (ncs == NULL) {
                SETERROR(REG_ESPACE);
                return (NULL);
        }
        p->g->sets = ncs;
        cs = &p->g->sets[p->g->ncsets++];
        memset(cs, 0, sizeof(*cs));

        return(cs);
}

/*
 - freeset - free a now-unused set
 == static void freeset(struct parse *p, cset *cs);
 */
static void
freeset(struct parse *p, cset *cs)
{
        cset *top = &p->g->sets[p->g->ncsets];

        free(cs->wides);
        free(cs->ranges);
        free(cs->types);
        memset(cs, 0, sizeof(*cs));
        if (cs == top-1)        /* recover only the easy case */
                p->g->ncsets--;
}

/*
 - singleton - Determine whether a set contains only one character,
 - returning it if so, otherwise returning OUT.
 */
static wint_t
singleton(cset *cs)
{
        wint_t i, s, n;

        /* Exclude the complicated cases we don't want to deal with */
        if (cs->nranges != 0 || cs->ntypes != 0 || cs->icase != 0)
                return (OUT);

        if (cs->nwides > 1)
                return (OUT);

        /* Count the number of characters present in the bitmap */
        for (i = n = 0; i < NC; i++)
                if (CHIN(cs, i)) {
                        n++;
                        s = i;
                }

        if (n > 1)
                return (OUT);

        if (n == 1) {
                if (cs->nwides == 0)
                        return (s);
                else
                        return (OUT);
        }
        if (cs->nwides == 1)
                return (cs->wides[0]);

        return (OUT);
}

/*
 - CHadd - add character to character set.
 */
static void
CHadd(struct parse *p, cset *cs, wint_t ch)
{
        wint_t nch, *newwides;
        assert(ch >= 0);
        if (ch < NC)
                cs->bmp[ch >> 3] |= 1 << (ch & 7);
        else {
                newwides = reallocarray(cs->wides, cs->nwides + 1,
                    sizeof(*cs->wides));
                if (newwides == NULL) {
                        SETERROR(REG_ESPACE);
                        return;
                }
                cs->wides = newwides;
                cs->wides[cs->nwides++] = ch;
        }
        if (cs->icase) {
                if ((nch = towlower(ch)) < NC)
                        cs->bmp[nch >> 3] |= 1 << (nch & 7);
                if ((nch = towupper(ch)) < NC)
                        cs->bmp[nch >> 3] |= 1 << (nch & 7);
        }
}

/*
 - CHaddrange - add all characters in the range [min,max] to a character set.
 */
static void
CHaddrange(struct parse *p, cset *cs, wint_t min, wint_t max)
{
        crange *newranges;

        for (; min < NC && min <= max; min++)
                CHadd(p, cs, min);
        if (min >= max)
                return;
        newranges = reallocarray(cs->ranges, cs->nranges + 1,
            sizeof(*cs->ranges));
        if (newranges == NULL) {
                SETERROR(REG_ESPACE);
                return;
        }
        cs->ranges = newranges;
        cs->ranges[cs->nranges].min = min;
        cs->ranges[cs->nranges].max = max;
        cs->nranges++;
}

/*
 - CHaddtype - add all characters of a certain type to a character set.
 */
static void
CHaddtype(struct parse *p, cset *cs, wctype_t wct)
{
        wint_t i;
        wctype_t *newtypes;

        for (i = 0; i < NC; i++)
                if (iswctype(i, wct))
                        CHadd(p, cs, i);
        newtypes = reallocarray(cs->types, cs->ntypes + 1,
            sizeof(*cs->types));
        if (newtypes == NULL) {
                SETERROR(REG_ESPACE);
                return;
        }
        cs->types = newtypes;
        cs->types[cs->ntypes++] = wct;
}

/*
 - dupl - emit a duplicate of a bunch of sops
 == static sopno dupl(struct parse *p, sopno start, sopno finish);
 */
static sopno                    /* start of duplicate */
dupl(struct parse *p,
        sopno start,            /* from here */
        sopno finish)           /* to this less one */
{
        sopno ret = HERE();
        sopno len = finish - start;

        assert(finish >= start);
        if (len == 0)
                return(ret);
        if (!enlarge(p, p->ssize + len)) /* this many unexpected additions */
                return(ret);
        (void) memcpy((char *)(p->strip + p->slen),
                (char *)(p->strip + start), (size_t)len*sizeof(sop));
        p->slen += len;
        return(ret);
}

/*
 - doemit - emit a strip operator
 == static void doemit(struct parse *p, sop op, size_t opnd);
 *
 * It might seem better to implement this as a macro with a function as
 * hard-case backup, but it's just too big and messy unless there are
 * some changes to the data structures.  Maybe later.
 */
static void
doemit(struct parse *p, sop op, size_t opnd)
{
        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        /* deal with oversize operands ("can't happen", more or less) */
        assert(opnd < 1<<OPSHIFT);

