duktape-1.5.2/src-separate/duk_api_stack.c

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/*
 *  API calls related to general value stack manipulation: resizing the value
 *  stack, pushing and popping values, type checking and reading values,
 *  coercing values, etc.
 *
 *  Also contains internal functions (such as duk_get_tval()), defined
 *  in duk_api_internal.h, with semantics similar to the public API.
 */
 
/* XXX: repetition of stack pre-checks -> helper or macro or inline */
/* XXX: shared api error strings, and perhaps even throw code for rare cases? */
 
#include "duk_internal.h"
 
/*
 *  Forward declarations
 */
 
DUK_LOCAL_DECL duk_idx_t duk__push_c_function_raw(duk_context *ctx, duk_c_function func, duk_idx_t nargs, duk_uint_t flags);
 
/*
 *  Global state for working around missing variadic macros
 */
 
#ifndef DUK_USE_VARIADIC_MACROS
DUK_EXTERNAL const char *duk_api_global_filename = NULL;
DUK_EXTERNAL duk_int_t duk_api_global_line = 0;
#endif
 
/*
 *  Misc helpers
 */
 
/* Check that there's room to push one value. */
#if defined(DUK_USE_VALSTACK_UNSAFE)
/* Faster but value stack overruns are memory unsafe. */
#define DUK__CHECK_SPACE() do { \
        DUK_ASSERT(!(thr->valstack_top >= thr->valstack_end)); \
    } while (0)
#else
#define DUK__CHECK_SPACE() do { \
        if (DUK_UNLIKELY(thr->valstack_top >= thr->valstack_end)) { \
            DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK); \
        } \
    } while (0)
#endif
 
DUK_LOCAL_DECL duk_heaphdr *duk__get_tagged_heaphdr_raw(duk_context *ctx, duk_idx_t index, duk_uint_t tag);
 
DUK_LOCAL duk_int_t duk__api_coerce_d2i(duk_context *ctx, duk_idx_t index, duk_bool_t require) {
    duk_hthread *thr;
    duk_tval *tv;
    duk_small_int_t c;
    duk_double_t d;
 
    thr = (duk_hthread *) ctx;
 
    tv = duk_get_tval(ctx, index);
    if (tv == NULL) {
        goto error_notnumber;
    }
 
    /*
     *  Special cases like NaN and +/- Infinity are handled explicitly
     *  because a plain C coercion from double to int handles these cases
     *  in undesirable ways.  For instance, NaN may coerce to INT_MIN
     *  (not zero), and INT_MAX + 1 may coerce to INT_MIN (not INT_MAX).
     *
     *  This double-to-int coercion differs from ToInteger() because it
     *  has a finite range (ToInteger() allows e.g. +/- Infinity).  It
     *  also differs from ToInt32() because the INT_MIN/INT_MAX clamping
     *  depends on the size of the int type on the platform.  In particular,
     *  on platforms with a 64-bit int type, the full range is allowed.
     */
 
#if defined(DUK_USE_FASTINT)
    if (DUK_TVAL_IS_FASTINT(tv)) {
        duk_int64_t t = DUK_TVAL_GET_FASTINT(tv);
#if (DUK_INT_MAX <= 0x7fffffffL)
        /* Clamping only necessary for 32-bit ints. */
        if (t < DUK_INT_MIN) {
            t = DUK_INT_MIN;
        } else if (t > DUK_INT_MAX) {
            t = DUK_INT_MAX;
        }
#endif
        return (duk_int_t) t;
    }
#endif
 
    if (DUK_TVAL_IS_NUMBER(tv)) {
        d = DUK_TVAL_GET_NUMBER(tv);
        c = (duk_small_int_t) DUK_FPCLASSIFY(d);
        if (c == DUK_FP_NAN) {
            return 0;
        } else if (d < (duk_double_t) DUK_INT_MIN) {
            /* covers -Infinity */
            return DUK_INT_MIN;
        } else if (d > (duk_double_t) DUK_INT_MAX) {
            /* covers +Infinity */
            return DUK_INT_MAX;
        } else {
            /* coerce towards zero */
            return (duk_int_t) d;
        }
    }
 
 error_notnumber:
 
    if (require) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "number", DUK_STR_NOT_NUMBER);
        /* not reachable */
    }
    return 0;
}
 
DUK_LOCAL duk_uint_t duk__api_coerce_d2ui(duk_context *ctx, duk_idx_t index, duk_bool_t require) {
    duk_hthread *thr;
    duk_tval *tv;
    duk_small_int_t c;
    duk_double_t d;
 
    /* Same as above but for unsigned int range. */
 
    thr = (duk_hthread *) ctx;
 
    tv = duk_get_tval(ctx, index);
    if (tv == NULL) {
        goto error_notnumber;
    }
 
#if defined(DUK_USE_FASTINT)
    if (DUK_TVAL_IS_FASTINT(tv)) {
        duk_int64_t t = DUK_TVAL_GET_FASTINT(tv);
        if (t < 0) {
            t = 0;
        }
#if (DUK_UINT_MAX <= 0xffffffffUL)
        /* Clamping only necessary for 32-bit ints. */
        else if (t > DUK_UINT_MAX) {
            t = DUK_UINT_MAX;
        }
#endif
        return (duk_uint_t) t;
    }
#endif
 
    if (DUK_TVAL_IS_NUMBER(tv)) {
        d = DUK_TVAL_GET_NUMBER(tv);
        c = (duk_small_int_t) DUK_FPCLASSIFY(d);
        if (c == DUK_FP_NAN) {
            return 0;
        } else if (d < 0.0) {
            /* covers -Infinity */
            return (duk_uint_t) 0;
        } else if (d > (duk_double_t) DUK_UINT_MAX) {
            /* covers +Infinity */
            return (duk_uint_t) DUK_UINT_MAX;
        } else {
            /* coerce towards zero */
            return (duk_uint_t) d;
        }
    }
 
 error_notnumber:
 
    if (require) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "number", DUK_STR_NOT_NUMBER);
        /* not reachable */
    }
    return 0;
}
 
/*
 *  Stack index validation/normalization and getting a stack duk_tval ptr.
 *
 *  These are called by many API entrypoints so the implementations must be
 *  fast and "inlined".
 *
 *  There's some repetition because of this; keep the functions in sync.
 */
 
DUK_EXTERNAL duk_idx_t duk_normalize_index(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_uidx_t vs_size;
    duk_uidx_t uindex;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(DUK_INVALID_INDEX < 0);
 
    /* Care must be taken to avoid pointer wrapping in the index
     * validation.  For instance, on a 32-bit platform with 8-byte
     * duk_tval the index 0x20000000UL would wrap the memory space
     * once.
     */
 
    /* Assume value stack sizes (in elements) fits into duk_idx_t. */
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    vs_size = (duk_uidx_t) (thr->valstack_top - thr->valstack_bottom);
    DUK_ASSERT_DISABLE(vs_size >= 0);  /* unsigned */
 
    if (index < 0) {
        uindex = vs_size + (duk_uidx_t) index;
    } else {
        /* since index non-negative */
        DUK_ASSERT(index != DUK_INVALID_INDEX);
        uindex = (duk_uidx_t) index;
    }
 
    /* DUK_INVALID_INDEX won't be accepted as a valid index. */
    DUK_ASSERT(vs_size + (duk_uidx_t) DUK_INVALID_INDEX >= vs_size);
 
    if (DUK_LIKELY(uindex < vs_size)) {
        return (duk_idx_t) uindex;
    }
    return DUK_INVALID_INDEX;
}
 
DUK_EXTERNAL duk_idx_t duk_require_normalize_index(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_uidx_t vs_size;
    duk_uidx_t uindex;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(DUK_INVALID_INDEX < 0);
 
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    vs_size = (duk_uidx_t) (thr->valstack_top - thr->valstack_bottom);
    DUK_ASSERT_DISABLE(vs_size >= 0);  /* unsigned */
 
    if (index < 0) {
        uindex = vs_size + (duk_uidx_t) index;
    } else {
        DUK_ASSERT(index != DUK_INVALID_INDEX);
        uindex = (duk_uidx_t) index;
    }
 
    /* DUK_INVALID_INDEX won't be accepted as a valid index. */
    DUK_ASSERT(vs_size + (duk_uidx_t) DUK_INVALID_INDEX >= vs_size);
 
    if (DUK_LIKELY(uindex < vs_size)) {
        return (duk_idx_t) uindex;
    }
    DUK_ERROR_API_INDEX(thr, index);
    return 0;  /* unreachable */
}
 
DUK_INTERNAL duk_tval *duk_get_tval(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_uidx_t vs_size;
    duk_uidx_t uindex;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(DUK_INVALID_INDEX < 0);
 
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    vs_size = (duk_uidx_t) (thr->valstack_top - thr->valstack_bottom);
    DUK_ASSERT_DISABLE(vs_size >= 0);  /* unsigned */
 
    if (index < 0) {
        uindex = vs_size + (duk_uidx_t) index;
    } else {
        DUK_ASSERT(index != DUK_INVALID_INDEX);
        uindex = (duk_uidx_t) index;
    }
 
    /* DUK_INVALID_INDEX won't be accepted as a valid index. */
    DUK_ASSERT(vs_size + (duk_uidx_t) DUK_INVALID_INDEX >= vs_size);
 
    if (DUK_LIKELY(uindex < vs_size)) {
        return thr->valstack_bottom + uindex;
    }
    return NULL;
}
 
DUK_INTERNAL duk_tval *duk_require_tval(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_uidx_t vs_size;
    duk_uidx_t uindex;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(DUK_INVALID_INDEX < 0);
 
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    vs_size = (duk_uidx_t) (thr->valstack_top - thr->valstack_bottom);
    DUK_ASSERT_DISABLE(vs_size >= 0);  /* unsigned */
 
    /* Use unsigned arithmetic to optimize comparison. */
    if (index < 0) {
        uindex = vs_size + (duk_uidx_t) index;
    } else {
        DUK_ASSERT(index != DUK_INVALID_INDEX);
        uindex = (duk_uidx_t) index;
    }
 
    /* DUK_INVALID_INDEX won't be accepted as a valid index. */
    DUK_ASSERT(vs_size + (duk_uidx_t) DUK_INVALID_INDEX >= vs_size);
 
    if (DUK_LIKELY(uindex < vs_size)) {
        return thr->valstack_bottom + uindex;
    }
    DUK_ERROR_API_INDEX(thr, index);
    return NULL;
}
 
/* Non-critical. */
DUK_EXTERNAL duk_bool_t duk_is_valid_index(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(DUK_INVALID_INDEX < 0);
 
    return (duk_normalize_index(ctx, index) >= 0);
}
 
/* Non-critical. */
DUK_EXTERNAL void duk_require_valid_index(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(DUK_INVALID_INDEX < 0);
 
    if (duk_normalize_index(ctx, index) < 0) {
        DUK_ERROR_API_INDEX(thr, index);
        return;  /* unreachable */
    }
}
 
/*
 *  Value stack top handling
 */
 
DUK_EXTERNAL duk_idx_t duk_get_top(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    return (duk_idx_t) (thr->valstack_top - thr->valstack_bottom);
}
 
/* Set stack top within currently allocated range, but don't reallocate.
 * This is performance critical especially for call handling, so whenever
 * changing, profile and look at generated code.
 */
DUK_EXTERNAL void duk_set_top(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_uidx_t vs_size;
    duk_uidx_t vs_limit;
    duk_uidx_t uindex;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(DUK_INVALID_INDEX < 0);
 
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    DUK_ASSERT(thr->valstack_end >= thr->valstack_bottom);
    vs_size = (duk_uidx_t) (thr->valstack_top - thr->valstack_bottom);
    vs_limit = (duk_uidx_t) (thr->valstack_end - thr->valstack_bottom);
 
    if (index < 0) {
        /* Negative indices are always within allocated stack but
         * must not go below zero index.
         */
        uindex = vs_size + (duk_uidx_t) index;
    } else {
        /* Positive index can be higher than valstack top but must
         * not go above allocated stack (equality is OK).
         */
        uindex = (duk_uidx_t) index;
    }
 
    /* DUK_INVALID_INDEX won't be accepted as a valid index. */
    DUK_ASSERT(vs_size + (duk_uidx_t) DUK_INVALID_INDEX >= vs_size);
    DUK_ASSERT(vs_size + (duk_uidx_t) DUK_INVALID_INDEX >= vs_limit);
 
#if defined(DUK_USE_VALSTACK_UNSAFE)
    DUK_ASSERT(uindex <= vs_limit);
    DUK_UNREF(vs_limit);
#else
    if (DUK_UNLIKELY(uindex > vs_limit)) {
        DUK_ERROR_API_INDEX(thr, index);
        return;  /* unreachable */
    }
#endif
    DUK_ASSERT(uindex <= vs_limit);
 
    /* Handle change in value stack top.  Respect value stack
     * initialization policy: 'undefined' above top.  Note that
     * DECREF may cause a side effect that reallocates valstack,
     * so must relookup after DECREF.
     */
 
    if (uindex >= vs_size) {
        /* Stack size increases or stays the same. */
#if defined(DUK_USE_ASSERTIONS)
        duk_uidx_t count;
 
        count = uindex - vs_size;
        while (count != 0) {
            count--;
            tv = thr->valstack_top + count;
            DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(tv));
        }
#endif
        thr->valstack_top = thr->valstack_bottom + uindex;
    } else {
        /* Stack size decreases. */
#if defined(DUK_USE_REFERENCE_COUNTING)
        duk_uidx_t count;
 
        count = vs_size - uindex;
        DUK_ASSERT(count > 0);
        while (count > 0) {
            count--;
            tv = --thr->valstack_top;  /* tv -> value just before prev top value; must relookup */
            DUK_ASSERT(tv >= thr->valstack_bottom);
            DUK_TVAL_SET_UNDEFINED_UPDREF(thr, tv);  /* side effects */
        }
#else  /* DUK_USE_REFERENCE_COUNTING */
        duk_uidx_t count;
        duk_tval *tv_end;
 
        count = vs_size - uindex;
        tv = thr->valstack_top;
        tv_end = tv - count;
        DUK_ASSERT(tv > tv_end);
        do {
            tv--;
            DUK_TVAL_SET_UNDEFINED(tv);
        } while (tv != tv_end);
        thr->valstack_top = tv_end;
#endif  /* DUK_USE_REFERENCE_COUNTING */
    }
}
 
DUK_EXTERNAL duk_idx_t duk_get_top_index(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_idx_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    ret = ((duk_idx_t) (thr->valstack_top - thr->valstack_bottom)) - 1;
    if (DUK_UNLIKELY(ret < 0)) {
        /* Return invalid index; if caller uses this without checking
         * in another API call, the index won't map to a valid stack
         * entry.
         */
        return DUK_INVALID_INDEX;
    }
    return ret;
}
 
