bump version to 12.2.12-pve1

[ceph.git] / ceph / src / civetweb / src / third_party / duktape-1.3.0 / src-separate / duk_bi_global.c

/*
 *  Global object built-ins
 */

#include "duk_internal.h"

/*
 *  Encoding/decoding helpers
 */

/* XXX: Could add fast path (for each transform callback) with direct byte
 * lookups (no shifting) and no explicit check for x < 0x80 before table
 * lookup.
 */

/* Macros for creating and checking bitmasks for character encoding.
 * Bit number is a bit counterintuitive, but minimizes code size.
 */
#define DUK__MKBITS(a,b,c,d,e,f,g,h)  ((duk_uint8_t) ( \
        ((a) << 0) | ((b) << 1) | ((c) << 2) | ((d) << 3) | \
        ((e) << 4) | ((f) << 5) | ((g) << 6) | ((h) << 7) \
        ))
#define DUK__CHECK_BITMASK(table,cp)  ((table)[(cp) >> 3] & (1 << ((cp) & 0x07)))

/* E5.1 Section 15.1.3.3: uriReserved + uriUnescaped + '#' */
DUK_LOCAL const duk_uint8_t duk__encode_uriunescaped_table[16] = {
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x00-0x0f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x10-0x1f */
        DUK__MKBITS(0, 1, 0, 1, 1, 0, 1, 1), DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1),  /* 0x20-0x2f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 1, 0, 1, 0, 1),  /* 0x30-0x3f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1),  /* 0x40-0x4f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 0, 0, 0, 0, 1),  /* 0x50-0x5f */
        DUK__MKBITS(0, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1),  /* 0x60-0x6f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 0, 0, 0, 1, 0),  /* 0x70-0x7f */
};

/* E5.1 Section 15.1.3.4: uriUnescaped */
DUK_LOCAL const duk_uint8_t duk__encode_uricomponent_unescaped_table[16] = {
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x00-0x0f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x10-0x1f */
        DUK__MKBITS(0, 1, 0, 0, 0, 0, 0, 1), DUK__MKBITS(1, 1, 1, 0, 0, 1, 1, 0),  /* 0x20-0x2f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 0, 0, 0, 0, 0, 0),  /* 0x30-0x3f */
        DUK__MKBITS(0, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1),  /* 0x40-0x4f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 0, 0, 0, 0, 1),  /* 0x50-0x5f */
        DUK__MKBITS(0, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1),  /* 0x60-0x6f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 0, 0, 0, 1, 0),  /* 0x70-0x7f */
};

/* E5.1 Section 15.1.3.1: uriReserved + '#' */
DUK_LOCAL const duk_uint8_t duk__decode_uri_reserved_table[16] = {
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x00-0x0f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x10-0x1f */
        DUK__MKBITS(0, 0, 0, 1, 1, 0, 1, 0), DUK__MKBITS(0, 0, 0, 1, 1, 0, 0, 1),  /* 0x20-0x2f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 1, 1, 0, 1, 0, 1),  /* 0x30-0x3f */
        DUK__MKBITS(1, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x40-0x4f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x50-0x5f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x60-0x6f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x70-0x7f */
};

/* E5.1 Section 15.1.3.2: empty */
DUK_LOCAL const duk_uint8_t duk__decode_uri_component_reserved_table[16] = {
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x00-0x0f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x10-0x1f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x20-0x2f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x30-0x3f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x40-0x4f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x50-0x5f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x60-0x6f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x70-0x7f */
};

#ifdef DUK_USE_SECTION_B
/* E5.1 Section B.2.2, step 7. */
DUK_LOCAL const duk_uint8_t duk__escape_unescaped_table[16] = {
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x00-0x0f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0),  /* 0x10-0x1f */
        DUK__MKBITS(0, 0, 0, 0, 0, 0, 0, 0), DUK__MKBITS(0, 0, 1, 1, 0, 1, 1, 1),  /* 0x20-0x2f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 0, 0, 0, 0, 0, 0),  /* 0x30-0x3f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1),  /* 0x40-0x4f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 0, 0, 0, 0, 1),  /* 0x50-0x5f */
        DUK__MKBITS(0, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1),  /* 0x60-0x6f */
        DUK__MKBITS(1, 1, 1, 1, 1, 1, 1, 1), DUK__MKBITS(1, 1, 1, 0, 0, 0, 0, 0)   /* 0x70-0x7f */
};
#endif  /* DUK_USE_SECTION_B */

#undef DUK__MKBITS

typedef struct {
        duk_hthread *thr;
        duk_hstring *h_str;
        duk_bufwriter_ctx bw;
        const duk_uint8_t *p;
        const duk_uint8_t *p_start;
        const duk_uint8_t *p_end;
} duk__transform_context;

typedef void (*duk__transform_callback)(duk__transform_context *tfm_ctx, void *udata, duk_codepoint_t cp);

/* XXX: refactor and share with other code */
DUK_LOCAL duk_small_int_t duk__decode_hex_escape(const duk_uint8_t *p, duk_small_int_t n) {
        duk_small_int_t ch;
        duk_small_int_t t = 0;

        while (n > 0) {
                t = t * 16;
                ch = (duk_small_int_t) duk_hex_dectab[*p++];
                if (DUK_LIKELY(ch >= 0)) {
                        t += ch;
                } else {
                        return -1;
                }
                n--;
        }
        return t;
}

DUK_LOCAL int duk__transform_helper(duk_context *ctx, duk__transform_callback callback, void *udata) {
        duk_hthread *thr = (duk_hthread *) ctx;
        duk__transform_context tfm_ctx_alloc;
        duk__transform_context *tfm_ctx = &tfm_ctx_alloc;
        duk_codepoint_t cp;

        tfm_ctx->thr = thr;

        tfm_ctx->h_str = duk_to_hstring(ctx, 0);
        DUK_ASSERT(tfm_ctx->h_str != NULL);

        DUK_BW_INIT_PUSHBUF(thr, &tfm_ctx->bw, DUK_HSTRING_GET_BYTELEN(tfm_ctx->h_str));  /* initial size guess */

        tfm_ctx->p_start = DUK_HSTRING_GET_DATA(tfm_ctx->h_str);
        tfm_ctx->p_end = tfm_ctx->p_start + DUK_HSTRING_GET_BYTELEN(tfm_ctx->h_str);
        tfm_ctx->p = tfm_ctx->p_start;

        while (tfm_ctx->p < tfm_ctx->p_end) {
                cp = (duk_codepoint_t) duk_unicode_decode_xutf8_checked(thr, &tfm_ctx->p, tfm_ctx->p_start, tfm_ctx->p_end);
                callback(tfm_ctx, udata, cp);
        }