        /* deal with undersized strip */
        if (p->slen >= p->ssize)
                if (!enlarge(p, (p->ssize+1) / 2 * 3))  /* +50% */
                        return;

        /* finally, it's all reduced to the easy case */
        p->strip[p->slen++] = SOP(op, opnd);
}

/*
 - doinsert - insert a sop into the strip
 == static void doinsert(struct parse *p, sop op, size_t opnd, sopno pos);
 */
static void
doinsert(struct parse *p, sop op, size_t opnd, sopno pos)
{
        sopno sn;
        sop s;
        int i;

        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        sn = HERE();
        EMIT(op, opnd);         /* do checks, ensure space */
        assert(HERE() == sn+1);
        s = p->strip[sn];

        /* adjust paren pointers */
        assert(pos > 0);
        for (i = 1; i < NPAREN; i++) {
                if (p->pbegin[i] >= pos) {
                        p->pbegin[i]++;
                }
                if (p->pend[i] >= pos) {
                        p->pend[i]++;
                }
        }

        memmove((char *)&p->strip[pos+1], (char *)&p->strip[pos],
                                                (HERE()-pos-1)*sizeof(sop));
        p->strip[pos] = s;
}

/*
 - dofwd - complete a forward reference
 == static void dofwd(struct parse *p, sopno pos, sop value);
 */
static void
dofwd(struct parse *p, sopno pos, sop value)
{
        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        assert(value < 1<<OPSHIFT);
        p->strip[pos] = OP(p->strip[pos]) | value;
}

/*
 - enlarge - enlarge the strip
 == static int enlarge(struct parse *p, sopno size);
 */
static int
enlarge(struct parse *p, sopno size)
{
        sop *sp;

        if (p->ssize >= size)
                return 1;

        sp = reallocarray(p->strip, size, sizeof(sop));
        if (sp == NULL) {
                SETERROR(REG_ESPACE);
                return 0;
        }
        p->strip = sp;
        p->ssize = size;
        return 1;
}

/*
 - stripsnug - compact the strip
 == static void stripsnug(struct parse *p, struct re_guts *g);
 */
static void
stripsnug(struct parse *p, struct re_guts *g)
{
        g->nstates = p->slen;
        g->strip = reallocarray((char *)p->strip, p->slen, sizeof(sop));
        if (g->strip == NULL) {
                SETERROR(REG_ESPACE);
                g->strip = p->strip;
        }
}

/*
 - findmust - fill in must and mlen with longest mandatory literal string
 == static void findmust(struct parse *p, struct re_guts *g);
 *
 * This algorithm could do fancy things like analyzing the operands of |
 * for common subsequences.  Someday.  This code is simple and finds most
 * of the interesting cases.
 *
 * Note that must and mlen got initialized during setup.
 */
static void
findmust(struct parse *p, struct re_guts *g)
{
        sop *scan;
        sop *start = NULL;
        sop *newstart = NULL;
        sopno newlen;
        sop s;
        char *cp;
        int offset;
        char buf[MB_LEN_MAX];
        size_t clen;
        mbstate_t mbs;

        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        /*
         * It's not generally safe to do a ``char'' substring search on
         * multibyte character strings, but it's safe for at least
         * UTF-8 (see RFC 3629).
         */
        if (MB_CUR_MAX > 1 &&
            strcmp(_CurrentRuneLocale->__encoding, "UTF-8") != 0)
                return;