DUK_EXTERNAL duk_idx_t duk_require_top_index(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_idx_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    ret = ((duk_idx_t) (thr->valstack_top - thr->valstack_bottom)) - 1;
    if (DUK_UNLIKELY(ret < 0)) {
        DUK_ERROR_API_INDEX(thr, -1);
        return 0;  /* unreachable */
    }
    return ret;
}
 
/*
 *  Value stack resizing.
 *
 *  This resizing happens above the current "top": the value stack can be
 *  grown or shrunk, but the "top" is not affected.  The value stack cannot
 *  be resized to a size below the current "top".
 *
 *  The low level reallocation primitive must carefully recompute all value
 *  stack pointers, and must also work if ALL pointers are NULL.  The resize
 *  is quite tricky because the valstack realloc may cause a mark-and-sweep,
 *  which may run finalizers.  Running finalizers may resize the valstack
 *  recursively (the same value stack we're working on).  So, after realloc
 *  returns, we know that the valstack "top" should still be the same (there
 *  should not be live values above the "top"), but its underlying size and
 *  pointer may have changed.
 */
 
/* XXX: perhaps refactor this to allow caller to specify some parameters, or
 * at least a 'compact' flag which skips any spare or round-up .. useful for
 * emergency gc.
 */
 
DUK_LOCAL duk_bool_t duk__resize_valstack(duk_context *ctx, duk_size_t new_size) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_ptrdiff_t old_bottom_offset;
    duk_ptrdiff_t old_top_offset;
    duk_ptrdiff_t old_end_offset_post;
#ifdef DUK_USE_DEBUG
    duk_ptrdiff_t old_end_offset_pre;
    duk_tval *old_valstack_pre;
    duk_tval *old_valstack_post;
#endif
    duk_tval *new_valstack;
    duk_size_t new_alloc_size;
    duk_tval *p;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(thr->valstack_bottom >= thr->valstack);
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    DUK_ASSERT(thr->valstack_end >= thr->valstack_top);
    DUK_ASSERT((duk_size_t) (thr->valstack_top - thr->valstack) <= new_size);  /* can't resize below 'top' */
    DUK_ASSERT(new_size <= thr->valstack_max);  /* valstack limit caller has check, prevents wrapping */
    DUK_ASSERT(new_size <= DUK_SIZE_MAX / sizeof(duk_tval));  /* specific assert for wrapping */
 
    /* get pointer offsets for tweaking below */
    old_bottom_offset = (((duk_uint8_t *) thr->valstack_bottom) - ((duk_uint8_t *) thr->valstack));
    old_top_offset = (((duk_uint8_t *) thr->valstack_top) - ((duk_uint8_t *) thr->valstack));
#ifdef DUK_USE_DEBUG
    old_end_offset_pre = (((duk_uint8_t *) thr->valstack_end) - ((duk_uint8_t *) thr->valstack));  /* not very useful, used for debugging */
    old_valstack_pre = thr->valstack;
#endif
 
    /* Allocate a new valstack.
     *
     * Note: cannot use a plain DUK_REALLOC() because a mark-and-sweep may
     * invalidate the original thr->valstack base pointer inside the realloc
     * process.  See doc/memory-management.rst.
     */
 
    new_alloc_size = sizeof(duk_tval) * new_size;
    new_valstack = (duk_tval *) DUK_REALLOC_INDIRECT(thr->heap, duk_hthread_get_valstack_ptr, (void *) thr, new_alloc_size);
    if (!new_valstack) {
        /* Because new_size != 0, if condition doesn't need to be
         * (new_valstack != NULL || new_size == 0).
         */
        DUK_ASSERT(new_size != 0);
        DUK_D(DUK_DPRINT("failed to resize valstack to %lu entries (%lu bytes)",
                         (unsigned long) new_size, (unsigned long) new_alloc_size));
        return 0;
    }
 
    /* Note: the realloc may have triggered a mark-and-sweep which may
     * have resized our valstack internally.  However, the mark-and-sweep
     * MUST NOT leave the stack bottom/top in a different state.  Particular
     * assumptions and facts:
     *
     *   - The thr->valstack pointer may be different after realloc,
     *     and the offset between thr->valstack_end <-> thr->valstack
     *     may have changed.
     *   - The offset between thr->valstack_bottom <-> thr->valstack
     *     and thr->valstack_top <-> thr->valstack MUST NOT have changed,
     *     because mark-and-sweep must adhere to a strict stack policy.
     *     In other words, logical bottom and top MUST NOT have changed.
     *   - All values above the top are unreachable but are initialized
     *     to UNDEFINED, up to the post-realloc valstack_end.
     *   - 'old_end_offset' must be computed after realloc to be correct.
     */
 
    DUK_ASSERT((((duk_uint8_t *) thr->valstack_bottom) - ((duk_uint8_t *) thr->valstack)) == old_bottom_offset);
    DUK_ASSERT((((duk_uint8_t *) thr->valstack_top) - ((duk_uint8_t *) thr->valstack)) == old_top_offset);
 
    /* success, fixup pointers */
    old_end_offset_post = (((duk_uint8_t *) thr->valstack_end) - ((duk_uint8_t *) thr->valstack));  /* must be computed after realloc */
#ifdef DUK_USE_DEBUG
    old_valstack_post = thr->valstack;
#endif
    thr->valstack = new_valstack;
    thr->valstack_end = new_valstack + new_size;
#if !defined(DUK_USE_PREFER_SIZE)
    thr->valstack_size = new_size;
#endif
    thr->valstack_bottom = (duk_tval *) (void *) ((duk_uint8_t *) new_valstack + old_bottom_offset);
    thr->valstack_top = (duk_tval *) (void *) ((duk_uint8_t *) new_valstack + old_top_offset);
 
    DUK_ASSERT(thr->valstack_bottom >= thr->valstack);
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    DUK_ASSERT(thr->valstack_end >= thr->valstack_top);
 
    /* useful for debugging */
#ifdef DUK_USE_DEBUG
    if (old_end_offset_pre != old_end_offset_post) {
        DUK_D(DUK_DPRINT("valstack was resized during valstack_resize(), probably by mark-and-sweep; "
                         "end offset changed: %lu -> %lu",
                         (unsigned long) old_end_offset_pre,
                         (unsigned long) old_end_offset_post));
    }
    if (old_valstack_pre != old_valstack_post) {
        DUK_D(DUK_DPRINT("valstack pointer changed during valstack_resize(), probably by mark-and-sweep: %p -> %p",
                         (void *) old_valstack_pre,
                         (void *) old_valstack_post));
    }
#endif
 
    DUK_DD(DUK_DDPRINT("resized valstack to %lu elements (%lu bytes), bottom=%ld, top=%ld, "
                       "new pointers: start=%p end=%p bottom=%p top=%p",
                       (unsigned long) new_size, (unsigned long) new_alloc_size,
                       (long) (thr->valstack_bottom - thr->valstack),
                       (long) (thr->valstack_top - thr->valstack),
                       (void *) thr->valstack, (void *) thr->valstack_end,
                       (void *) thr->valstack_bottom, (void *) thr->valstack_top));
 
    /* Init newly allocated slots (only). */
    p = (duk_tval *) (void *) ((duk_uint8_t *) thr->valstack + old_end_offset_post);
    while (p < thr->valstack_end) {
        /* Never executed if new size is smaller. */
        DUK_TVAL_SET_UNDEFINED(p);
        p++;
    }
 
    /* Assert for value stack initialization policy. */
#if defined(DUK_USE_ASSERTIONS)
    p = thr->valstack_top;
    while (p < thr->valstack_end) {
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(p));
        p++;
    }
#endif
 
    return 1;
}
 
DUK_INTERNAL
duk_bool_t duk_valstack_resize_raw(duk_context *ctx,
                                   duk_size_t min_new_size,
                                   duk_small_uint_t flags) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_size_t old_size;
    duk_size_t new_size;
    duk_bool_t is_shrink = 0;
    duk_small_uint_t shrink_flag = (flags & DUK_VSRESIZE_FLAG_SHRINK);
    duk_small_uint_t compact_flag = (flags & DUK_VSRESIZE_FLAG_COMPACT);
    duk_small_uint_t throw_flag = (flags & DUK_VSRESIZE_FLAG_THROW);
 
    DUK_DDD(DUK_DDDPRINT("check valstack resize: min_new_size=%lu, curr_size=%ld, curr_top=%ld, "
                         "curr_bottom=%ld, shrink=%d, compact=%d, throw=%d",
                         (unsigned long) min_new_size,
                         (long) (thr->valstack_end - thr->valstack),
                         (long) (thr->valstack_top - thr->valstack),
                         (long) (thr->valstack_bottom - thr->valstack),
                         (int) shrink_flag, (int) compact_flag, (int) throw_flag));
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(thr->valstack_bottom >= thr->valstack);
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    DUK_ASSERT(thr->valstack_end >= thr->valstack_top);
 
#if defined(DUK_USE_PREFER_SIZE)
    old_size = (duk_size_t) (thr->valstack_end - thr->valstack);
#else
    DUK_ASSERT((duk_size_t) (thr->valstack_end - thr->valstack) == thr->valstack_size);
    old_size = thr->valstack_size;
#endif
 
    if (min_new_size <= old_size) {
        is_shrink = 1;
        if (!shrink_flag ||
            old_size - min_new_size < DUK_VALSTACK_SHRINK_THRESHOLD) {
            DUK_DDD(DUK_DDDPRINT("no need to grow or shrink valstack"));
            return 1;
        }
    }
 
    new_size = min_new_size;
    if (!compact_flag) {
        if (is_shrink) {
            /* shrink case; leave some spare */
            new_size += DUK_VALSTACK_SHRINK_SPARE;
        }
 
        /* round up roughly to next 'grow step' */
        new_size = (new_size / DUK_VALSTACK_GROW_STEP + 1) * DUK_VALSTACK_GROW_STEP;
    }
 
    DUK_DD(DUK_DDPRINT("want to %s valstack: %lu -> %lu elements (min_new_size %lu)",
                       (const char *) (new_size > old_size ? "grow" : "shrink"),
                       (unsigned long) old_size, (unsigned long) new_size,
                       (unsigned long) min_new_size));
 
    if (new_size > thr->valstack_max) {
        /* Note: may be triggered even if minimal new_size would not reach the limit,
         * plan limit accordingly (taking DUK_VALSTACK_GROW_STEP into account).
         */
        if (throw_flag) {
            DUK_ERROR_RANGE(thr, DUK_STR_VALSTACK_LIMIT);
        } else {
            return 0;
        }
    }
 
    /*
     *  When resizing the valstack, a mark-and-sweep may be triggered for
     *  the allocation of the new valstack.  If the mark-and-sweep needs
     *  to use our thread for something, it may cause *the same valstack*
     *  to be resized recursively.  This happens e.g. when mark-and-sweep
     *  finalizers are called.  This is taken into account carefully in
     *  duk__resize_valstack().
     *
     *  'new_size' is known to be <= valstack_max, which ensures that
     *  size_t and pointer arithmetic won't wrap in duk__resize_valstack().
     */
 
    if (!duk__resize_valstack(ctx, new_size)) {
        if (is_shrink) {
            DUK_DD(DUK_DDPRINT("valstack resize failed, but is a shrink, ignore"));
            return 1;
        }
 
        DUK_DD(DUK_DDPRINT("valstack resize failed"));
 
        if (throw_flag) {
            DUK_ERROR_ALLOC_DEFMSG(thr);
        } else {
            return 0;
        }
    }
 
    DUK_DDD(DUK_DDDPRINT("valstack resize successful"));
    return 1;
}
 
DUK_EXTERNAL duk_bool_t duk_check_stack(duk_context *ctx, duk_idx_t extra) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_size_t min_new_size;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
 
    if (DUK_UNLIKELY(extra < 0)) {
        /* Clamping to zero makes the API more robust to calling code
         * calculation errors.
         */
        extra = 0;
    }
 
    min_new_size = (thr->valstack_top - thr->valstack) + extra + DUK_VALSTACK_INTERNAL_EXTRA;
    return duk_valstack_resize_raw(ctx,
                                   min_new_size,         /* min_new_size */
                                   0 /* no shrink */ |   /* flags */
                                   0 /* no compact */ |
                                   0 /* no throw */);
}
 
DUK_EXTERNAL void duk_require_stack(duk_context *ctx, duk_idx_t extra) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_size_t min_new_size;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
 
    if (DUK_UNLIKELY(extra < 0)) {
        /* Clamping to zero makes the API more robust to calling code
         * calculation errors.
         */
        extra = 0;
    }
 
    min_new_size = (thr->valstack_top - thr->valstack) + extra + DUK_VALSTACK_INTERNAL_EXTRA;
    (void) duk_valstack_resize_raw(ctx,
                                   min_new_size,  /* min_new_size */
                                   0 /* no shrink */ |   /* flags */
                                   0 /* no compact */ |
                                   DUK_VSRESIZE_FLAG_THROW);
}
 
DUK_EXTERNAL duk_bool_t duk_check_stack_top(duk_context *ctx, duk_idx_t top) {
    duk_size_t min_new_size;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    if (DUK_UNLIKELY(top < 0)) {
        /* Clamping to zero makes the API more robust to calling code
         * calculation errors.
         */
        top = 0;
    }
 
    min_new_size = top + DUK_VALSTACK_INTERNAL_EXTRA;
    return duk_valstack_resize_raw(ctx,
                                   min_new_size,  /* min_new_size */
                                   0 /* no shrink */ |   /* flags */
                                   0 /* no compact */ |
                                   0 /* no throw */);
}
 
DUK_EXTERNAL void duk_require_stack_top(duk_context *ctx, duk_idx_t top) {
    duk_size_t min_new_size;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    if (DUK_UNLIKELY(top < 0)) {
        /* Clamping to zero makes the API more robust to calling code
         * calculation errors.
         */
        top = 0;
    }
 
    min_new_size = top + DUK_VALSTACK_INTERNAL_EXTRA;
    (void) duk_valstack_resize_raw(ctx,
                                   min_new_size,  /* min_new_size */
                                   0 /* no shrink */ |   /* flags */
                                   0 /* no compact */ |
                                   DUK_VSRESIZE_FLAG_THROW);
}
 