        DUK_BW_COMPACT(thr, &tfm_ctx->bw);

        duk_to_string(ctx, -1);
        return 1;
}

DUK_LOCAL void duk__transform_callback_encode_uri(duk__transform_context *tfm_ctx, void *udata, duk_codepoint_t cp) {
        duk_uint8_t xutf8_buf[DUK_UNICODE_MAX_XUTF8_LENGTH];
        duk_small_int_t len;
        duk_codepoint_t cp1, cp2;
        duk_small_int_t i, t;
        const duk_uint8_t *unescaped_table = (duk_uint8_t *) udata;

        /* UTF-8 encoded bytes escaped as %xx%xx%xx... -> 3 * nbytes.
         * Codepoint range is restricted so this is a slightly too large
         * but doesn't matter.
         */
        DUK_BW_ENSURE(tfm_ctx->thr, &tfm_ctx->bw, 3 * DUK_UNICODE_MAX_XUTF8_LENGTH);

        if (cp < 0) {
                goto uri_error;
        } else if ((cp < 0x80L) && DUK__CHECK_BITMASK(unescaped_table, cp)) {
                DUK_BW_WRITE_RAW_U8(tfm_ctx->thr, &tfm_ctx->bw, (duk_uint8_t) cp);
                return;
        } else if (cp >= 0xdc00L && cp <= 0xdfffL) {
                goto uri_error;
        } else if (cp >= 0xd800L && cp <= 0xdbffL) {
                /* Needs lookahead */
                if (duk_unicode_decode_xutf8(tfm_ctx->thr, &tfm_ctx->p, tfm_ctx->p_start, tfm_ctx->p_end, (duk_ucodepoint_t *) &cp2) == 0) {
                        goto uri_error;
                }
                if (!(cp2 >= 0xdc00L && cp2 <= 0xdfffL)) {
                        goto uri_error;
                }
                cp1 = cp;
                cp = ((cp1 - 0xd800L) << 10) + (cp2 - 0xdc00L) + 0x10000L;
        } else if (cp > 0x10ffffL) {
                /* Although we can allow non-BMP characters (they'll decode
                 * back into surrogate pairs), we don't allow extended UTF-8
                 * characters; they would encode to URIs which won't decode
                 * back because of strict UTF-8 checks in URI decoding.
                 * (However, we could just as well allow them here.)
                 */
                goto uri_error;
        } else {
                /* Non-BMP characters within valid UTF-8 range: encode as is.
                 * They'll decode back into surrogate pairs if the escaped
                 * output is decoded.
                 */
                ;
        }

        len = duk_unicode_encode_xutf8((duk_ucodepoint_t) cp, xutf8_buf);
        for (i = 0; i < len; i++) {
                t = (int) xutf8_buf[i];
                DUK_BW_WRITE_RAW_U8_3(tfm_ctx->thr,
                                      &tfm_ctx->bw,
                                      DUK_ASC_PERCENT,
                                      (duk_uint8_t) duk_uc_nybbles[t >> 4],
                                      (duk_uint8_t) duk_uc_nybbles[t & 0x0f]);
        }

        return;

 uri_error:
        DUK_ERROR(tfm_ctx->thr, DUK_ERR_URI_ERROR, "invalid input");
}

DUK_LOCAL void duk__transform_callback_decode_uri(duk__transform_context *tfm_ctx, void *udata, duk_codepoint_t cp) {
        const duk_uint8_t *reserved_table = (duk_uint8_t *) udata;
        duk_small_uint_t utf8_blen;
        duk_codepoint_t min_cp;
        duk_small_int_t t;  /* must be signed */
        duk_small_uint_t i;

        /* Maximum write size: XUTF8 path writes max DUK_UNICODE_MAX_XUTF8_LENGTH,
         * percent escape path writes max two times CESU-8 encoded BMP length.
         */
        DUK_BW_ENSURE(tfm_ctx->thr,
                      &tfm_ctx->bw,
                      (DUK_UNICODE_MAX_XUTF8_LENGTH >= 2 * DUK_UNICODE_MAX_CESU8_BMP_LENGTH ?
                      DUK_UNICODE_MAX_XUTF8_LENGTH : DUK_UNICODE_MAX_CESU8_BMP_LENGTH));

        if (cp == (duk_codepoint_t) '%') {
                const duk_uint8_t *p = tfm_ctx->p;
                duk_size_t left = (duk_size_t) (tfm_ctx->p_end - p);  /* bytes left */

                DUK_DDD(DUK_DDDPRINT("percent encoding, left=%ld", (long) left));

                if (left < 2) {
                        goto uri_error;
                }

                t = duk__decode_hex_escape(p, 2);
                DUK_DDD(DUK_DDDPRINT("first byte: %ld", (long) t));
                if (t < 0) {
                        goto uri_error;
                }

                if (t < 0x80) {
                        if (DUK__CHECK_BITMASK(reserved_table, t)) {
                                /* decode '%xx' to '%xx' if decoded char in reserved set */
                                DUK_ASSERT(tfm_ctx->p - 1 >= tfm_ctx->p_start);
                                DUK_BW_WRITE_RAW_U8_3(tfm_ctx->thr,
                                                      &tfm_ctx->bw,
                                                      DUK_ASC_PERCENT,
                                                      p[0],
                                                      p[1]);
                        } else {
                                DUK_BW_WRITE_RAW_U8(tfm_ctx->thr, &tfm_ctx->bw, (duk_uint8_t) t);
                        }
                        tfm_ctx->p += 2;
                        return;
                }

                /* Decode UTF-8 codepoint from a sequence of hex escapes.  The
                 * first byte of the sequence has been decoded to 't'.
                 *
                 * Note that UTF-8 validation must be strict according to the
                 * specification: E5.1 Section 15.1.3, decode algorithm step
                 * 4.d.vii.8.  URIError from non-shortest encodings is also
                 * specifically noted in the spec.
                 */

                DUK_ASSERT(t >= 0x80);
                if (t < 0xc0) {
                        /* continuation byte */
                        goto uri_error;
                } else if (t < 0xe0) {
                        /* 110x xxxx; 2 bytes */
                        utf8_blen = 2;
                        min_cp = 0x80L;
                        cp = t & 0x1f;
                } else if (t < 0xf0) {
                        /* 1110 xxxx; 3 bytes */
                        utf8_blen = 3;
                        min_cp = 0x800L;
                        cp = t & 0x0f;
                } else if (t < 0xf8) {
                        /* 1111 0xxx; 4 bytes */
                        utf8_blen = 4;
                        min_cp = 0x10000L;
                        cp = t & 0x07;
                } else {
                        /* extended utf-8 not allowed for URIs */
                        goto uri_error;
                }

                if (left < utf8_blen * 3 - 1) {
                        /* '%xx%xx...%xx', p points to char after first '%' */
                        goto uri_error;
                }

                p += 3;
                for (i = 1; i < utf8_blen; i++) {
                        /* p points to digit part ('%xy', p points to 'x') */
                        t = duk__decode_hex_escape(p, 2);
                        DUK_DDD(DUK_DDDPRINT("i=%ld utf8_blen=%ld cp=%ld t=0x%02lx",
                                             (long) i, (long) utf8_blen, (long) cp, (unsigned long) t));
                        if (t < 0) {
                                goto uri_error;
                        }
                        if ((t & 0xc0) != 0x80) {
                                goto uri_error;
                        }
                        cp = (cp << 6) + (t & 0x3f);
                        p += 3;
                }
                p--;  /* p overshoots */
                tfm_ctx->p = p;