        /* find the longest OCHAR sequence in strip */
        newlen = 0;
        offset = 0;
        g->moffset = 0;
        scan = g->strip + 1;
        do {
                s = *scan++;
                switch (OP(s)) {
                case OCHAR:             /* sequence member */
                        if (newlen == 0) {              /* new sequence */
                                memset(&mbs, 0, sizeof(mbs));
                                newstart = scan - 1;
                        }
                        clen = wcrtomb(buf, OPND(s), &mbs);
                        if (clen == (size_t)-1)
                                goto toohard;
                        newlen += clen;
                        break;
                case OPLUS_:            /* things that don't break one */
                case OLPAREN:
                case ORPAREN:
                        break;
                case OQUEST_:           /* things that must be skipped */
                case OCH_:
                        offset = altoffset(scan, offset);
                        scan--;
                        do {
                                scan += OPND(s);
                                s = *scan;
                                /* assert() interferes w debug printouts */
                                if (OP(s) != (sop)O_QUEST &&
                                    OP(s) != (sop)O_CH && OP(s) != (sop)OOR2) {
                                        g->iflags |= BAD;
                                        return;
                                }
                        } while (OP(s) != (sop)O_QUEST && OP(s) != (sop)O_CH);
                        /* FALLTHROUGH */
                case OBOW:              /* things that break a sequence */
                case OEOW:
                case OBOL:
                case OEOL:
                case OBOS:
                case OEOS:
                case OWBND:
                case ONWBND:
                case O_QUEST:
                case O_CH:
                case OEND:
                        if (newlen > (sopno)g->mlen) {          /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1) {
                                        g->moffset += offset;
                                        offset = newlen;
                                } else
                                        g->moffset = offset;
                        } else {
                                if (offset > -1)
                                        offset += newlen;
                        }
                        newlen = 0;
                        break;
                case OANY:
                        if (newlen > (sopno)g->mlen) {          /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1) {
                                        g->moffset += offset;
                                        offset = newlen;
                                } else
                                        g->moffset = offset;
                        } else {
                                if (offset > -1)
                                        offset += newlen;
                        }
                        if (offset > -1)
                                offset++;
                        newlen = 0;
                        break;
                case OANYOF:            /* may or may not invalidate offset */
                        /* First, everything as OANY */
                        if (newlen > (sopno)g->mlen) {          /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1) {
                                        g->moffset += offset;
                                        offset = newlen;
                                } else
                                        g->moffset = offset;
                        } else {
                                if (offset > -1)
                                        offset += newlen;
                        }
                        if (offset > -1)
                                offset++;
                        newlen = 0;
                        break;
                toohard:
                default:
                        /* Anything here makes it impossible or too hard
                         * to calculate the offset -- so we give up;
                         * save the last known good offset, in case the
                         * must sequence doesn't occur later.
                         */
                        if (newlen > (sopno)g->mlen) {          /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1)
                                        g->moffset += offset;
                                else
                                        g->moffset = offset;
                        }
                        offset = -1;
                        newlen = 0;
                        break;
                }
        } while (OP(s) != OEND);

        if (g->mlen == 0) {             /* there isn't one */
                g->moffset = -1;
                return;
        }

        /* turn it into a character string */
        g->must = malloc((size_t)g->mlen + 1);
        if (g->must == NULL) {          /* argh; just forget it */
                g->mlen = 0;
                g->moffset = -1;
                return;
        }
        cp = g->must;
        scan = start;
        memset(&mbs, 0, sizeof(mbs));
        while (cp < g->must + g->mlen) {
                while (OP(s = *scan++) != OCHAR)
                        continue;
                clen = wcrtomb(cp, OPND(s), &mbs);
                assert(clen != (size_t)-1);
                cp += clen;
        }
        assert(cp == g->must + g->mlen);
        *cp++ = '\0';           /* just on general principles */
}

/*
 - altoffset - choose biggest offset among multiple choices
 == static int altoffset(sop *scan, int offset);
 *
 * Compute, recursively if necessary, the largest offset among multiple
 * re paths.
 */
static int
altoffset(sop *scan, int offset)
{
        int largest;
        int try;
        sop s;

        /* If we gave up already on offsets, return */
        if (offset == -1)
                return -1;

        largest = 0;
        try = 0;
        s = *scan++;
        while (OP(s) != (sop)O_QUEST && OP(s) != (sop)O_CH) {
                switch (OP(s)) {
                case OOR1:
                        if (try > largest)
                                largest = try;
                        try = 0;
                        break;
                case OQUEST_:
                case OCH_:
                        try = altoffset(scan, try);
                        if (try == -1)
                                return -1;
                        scan--;
                        do {
                                scan += OPND(s);
                                s = *scan;
                                if (OP(s) != (sop)O_QUEST &&
                                    OP(s) != (sop)O_CH && OP(s) != (sop)OOR2)
                                        return -1;
                        } while (OP(s) != (sop)O_QUEST && OP(s) != (sop)O_CH);
                        /* We must skip to the next position, or we'll
                         * leave altoffset() too early.
                         */
                        scan++;
                        break;
                case OANYOF:
                case OCHAR:
                case OANY:
                        try++;
                case OBOW:
                case OEOW:
                case OWBND:
                case ONWBND:
                case OLPAREN:
                case ORPAREN:
                case OOR2:
                        break;
                default:
                        try = -1;
                        break;
                }
                if (try == -1)
                        return -1;
                s = *scan++;
        }

        if (try > largest)
                largest = try;

        return largest+offset;
}

/*
 - computejumps - compute char jumps for BM scan
 == static void computejumps(struct parse *p, struct re_guts *g);
 *
 * This algorithm assumes g->must exists and is has size greater than
 * zero. It's based on the algorithm found on Computer Algorithms by
 * Sara Baase.
 *
 * A char jump is the number of characters one needs to jump based on
 * the value of the character from the text that was mismatched.
 */
static void
computejumps(struct parse *p, struct re_guts *g)
{
        int ch;
        int mindex;