/*
 *  Basic stack manipulation: swap, dup, insert, replace, etc
 */
 
DUK_EXTERNAL void duk_swap(duk_context *ctx, duk_idx_t index1, duk_idx_t index2) {
    duk_tval *tv1;
    duk_tval *tv2;
    duk_tval tv_tmp;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv1 = duk_require_tval(ctx, index1);
    DUK_ASSERT(tv1 != NULL);
    tv2 = duk_require_tval(ctx, index2);
    DUK_ASSERT(tv2 != NULL);
 
    /* If tv1==tv2 this is a NOP, no check is needed */
    DUK_TVAL_SET_TVAL(&tv_tmp, tv1);
    DUK_TVAL_SET_TVAL(tv1, tv2);
    DUK_TVAL_SET_TVAL(tv2, &tv_tmp);
}
 
DUK_EXTERNAL void duk_swap_top(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk_swap(ctx, index, -1);
}
 
DUK_EXTERNAL void duk_dup(duk_context *ctx, duk_idx_t from_index) {
    duk_hthread *thr;
    duk_tval *tv_from;
    duk_tval *tv_to;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
 
    tv_from = duk_require_tval(ctx, from_index);
    tv_to = thr->valstack_top++;
    DUK_ASSERT(tv_from != NULL);
    DUK_ASSERT(tv_to != NULL);
    DUK_TVAL_SET_TVAL(tv_to, tv_from);
    DUK_TVAL_INCREF(thr, tv_to);  /* no side effects */
}
 
DUK_EXTERNAL void duk_dup_top(duk_context *ctx) {
    duk_hthread *thr;
    duk_tval *tv_from;
    duk_tval *tv_to;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
 
    if (thr->valstack_top - thr->valstack_bottom <= 0) {
        DUK_ERROR_API_INDEX(thr, -1);
        return;  /* unreachable */
    }
    tv_from = thr->valstack_top - 1;
    tv_to = thr->valstack_top++;
    DUK_ASSERT(tv_from != NULL);
    DUK_ASSERT(tv_to != NULL);
    DUK_TVAL_SET_TVAL(tv_to, tv_from);
    DUK_TVAL_INCREF(thr, tv_to);  /* no side effects */
}
 
DUK_EXTERNAL void duk_insert(duk_context *ctx, duk_idx_t to_index) {
    duk_tval *p;
    duk_tval *q;
    duk_tval tv_tmp;
    duk_size_t nbytes;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    p = duk_require_tval(ctx, to_index);
    DUK_ASSERT(p != NULL);
    q = duk_require_tval(ctx, -1);
    DUK_ASSERT(q != NULL);
 
    DUK_ASSERT(q >= p);
 
    /*              nbytes
     *           <--------->
     *    [ ... | p | x | x | q ]
     * => [ ... | q | p | x | x ]
     */
 
    nbytes = (duk_size_t) (((duk_uint8_t *) q) - ((duk_uint8_t *) p));  /* Note: 'q' is top-1 */
 
    DUK_DDD(DUK_DDDPRINT("duk_insert: to_index=%ld, p=%p, q=%p, nbytes=%lu",
                         (long) to_index, (void *) p, (void *) q, (unsigned long) nbytes));
 
    /* No net refcount changes. */
 
    if (nbytes > 0) {
        DUK_TVAL_SET_TVAL(&tv_tmp, q);
        DUK_ASSERT(nbytes > 0);
        DUK_MEMMOVE((void *) (p + 1), (const void *) p, (size_t) nbytes);
        DUK_TVAL_SET_TVAL(p, &tv_tmp);
    } else {
        /* nop: insert top to top */
        DUK_ASSERT(nbytes == 0);
        DUK_ASSERT(p == q);
    }
}
 
DUK_EXTERNAL void duk_replace(duk_context *ctx, duk_idx_t to_index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv1;
    duk_tval *tv2;
    duk_tval tv_tmp;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv1 = duk_require_tval(ctx, -1);
    DUK_ASSERT(tv1 != NULL);
    tv2 = duk_require_tval(ctx, to_index);
    DUK_ASSERT(tv2 != NULL);
 
    /* For tv1 == tv2, both pointing to stack top, the end result
     * is same as duk_pop(ctx).
     */
    DUK_TVAL_SET_TVAL(&tv_tmp, tv2);
    DUK_TVAL_SET_TVAL(tv2, tv1);
    DUK_TVAL_SET_UNDEFINED(tv1);
    thr->valstack_top--;
    DUK_TVAL_DECREF(thr, &tv_tmp);  /* side effects */
}
 
DUK_EXTERNAL void duk_copy(duk_context *ctx, duk_idx_t from_index, duk_idx_t to_index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv1;
    duk_tval *tv2;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);  /* w/o refcounting */
 
    tv1 = duk_require_tval(ctx, from_index);
    DUK_ASSERT(tv1 != NULL);
    tv2 = duk_require_tval(ctx, to_index);
    DUK_ASSERT(tv2 != NULL);
 
    /* For tv1 == tv2, this is a no-op (no explicit check needed). */
    DUK_TVAL_SET_TVAL_UPDREF(thr, tv2, tv1);  /* side effects */
}
 
DUK_EXTERNAL void duk_remove(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *p;
    duk_tval *q;
#ifdef DUK_USE_REFERENCE_COUNTING
    duk_tval tv_tmp;
#endif
    duk_size_t nbytes;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    p = duk_require_tval(ctx, index);
    DUK_ASSERT(p != NULL);
    q = duk_require_tval(ctx, -1);
    DUK_ASSERT(q != NULL);
 
    DUK_ASSERT(q >= p);
 
    /*              nbytes            zero size case
     *           <--------->
     *    [ ... | p | x | x | q ]     [ ... | p==q ]
     * => [ ... | x | x | q ]         [ ... ]
     */
 
#ifdef DUK_USE_REFERENCE_COUNTING
    /* use a temp: decref only when valstack reachable values are correct */
    DUK_TVAL_SET_TVAL(&tv_tmp, p);
#endif
 
    nbytes = (duk_size_t) (((duk_uint8_t *) q) - ((duk_uint8_t *) p));  /* Note: 'q' is top-1 */
    DUK_MEMMOVE((void *) p, (const void *) (p + 1), (size_t) nbytes);  /* zero size not an issue: pointers are valid */
 
    DUK_TVAL_SET_UNDEFINED(q);
    thr->valstack_top--;
 
#ifdef DUK_USE_REFERENCE_COUNTING
    DUK_TVAL_DECREF(thr, &tv_tmp);  /* side effects */
#endif
}
 
/*
 *  Stack slice primitives
 */
 
DUK_EXTERNAL void duk_xcopymove_raw(duk_context *to_ctx, duk_context *from_ctx, duk_idx_t count, duk_bool_t is_copy) {
    duk_hthread *to_thr = (duk_hthread *) to_ctx;
    duk_hthread *from_thr = (duk_hthread *) from_ctx;
    void *src;
    duk_size_t nbytes;
    duk_tval *p;
    duk_tval *q;
 
    /* XXX: several pointer comparison issues here */
 
    DUK_ASSERT_CTX_VALID(to_ctx);
    DUK_ASSERT_CTX_VALID(from_ctx);
    DUK_ASSERT(to_ctx != NULL);
    DUK_ASSERT(from_ctx != NULL);
 
    if (to_ctx == from_ctx) {
        DUK_ERROR_API(to_thr, DUK_STR_INVALID_CONTEXT);
        return;
    }
    if ((count < 0) ||
        (count > (duk_idx_t) to_thr->valstack_max)) {
        /* Maximum value check ensures 'nbytes' won't wrap below. */
        DUK_ERROR_API(to_thr, DUK_STR_INVALID_COUNT);
        return;
    }
 
    nbytes = sizeof(duk_tval) * count;
    if (nbytes == 0) {
        return;
    }
    DUK_ASSERT(to_thr->valstack_top <= to_thr->valstack_end);
    if ((duk_size_t) ((duk_uint8_t *) to_thr->valstack_end - (duk_uint8_t *) to_thr->valstack_top) < nbytes) {
        DUK_ERROR_API(to_thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
    src = (void *) ((duk_uint8_t *) from_thr->valstack_top - nbytes);
    if (src < (void *) from_thr->valstack_bottom) {
        DUK_ERROR_API(to_thr, DUK_STR_INVALID_COUNT);
    }
 
    /* copy values (no overlap even if to_ctx == from_ctx; that's not
     * allowed now anyway)
     */
    DUK_ASSERT(nbytes > 0);
    DUK_MEMCPY((void *) to_thr->valstack_top, (const void *) src, (size_t) nbytes);
 
    p = to_thr->valstack_top;
    to_thr->valstack_top = (duk_tval *) (void *) (((duk_uint8_t *) p) + nbytes);
 
    if (is_copy) {
        /* Incref copies, keep originals. */
        q = to_thr->valstack_top;
        while (p < q) {
            DUK_TVAL_INCREF(to_thr, p);  /* no side effects */
            p++;
        }
    } else {
        /* No net refcount change. */
        p = from_thr->valstack_top;
        q = (duk_tval *) (void *) (((duk_uint8_t *) p) - nbytes);
        from_thr->valstack_top = q;
 
        while (p > q) {
            p--;
            DUK_TVAL_SET_UNDEFINED(p);
            /* XXX: fast primitive to set a bunch of values to UNDEFINED */
        }
    }
}
 
/*
 *  Get/require
 */
 
DUK_EXTERNAL void duk_require_undefined(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_UNDEFINED(tv)) {
        return;
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "undefined", DUK_STR_NOT_UNDEFINED);
    return;  /* not reachable */
}
 
DUK_EXTERNAL void duk_require_null(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_NULL(tv)) {
        return;
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "null", DUK_STR_NOT_NULL);
    return;  /* not reachable */
}
 
DUK_EXTERNAL duk_bool_t duk_get_boolean(duk_context *ctx, duk_idx_t index) {
    duk_bool_t ret = 0;  /* default: false */
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_BOOLEAN(tv)) {
        ret = DUK_TVAL_GET_BOOLEAN(tv);
    }
 
    DUK_ASSERT(ret == 0 || ret == 1);
    return ret;
}
 
DUK_EXTERNAL duk_bool_t duk_require_boolean(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_BOOLEAN(tv)) {
        duk_bool_t ret = DUK_TVAL_GET_BOOLEAN(tv);
        DUK_ASSERT(ret == 0 || ret == 1);
        return ret;
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "boolean", DUK_STR_NOT_BOOLEAN);
    return 0;  /* not reachable */
}
 
DUK_EXTERNAL duk_double_t duk_get_number(duk_context *ctx, duk_idx_t index) {
    duk_double_union ret;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    ret.d = DUK_DOUBLE_NAN;  /* default: NaN */
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_NUMBER(tv)) {
        ret.d = DUK_TVAL_GET_NUMBER(tv);
    }
 
    /*
     *  Number should already be in NaN-normalized form, but let's
     *  normalize anyway.
     */
 
    DUK_DBLUNION_NORMALIZE_NAN_CHECK(&ret);
    return ret.d;
}
 
DUK_EXTERNAL duk_double_t duk_require_number(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_NUMBER(tv)) {
        duk_double_union ret;
        ret.d = DUK_TVAL_GET_NUMBER(tv);
 
        /*
         *  Number should already be in NaN-normalized form,
         *  but let's normalize anyway.
         */
 
        DUK_DBLUNION_NORMALIZE_NAN_CHECK(&ret);
        return ret.d;
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "number", DUK_STR_NOT_NUMBER);
    return DUK_DOUBLE_NAN;  /* not reachable */
}
 
DUK_EXTERNAL duk_int_t duk_get_int(duk_context *ctx, duk_idx_t index) {
    /* Custom coercion for API */
    DUK_ASSERT_CTX_VALID(ctx);
    return (duk_int_t) duk__api_coerce_d2i(ctx, index, 0 /*require*/);
}
 
DUK_EXTERNAL duk_uint_t duk_get_uint(duk_context *ctx, duk_idx_t index) {
    /* Custom coercion for API */
    DUK_ASSERT_CTX_VALID(ctx);
    return (duk_uint_t) duk__api_coerce_d2ui(ctx, index, 0 /*require*/);
}
 
DUK_EXTERNAL duk_int_t duk_require_int(duk_context *ctx, duk_idx_t index) {
    /* Custom coercion for API */
    DUK_ASSERT_CTX_VALID(ctx);
    return (duk_int_t) duk__api_coerce_d2i(ctx, index, 1 /*require*/);
}
 
DUK_EXTERNAL duk_uint_t duk_require_uint(duk_context *ctx, duk_idx_t index) {
    /* Custom coercion for API */
    DUK_ASSERT_CTX_VALID(ctx);
    return (duk_uint_t) duk__api_coerce_d2ui(ctx, index, 1 /*require*/);
}
 
DUK_EXTERNAL const char *duk_get_lstring(duk_context *ctx, duk_idx_t index, duk_size_t *out_len) {
    const char *ret;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* default: NULL, length 0 */
    ret = NULL;
    if (out_len) {
        *out_len = 0;
    }
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_STRING(tv)) {
        /* Here we rely on duk_hstring instances always being zero
         * terminated even if the actual string is not.
         */
        duk_hstring *h = DUK_TVAL_GET_STRING(tv);
        DUK_ASSERT(h != NULL);
        ret = (const char *) DUK_HSTRING_GET_DATA(h);
        if (out_len) {
            *out_len = DUK_HSTRING_GET_BYTELEN(h);
        }
    }
 
    return ret;
}
 
DUK_EXTERNAL const char *duk_require_lstring(duk_context *ctx, duk_idx_t index, duk_size_t *out_len) {
    duk_hthread *thr = (duk_hthread *) ctx;
    const char *ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* Note: this check relies on the fact that even a zero-size string
     * has a non-NULL pointer.
     */
    ret = duk_get_lstring(ctx, index, out_len);
    if (ret) {
        return ret;
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "string", DUK_STR_NOT_STRING);
    return NULL;  /* not reachable */
}
 
DUK_EXTERNAL const char *duk_get_string(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    return duk_get_lstring(ctx, index, NULL);
}
 
DUK_EXTERNAL const char *duk_require_string(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    return duk_require_lstring(ctx, index, NULL);
}
 
DUK_EXTERNAL void *duk_get_pointer(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_POINTER(tv)) {
        void *p = DUK_TVAL_GET_POINTER(tv);  /* may be NULL */
        return (void *) p;
    }
 
    return NULL;
}
 
DUK_EXTERNAL void *duk_require_pointer(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* Note: here we must be wary of the fact that a pointer may be
     * valid and be a NULL.
     */
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_POINTER(tv)) {
        void *p = DUK_TVAL_GET_POINTER(tv);  /* may be NULL */
        return (void *) p;
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "pointer", DUK_STR_NOT_POINTER);
    return NULL;  /* not reachable */
}
 