                DUK_DDD(DUK_DDDPRINT("final cp=%ld, min_cp=%ld", (long) cp, (long) min_cp));

                if (cp < min_cp || cp > 0x10ffffL || (cp >= 0xd800L && cp <= 0xdfffL)) {
                        goto uri_error;
                }

                /* The E5.1 algorithm checks whether or not a decoded codepoint
                 * is below 0x80 and perhaps may be in the "reserved" set.
                 * This seems pointless because the single byte UTF-8 case is
                 * handled separately, and non-shortest encodings are rejected.
                 * So, 'cp' cannot be below 0x80 here, and thus cannot be in
                 * the reserved set.
                 */

                /* utf-8 validation ensures these */
                DUK_ASSERT(cp >= 0x80L && cp <= 0x10ffffL);

                if (cp >= 0x10000L) {
                        cp -= 0x10000L;
                        DUK_ASSERT(cp < 0x100000L);

                        DUK_BW_WRITE_RAW_XUTF8(tfm_ctx->thr, &tfm_ctx->bw, ((cp >> 10) + 0xd800L));
                        DUK_BW_WRITE_RAW_XUTF8(tfm_ctx->thr, &tfm_ctx->bw, ((cp & 0x03ffUL) + 0xdc00L));
                } else {
                        DUK_BW_WRITE_RAW_XUTF8(tfm_ctx->thr, &tfm_ctx->bw, cp);
                }
        } else {
                DUK_BW_WRITE_RAW_XUTF8(tfm_ctx->thr, &tfm_ctx->bw, cp);
        }
        return;

 uri_error:
        DUK_ERROR(tfm_ctx->thr, DUK_ERR_URI_ERROR, "invalid input");
}

#ifdef DUK_USE_SECTION_B
DUK_LOCAL void duk__transform_callback_escape(duk__transform_context *tfm_ctx, void *udata, duk_codepoint_t cp) {
        DUK_UNREF(udata);

        DUK_BW_ENSURE(tfm_ctx->thr, &tfm_ctx->bw, 6);

        if (cp < 0) {
                goto esc_error;
        } else if ((cp < 0x80L) && DUK__CHECK_BITMASK(duk__escape_unescaped_table, cp)) {
                DUK_BW_WRITE_RAW_U8(tfm_ctx->thr, &tfm_ctx->bw, (duk_uint8_t) cp);
        } else if (cp < 0x100L) {
                DUK_BW_WRITE_RAW_U8_3(tfm_ctx->thr,
                                      &tfm_ctx->bw,
                                      (duk_uint8_t) DUK_ASC_PERCENT,
                                      (duk_uint8_t) duk_uc_nybbles[cp >> 4],
                                      (duk_uint8_t) duk_uc_nybbles[cp & 0x0f]);
        } else if (cp < 0x10000L) {
                DUK_BW_WRITE_RAW_U8_6(tfm_ctx->thr,
                                      &tfm_ctx->bw,
                                      (duk_uint8_t) DUK_ASC_PERCENT,
                                      (duk_uint8_t) DUK_ASC_LC_U,
                                      (duk_uint8_t) duk_uc_nybbles[cp >> 12],
                                      (duk_uint8_t) duk_uc_nybbles[(cp >> 8) & 0x0f],
                                      (duk_uint8_t) duk_uc_nybbles[(cp >> 4) & 0x0f],
                                      (duk_uint8_t) duk_uc_nybbles[cp & 0x0f]);
        } else {
                /* Characters outside BMP cannot be escape()'d.  We could
                 * encode them as surrogate pairs (for codepoints inside
                 * valid UTF-8 range, but not extended UTF-8).  Because
                 * escape() and unescape() are legacy functions, we don't.
                 */
                goto esc_error;
        }

        return;

 esc_error:
        DUK_ERROR(tfm_ctx->thr, DUK_ERR_TYPE_ERROR, "invalid input");
}

DUK_LOCAL void duk__transform_callback_unescape(duk__transform_context *tfm_ctx, void *udata, duk_codepoint_t cp) {
        duk_small_int_t t;

        DUK_UNREF(udata);

        if (cp == (duk_codepoint_t) '%') {
                const duk_uint8_t *p = tfm_ctx->p;
                duk_size_t left = (duk_size_t) (tfm_ctx->p_end - p);  /* bytes left */

                if (left >= 5 && p[0] == 'u' &&
                    ((t = duk__decode_hex_escape(p + 1, 4)) >= 0)) {
                        cp = (duk_codepoint_t) t;
                        tfm_ctx->p += 5;
                } else if (left >= 2 &&
                           ((t = duk__decode_hex_escape(p, 2)) >= 0)) {
                        cp = (duk_codepoint_t) t;
                        tfm_ctx->p += 2;
                }
        }

        DUK_BW_WRITE_ENSURE_XUTF8(tfm_ctx->thr, &tfm_ctx->bw, cp);
}
#endif  /* DUK_USE_SECTION_B */

/*
 *  Eval
 *
 *  Eval needs to handle both a "direct eval" and an "indirect eval".
 *  Direct eval handling needs access to the caller's activation so that its
 *  lexical environment can be accessed.  A direct eval is only possible from
 *  Ecmascript code; an indirect eval call is possible also from C code.
 *  When an indirect eval call is made from C code, there may not be a
 *  calling activation at all which needs careful handling.
 */

DUK_INTERNAL duk_ret_t duk_bi_global_object_eval(duk_context *ctx) {
        duk_hthread *thr = (duk_hthread *) ctx;
        duk_hstring *h;
        duk_activation *act_caller;
        duk_activation *act_eval;
        duk_activation *act;
        duk_hcompiledfunction *func;
        duk_hobject *outer_lex_env;
        duk_hobject *outer_var_env;
        duk_bool_t this_to_global = 1;
        duk_small_uint_t comp_flags;