        /* Avoid making errors worse */
        if (p->error != 0)
                return;

        g->charjump = (int *)malloc((NC_MAX + 1) * sizeof(int));
        if (g->charjump == NULL)        /* Not a fatal error */
                return;
        /* Adjust for signed chars, if necessary */
        g->charjump = &g->charjump[-(CHAR_MIN)];

        /* If the character does not exist in the pattern, the jump
         * is equal to the number of characters in the pattern.
         */
        for (ch = CHAR_MIN; ch < (CHAR_MAX + 1); ch++)
                g->charjump[ch] = g->mlen;

        /* If the character does exist, compute the jump that would
         * take us to the last character in the pattern equal to it
         * (notice that we match right to left, so that last character
         * is the first one that would be matched).
         */
        for (mindex = 0; mindex < g->mlen; mindex++)
                g->charjump[(int)g->must[mindex]] = g->mlen - mindex - 1;
}

/*
 - computematchjumps - compute match jumps for BM scan
 == static void computematchjumps(struct parse *p, struct re_guts *g);
 *
 * This algorithm assumes g->must exists and is has size greater than
 * zero. It's based on the algorithm found on Computer Algorithms by
 * Sara Baase.
 *
 * A match jump is the number of characters one needs to advance based
 * on the already-matched suffix.
 * Notice that all values here are minus (g->mlen-1), because of the way
 * the search algorithm works.
 */
static void
computematchjumps(struct parse *p, struct re_guts *g)
{
        int mindex;             /* General "must" iterator */
        int suffix;             /* Keeps track of matching suffix */
        int ssuffix;            /* Keeps track of suffixes' suffix */
        int* pmatches;          /* pmatches[k] points to the next i
                                 * such that i+1...mlen is a substring
                                 * of k+1...k+mlen-i-1
                                 */

        /* Avoid making errors worse */
        if (p->error != 0)
                return;

        pmatches = (int*) malloc(g->mlen * sizeof(int));
        if (pmatches == NULL) {
                g->matchjump = NULL;
                return;
        }

        g->matchjump = (int*) malloc(g->mlen * sizeof(int));
        if (g->matchjump == NULL) {     /* Not a fatal error */
                free(pmatches);
                return;
        }

        /* Set maximum possible jump for each character in the pattern */
        for (mindex = 0; mindex < g->mlen; mindex++)
                g->matchjump[mindex] = 2*g->mlen - mindex - 1;

        /* Compute pmatches[] */
        for (mindex = g->mlen - 1, suffix = g->mlen; mindex >= 0;
            mindex--, suffix--) {
                pmatches[mindex] = suffix;

                /* If a mismatch is found, interrupting the substring,
                 * compute the matchjump for that position. If no
                 * mismatch is found, then a text substring mismatched
                 * against the suffix will also mismatch against the
                 * substring.
                 */
                while (suffix < g->mlen
                    && g->must[mindex] != g->must[suffix]) {
                        g->matchjump[suffix] = MIN(g->matchjump[suffix],
                            g->mlen - mindex - 1);
                        suffix = pmatches[suffix];
                }
        }

        /* Compute the matchjump up to the last substring found to jump
         * to the beginning of the largest must pattern prefix matching
         * it's own suffix.
         */
        for (mindex = 0; mindex <= suffix; mindex++)
                g->matchjump[mindex] = MIN(g->matchjump[mindex],
                    g->mlen + suffix - mindex);

        ssuffix = pmatches[suffix];
        while (suffix < g->mlen) {
                while (suffix <= ssuffix && suffix < g->mlen) {
                        g->matchjump[suffix] = MIN(g->matchjump[suffix],
                            g->mlen + ssuffix - suffix);
                        suffix++;
                }
                if (suffix < g->mlen)
                        ssuffix = pmatches[ssuffix];
        }

        free(pmatches);
}

/*
 - pluscount - count + nesting
 == static sopno pluscount(struct parse *p, struct re_guts *g);
 */
static sopno                    /* nesting depth */
pluscount(struct parse *p, struct re_guts *g)
{
        sop *scan;
        sop s;
        sopno plusnest = 0;
        sopno maxnest = 0;

        if (p->error != 0)
                return(0);      /* there may not be an OEND */

        scan = g->strip + 1;
        do {
                s = *scan++;
                switch (OP(s)) {
                case OPLUS_:
                        plusnest++;
                        break;
                case O_PLUS:
                        if (plusnest > maxnest)
                                maxnest = plusnest;
                        plusnest--;
                        break;
                }
        } while (OP(s) != OEND);
        if (plusnest != 0)
                g->iflags |= BAD;
        return(maxnest);
}