#if 0  /*unused*/
DUK_INTERNAL void *duk_get_voidptr(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
        duk_heaphdr *h = DUK_TVAL_GET_HEAPHDR(tv);
        DUK_ASSERT(h != NULL);
        return (void *) h;
    }
 
    return NULL;
}
#endif
 
DUK_LOCAL void *duk__get_buffer_helper(duk_context *ctx, duk_idx_t index, duk_size_t *out_size, duk_bool_t throw_flag) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);
 
    if (out_size != NULL) {
        *out_size = 0;
    }
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_BUFFER(tv)) {
        duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
        DUK_ASSERT(h != NULL);
        if (out_size) {
            *out_size = DUK_HBUFFER_GET_SIZE(h);
        }
        return (void *) DUK_HBUFFER_GET_DATA_PTR(thr->heap, h);  /* may be NULL (but only if size is 0) */
    }
 
    if (throw_flag) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "buffer", DUK_STR_NOT_BUFFER);
    }
    return NULL;
}
 
DUK_EXTERNAL void *duk_get_buffer(duk_context *ctx, duk_idx_t index, duk_size_t *out_size) {
    return duk__get_buffer_helper(ctx, index, out_size, 0 /*throw_flag*/);
}
 
DUK_EXTERNAL void *duk_require_buffer(duk_context *ctx, duk_idx_t index, duk_size_t *out_size) {
    return duk__get_buffer_helper(ctx, index, out_size, 1 /*throw_flag*/);
}
 
DUK_LOCAL void *duk__get_buffer_data_helper(duk_context *ctx, duk_idx_t index, duk_size_t *out_size, duk_bool_t throw_flag) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);
 
    if (out_size != NULL) {
        *out_size = 0;
    }
 
    tv = duk_get_tval(ctx, index);
    if (tv == NULL) {
        goto fail;
    }
 
    if (DUK_TVAL_IS_BUFFER(tv)) {
        duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
        DUK_ASSERT(h != NULL);
        if (out_size) {
            *out_size = DUK_HBUFFER_GET_SIZE(h);
        }
        return (void *) DUK_HBUFFER_GET_DATA_PTR(thr->heap, h);  /* may be NULL (but only if size is 0) */
    } else if (DUK_TVAL_IS_OBJECT(tv)) {
        duk_hobject *h = DUK_TVAL_GET_OBJECT(tv);
        DUK_ASSERT(h != NULL);
        if (DUK_HOBJECT_IS_BUFFEROBJECT(h)) {
            /* XXX: this is probably a useful shared helper: for a
             * duk_hbufferobject, get a validated buffer pointer/length.
             */
            duk_hbufferobject *h_bufobj = (duk_hbufferobject *) h;
            DUK_ASSERT_HBUFFEROBJECT_VALID(h_bufobj);
 
            if (h_bufobj->buf != NULL &&
                DUK_HBUFFEROBJECT_VALID_SLICE(h_bufobj)) {
                duk_uint8_t *p;
 
                p = (duk_uint8_t *) DUK_HBUFFER_GET_DATA_PTR(thr->heap, h_bufobj->buf);
                if (out_size != NULL) {
                    *out_size = (duk_size_t) h_bufobj->length;
                }
                return (void *) (p + h_bufobj->offset);
            }
            /* if slice not fully valid, treat as error */
        }
    }
 
 fail:
    if (throw_flag) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "buffer", DUK_STR_NOT_BUFFER);
    }
    return NULL;
}
 
DUK_EXTERNAL void *duk_get_buffer_data(duk_context *ctx, duk_idx_t index, duk_size_t *out_size) {
    return duk__get_buffer_data_helper(ctx, index, out_size, 0 /*throw_flag*/);
}
 
DUK_EXTERNAL void *duk_require_buffer_data(duk_context *ctx, duk_idx_t index, duk_size_t *out_size) {
    return duk__get_buffer_data_helper(ctx, index, out_size, 1 /*throw_flag*/);
}
 
/* Raw helper for getting a value from the stack, checking its tag.
 * The tag cannot be a number because numbers don't have an internal
 * tag in the packed representation.
 */
 
DUK_LOCAL duk_heaphdr *duk__get_tagged_heaphdr_raw(duk_context *ctx, duk_idx_t index, duk_uint_t tag) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && (DUK_TVAL_GET_TAG(tv) == tag)) {
        duk_heaphdr *ret;
        ret = DUK_TVAL_GET_HEAPHDR(tv);
        DUK_ASSERT(ret != NULL);  /* tagged null pointers should never occur */
        return ret;
    }
 
    return (duk_heaphdr *) NULL;
}
 
DUK_INTERNAL duk_hstring *duk_get_hstring(duk_context *ctx, duk_idx_t index) {
    return (duk_hstring *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_STRING);
}
 
DUK_INTERNAL duk_hstring *duk_require_hstring(duk_context *ctx, duk_idx_t index) {
    duk_heaphdr *h;
    h = duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_STRING);
    if (h == NULL) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(ctx, index, "string", DUK_STR_NOT_STRING);
    }
    return (duk_hstring *) h;
}
 
DUK_INTERNAL duk_hobject *duk_get_hobject(duk_context *ctx, duk_idx_t index) {
    return (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
}
 
DUK_INTERNAL duk_hobject *duk_require_hobject(duk_context *ctx, duk_idx_t index) {
    duk_heaphdr *h;
    h = duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (h == NULL) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(ctx, index, "object", DUK_STR_NOT_OBJECT);
    }
    return (duk_hobject *) h;
}
 
DUK_INTERNAL duk_hbuffer *duk_get_hbuffer(duk_context *ctx, duk_idx_t index) {
    return (duk_hbuffer *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_BUFFER);
}
 
DUK_INTERNAL duk_hbuffer *duk_require_hbuffer(duk_context *ctx, duk_idx_t index) {
    duk_heaphdr *h;
    h = duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_BUFFER);
    if (h == NULL) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(ctx, index, "buffer", DUK_STR_NOT_BUFFER);
    }
    return (duk_hbuffer *) h;
}
 
DUK_INTERNAL duk_hthread *duk_get_hthread(duk_context *ctx, duk_idx_t index) {
    duk_hobject *h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (h != NULL && !DUK_HOBJECT_IS_THREAD(h)) {
        h = NULL;
    }
    return (duk_hthread *) h;
}
 
DUK_INTERNAL duk_hthread *duk_require_hthread(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hobject *h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (!(h != NULL && DUK_HOBJECT_IS_THREAD(h))) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "thread", DUK_STR_NOT_THREAD);
    }
    return (duk_hthread *) h;
}
 
DUK_INTERNAL duk_hcompiledfunction *duk_get_hcompiledfunction(duk_context *ctx, duk_idx_t index) {
    duk_hobject *h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (h != NULL && !DUK_HOBJECT_IS_COMPILEDFUNCTION(h)) {
        h = NULL;
    }
    return (duk_hcompiledfunction *) h;
}
 
DUK_INTERNAL duk_hcompiledfunction *duk_require_hcompiledfunction(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hobject *h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (!(h != NULL && DUK_HOBJECT_IS_COMPILEDFUNCTION(h))) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "compiledfunction", DUK_STR_NOT_COMPILEDFUNCTION);
    }
    return (duk_hcompiledfunction *) h;
}
 
DUK_INTERNAL duk_hnativefunction *duk_get_hnativefunction(duk_context *ctx, duk_idx_t index) {
    duk_hobject *h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (h != NULL && !DUK_HOBJECT_IS_NATIVEFUNCTION(h)) {
        h = NULL;
    }
    return (duk_hnativefunction *) h;
}
 
DUK_INTERNAL duk_hnativefunction *duk_require_hnativefunction(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hobject *h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (!(h != NULL && DUK_HOBJECT_IS_NATIVEFUNCTION(h))) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "nativefunction", DUK_STR_NOT_NATIVEFUNCTION);
    }
    return (duk_hnativefunction *) h;
}
 
DUK_EXTERNAL duk_c_function duk_get_c_function(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
    duk_hobject *h;
    duk_hnativefunction *f;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (!tv) {
        return NULL;
    }
    if (!DUK_TVAL_IS_OBJECT(tv)) {
        return NULL;
    }
    h = DUK_TVAL_GET_OBJECT(tv);
    DUK_ASSERT(h != NULL);
 
    if (!DUK_HOBJECT_IS_NATIVEFUNCTION(h)) {
        return NULL;
    }
    DUK_ASSERT(DUK_HOBJECT_HAS_NATIVEFUNCTION(h));
    f = (duk_hnativefunction *) h;
 
    return f->func;
}
 
DUK_EXTERNAL duk_c_function duk_require_c_function(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_c_function ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    ret = duk_get_c_function(ctx, index);
    if (!ret) {
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "nativefunction", DUK_STR_NOT_NATIVEFUNCTION);
    }
    return ret;
}
 
DUK_EXTERNAL void duk_require_function(duk_context *ctx, duk_idx_t index) {
    if (!duk_is_function(ctx, index)) {
        DUK_ERROR_REQUIRE_TYPE_INDEX((duk_hthread *) ctx, index, "function", DUK_STR_NOT_FUNCTION);
    }
}
 
DUK_EXTERNAL duk_context *duk_get_context(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    return (duk_context *) duk_get_hthread(ctx, index);
}
 
DUK_EXTERNAL duk_context *duk_require_context(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    return (duk_context *) duk_require_hthread(ctx, index);
}
 
DUK_EXTERNAL void *duk_get_heapptr(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
    void *ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
        ret = (void *) DUK_TVAL_GET_HEAPHDR(tv);
        DUK_ASSERT(ret != NULL);
        return ret;
    }
 
    return (void *) NULL;
}
 
DUK_EXTERNAL void *duk_require_heapptr(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    void *ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    if (DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
        ret = (void *) DUK_TVAL_GET_HEAPHDR(tv);
        DUK_ASSERT(ret != NULL);
        return ret;
    }
 
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "heapobject", DUK_STR_UNEXPECTED_TYPE);
    return (void *) NULL;  /* not reachable */
}
 
#if 0
/* This would be pointless: we'd return NULL for both lightfuncs and
 * unexpected types.
 */
DUK_INTERNAL duk_hobject *duk_get_hobject_or_lfunc(duk_context *ctx, duk_idx_t index) {
}
#endif
 
/* Useful for internal call sites where we either expect an object (function)
 * or a lightfunc.  Accepts an object (returned as is) or a lightfunc (coerced
 * to an object).  Return value is NULL if value is neither an object nor a
 * lightfunc.
 */
DUK_INTERNAL duk_hobject *duk_get_hobject_or_lfunc_coerce(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    if (DUK_TVAL_IS_OBJECT(tv)) {
        return DUK_TVAL_GET_OBJECT(tv);
    } else if (DUK_TVAL_IS_LIGHTFUNC(tv)) {
        duk_to_object(ctx, index);
        return duk_require_hobject(ctx, index);
    }
 
    return NULL;
}
 
/* Useful for internal call sites where we either expect an object (function)
 * or a lightfunc.  Returns NULL for a lightfunc.
 */
DUK_INTERNAL duk_hobject *duk_require_hobject_or_lfunc(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    if (DUK_TVAL_IS_OBJECT(tv)) {
        return DUK_TVAL_GET_OBJECT(tv);
    } else if (DUK_TVAL_IS_LIGHTFUNC(tv)) {
        return NULL;
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "object", DUK_STR_NOT_OBJECT);
    return NULL;  /* not reachable */
}
 
/* Useful for internal call sites where we either expect an object (function)
 * or a lightfunc.  Accepts an object (returned as is) or a lightfunc (coerced
 * to an object).  Return value is never NULL.
 */
DUK_INTERNAL duk_hobject *duk_require_hobject_or_lfunc_coerce(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    if (DUK_TVAL_IS_OBJECT(tv)) {
        return DUK_TVAL_GET_OBJECT(tv);
    } else if (DUK_TVAL_IS_LIGHTFUNC(tv)) {
        duk_to_object(ctx, index);
        return duk_require_hobject(ctx, index);
    }
    DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, "object", DUK_STR_NOT_OBJECT);
    return NULL;  /* not reachable */
}
 
DUK_INTERNAL duk_hobject *duk_get_hobject_with_class(duk_context *ctx, duk_idx_t index, duk_small_uint_t classnum) {
    duk_hobject *h;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT_DISABLE(classnum >= 0);  /* unsigned */
    DUK_ASSERT(classnum <= DUK_HOBJECT_CLASS_MAX);
 
    h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (h != NULL && DUK_HOBJECT_GET_CLASS_NUMBER(h) != classnum) {
        h = NULL;
    }
    return h;
}
 
DUK_INTERNAL duk_hobject *duk_require_hobject_with_class(duk_context *ctx, duk_idx_t index, duk_small_uint_t classnum) {
    duk_hthread *thr;
    duk_hobject *h;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT_DISABLE(classnum >= 0);  /* unsigned */
    DUK_ASSERT(classnum <= DUK_HOBJECT_CLASS_MAX);
    thr = (duk_hthread *) ctx;
 
    h = (duk_hobject *) duk__get_tagged_heaphdr_raw(ctx, index, DUK_TAG_OBJECT);
    if (!(h != NULL && DUK_HOBJECT_GET_CLASS_NUMBER(h) == classnum)) {
        duk_hstring *h_class;
        h_class = DUK_HTHREAD_GET_STRING(thr, DUK_HOBJECT_CLASS_NUMBER_TO_STRIDX(classnum));
        DUK_UNREF(h_class);
 
        DUK_ERROR_REQUIRE_TYPE_INDEX(thr, index, (const char *) DUK_HSTRING_GET_DATA(h_class), DUK_STR_UNEXPECTED_TYPE);
    }
    return h;
}
 
DUK_EXTERNAL duk_size_t duk_get_length(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (!tv) {
        return 0;
    }
 
    switch (DUK_TVAL_GET_TAG(tv)) {
    case DUK_TAG_UNDEFINED:
    case DUK_TAG_NULL:
    case DUK_TAG_BOOLEAN:
    case DUK_TAG_POINTER:
        return 0;
    case DUK_TAG_STRING: {
        duk_hstring *h = DUK_TVAL_GET_STRING(tv);
        DUK_ASSERT(h != NULL);
        return (duk_size_t) DUK_HSTRING_GET_CHARLEN(h);
    }
    case DUK_TAG_OBJECT: {
        duk_hobject *h = DUK_TVAL_GET_OBJECT(tv);
        DUK_ASSERT(h != NULL);
        return (duk_size_t) duk_hobject_get_length((duk_hthread *) ctx, h);
    }
    case DUK_TAG_BUFFER: {
        duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
        DUK_ASSERT(h != NULL);
        return (duk_size_t) DUK_HBUFFER_GET_SIZE(h);
    }
    case DUK_TAG_LIGHTFUNC: {
        duk_small_uint_t lf_flags;
        lf_flags = DUK_TVAL_GET_LIGHTFUNC_FLAGS(tv);
        return (duk_size_t) DUK_LFUNC_FLAGS_GET_LENGTH(lf_flags);
    }
#if defined(DUK_USE_FASTINT)
    case DUK_TAG_FASTINT:
#endif
    default:
        /* number */
        DUK_ASSERT(!DUK_TVAL_IS_UNUSED(tv));
        DUK_ASSERT(DUK_TVAL_IS_NUMBER(tv));
        return 0;
    }
 