        DUK_ASSERT_TOP(ctx, 1);
        DUK_ASSERT(thr->callstack_top >= 1);  /* at least this function exists */
        DUK_ASSERT(((thr->callstack + thr->callstack_top - 1)->flags & DUK_ACT_FLAG_DIRECT_EVAL) == 0 || /* indirect eval */
                   (thr->callstack_top >= 2));  /* if direct eval, calling activation must exist */

        /*
         *  callstack_top - 1 --> this function
         *  callstack_top - 2 --> caller (may not exist)
         *
         *  If called directly from C, callstack_top might be 1.  If calling
         *  activation doesn't exist, call must be indirect.
         */

        h = duk_get_hstring(ctx, 0);
        if (!h) {
                return 1;  /* return arg as-is */
        }

        /* [ source ] */

        comp_flags = DUK_JS_COMPILE_FLAG_EVAL;
        act_eval = thr->callstack + thr->callstack_top - 1;    /* this function */
        if (thr->callstack_top >= 2) {
                /* Have a calling activation, check for direct eval (otherwise
                 * assume indirect eval.
                 */
                act_caller = thr->callstack + thr->callstack_top - 2;  /* caller */
                if ((act_caller->flags & DUK_ACT_FLAG_STRICT) &&
                    (act_eval->flags & DUK_ACT_FLAG_DIRECT_EVAL)) {
                        /* Only direct eval inherits strictness from calling code
                         * (E5.1 Section 10.1.1).
                         */
                        comp_flags |= DUK_JS_COMPILE_FLAG_STRICT;
                }
        } else {
                DUK_ASSERT((act_eval->flags & DUK_ACT_FLAG_DIRECT_EVAL) == 0);
        }
        act_caller = NULL;  /* avoid dereference after potential callstack realloc */
        act_eval = NULL;

        duk_push_hstring_stridx(ctx, DUK_STRIDX_INPUT);  /* XXX: copy from caller? */
        duk_js_compile(thr,
                       (const duk_uint8_t *) DUK_HSTRING_GET_DATA(h),
                       (duk_size_t) DUK_HSTRING_GET_BYTELEN(h),
                       comp_flags);
        func = (duk_hcompiledfunction *) duk_get_hobject(ctx, -1);
        DUK_ASSERT(func != NULL);
        DUK_ASSERT(DUK_HOBJECT_IS_COMPILEDFUNCTION((duk_hobject *) func));

        /* [ source template ] */

        /* E5 Section 10.4.2 */
        DUK_ASSERT(thr->callstack_top >= 1);
        act = thr->callstack + thr->callstack_top - 1;  /* this function */
        if (act->flags & DUK_ACT_FLAG_DIRECT_EVAL) {
                DUK_ASSERT(thr->callstack_top >= 2);
                act = thr->callstack + thr->callstack_top - 2;  /* caller */
                if (act->lex_env == NULL) {
                        DUK_ASSERT(act->var_env == NULL);
                        DUK_DDD(DUK_DDDPRINT("delayed environment initialization"));

                        /* this may have side effects, so re-lookup act */
                        duk_js_init_activation_environment_records_delayed(thr, act);
                        act = thr->callstack + thr->callstack_top - 2;
                }
                DUK_ASSERT(act->lex_env != NULL);
                DUK_ASSERT(act->var_env != NULL);

                this_to_global = 0;

                if (DUK_HOBJECT_HAS_STRICT((duk_hobject *) func)) {
                        duk_hobject *new_env;
                        duk_hobject *act_lex_env;

                        DUK_DDD(DUK_DDDPRINT("direct eval call to a strict function -> "
                                             "var_env and lex_env to a fresh env, "
                                             "this_binding to caller's this_binding"));

                        act = thr->callstack + thr->callstack_top - 2;  /* caller */
                        act_lex_env = act->lex_env;
                        act = NULL;  /* invalidated */

                        (void) duk_push_object_helper_proto(ctx,
                                                            DUK_HOBJECT_FLAG_EXTENSIBLE |
                                                            DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_DECENV),
                                                            act_lex_env);
                        new_env = duk_require_hobject(ctx, -1);
                        DUK_ASSERT(new_env != NULL);
                        DUK_DDD(DUK_DDDPRINT("new_env allocated: %!iO",
                                             (duk_heaphdr *) new_env));

                        outer_lex_env = new_env;
                        outer_var_env = new_env;

                        duk_insert(ctx, 0);  /* stash to bottom of value stack to keep new_env reachable */

                        /* compiler's responsibility */
                        DUK_ASSERT(DUK_HOBJECT_HAS_NEWENV((duk_hobject *) func));
                } else {
                        DUK_DDD(DUK_DDDPRINT("direct eval call to a non-strict function -> "
                                             "var_env and lex_env to caller's envs, "
                                             "this_binding to caller's this_binding"));

                        outer_lex_env = act->lex_env;
                        outer_var_env = act->var_env;

                        /* compiler's responsibility */
                        DUK_ASSERT(!DUK_HOBJECT_HAS_NEWENV((duk_hobject *) func));
                }
        } else {
                DUK_DDD(DUK_DDDPRINT("indirect eval call -> var_env and lex_env to "
                                     "global object, this_binding to global object"));

                this_to_global = 1;
                outer_lex_env = thr->builtins[DUK_BIDX_GLOBAL_ENV];
                outer_var_env = thr->builtins[DUK_BIDX_GLOBAL_ENV];
        }
        act = NULL;

        duk_js_push_closure(thr, func, outer_var_env, outer_lex_env);

        /* [ source template closure ] */

        if (this_to_global) {
                DUK_ASSERT(thr->builtins[DUK_BIDX_GLOBAL] != NULL);
                duk_push_hobject_bidx(ctx, DUK_BIDX_GLOBAL);
        } else {
                duk_tval *tv;
                DUK_ASSERT(thr->callstack_top >= 2);
                act = thr->callstack + thr->callstack_top - 2;  /* caller */
                tv = thr->valstack + act->idx_bottom - 1;  /* this is just beneath bottom */
                DUK_ASSERT(tv >= thr->valstack);
                duk_push_tval(ctx, tv);
        }

        DUK_DDD(DUK_DDDPRINT("eval -> lex_env=%!iO, var_env=%!iO, this_binding=%!T",
                             (duk_heaphdr *) outer_lex_env,
                             (duk_heaphdr *) outer_var_env,
                             (duk_tval *) duk_get_tval(ctx, -1)));

        /* [ source template closure this ] */

        duk_call_method(ctx, 0);

        /* [ source template result ] */

        return 1;
}

/*
 *  Parsing of ints and floats
 */

DUK_INTERNAL duk_ret_t duk_bi_global_object_parse_int(duk_context *ctx) {
        duk_bool_t strip_prefix;
        duk_int32_t radix;
        duk_small_uint_t s2n_flags;

        DUK_ASSERT_TOP(ctx, 2);
        duk_to_string(ctx, 0);

        strip_prefix = 1;
        radix = duk_to_int32(ctx, 1);
        if (radix != 0) {
                if (radix < 2 || radix > 36) {
                        goto ret_nan;
                }
                /* For octal, setting strip_prefix=0 is not necessary, as zero
                 * is tolerated anyway:
                 *
                 *   parseInt('123', 8) === parseInt('0123', 8)     with or without strip_prefix
                 *   parseInt('123', 16) === parseInt('0x123', 16)  requires strip_prefix = 1
                 */
                if (radix != 16) {
                        strip_prefix = 0;
                }
        } else {
                radix = 10;
        }

        s2n_flags = DUK_S2N_FLAG_TRIM_WHITE |
                    DUK_S2N_FLAG_ALLOW_GARBAGE |
                    DUK_S2N_FLAG_ALLOW_PLUS |
                    DUK_S2N_FLAG_ALLOW_MINUS |
                    DUK_S2N_FLAG_ALLOW_LEADING_ZERO |
#ifdef DUK_USE_OCTAL_SUPPORT
                    (strip_prefix ? (DUK_S2N_FLAG_ALLOW_AUTO_HEX_INT | DUK_S2N_FLAG_ALLOW_AUTO_OCT_INT) : 0)
#else
                    (strip_prefix ? DUK_S2N_FLAG_ALLOW_AUTO_HEX_INT : 0)
#endif
                    ;

        duk_dup(ctx, 0);
        duk_numconv_parse(ctx, radix, s2n_flags);
        return 1;

 ret_nan:
        duk_push_nan(ctx);
        return 1;
}

DUK_INTERNAL duk_ret_t duk_bi_global_object_parse_float(duk_context *ctx) {
        duk_small_uint_t s2n_flags;
        duk_int32_t radix;

        DUK_ASSERT_TOP(ctx, 1);
        duk_to_string(ctx, 0);

        radix = 10;

        /* XXX: check flags */
        s2n_flags = DUK_S2N_FLAG_TRIM_WHITE |
                    DUK_S2N_FLAG_ALLOW_EXP |
                    DUK_S2N_FLAG_ALLOW_GARBAGE |
                    DUK_S2N_FLAG_ALLOW_PLUS |
                    DUK_S2N_FLAG_ALLOW_MINUS |
                    DUK_S2N_FLAG_ALLOW_INF |
                    DUK_S2N_FLAG_ALLOW_FRAC |
                    DUK_S2N_FLAG_ALLOW_NAKED_FRAC |
                    DUK_S2N_FLAG_ALLOW_EMPTY_FRAC |
                    DUK_S2N_FLAG_ALLOW_LEADING_ZERO;

        duk_numconv_parse(ctx, radix, s2n_flags);
        return 1;
}

/*
 *  Number checkers
 */

DUK_INTERNAL duk_ret_t duk_bi_global_object_is_nan(duk_context *ctx) {
        duk_double_t d = duk_to_number(ctx, 0);
        duk_push_boolean(ctx, DUK_ISNAN(d));
        return 1;
}

DUK_INTERNAL duk_ret_t duk_bi_global_object_is_finite(duk_context *ctx) {
        duk_double_t d = duk_to_number(ctx, 0);
        duk_push_boolean(ctx, DUK_ISFINITE(d));
        return 1;
}

/*
 *  URI handling
 */

DUK_INTERNAL duk_ret_t duk_bi_global_object_decode_uri(duk_context *ctx) {
        return duk__transform_helper(ctx, duk__transform_callback_decode_uri, (void *) duk__decode_uri_reserved_table);
}

DUK_INTERNAL duk_ret_t duk_bi_global_object_decode_uri_component(duk_context *ctx) {
        return duk__transform_helper(ctx, duk__transform_callback_decode_uri, (void *) duk__decode_uri_component_reserved_table);
}

DUK_INTERNAL duk_ret_t duk_bi_global_object_encode_uri(duk_context *ctx) {
        return duk__transform_helper(ctx, duk__transform_callback_encode_uri, (void *) duk__encode_uriunescaped_table);
}

DUK_INTERNAL duk_ret_t duk_bi_global_object_encode_uri_component(duk_context *ctx) {
        return duk__transform_helper(ctx, duk__transform_callback_encode_uri, (void *) duk__encode_uricomponent_unescaped_table);
}

#ifdef DUK_USE_SECTION_B
DUK_INTERNAL duk_ret_t duk_bi_global_object_escape(duk_context *ctx) {
        return duk__transform_helper(ctx, duk__transform_callback_escape, (void *) NULL);
}

DUK_INTERNAL duk_ret_t duk_bi_global_object_unescape(duk_context *ctx) {
        return duk__transform_helper(ctx, duk__transform_callback_unescape, (void *) NULL);
}
#else  /* DUK_USE_SECTION_B */
DUK_INTERNAL duk_ret_t duk_bi_global_object_escape(duk_context *ctx) {
        DUK_UNREF(ctx);
        return DUK_RET_UNSUPPORTED_ERROR;
}

DUK_INTERNAL duk_ret_t duk_bi_global_object_unescape(duk_context *ctx) {
        DUK_UNREF(ctx);
        return DUK_RET_UNSUPPORTED_ERROR;
}
#endif  /* DUK_USE_SECTION_B */

#if defined(DUK_USE_BROWSER_LIKE) && (defined(DUK_USE_FILE_IO) || defined(DUK_USE_DEBUGGER_SUPPORT))
DUK_INTERNAL duk_ret_t duk_bi_global_object_print_helper(duk_context *ctx) {
        duk_hthread *thr = (duk_hthread *) ctx;
        duk_int_t magic;
        duk_idx_t nargs;
        const duk_uint8_t *buf;
        duk_size_t sz_buf;
        const char nl = (const char) DUK_ASC_LF;
#ifndef DUK_USE_PREFER_SIZE
        duk_uint8_t buf_stack[256];
#endif
#ifdef DUK_USE_FILE_IO
        duk_file *f_out;
#endif

        magic = duk_get_current_magic(ctx);
        DUK_UNREF(magic);

        nargs = duk_get_top(ctx);