    DUK_UNREACHABLE();
}
 
DUK_INTERNAL void duk_set_length(duk_context *ctx, duk_idx_t index, duk_size_t length) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hobject *h;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    h = duk_get_hobject(ctx, index);
    if (!h) {
        return;
    }
 
    duk_hobject_set_length(thr, h, (duk_uint32_t) length);  /* XXX: typing */
}
 
/*
 *  Conversions and coercions
 *
 *  The conversion/coercions are in-place operations on the value stack.
 *  Some operations are implemented here directly, while others call a
 *  helper in duk_js_ops.c after validating arguments.
 */
 
/* E5 Section 8.12.8 */
 
DUK_LOCAL duk_bool_t duk__defaultvalue_coerce_attempt(duk_context *ctx, duk_idx_t index, duk_small_int_t func_stridx) {
    if (duk_get_prop_stridx(ctx, index, func_stridx)) {
        /* [ ... func ] */
        if (duk_is_callable(ctx, -1)) {
            duk_dup(ctx, index);         /* -> [ ... func this ] */
            duk_call_method(ctx, 0);     /* -> [ ... retval ] */
            if (duk_is_primitive(ctx, -1)) {
                duk_replace(ctx, index);
                return 1;
            }
            /* [ ... retval ]; popped below */
        }
    }
    duk_pop(ctx);  /* [ ... func/retval ] -> [ ... ] */
    return 0;
}
 
DUK_EXTERNAL void duk_to_defaultvalue(duk_context *ctx, duk_idx_t index, duk_int_t hint) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hobject *obj;
    /* inline initializer for coercers[] is not allowed by old compilers like BCC */
    duk_small_int_t coercers[2];
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
 
    coercers[0] = DUK_STRIDX_VALUE_OF;
    coercers[1] = DUK_STRIDX_TO_STRING;
 
    index = duk_require_normalize_index(ctx, index);
    obj = duk_require_hobject_or_lfunc(ctx, index);
 
    if (hint == DUK_HINT_NONE) {
        if (obj != NULL && DUK_HOBJECT_GET_CLASS_NUMBER(obj) == DUK_HOBJECT_CLASS_DATE) {
            hint = DUK_HINT_STRING;
        } else {
            hint = DUK_HINT_NUMBER;
        }
    }
 
    if (hint == DUK_HINT_STRING) {
        coercers[0] = DUK_STRIDX_TO_STRING;
        coercers[1] = DUK_STRIDX_VALUE_OF;
    }
 
    if (duk__defaultvalue_coerce_attempt(ctx, index, coercers[0])) {
        return;
    }
 
    if (duk__defaultvalue_coerce_attempt(ctx, index, coercers[1])) {
        return;
    }
 
    DUK_ERROR_TYPE(thr, DUK_STR_DEFAULTVALUE_COERCE_FAILED);
}
 
DUK_EXTERNAL void duk_to_undefined(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    DUK_TVAL_SET_UNDEFINED_UPDREF(thr, tv);  /* side effects */
}
 
DUK_EXTERNAL void duk_to_null(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    DUK_TVAL_SET_NULL_UPDREF(thr, tv);  /* side effects */
}
 
/* E5 Section 9.1 */
DUK_EXTERNAL void duk_to_primitive(duk_context *ctx, duk_idx_t index, duk_int_t hint) {
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(hint == DUK_HINT_NONE || hint == DUK_HINT_NUMBER || hint == DUK_HINT_STRING);
 
    index = duk_require_normalize_index(ctx, index);
 
    if (!duk_check_type_mask(ctx, index, DUK_TYPE_MASK_OBJECT |
                                         DUK_TYPE_MASK_LIGHTFUNC)) {
        /* everything except object stay as is */
        return;
    }
    duk_to_defaultvalue(ctx, index, hint);
}
 
/* E5 Section 9.2 */
DUK_EXTERNAL duk_bool_t duk_to_boolean(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_bool_t val;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);
 
    index = duk_require_normalize_index(ctx, index);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
 
    val = duk_js_toboolean(tv);
    DUK_ASSERT(val == 0 || val == 1);
 
    /* Note: no need to re-lookup tv, conversion is side effect free */
    DUK_ASSERT(tv != NULL);
    DUK_TVAL_SET_BOOLEAN_UPDREF(thr, tv, val);  /* side effects */
    return val;
}
 
DUK_EXTERNAL duk_double_t duk_to_number(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_double_t d;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    /* XXX: fastint? */
    d = duk_js_tonumber(thr, tv);
 
    /* Note: need to re-lookup because ToNumber() may have side effects */
    tv = duk_require_tval(ctx, index);
    DUK_TVAL_SET_NUMBER_UPDREF(thr, tv, d);  /* side effects */
    return d;
}
 
/* XXX: combine all the integer conversions: they share everything
 * but the helper function for coercion.
 */
 
typedef duk_double_t (*duk__toint_coercer)(duk_hthread *thr, duk_tval *tv);
 
DUK_LOCAL duk_double_t duk__to_int_uint_helper(duk_context *ctx, duk_idx_t index, duk__toint_coercer coerce_func) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_double_t d;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    d = coerce_func(thr, tv);
 
    /* XXX: fastint? */
 
    /* Relookup in case coerce_func() has side effects, e.g. ends up coercing an object */
    tv = duk_require_tval(ctx, index);
    DUK_TVAL_SET_NUMBER_UPDREF(thr, tv, d);  /* side effects */
    return d;
}
 
DUK_EXTERNAL duk_int_t duk_to_int(duk_context *ctx, duk_idx_t index) {
    /* Value coercion (in stack): ToInteger(), E5 Section 9.4
     * API return value coercion: custom
     */
    DUK_ASSERT_CTX_VALID(ctx);
    (void) duk__to_int_uint_helper(ctx, index, duk_js_tointeger);
    return (duk_int_t) duk__api_coerce_d2i(ctx, index, 0 /*require*/);
}
 
DUK_EXTERNAL duk_uint_t duk_to_uint(duk_context *ctx, duk_idx_t index) {
    /* Value coercion (in stack): ToInteger(), E5 Section 9.4
     * API return value coercion: custom
     */
    DUK_ASSERT_CTX_VALID(ctx);
    (void) duk__to_int_uint_helper(ctx, index, duk_js_tointeger);
    return (duk_uint_t) duk__api_coerce_d2ui(ctx, index, 0 /*require*/);
}
 
DUK_EXTERNAL duk_int32_t duk_to_int32(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_int32_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    ret = duk_js_toint32(thr, tv);
 
    /* Relookup in case coerce_func() has side effects, e.g. ends up coercing an object */
    tv = duk_require_tval(ctx, index);
    DUK_TVAL_SET_FASTINT_I32_UPDREF(thr, tv, ret);  /* side effects */
    return ret;
}
 
DUK_EXTERNAL duk_uint32_t duk_to_uint32(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_uint32_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    ret = duk_js_touint32(thr, tv);
 
    /* Relookup in case coerce_func() has side effects, e.g. ends up coercing an object */
    tv = duk_require_tval(ctx, index);
    DUK_TVAL_SET_FASTINT_U32_UPDREF(thr, tv, ret);  /* side effects */
    return ret;
}
 
DUK_EXTERNAL duk_uint16_t duk_to_uint16(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_uint16_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    ret = duk_js_touint16(thr, tv);
 
    /* Relookup in case coerce_func() has side effects, e.g. ends up coercing an object */
    tv = duk_require_tval(ctx, index);
    DUK_TVAL_SET_FASTINT_U32_UPDREF(thr, tv, ret);  /* side effects */
    return ret;
}
 
#if defined(DUK_USE_BUFFEROBJECT_SUPPORT)
/* Special coercion for Uint8ClampedArray. */
DUK_INTERNAL duk_uint8_t duk_to_uint8clamped(duk_context *ctx, duk_idx_t index) {
    duk_double_t d;
    duk_double_t t;
    duk_uint8_t ret;
 
    /* XXX: Simplify this algorithm, should be possible to come up with
     * a shorter and faster algorithm by inspecting IEEE representation
     * directly.
     */
 
    d = duk_to_number(ctx, index);
    if (d <= 0.0) {
        return 0;
    } else if (d >= 255) {
        return 255;
    } else if (DUK_ISNAN(d)) {
        /* Avoid NaN-to-integer coercion as it is compiler specific. */
        return 0;
    }
 
    t = d - DUK_FLOOR(d);
    if (t == 0.5) {
        /* Exact halfway, round to even. */
        ret = (duk_uint8_t) d;
        ret = (ret + 1) & 0xfe;  /* Example: d=3.5, t=0.5 -> ret = (3 + 1) & 0xfe = 4 & 0xfe = 4
                                  * Example: d=4.5, t=0.5 -> ret = (4 + 1) & 0xfe = 5 & 0xfe = 4
                                  */
    } else {
        /* Not halfway, round to nearest. */
        ret = (duk_uint8_t) (d + 0.5);
    }
    return ret;
}
#endif  /* DUK_USE_BUFFEROBJECT_SUPPORT */
 
DUK_EXTERNAL const char *duk_to_lstring(duk_context *ctx, duk_idx_t index, duk_size_t *out_len) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    (void) duk_to_string(ctx, index);
    return duk_require_lstring(ctx, index, out_len);
}
 
DUK_LOCAL duk_ret_t duk__safe_to_string_raw(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk_to_string(ctx, -1);
    return 1;
}
 
DUK_EXTERNAL const char *duk_safe_to_lstring(duk_context *ctx, duk_idx_t index, duk_size_t *out_len) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    index = duk_require_normalize_index(ctx, index);
 
    /* We intentionally ignore the duk_safe_call() return value and only
     * check the output type.  This way we don't also need to check that
     * the returned value is indeed a string in the success case.
     */
 
    duk_dup(ctx, index);
    (void) duk_safe_call(ctx, duk__safe_to_string_raw, 1 /*nargs*/, 1 /*nrets*/);
    if (!duk_is_string(ctx, -1)) {
        /* Error: try coercing error to string once. */
        (void) duk_safe_call(ctx, duk__safe_to_string_raw, 1 /*nargs*/, 1 /*nrets*/);
        if (!duk_is_string(ctx, -1)) {
            /* Double error */
            duk_pop(ctx);
            duk_push_hstring_stridx(ctx, DUK_STRIDX_UC_ERROR);
        } else {
            ;
        }
    } else {
        ;
    }
    DUK_ASSERT(duk_is_string(ctx, -1));
    DUK_ASSERT(duk_get_string(ctx, -1) != NULL);
 
    duk_replace(ctx, index);
    return duk_get_lstring(ctx, index, out_len);
}
 
#if defined(DUK_USE_DEBUGGER_SUPPORT)  /* only needed by debugger for now */
DUK_INTERNAL duk_hstring *duk_safe_to_hstring(duk_context *ctx, duk_idx_t index) {
    (void) duk_safe_to_string(ctx, index);
    DUK_ASSERT(duk_is_string(ctx, index));
    DUK_ASSERT(duk_get_hstring(ctx, index) != NULL);
    return duk_get_hstring(ctx, index);
}
#endif
 
/* Coerce top into Object.prototype.toString() output. */
DUK_INTERNAL void duk_to_object_class_string_top(duk_context *ctx) {
    duk_hthread *thr;
    duk_uint_t typemask;
    duk_hstring *h_strclass;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK_UNREF(thr);
 
    typemask = duk_get_type_mask(ctx, -1);
    if (typemask & DUK_TYPE_MASK_UNDEFINED) {
        h_strclass = DUK_HTHREAD_STRING_UC_UNDEFINED(thr);
    } else if (typemask & DUK_TYPE_MASK_NULL) {
        h_strclass = DUK_HTHREAD_STRING_UC_NULL(thr);
    } else {
        duk_hobject *h_obj;
 
        duk_to_object(ctx, -1);
        h_obj = duk_get_hobject(ctx, -1);
        DUK_ASSERT(h_obj != NULL);
 
        h_strclass = DUK_HOBJECT_GET_CLASS_STRING(thr->heap, h_obj);
    }
    DUK_ASSERT(h_strclass != NULL);
 
    duk_pop(ctx);
    duk_push_sprintf(ctx, "[object %s]", (const char *) DUK_HSTRING_GET_DATA(h_strclass));
}
 
#if !defined(DUK_USE_PARANOID_ERRORS)
DUK_INTERNAL void duk_push_hobject_class_string(duk_context *ctx, duk_hobject *h) {
    duk_hthread *thr;
    duk_hstring *h_strclass;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(h != NULL);
    thr = (duk_hthread *) ctx;
    DUK_UNREF(thr);
 
    h_strclass = DUK_HOBJECT_GET_CLASS_STRING(thr->heap, h);
    DUK_ASSERT(h_strclass != NULL);
    duk_push_sprintf(ctx, "[object %s]", (const char *) DUK_HSTRING_GET_DATA(h_strclass));
}
#endif  /* !DUK_USE_PARANOID_ERRORS */
 
/* XXX: other variants like uint, u32 etc */
DUK_INTERNAL duk_int_t duk_to_int_clamped_raw(duk_context *ctx, duk_idx_t index, duk_int_t minval, duk_int_t maxval, duk_bool_t *out_clamped) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_tval tv_tmp;
    duk_double_t d, dmin, dmax;
    duk_int_t res;
    duk_bool_t clamped = 0;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
    d = duk_js_tointeger(thr, tv);  /* E5 Section 9.4, ToInteger() */
 
    dmin = (duk_double_t) minval;
    dmax = (duk_double_t) maxval;
 
    if (d < dmin) {
        clamped = 1;
        res = minval;
        d = dmin;
    } else if (d > dmax) {
        clamped = 1;
        res = maxval;
        d = dmax;
    } else {
        res = (duk_int_t) d;
    }
    DUK_UNREF(d);  /* SCANBUILD: with suitable dmin/dmax limits 'd' is unused */
    /* 'd' and 'res' agree here */
 