        /* If argument count is 1 and first argument is a buffer, write the buffer
         * as raw data into the file without a newline; this allows exact control
         * over stdout/stderr without an additional entrypoint (useful for now).
         *
         * Otherwise current print/alert semantics are to ToString() coerce
         * arguments, join them with a single space, and append a newline.
         */

        if (nargs == 1 && duk_is_buffer(ctx, 0)) {
                buf = (const duk_uint8_t *) duk_get_buffer(ctx, 0, &sz_buf);
                DUK_ASSERT(buf != NULL);
        } else if (nargs > 0) {
#ifdef DUK_USE_PREFER_SIZE
                /* Compact but lots of churn. */
                duk_push_hstring_stridx(thr, DUK_STRIDX_SPACE);
                duk_insert(ctx, 0);
                duk_join(ctx, nargs);
                duk_push_string(thr, "\n");
                duk_concat(ctx, 2);
                buf = (const duk_uint8_t *) duk_get_lstring(ctx, -1, &sz_buf);
                DUK_ASSERT(buf != NULL);
#else  /* DUK_USE_PREFER_SIZE */
                /* Higher footprint, less churn. */
                duk_idx_t i;
                duk_size_t sz_str;
                const duk_uint8_t *p_str;
                duk_uint8_t *p;

                sz_buf = (duk_size_t) nargs;  /* spaces (nargs - 1) + newline */
                for (i = 0; i < nargs; i++) {
                        (void) duk_to_lstring(ctx, i, &sz_str);
                        sz_buf += sz_str;
                }

                if (sz_buf <= sizeof(buf_stack)) {
                        buf = (const duk_uint8_t *) buf_stack;
                } else {
                        buf = (const duk_uint8_t *) duk_push_fixed_buffer(ctx, sz_buf);
                        DUK_ASSERT(buf != NULL);
                }

                p = (duk_uint8_t *) buf;
                for (i = 0; i < nargs; i++) {
                        p_str = (const duk_uint8_t *) duk_get_lstring(ctx, i, &sz_str);
                        DUK_ASSERT(p_str != NULL);
                        DUK_MEMCPY((void *) p, (const void *) p_str, sz_str);
                        p += sz_str;
                        *p++ = (duk_uint8_t) (i == nargs - 1 ? DUK_ASC_LF : DUK_ASC_SPACE);
                }
                DUK_ASSERT((const duk_uint8_t *) p == buf + sz_total);
#endif  /* DUK_USE_PREFER_SIZE */
        } else {
                buf = (const duk_uint8_t *) &nl;
                sz_buf = 1;
        }

        /* 'buf' contains the string to write, 'sz_buf' contains the length
         * (which may be zero).
         */
        DUK_ASSERT(buf != NULL);

        if (sz_buf == 0) {
                return 0;
        }

#ifdef DUK_USE_FILE_IO
        f_out = (magic ? DUK_STDERR : DUK_STDOUT);
        DUK_FWRITE((const void *) buf, 1, (size_t) sz_buf, f_out);
        DUK_FFLUSH(f_out);
#endif

#if defined(DUK_USE_DEBUGGER_SUPPORT) && defined(DUK_USE_DEBUGGER_FWD_PRINTALERT)
        if (DUK_HEAP_IS_DEBUGGER_ATTACHED(thr->heap)) {
                duk_debug_write_notify(thr, magic ? DUK_DBG_CMD_ALERT : DUK_DBG_CMD_PRINT);
                duk_debug_write_string(thr, (const char *) buf, sz_buf);
                duk_debug_write_eom(thr);
        }
#endif
        return 0;
}
#elif defined(DUK_USE_BROWSER_LIKE)  /* print provider */
DUK_INTERNAL duk_ret_t duk_bi_global_object_print_helper(duk_context *ctx) {
        DUK_UNREF(ctx);
        return 0;
}
#else  /* print provider */
DUK_INTERNAL duk_ret_t duk_bi_global_object_print_helper(duk_context *ctx) {
        DUK_UNREF(ctx);
        return DUK_RET_UNSUPPORTED_ERROR;
}
#endif  /* print provider */

/*
 *  CommonJS require() and modules support
 */

#if defined(DUK_USE_COMMONJS_MODULES)
DUK_LOCAL void duk__bi_global_resolve_module_id(duk_context *ctx, const char *req_id, const char *mod_id) {
        duk_hthread *thr = (duk_hthread *) ctx;
        duk_size_t mod_id_len;
        duk_size_t req_id_len;
        duk_uint8_t buf_in[DUK_BI_COMMONJS_MODULE_ID_LIMIT];
        duk_uint8_t buf_out[DUK_BI_COMMONJS_MODULE_ID_LIMIT];
        duk_uint8_t *p;
        duk_uint8_t *q;

        DUK_ASSERT(req_id != NULL);
        /* mod_id may be NULL */
        DUK_ASSERT(sizeof(buf_out) >= sizeof(buf_in));  /* bound checking requires this */

        /*
         *  A few notes on the algorithm:
         *
         *    - Terms are not allowed to begin with a period unless the term
         *      is either '.' or '..'.  This simplifies implementation (and
         *      is within CommonJS modules specification).
         *
         *    - There are few output bound checks here.  This is on purpose:
         *      we check the input length and rely on the output never being
         *      longer than the input, so we cannot run out of output space.
         *
         *    - Non-ASCII characters are processed as individual bytes and
         *      need no special treatment.  However, U+0000 terminates the
         *      algorithm; this is not an issue because U+0000 is not a
         *      desirable term character anyway.
         */

        /*
         *  Set up the resolution input which is the requested ID directly
         *  (if absolute or no current module path) or with current module
         *  ID prepended (if relative and current module path exists).
         *
         *  Suppose current module is 'foo/bar' and relative path is './quux'.
         *  The 'bar' component must be replaced so the initial input here is
         *  'foo/bar/.././quux'.
         */

        req_id_len = DUK_STRLEN(req_id);
        if (mod_id != NULL && req_id[0] == '.') {
                mod_id_len = DUK_STRLEN(mod_id);
                if (mod_id_len + 4 + req_id_len + 1 >= sizeof(buf_in)) {
                        DUK_DD(DUK_DDPRINT("resolve error: current and requested module ID don't fit into resolve input buffer"));
                        goto resolve_error;
                }
                (void) DUK_SNPRINTF((char *) buf_in, sizeof(buf_in), "%s/../%s", (const char *) mod_id, (const char *) req_id);
        } else {
                if (req_id_len + 1 >= sizeof(buf_in)) {
                        DUK_DD(DUK_DDPRINT("resolve error: requested module ID doesn't fit into resolve input buffer"));
                        goto resolve_error;
                }
                (void) DUK_SNPRINTF((char *) buf_in, sizeof(buf_in), "%s", (const char *) req_id);
        }
        buf_in[sizeof(buf_in) - 1] = (duk_uint8_t) 0;

        DUK_DDD(DUK_DDDPRINT("input module id: '%s'", (const char *) buf_in));

        /*
         *  Resolution loop.  At the top of the loop we're expecting a valid
         *  term: '.', '..', or a non-empty identifier not starting with a period.
         */

        p = buf_in;
        q = buf_out;
        for (;;) {
                duk_uint_fast8_t c;