    /* Relookup in case duk_js_tointeger() ends up e.g. coercing an object. */
    tv = duk_get_tval(ctx, index);
    DUK_ASSERT(tv != NULL);  /* not popped by side effect */
    DUK_TVAL_SET_TVAL(&tv_tmp, tv);
#if defined(DUK_USE_FASTINT)
#if (DUK_INT_MAX <= 0x7fffffffL)
    DUK_TVAL_SET_FASTINT_I32(tv, res);
#else
    /* Clamping needed if duk_int_t is 64 bits. */
    if (res >= DUK_FASTINT_MIN && res <= DUK_FASTINT_MAX) {
        DUK_TVAL_SET_FASTINT(tv, res);
    } else {
        DUK_TVAL_SET_NUMBER(tv, d);
    }
#endif
#else
    DUK_TVAL_SET_NUMBER(tv, d);  /* no need to incref */
#endif
    DUK_TVAL_DECREF(thr, &tv_tmp);  /* side effects */
 
    if (out_clamped) {
        *out_clamped = clamped;
    } else {
        /* coerced value is updated to value stack even when RangeError thrown */
        if (clamped) {
            DUK_ERROR_RANGE(thr, DUK_STR_NUMBER_OUTSIDE_RANGE);
        }
    }
 
    return res;
}
 
DUK_INTERNAL duk_int_t duk_to_int_clamped(duk_context *ctx, duk_idx_t index, duk_idx_t minval, duk_idx_t maxval) {
    duk_bool_t dummy;
    return duk_to_int_clamped_raw(ctx, index, minval, maxval, &dummy);
}
 
DUK_INTERNAL duk_int_t duk_to_int_check_range(duk_context *ctx, duk_idx_t index, duk_int_t minval, duk_int_t maxval) {
    return duk_to_int_clamped_raw(ctx, index, minval, maxval, NULL);  /* out_clamped==NULL -> RangeError if outside range */
}
 
DUK_EXTERNAL const char *duk_to_string(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);
 
    index = duk_require_normalize_index(ctx, index);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
 
    switch (DUK_TVAL_GET_TAG(tv)) {
    case DUK_TAG_UNDEFINED: {
        duk_push_hstring_stridx(ctx, DUK_STRIDX_LC_UNDEFINED);
        break;
    }
    case DUK_TAG_NULL: {
        duk_push_hstring_stridx(ctx, DUK_STRIDX_LC_NULL);
        break;
    }
    case DUK_TAG_BOOLEAN: {
        if (DUK_TVAL_GET_BOOLEAN(tv)) {
            duk_push_hstring_stridx(ctx, DUK_STRIDX_TRUE);
        } else {
            duk_push_hstring_stridx(ctx, DUK_STRIDX_FALSE);
        }
        break;
    }
    case DUK_TAG_STRING: {
        /* nop */
        goto skip_replace;
    }
    case DUK_TAG_OBJECT: {
        duk_to_primitive(ctx, index, DUK_HINT_STRING);
        return duk_to_string(ctx, index);  /* Note: recursive call */
    }
    case DUK_TAG_BUFFER: {
        duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
 
        /* Note: this allows creation of internal strings. */
 
        DUK_ASSERT(h != NULL);
        duk_push_lstring(ctx,
                         (const char *) DUK_HBUFFER_GET_DATA_PTR(thr->heap, h),
                         (duk_size_t) DUK_HBUFFER_GET_SIZE(h));
        break;
    }
    case DUK_TAG_POINTER: {
        void *ptr = DUK_TVAL_GET_POINTER(tv);
        if (ptr != NULL) {
            duk_push_sprintf(ctx, DUK_STR_FMT_PTR, (void *) ptr);
        } else {
            /* Represent a null pointer as 'null' to be consistent with
             * the JX format variant.  Native '%p' format for a NULL
             * pointer may be e.g. '(nil)'.
             */
            duk_push_hstring_stridx(ctx, DUK_STRIDX_LC_NULL);
        }
        break;
    }
    case DUK_TAG_LIGHTFUNC: {
        /* Should match Function.prototype.toString() */
        duk_push_lightfunc_tostring(ctx, tv);
        break;
    }
#if defined(DUK_USE_FASTINT)
    case DUK_TAG_FASTINT:
#endif
    default: {
        /* number */
        DUK_ASSERT(!DUK_TVAL_IS_UNUSED(tv));
        DUK_ASSERT(DUK_TVAL_IS_NUMBER(tv));
        duk_push_tval(ctx, tv);
        duk_numconv_stringify(ctx,
                              10 /*radix*/,
                              0 /*precision:shortest*/,
                              0 /*force_exponential*/);
        break;
    }
    }
 
    duk_replace(ctx, index);
 
 skip_replace:
    return duk_require_string(ctx, index);
}
 
DUK_INTERNAL duk_hstring *duk_to_hstring(duk_context *ctx, duk_idx_t index) {
    duk_hstring *ret;
    DUK_ASSERT_CTX_VALID(ctx);
    duk_to_string(ctx, index);
    ret = duk_get_hstring(ctx, index);
    DUK_ASSERT(ret != NULL);
    return ret;
}
 
DUK_EXTERNAL void *duk_to_buffer_raw(duk_context *ctx, duk_idx_t index, duk_size_t *out_size, duk_uint_t mode) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hbuffer *h_buf;
    const duk_uint8_t *src_data;
    duk_size_t src_size;
    duk_uint8_t *dst_data;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(thr);
 
    index = duk_require_normalize_index(ctx, index);
 
    h_buf = duk_get_hbuffer(ctx, index);
    if (h_buf != NULL) {
        /* Buffer is kept as is, with the fixed/dynamic nature of the
         * buffer only changed if requested.  An external buffer
         * is converted into a non-external dynamic buffer in a
         * duk_to_dynamic_buffer() call.
         */
        duk_uint_t tmp;
        duk_uint8_t *tmp_ptr;
 
        tmp_ptr = (duk_uint8_t *) DUK_HBUFFER_GET_DATA_PTR(thr->heap, h_buf);
        src_data = (const duk_uint8_t *) tmp_ptr;
        src_size = DUK_HBUFFER_GET_SIZE(h_buf);
 
        tmp = (DUK_HBUFFER_HAS_DYNAMIC(h_buf) ? DUK_BUF_MODE_DYNAMIC : DUK_BUF_MODE_FIXED);
        if ((tmp == mode && !DUK_HBUFFER_HAS_EXTERNAL(h_buf)) ||
            mode == DUK_BUF_MODE_DONTCARE) {
            /* Note: src_data may be NULL if input is a zero-size
             * dynamic buffer.
             */
            dst_data = tmp_ptr;
            goto skip_copy;
        }
    } else {
        /* Non-buffer value is first ToString() coerced, then converted
         * to a buffer (fixed buffer is used unless a dynamic buffer is
         * explicitly requested).
         */
 
        src_data = (const duk_uint8_t *) duk_to_lstring(ctx, index, &src_size);
    }
 
    dst_data = (duk_uint8_t *) duk_push_buffer(ctx, src_size, (mode == DUK_BUF_MODE_DYNAMIC) /*dynamic*/);
    if (DUK_LIKELY(src_size > 0)) {
        /* When src_size == 0, src_data may be NULL (if source
         * buffer is dynamic), and dst_data may be NULL (if
         * target buffer is dynamic).  Avoid zero-size memcpy()
         * with an invalid pointer.
         */
        DUK_MEMCPY((void *) dst_data, (const void *) src_data, (size_t) src_size);
    }
    duk_replace(ctx, index);
 skip_copy:
 
    if (out_size) {
        *out_size = src_size;
    }
    return dst_data;
}
 
DUK_EXTERNAL void *duk_to_pointer(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
    void *res;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    index = duk_require_normalize_index(ctx, index);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
 
    switch (DUK_TVAL_GET_TAG(tv)) {
    case DUK_TAG_UNDEFINED:
    case DUK_TAG_NULL:
    case DUK_TAG_BOOLEAN:
        res = NULL;
        break;
    case DUK_TAG_POINTER:
        res = DUK_TVAL_GET_POINTER(tv);
        break;
    case DUK_TAG_STRING:
    case DUK_TAG_OBJECT:
    case DUK_TAG_BUFFER:
        /* Heap allocated: return heap pointer which is NOT useful
         * for the caller, except for debugging.
         */
        res = (void *) DUK_TVAL_GET_HEAPHDR(tv);
        break;
    case DUK_TAG_LIGHTFUNC:
        /* Function pointers do not always cast correctly to void *
         * (depends on memory and segmentation model for instance),
         * so they coerce to NULL.
         */
        res = NULL;
        break;
#if defined(DUK_USE_FASTINT)
    case DUK_TAG_FASTINT:
#endif
    default:
        /* number */
        DUK_ASSERT(!DUK_TVAL_IS_UNUSED(tv));
        DUK_ASSERT(DUK_TVAL_IS_NUMBER(tv));
        res = NULL;
        break;
    }
 
    duk_push_pointer(ctx, res);
    duk_replace(ctx, index);
    return res;
}
 
DUK_EXTERNAL void duk_to_object(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    duk_uint_t flags = 0;   /* shared flags for a subset of types */
    duk_small_int_t proto = 0;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    index = duk_require_normalize_index(ctx, index);
 
    tv = duk_require_tval(ctx, index);
    DUK_ASSERT(tv != NULL);
 
    switch (DUK_TVAL_GET_TAG(tv)) {
    case DUK_TAG_UNDEFINED:
    case DUK_TAG_NULL: {
        DUK_ERROR_TYPE(thr, DUK_STR_NOT_OBJECT_COERCIBLE);
        break;
    }
    case DUK_TAG_BOOLEAN: {
        flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
                DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_BOOLEAN);
        proto = DUK_BIDX_BOOLEAN_PROTOTYPE;
        goto create_object;
    }
    case DUK_TAG_STRING: {
        flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
                DUK_HOBJECT_FLAG_EXOTIC_STRINGOBJ |
                DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_STRING);
        proto = DUK_BIDX_STRING_PROTOTYPE;
        goto create_object;
    }
    case DUK_TAG_OBJECT: {
        /* nop */
        break;
    }
    case DUK_TAG_BUFFER: {
        /* A plain buffer coerces to a Duktape.Buffer because it's the
         * object counterpart of the plain buffer value.  But it might
         * still make more sense to produce an ArrayBuffer here?
         */
 
        duk_hbufferobject *h_bufobj;
        duk_hbuffer *h_val;
 
        h_val = DUK_TVAL_GET_BUFFER(tv);
        DUK_ASSERT(h_val != NULL);
 
        h_bufobj = duk_push_bufferobject_raw(ctx,
                                             DUK_HOBJECT_FLAG_EXTENSIBLE |
                                             DUK_HOBJECT_FLAG_BUFFEROBJECT |
                                             DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_BUFFER),
                                             DUK_BIDX_BUFFER_PROTOTYPE);
        DUK_ASSERT(h_bufobj != NULL);
        DUK_ASSERT(DUK_HOBJECT_HAS_EXTENSIBLE((duk_hobject *) h_bufobj));
        DUK_ASSERT(DUK_HOBJECT_IS_BUFFEROBJECT((duk_hobject *) h_bufobj));
 
        h_bufobj->buf = h_val;
        DUK_HBUFFER_INCREF(thr, h_val);
        DUK_ASSERT(h_bufobj->offset == 0);
        h_bufobj->length = (duk_uint_t) DUK_HBUFFER_GET_SIZE(h_val);
        DUK_ASSERT(h_bufobj->shift == 0);
        DUK_ASSERT(h_bufobj->elem_type == DUK_HBUFFEROBJECT_ELEM_UINT8);
 
        DUK_ASSERT_HBUFFEROBJECT_VALID(h_bufobj);
        goto replace_value;
    }
    case DUK_TAG_POINTER: {
        flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
                DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_POINTER);
        proto = DUK_BIDX_POINTER_PROTOTYPE;
        goto create_object;
    }
    case DUK_TAG_LIGHTFUNC: {
        /* Lightfunc coerces to a Function instance with concrete
         * properties.  Since 'length' is virtual for Duktape/C
         * functions, don't need to define that.
         *
         * The result is made extensible to mimic what happens to
         * strings:
         *   > Object.isExtensible(Object('foo'))
         *   true
         */
        duk_small_uint_t lf_flags;
        duk_idx_t nargs;
        duk_small_uint_t lf_len;
        duk_c_function func;
        duk_hnativefunction *nf;
 
        DUK_TVAL_GET_LIGHTFUNC(tv, func, lf_flags);
 
        nargs = (duk_idx_t) DUK_LFUNC_FLAGS_GET_NARGS(lf_flags);
        if (nargs == DUK_LFUNC_NARGS_VARARGS) {
            nargs = (duk_idx_t) DUK_VARARGS;
        }
        flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
                DUK_HOBJECT_FLAG_CONSTRUCTABLE |
                DUK_HOBJECT_FLAG_NATIVEFUNCTION |
                    DUK_HOBJECT_FLAG_NEWENV |
                    DUK_HOBJECT_FLAG_STRICT |
                    DUK_HOBJECT_FLAG_NOTAIL |
            /* DUK_HOBJECT_FLAG_EXOTIC_DUKFUNC: omitted here intentionally */
                    DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_FUNCTION);
        (void) duk__push_c_function_raw(ctx, func, nargs, flags);
 
        lf_len = DUK_LFUNC_FLAGS_GET_LENGTH(lf_flags);
        if ((duk_idx_t) lf_len != nargs) {
            /* Explicit length is only needed if it differs from 'nargs'. */
            duk_push_int(ctx, (duk_int_t) lf_len);
            duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_LENGTH, DUK_PROPDESC_FLAGS_NONE);
        }
        duk_push_lightfunc_name(ctx, tv);
        duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_NAME, DUK_PROPDESC_FLAGS_NONE);
 
        nf = duk_get_hnativefunction(ctx, -1);
        DUK_ASSERT(nf != NULL);
        nf->magic = (duk_int16_t) DUK_LFUNC_FLAGS_GET_MAGIC(lf_flags);
 
        /* Enable DUKFUNC exotic behavior once properties are set up. */
        DUK_HOBJECT_SET_EXOTIC_DUKFUNC((duk_hobject *) nf);
        goto replace_value;
    }
#if defined(DUK_USE_FASTINT)
    case DUK_TAG_FASTINT:
#endif
    default: {
        DUK_ASSERT(!DUK_TVAL_IS_UNUSED(tv));
        DUK_ASSERT(DUK_TVAL_IS_NUMBER(tv));
        flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
                       DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_NUMBER);
        proto = DUK_BIDX_NUMBER_PROTOTYPE;
        goto create_object;
    }
    }
    return;
 
 create_object:
    (void) duk_push_object_helper(ctx, flags, proto);
 