                /* Here 'p' always points to the start of a term. */
                DUK_DDD(DUK_DDDPRINT("resolve loop top: p -> '%s', q=%p, buf_out=%p",
                                     (const char *) p, (void *) q, (void *) buf_out));

                c = *p++;
                if (DUK_UNLIKELY(c == 0)) {
                        DUK_DD(DUK_DDPRINT("resolve error: requested ID must end with a non-empty term"));
                        goto resolve_error;
                } else if (DUK_UNLIKELY(c == '.')) {
                        c = *p++;
                        if (c == '/') {
                                /* Term was '.' and is eaten entirely (including dup slashes). */
                                goto eat_dup_slashes;
                        }
                        if (c == '.' && *p == '/') {
                                /* Term was '..', backtrack resolved name by one component.
                                 *  q[-1] = previous slash (or beyond start of buffer)
                                 *  q[-2] = last char of previous component (or beyond start of buffer)
                                 */
                                p++;  /* eat (first) input slash */
                                DUK_ASSERT(q >= buf_out);
                                if (q == buf_out) {
                                        DUK_DD(DUK_DDPRINT("resolve error: term was '..' but nothing to backtrack"));
                                        goto resolve_error;
                                }
                                DUK_ASSERT(*(q - 1) == '/');
                                q--;  /* backtrack to last output slash */
                                for (;;) {
                                        /* Backtrack to previous slash or start of buffer. */
                                        DUK_ASSERT(q >= buf_out);
                                        if (q == buf_out) {
                                                break;
                                        }
                                        if (*(q - 1) == '/') {
                                                break;
                                        }
                                        q--;
                                }
                                goto eat_dup_slashes;
                        }
                        DUK_DD(DUK_DDPRINT("resolve error: term begins with '.' but is not '.' or '..' (not allowed now)"));
                        goto resolve_error;
                } else if (DUK_UNLIKELY(c == '/')) {
                        /* e.g. require('/foo'), empty terms not allowed */
                        DUK_DD(DUK_DDPRINT("resolve error: empty term (not allowed now)"));
                        goto resolve_error;
                } else {
                        for (;;) {
                                /* Copy term name until end or '/'. */
                                *q++ = c;
                                c = *p++;
                                if (DUK_UNLIKELY(c == 0)) {
                                        goto loop_done;
                                } else if (DUK_UNLIKELY(c == '/')) {
                                        *q++ = '/';
                                        break;
                                } else {
                                        /* write on next loop */
                                }
                        }
                }

         eat_dup_slashes:
                for (;;) {
                        /* eat dup slashes */
                        c = *p;
                        if (DUK_LIKELY(c != '/')) {
                                break;
                        }
                        p++;
                }
        }
 loop_done:

        duk_push_lstring(ctx, (const char *) buf_out, (size_t) (q - buf_out));
        return;

 resolve_error:
        DUK_ERROR(thr, DUK_ERR_TYPE_ERROR, "cannot resolve module id: %s", (const char *) req_id);
}
#endif  /* DUK_USE_COMMONJS_MODULES */

#if defined(DUK_USE_COMMONJS_MODULES)
DUK_INTERNAL duk_ret_t duk_bi_global_object_require(duk_context *ctx) {
        const char *str_req_id;  /* requested identifier */
        const char *str_mod_id;  /* require.id of current module */
        duk_int_t pcall_rc;

        /* NOTE: we try to minimize code size by avoiding unnecessary pops,
         * so the stack looks a bit cluttered in this function.  DUK_ASSERT_TOP()
         * assertions are used to ensure stack configuration is correct at each
         * step.
         */

        /*
         *  Resolve module identifier into canonical absolute form.
         */

        str_req_id = duk_require_string(ctx, 0);
        duk_push_current_function(ctx);
        duk_get_prop_stridx(ctx, -1, DUK_STRIDX_ID);
        str_mod_id = duk_get_string(ctx, 2);  /* ignore non-strings */
        DUK_DDD(DUK_DDDPRINT("resolve module id: requested=%!T, currentmodule=%!T",
                             (duk_tval *) duk_get_tval(ctx, 0),
                             (duk_tval *) duk_get_tval(ctx, 2)));
        duk__bi_global_resolve_module_id(ctx, str_req_id, str_mod_id);
        str_req_id = NULL;
        str_mod_id = NULL;
        DUK_DDD(DUK_DDDPRINT("resolved module id: requested=%!T, currentmodule=%!T, result=%!T",
                             (duk_tval *) duk_get_tval(ctx, 0),
                             (duk_tval *) duk_get_tval(ctx, 2),
                             (duk_tval *) duk_get_tval(ctx, 3)));

        /* [ requested_id require require.id resolved_id ] */
        DUK_ASSERT_TOP(ctx, 4);

        /*
         *  Cached module check.
         *
         *  If module has been loaded or its loading has already begun without
         *  finishing, return the same cached value ('exports').  The value is
         *  registered when module load starts so that circular references can
         *  be supported to some extent.
         */

        /* [ requested_id require require.id resolved_id ] */
        DUK_ASSERT_TOP(ctx, 4);

        duk_push_hobject_bidx(ctx, DUK_BIDX_DUKTAPE);
        duk_get_prop_stridx(ctx, 4, DUK_STRIDX_MOD_LOADED);  /* Duktape.modLoaded */
        (void) duk_require_hobject(ctx, 5);

        /* [ requested_id require require.id resolved_id Duktape Duktape.modLoaded ] */
        DUK_ASSERT_TOP(ctx, 6);

        duk_dup(ctx, 3);
        if (duk_get_prop(ctx, 5)) {
                /* [ requested_id require require.id resolved_id Duktape Duktape.modLoaded Duktape.modLoaded[id] ] */
                DUK_DD(DUK_DDPRINT("module already loaded: %!T",
                                   (duk_tval *) duk_get_tval(ctx, 3)));
                duk_get_prop_stridx(ctx, -1, DUK_STRIDX_EXPORTS);  /* return module.exports */
                return 1;
        }

        /* [ requested_id require require.id resolved_id Duktape Duktape.modLoaded undefined ] */
        DUK_ASSERT_TOP(ctx, 7);

        /*
         *  Module not loaded (and loading not started previously).
         *
         *  Create a new require() function with 'id' set to resolved ID
         *  of module being loaded.  Also create 'exports' and 'module'
         *  tables but don't register exports to the loaded table yet.
         *  We don't want to do that unless the user module search callbacks
         *  succeeds in finding the module.
         */

        DUK_DD(DUK_DDPRINT("module not yet loaded: %!T",
                           (duk_tval *) duk_get_tval(ctx, 3)));

        /* Fresh require: require.id is left configurable (but not writable)
         * so that is not easy to accidentally tweak it, but it can still be
         * done with Object.defineProperty().
         *
         * XXX: require.id could also be just made non-configurable, as there
         * is no practical reason to touch it.
         */
        duk_push_c_function(ctx, duk_bi_global_object_require, 1 /*nargs*/);
        duk_dup(ctx, 3);
        duk_xdef_prop_stridx(ctx, 7, DUK_STRIDX_ID, DUK_PROPDESC_FLAGS_C);  /* a fresh require() with require.id = resolved target module id */

        /* Module table:
         * - module.exports: initial exports table (may be replaced by user)
         * - module.id is non-writable and non-configurable, as the CommonJS
         *   spec suggests this if possible.
         */
        duk_push_object(ctx);  /* exports */
        duk_push_object(ctx);  /* module */
        duk_dup(ctx, -2);
        duk_xdef_prop_stridx(ctx, 9, DUK_STRIDX_EXPORTS, DUK_PROPDESC_FLAGS_WC);  /* module.exports = exports */
        duk_dup(ctx, 3);  /* resolved id: require(id) must return this same module */
        duk_xdef_prop_stridx(ctx, 9, DUK_STRIDX_ID, DUK_PROPDESC_FLAGS_NONE);  /* module.id = resolved_id */
        duk_compact(ctx, 9);  /* module table remains registered to modLoaded, minimize its size */

        /* [ requested_id require require.id resolved_id Duktape Duktape.modLoaded undefined fresh_require exports module ] */
        DUK_ASSERT_TOP(ctx, 10);

        /* Register the module table early to modLoaded[] so that we can
         * support circular references even in modSearch().  If an error
         * is thrown, we'll delete the reference.
         */
        duk_dup(ctx, 3);
        duk_dup(ctx, 9);
        duk_put_prop(ctx, 5);  /* Duktape.modLoaded[resolved_id] = module */

        /*
         *  Call user provided module search function and build the wrapped
         *  module source code (if necessary).  The module search function
         *  can be used to implement pure Ecmacsript, pure C, and mixed
         *  Ecmascript/C modules.
         *
         *  The module search function can operate on the exports table directly
         *  (e.g. DLL code can register values to it).  It can also return a
         *  string which is interpreted as module source code (if a non-string
         *  is returned the module is assumed to be a pure C one).  If a module
         *  cannot be found, an error must be thrown by the user callback.
         *
         *  Because Duktape.modLoaded[] already contains the module being
         *  loaded, circular references for C modules should also work
         *  (although expected to be quite rare).
         */

        duk_push_string(ctx, "(function(require,exports,module){");

        /* Duktape.modSearch(resolved_id, fresh_require, exports, module). */
        duk_get_prop_stridx(ctx, 4, DUK_STRIDX_MOD_SEARCH);  /* Duktape.modSearch */
        duk_dup(ctx, 3);
        duk_dup(ctx, 7);
        duk_dup(ctx, 8);
        duk_dup(ctx, 9);  /* [ ... Duktape.modSearch resolved_id fresh_require exports module ] */
        pcall_rc = duk_pcall(ctx, 4 /*nargs*/);  /* -> [ ... source ] */
        DUK_ASSERT_TOP(ctx, 12);

        if (pcall_rc != DUK_EXEC_SUCCESS) {
                /* Delete entry in Duktape.modLoaded[] and rethrow. */
                goto delete_rethrow;
        }

        /* If user callback did not return source code, module loading
         * is finished (user callback initialized exports table directly).
         */
        if (!duk_is_string(ctx, 11)) {
                /* User callback did not return source code, so module loading
                 * is finished: just update modLoaded with final module.exports
                 * and we're done.
                 */
                goto return_exports;
        }

        /* Finish the wrapped module source.  Force resolved module ID as the
         * fileName so it gets set for functions defined within a module.  This
         * also ensures loggers created within the module get the module ID as
         * their default logger name.
         */
        duk_push_string(ctx, "})");
        duk_concat(ctx, 3);
        duk_dup(ctx, 3);  /* resolved module ID for fileName */
        duk_eval_raw(ctx, NULL, 0, DUK_COMPILE_EVAL);

        /* XXX: The module wrapper function is currently anonymous and is shown
         * in stack traces.  It would be nice to force it to match the module
         * name (perhaps just the cleaned up last term).  At the moment 'name'
         * is write protected so we can't change it directly.  Note that we must
         * not introduce an actual name binding into the function scope (which
         * is usually the case with a named function) because it would affect
         * the scope seen by the module and shadow accesses to globals of the
         * same name.
         */

        /*
         *  Call the wrapped module function.
         *
         *  Use a protected call so that we can update Duktape.modLoaded[resolved_id]
         *  even if the module throws an error.
         */

        /* [ requested_id require require.id resolved_id Duktape Duktape.modLoaded undefined fresh_require exports module mod_func ] */
        DUK_ASSERT_TOP(ctx, 11);

        duk_dup(ctx, 8);  /* exports (this binding) */
        duk_dup(ctx, 7);  /* fresh require (argument) */
        duk_get_prop_stridx(ctx, 9, DUK_STRIDX_EXPORTS);  /* relookup exports from module.exports in case it was changed by modSearch */
        duk_dup(ctx, 9);  /* module (argument) */

        /* [ requested_id require require.id resolved_id Duktape Duktape.modLoaded undefined fresh_require exports module mod_func exports fresh_require exports module ] */
        DUK_ASSERT_TOP(ctx, 15);

        pcall_rc = duk_pcall_method(ctx, 3 /*nargs*/);
        if (pcall_rc != DUK_EXEC_SUCCESS) {
                /* Module loading failed.  Node.js will forget the module
                 * registration so that another require() will try to load
                 * the module again.  Mimic that behavior.
                 */
                goto delete_rethrow;
        }

        /* [ requested_id require require.id resolved_id Duktape Duktape.modLoaded undefined fresh_require exports module result(ignored) ] */
        DUK_ASSERT_TOP(ctx, 11);

        /* fall through */

 return_exports:
        duk_get_prop_stridx(ctx, 9, DUK_STRIDX_EXPORTS);
        return 1;  /* return module.exports */

 delete_rethrow:
        duk_dup(ctx, 3);
        duk_del_prop(ctx, 5);  /* delete Duktape.modLoaded[resolved_id] */
        duk_throw(ctx);  /* rethrow original error */
        return 0;  /* not reachable */
}
#else
DUK_INTERNAL duk_ret_t duk_bi_global_object_require(duk_context *ctx) {
        DUK_UNREF(ctx);
        return DUK_RET_UNSUPPORTED_ERROR;
}
#endif  /* DUK_USE_COMMONJS_MODULES */