    /* Note: Boolean prototype's internal value property is not writable,
     * but duk_xdef_prop_stridx() disregards the write protection.  Boolean
     * instances are immutable.
     *
     * String and buffer special behaviors are already enabled which is not
     * ideal, but a write to the internal value is not affected by them.
     */
    duk_dup(ctx, index);
    duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_INT_VALUE, DUK_PROPDESC_FLAGS_NONE);
 
 replace_value:
    duk_replace(ctx, index);
}
 
/*
 *  Type checking
 */
 
DUK_LOCAL duk_bool_t duk__tag_check(duk_context *ctx, duk_idx_t index, duk_small_uint_t tag) {
    duk_tval *tv;
 
    tv = duk_get_tval(ctx, index);
    if (!tv) {
        return 0;
    }
    return (DUK_TVAL_GET_TAG(tv) == tag);
}
 
DUK_LOCAL duk_bool_t duk__obj_flag_any_default_false(duk_context *ctx, duk_idx_t index, duk_uint_t flag_mask) {
    duk_hobject *obj;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    obj = duk_get_hobject(ctx, index);
    if (obj) {
        return (DUK_HEAPHDR_CHECK_FLAG_BITS((duk_heaphdr *) obj, flag_mask) ? 1 : 0);
    }
    return 0;
}
 
DUK_EXTERNAL duk_int_t duk_get_type(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (!tv) {
        return DUK_TYPE_NONE;
    }
    switch (DUK_TVAL_GET_TAG(tv)) {
    case DUK_TAG_UNDEFINED:
        return DUK_TYPE_UNDEFINED;
    case DUK_TAG_NULL:
        return DUK_TYPE_NULL;
    case DUK_TAG_BOOLEAN:
        return DUK_TYPE_BOOLEAN;
    case DUK_TAG_STRING:
        return DUK_TYPE_STRING;
    case DUK_TAG_OBJECT:
        return DUK_TYPE_OBJECT;
    case DUK_TAG_BUFFER:
        return DUK_TYPE_BUFFER;
    case DUK_TAG_POINTER:
        return DUK_TYPE_POINTER;
    case DUK_TAG_LIGHTFUNC:
        return DUK_TYPE_LIGHTFUNC;
#if defined(DUK_USE_FASTINT)
    case DUK_TAG_FASTINT:
#endif
    default:
        /* Note: number has no explicit tag (in 8-byte representation) */
        DUK_ASSERT(!DUK_TVAL_IS_UNUSED(tv));
        DUK_ASSERT(DUK_TVAL_IS_NUMBER(tv));
        return DUK_TYPE_NUMBER;
    }
    DUK_UNREACHABLE();
}
 
#if defined(DUK_USE_VERBOSE_ERRORS) && defined(DUK_USE_PARANOID_ERRORS)
DUK_LOCAL const char *duk__type_names[] = {
    "none",
    "undefined",
    "null",
    "boolean",
    "number",
    "string",
    "object",
    "buffer",
    "pointer",
    "lightfunc"
};
 
DUK_INTERNAL const char *duk_get_type_name(duk_context *ctx, duk_idx_t index) {
    duk_int_t type_tag;
 
    type_tag = duk_get_type(ctx, index);
    DUK_ASSERT(type_tag >= DUK_TYPE_MIN && type_tag <= DUK_TYPE_MAX);
    DUK_ASSERT(DUK_TYPE_MIN == 0 && sizeof(duk__type_names) / sizeof(const char *) == DUK_TYPE_MAX + 1);
 
    return duk__type_names[type_tag];
}
#endif
 
DUK_EXTERNAL duk_bool_t duk_check_type(duk_context *ctx, duk_idx_t index, duk_int_t type) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    return (duk_get_type(ctx, index) == type) ? 1 : 0;
}
 
DUK_EXTERNAL duk_uint_t duk_get_type_mask(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (!tv) {
        return DUK_TYPE_MASK_NONE;
    }
    switch (DUK_TVAL_GET_TAG(tv)) {
    case DUK_TAG_UNDEFINED:
        return DUK_TYPE_MASK_UNDEFINED;
    case DUK_TAG_NULL:
        return DUK_TYPE_MASK_NULL;
    case DUK_TAG_BOOLEAN:
        return DUK_TYPE_MASK_BOOLEAN;
    case DUK_TAG_STRING:
        return DUK_TYPE_MASK_STRING;
    case DUK_TAG_OBJECT:
        return DUK_TYPE_MASK_OBJECT;
    case DUK_TAG_BUFFER:
        return DUK_TYPE_MASK_BUFFER;
    case DUK_TAG_POINTER:
        return DUK_TYPE_MASK_POINTER;
    case DUK_TAG_LIGHTFUNC:
        return DUK_TYPE_MASK_LIGHTFUNC;
#if defined(DUK_USE_FASTINT)
    case DUK_TAG_FASTINT:
#endif
    default:
        /* Note: number has no explicit tag (in 8-byte representation) */
        DUK_ASSERT(!DUK_TVAL_IS_UNUSED(tv));
        DUK_ASSERT(DUK_TVAL_IS_NUMBER(tv));
        return DUK_TYPE_MASK_NUMBER;
    }
    DUK_UNREACHABLE();
}
 
DUK_EXTERNAL duk_bool_t duk_check_type_mask(duk_context *ctx, duk_idx_t index, duk_uint_t mask) {
    duk_hthread *thr = (duk_hthread *) ctx;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    if (duk_get_type_mask(ctx, index) & mask) {
        return 1;
    }
    if (mask & DUK_TYPE_MASK_THROW) {
        DUK_ERROR_TYPE(thr, DUK_STR_UNEXPECTED_TYPE);
        DUK_UNREACHABLE();
    }
    return 0;
}
 
DUK_EXTERNAL duk_bool_t duk_is_undefined(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_UNDEFINED);
}
 
DUK_EXTERNAL duk_bool_t duk_is_null(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_NULL);
}
 
DUK_EXTERNAL duk_bool_t duk_is_null_or_undefined(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
    duk_small_uint_t tag;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (!tv) {
        return 0;
    }
    tag = DUK_TVAL_GET_TAG(tv);
    return (tag == DUK_TAG_UNDEFINED) || (tag == DUK_TAG_NULL);
}
 
DUK_EXTERNAL duk_bool_t duk_is_boolean(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_BOOLEAN);
}
 
DUK_EXTERNAL duk_bool_t duk_is_number(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /*
     *  Number is special because it doesn't have a specific
     *  tag in the 8-byte representation.
     */
 
    /* XXX: shorter version for 12-byte representation? */
 
    tv = duk_get_tval(ctx, index);
    if (!tv) {
        return 0;
    }
    return DUK_TVAL_IS_NUMBER(tv);
}
 
DUK_EXTERNAL duk_bool_t duk_is_nan(duk_context *ctx, duk_idx_t index) {
    /* XXX: This will now return false for non-numbers, even though they would
     * coerce to NaN (as a general rule).  In particular, duk_get_number()
     * returns a NaN for non-numbers, so should this function also return
     * true for non-numbers?
     */
 
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (!tv || !DUK_TVAL_IS_NUMBER(tv)) {
        return 0;
    }
    return DUK_ISNAN(DUK_TVAL_GET_NUMBER(tv));
}
 
DUK_EXTERNAL duk_bool_t duk_is_string(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_STRING);
}
 
DUK_EXTERNAL duk_bool_t duk_is_object(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_OBJECT);
}
 
DUK_EXTERNAL duk_bool_t duk_is_buffer(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_BUFFER);
}
 
DUK_EXTERNAL duk_bool_t duk_is_pointer(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_POINTER);
}
 
DUK_EXTERNAL duk_bool_t duk_is_lightfunc(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__tag_check(ctx, index, DUK_TAG_LIGHTFUNC);
}
 
DUK_EXTERNAL duk_bool_t duk_is_array(duk_context *ctx, duk_idx_t index) {
    duk_hobject *obj;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    obj = duk_get_hobject(ctx, index);
    if (obj) {
        return (DUK_HOBJECT_GET_CLASS_NUMBER(obj) == DUK_HOBJECT_CLASS_ARRAY ? 1 : 0);
    }
    return 0;
}
 
DUK_EXTERNAL duk_bool_t duk_is_function(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_LIGHTFUNC(tv)) {
        return 1;
    }
    return duk__obj_flag_any_default_false(ctx,
                                           index,
                                           DUK_HOBJECT_FLAG_COMPILEDFUNCTION |
                                           DUK_HOBJECT_FLAG_NATIVEFUNCTION |
                                           DUK_HOBJECT_FLAG_BOUND);
}
 
DUK_EXTERNAL duk_bool_t duk_is_c_function(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__obj_flag_any_default_false(ctx,
                                           index,
                                           DUK_HOBJECT_FLAG_NATIVEFUNCTION);
}
 
DUK_EXTERNAL duk_bool_t duk_is_ecmascript_function(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__obj_flag_any_default_false(ctx,
                                           index,
                                           DUK_HOBJECT_FLAG_COMPILEDFUNCTION);
}
 
DUK_EXTERNAL duk_bool_t duk_is_bound_function(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__obj_flag_any_default_false(ctx,
                                           index,
                                           DUK_HOBJECT_FLAG_BOUND);
}
 
DUK_EXTERNAL duk_bool_t duk_is_thread(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk__obj_flag_any_default_false(ctx,
                                           index,
                                           DUK_HOBJECT_FLAG_THREAD);
}
 
DUK_EXTERNAL duk_bool_t duk_is_fixed_buffer(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_BUFFER(tv)) {
        duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
        DUK_ASSERT(h != NULL);
        return (DUK_HBUFFER_HAS_DYNAMIC(h) ? 0 : 1);
    }
    return 0;
}
 
DUK_EXTERNAL duk_bool_t duk_is_dynamic_buffer(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_BUFFER(tv)) {
        duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
        DUK_ASSERT(h != NULL);
        return (DUK_HBUFFER_HAS_DYNAMIC(h) && !DUK_HBUFFER_HAS_EXTERNAL(h) ? 1 : 0);
    }
    return 0;
}
 
DUK_EXTERNAL duk_bool_t duk_is_external_buffer(duk_context *ctx, duk_idx_t index) {
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv = duk_get_tval(ctx, index);
    if (tv && DUK_TVAL_IS_BUFFER(tv)) {
        duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
        DUK_ASSERT(h != NULL);
        return (DUK_HBUFFER_HAS_DYNAMIC(h) && DUK_HBUFFER_HAS_EXTERNAL(h) ? 1 : 0);
    }
    return 0;
}
 
DUK_EXTERNAL duk_errcode_t duk_get_error_code(duk_context *ctx, duk_idx_t index) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hobject *h;
    duk_uint_t sanity;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    h = duk_get_hobject(ctx, index);
 
    sanity = DUK_HOBJECT_PROTOTYPE_CHAIN_SANITY;
    do {
        if (!h) {
            return DUK_ERR_NONE;
        }
        if (h == thr->builtins[DUK_BIDX_EVAL_ERROR_PROTOTYPE]) {
            return DUK_ERR_EVAL_ERROR;
        }
        if (h == thr->builtins[DUK_BIDX_RANGE_ERROR_PROTOTYPE]) {
            return DUK_ERR_RANGE_ERROR;
        }
        if (h == thr->builtins[DUK_BIDX_REFERENCE_ERROR_PROTOTYPE]) {
            return DUK_ERR_REFERENCE_ERROR;
        }
        if (h == thr->builtins[DUK_BIDX_SYNTAX_ERROR_PROTOTYPE]) {
            return DUK_ERR_SYNTAX_ERROR;
        }
        if (h == thr->builtins[DUK_BIDX_TYPE_ERROR_PROTOTYPE]) {
            return DUK_ERR_TYPE_ERROR;
        }
        if (h == thr->builtins[DUK_BIDX_URI_ERROR_PROTOTYPE]) {
            return DUK_ERR_URI_ERROR;
        }
        if (h == thr->builtins[DUK_BIDX_ERROR_PROTOTYPE]) {
            return DUK_ERR_ERROR;
        }
 
        h = DUK_HOBJECT_GET_PROTOTYPE(thr->heap, h);
    } while (--sanity > 0);
 
    return DUK_ERR_NONE;
}
 
/*
 *  Pushers
 */
 
DUK_INTERNAL void duk_push_tval(duk_context *ctx, duk_tval *tv) {
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(tv != NULL);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_TVAL(tv_slot, tv);
    DUK_TVAL_INCREF(thr, tv);  /* no side effects */
}
 
DUK_EXTERNAL void duk_push_undefined(duk_context *ctx) {
    duk_hthread *thr;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
 
    /* Because value stack init policy is 'undefined above top',
     * we don't need to write, just assert.
     */
    thr->valstack_top++;
    DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(thr->valstack_top - 1));
}
 
DUK_EXTERNAL void duk_push_null(duk_context *ctx) {
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_NULL(tv_slot);
}
 
DUK_EXTERNAL void duk_push_boolean(duk_context *ctx, duk_bool_t val) {
    duk_hthread *thr;
    duk_tval *tv_slot;
    duk_small_int_t b;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    b = (val ? 1 : 0);  /* ensure value is 1 or 0 (not other non-zero) */
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_BOOLEAN(tv_slot, b);
}
 
DUK_EXTERNAL void duk_push_true(duk_context *ctx) {
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_BOOLEAN_TRUE(tv_slot);
}
 
DUK_EXTERNAL void duk_push_false(duk_context *ctx) {
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_BOOLEAN_FALSE(tv_slot);
}
 
/* normalize NaN which may not match our canonical internal NaN */
DUK_EXTERNAL void duk_push_number(duk_context *ctx, duk_double_t val) {
    duk_hthread *thr;
    duk_tval *tv_slot;
    duk_double_union du;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    du.d = val;
    DUK_DBLUNION_NORMALIZE_NAN_CHECK(&du);
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_NUMBER(tv_slot, du.d);
}
 
DUK_EXTERNAL void duk_push_int(duk_context *ctx, duk_int_t val) {
#if defined(DUK_USE_FASTINT)
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    tv_slot = thr->valstack_top++;
#if DUK_INT_MAX <= 0x7fffffffL
    DUK_TVAL_SET_FASTINT_I32(tv_slot, (duk_int32_t) val);
#else
    if (val >= DUK_FASTINT_MIN && val <= DUK_FASTINT_MAX) {
        DUK_TVAL_SET_FASTINT(tv_slot, (duk_int64_t) val);
    } else {
        duk_double_t = (duk_double_t) val;
        DUK_TVAL_SET_NUMBER(tv_slot, d);
    }
#endif
#else  /* DUK_USE_FASTINT */
    duk_hthread *thr;
    duk_tval *tv_slot;
    duk_double_t d;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    d = (duk_double_t) val;
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_NUMBER(tv_slot, d);
#endif  /* DUK_USE_FASTINT */
}
 
DUK_EXTERNAL void duk_push_uint(duk_context *ctx, duk_uint_t val) {
#if defined(DUK_USE_FASTINT)
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    tv_slot = thr->valstack_top++;
#if DUK_UINT_MAX <= 0xffffffffUL
    DUK_TVAL_SET_FASTINT_U32(tv_slot, (duk_uint32_t) val);
#else
    if (val <= DUK_FASTINT_MAX) {  /* val is unsigned so >= 0 */
        /* XXX: take advantage of val being unsigned, no need to mask */
        DUK_TVAL_SET_FASTINT(tv_slot, (duk_int64_t) val);
    } else {
        duk_double_t = (duk_double_t) val;
        DUK_TVAL_SET_NUMBER(tv_slot, d);
    }
#endif
#else  /* DUK_USE_FASTINT */
    duk_hthread *thr;
    duk_tval *tv_slot;
    duk_double_t d;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    d = (duk_double_t) val;
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_NUMBER(tv_slot, d);
#endif  /* DUK_USE_FASTINT */
}
 
DUK_EXTERNAL void duk_push_nan(duk_context *ctx) {
    duk_hthread *thr;
    duk_tval *tv_slot;
    duk_double_union du;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    DUK_DBLUNION_SET_NAN(&du);
    DUK_ASSERT(DUK_DBLUNION_IS_NORMALIZED(&du));
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_NUMBER(tv_slot, du.d);
}
 
DUK_EXTERNAL const char *duk_push_lstring(duk_context *ctx, const char *str, duk_size_t len) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hstring *h;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* check stack before interning (avoid hanging temp) */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
 
    /* NULL with zero length represents an empty string; NULL with higher
     * length is also now trated like an empty string although it is
     * a bit dubious.  This is unlike duk_push_string() which pushes a
     * 'null' if the input string is a NULL.
     */
    if (!str) {
        len = 0;
    }
 
    /* Check for maximum string length */
    if (len > DUK_HSTRING_MAX_BYTELEN) {
        DUK_ERROR_RANGE(thr, DUK_STR_STRING_TOO_LONG);
    }
 
    h = duk_heap_string_intern_checked(thr, (const duk_uint8_t *) str, (duk_uint32_t) len);
    DUK_ASSERT(h != NULL);
 
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_STRING(tv_slot, h);
    DUK_HSTRING_INCREF(thr, h);  /* no side effects */
 
    return (const char *) DUK_HSTRING_GET_DATA(h);
}
 
DUK_EXTERNAL const char *duk_push_string(duk_context *ctx, const char *str) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    if (str) {
        return duk_push_lstring(ctx, str, DUK_STRLEN(str));
    } else {
        duk_push_null(ctx);
        return NULL;
    }
}
 
#ifdef DUK_USE_FILE_IO
/* This is a bit clunky because it is ANSI C portable.  Should perhaps
 * relocate to another file because this is potentially platform
 * dependent.
 */
DUK_EXTERNAL const char *duk_push_string_file_raw(duk_context *ctx, const char *path, duk_uint_t flags) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_file *f = NULL;
    char *buf;
    long sz;  /* ANSI C typing */
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    if (!path) {
        goto fail;
    }
    f = DUK_FOPEN(path, "rb");
    if (!f) {
        goto fail;
    }
    if (DUK_FSEEK(f, 0, SEEK_END) < 0) {
        goto fail;
    }
    sz = DUK_FTELL(f);
    if (sz < 0) {
        goto fail;
    }
    if (DUK_FSEEK(f, 0, SEEK_SET) < 0) {
        goto fail;
    }
    buf = (char *) duk_push_fixed_buffer(ctx, (duk_size_t) sz);
    DUK_ASSERT(buf != NULL);
    if ((duk_size_t) DUK_FREAD(buf, 1, (size_t) sz, f) != (duk_size_t) sz) {
        goto fail;
    }
    (void) DUK_FCLOSE(f);  /* ignore fclose() error */
    f = NULL;
    return duk_to_string(ctx, -1);
 
 fail:
    if (f) {
        DUK_FCLOSE(f);
    }
 
    if (flags != 0) {
        DUK_ASSERT(flags == DUK_STRING_PUSH_SAFE);  /* only flag now */
        duk_push_undefined(ctx);
    } else {
        /* XXX: string not shared because it is conditional */
        DUK_ERROR_TYPE(thr, "read file error");
    }
    return NULL;
}
#else
DUK_EXTERNAL const char *duk_push_string_file_raw(duk_context *ctx, const char *path, duk_uint_t flags) {
    duk_hthread *thr = (duk_hthread *) ctx;
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(path);
 
    if (flags != 0) {
        DUK_ASSERT(flags == DUK_STRING_PUSH_SAFE);  /* only flag now */
        duk_push_undefined(ctx);
    } else {
        /* XXX: string not shared because it is conditional */
        DUK_ERROR_UNSUPPORTED(thr, "file I/O disabled");
    }
    return NULL;
}
#endif  /* DUK_USE_FILE_IO */
 
DUK_EXTERNAL void duk_push_pointer(duk_context *ctx, void *val) {
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK__CHECK_SPACE();
    tv_slot = thr->valstack_top++;
    DUK_TVAL_SET_POINTER(tv_slot, val);
}
 
DUK_LOCAL void duk__push_this_helper(duk_context *ctx, duk_small_uint_t check_object_coercible) {
    duk_hthread *thr;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT_DISABLE(thr->callstack_top >= 0);  /* avoid warning (unsigned) */
    thr = (duk_hthread *) ctx;
    DUK_ASSERT(thr->callstack_top <= thr->callstack_size);
    DUK__CHECK_SPACE();
 
    DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(thr->valstack_top));  /* because of valstack init policy */
    tv_slot = thr->valstack_top++;
 
    if (DUK_UNLIKELY(thr->callstack_top == 0)) {
        if (check_object_coercible) {
            goto type_error;
        }
        /* 'undefined' already on stack top */
    } else {
        duk_tval *tv;
 
        /* 'this' binding is just before current activation's bottom */
        DUK_ASSERT(thr->valstack_bottom > thr->valstack);
        tv = thr->valstack_bottom - 1;
        if (check_object_coercible &&
            (DUK_TVAL_IS_UNDEFINED(tv) || DUK_TVAL_IS_NULL(tv))) {
            /* XXX: better macro for DUK_TVAL_IS_UNDEFINED_OR_NULL(tv) */
            goto type_error;
        }
 
        DUK_TVAL_SET_TVAL(tv_slot, tv);
        DUK_TVAL_INCREF(thr, tv);
    }
    return;
 
 type_error:
    DUK_ERROR_TYPE(thr, DUK_STR_NOT_OBJECT_COERCIBLE);
}
 
DUK_EXTERNAL void duk_push_this(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk__push_this_helper(ctx, 0 /*check_object_coercible*/);
}
 
DUK_INTERNAL void duk_push_this_check_object_coercible(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk__push_this_helper(ctx, 1 /*check_object_coercible*/);
}
 
DUK_INTERNAL duk_hobject *duk_push_this_coercible_to_object(duk_context *ctx) {
    duk_hobject *h;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk__push_this_helper(ctx, 1 /*check_object_coercible*/);
    duk_to_object(ctx, -1);
    h = duk_get_hobject(ctx, -1);
    DUK_ASSERT(h != NULL);
    return h;
}
 
DUK_INTERNAL duk_hstring *duk_push_this_coercible_to_string(duk_context *ctx) {
    duk_hstring *h;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk__push_this_helper(ctx, 1 /*check_object_coercible*/);
    duk_to_string(ctx, -1);
    h = duk_get_hstring(ctx, -1);
    DUK_ASSERT(h != NULL);
    return h;
}
 
DUK_INTERNAL duk_tval *duk_get_borrowed_this_tval(duk_context *ctx) {
    duk_hthread *thr;
 
    DUK_ASSERT(ctx != NULL);
    thr = (duk_hthread *) ctx;
 
    DUK_ASSERT(thr->callstack_top > 0);  /* caller required to know */
    DUK_ASSERT(thr->valstack_bottom > thr->valstack);  /* consequence of above */
    DUK_ASSERT(thr->valstack_bottom - 1 >= thr->valstack);  /* 'this' binding exists */
 
    return thr->valstack_bottom - 1;
}
 
DUK_EXTERNAL void duk_push_current_function(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_activation *act;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT_DISABLE(thr->callstack_top >= 0);
    DUK_ASSERT(thr->callstack_top <= thr->callstack_size);
 
    act = duk_hthread_get_current_activation(thr);
    if (act) {
        duk_push_tval(ctx, &act->tv_func);
    } else {
        duk_push_undefined(ctx);
    }
}
 
DUK_EXTERNAL void duk_push_current_thread(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
 
    if (thr->heap->curr_thread) {
        duk_push_hobject(ctx, (duk_hobject *) thr->heap->curr_thread);
    } else {
        duk_push_undefined(ctx);
    }
}
 
DUK_EXTERNAL void duk_push_global_object(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk_push_hobject_bidx(ctx, DUK_BIDX_GLOBAL);
}
 
/* XXX: size optimize */
DUK_LOCAL void duk__push_stash(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
    if (!duk_get_prop_stridx(ctx, -1, DUK_STRIDX_INT_VALUE)) {
        DUK_DDD(DUK_DDDPRINT("creating heap/global/thread stash on first use"));
        duk_pop(ctx);
        duk_push_object_internal(ctx);
        duk_dup_top(ctx);
        duk_xdef_prop_stridx(ctx, -3, DUK_STRIDX_INT_VALUE, DUK_PROPDESC_FLAGS_C);  /* [ ... parent stash stash ] -> [ ... parent stash ] */
    }
    duk_remove(ctx, -2);
}
 
DUK_EXTERNAL void duk_push_heap_stash(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_heap *heap;
    DUK_ASSERT_CTX_VALID(ctx);
    heap = thr->heap;
    DUK_ASSERT(heap->heap_object != NULL);
    duk_push_hobject(ctx, heap->heap_object);
    duk__push_stash(ctx);
}
 
DUK_EXTERNAL void duk_push_global_stash(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
    duk_push_global_object(ctx);
    duk__push_stash(ctx);
}
 
DUK_EXTERNAL void duk_push_thread_stash(duk_context *ctx, duk_context *target_ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    DUK_ASSERT_CTX_VALID(ctx);
    if (!target_ctx) {
        DUK_ERROR_API(thr, DUK_STR_INVALID_CALL_ARGS);
        return;  /* not reached */
    }
    duk_push_hobject(ctx, (duk_hobject *) target_ctx);
    duk__push_stash(ctx);
}
 
/* XXX: duk_ssize_t would be useful here */
DUK_LOCAL duk_int_t duk__try_push_vsprintf(duk_context *ctx, void *buf, duk_size_t sz, const char *fmt, va_list ap) {
    duk_int_t len;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(ctx);
 
    /* NUL terminator handling doesn't matter here */
    len = DUK_VSNPRINTF((char *) buf, sz, fmt, ap);
    if (len < (duk_int_t) sz) {
        /* Return value of 'sz' or more indicates output was (potentially)
         * truncated.
         */
        return (duk_int_t) len;
    }
    return -1;
}
 
DUK_EXTERNAL const char *duk_push_vsprintf(duk_context *ctx, const char *fmt, va_list ap) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_uint8_t stack_buf[DUK_PUSH_SPRINTF_INITIAL_SIZE];
    duk_size_t sz = DUK_PUSH_SPRINTF_INITIAL_SIZE;
    duk_bool_t pushed_buf = 0;
    void *buf;
    duk_int_t len;  /* XXX: duk_ssize_t */
    const char *res;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* special handling of fmt==NULL */
    if (!fmt) {
        duk_hstring *h_str;
        duk_push_hstring_stridx(ctx, DUK_STRIDX_EMPTY_STRING);
        h_str = DUK_HTHREAD_STRING_EMPTY_STRING(thr);  /* rely on interning, must be this string */
        return (const char *) DUK_HSTRING_GET_DATA(h_str);
    }
 
    /* initial estimate based on format string */
    sz = DUK_STRLEN(fmt) + 16;  /* format plus something to avoid just missing */
    if (sz < DUK_PUSH_SPRINTF_INITIAL_SIZE) {
        sz = DUK_PUSH_SPRINTF_INITIAL_SIZE;
    }
    DUK_ASSERT(sz > 0);
 
    /* Try to make do with a stack buffer to avoid allocating a temporary buffer.
     * This works 99% of the time which is quite nice.
     */
    for (;;) {
        va_list ap_copy;  /* copied so that 'ap' can be reused */
 
        if (sz <= sizeof(stack_buf)) {
            buf = stack_buf;
        } else if (!pushed_buf) {
            pushed_buf = 1;
            buf = duk_push_dynamic_buffer(ctx, sz);
        } else {
            buf = duk_resize_buffer(ctx, -1, sz);
        }
        DUK_ASSERT(buf != NULL);
 
        DUK_VA_COPY(ap_copy, ap);
        len = duk__try_push_vsprintf(ctx, buf, sz, fmt, ap_copy);
        va_end(ap_copy);
        if (len >= 0) {
            break;
        }
 
        /* failed, resize and try again */
        sz = sz * 2;
        if (sz >= DUK_PUSH_SPRINTF_SANITY_LIMIT) {
            DUK_ERROR_API(thr, DUK_STR_SPRINTF_TOO_LONG);
        }
    }
 
    /* Cannot use duk_to_string() on the buffer because it is usually
     * larger than 'len'.  Also, 'buf' is usually a stack buffer.
     */
    res = duk_push_lstring(ctx, (const char *) buf, (duk_size_t) len);  /* [ buf? res ] */
    if (pushed_buf) {
        duk_remove(ctx, -2);
    }
    return res;
}
 
DUK_EXTERNAL const char *duk_push_sprintf(duk_context *ctx, const char *fmt, ...) {
    va_list ap;
    const char *ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* allow fmt==NULL */
    va_start(ap, fmt);
    ret = duk_push_vsprintf(ctx, fmt, ap);
    va_end(ap);
 
    return ret;
}
 
DUK_INTERNAL duk_idx_t duk_push_object_helper(duk_context *ctx, duk_uint_t hobject_flags_and_class, duk_small_int_t prototype_bidx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv_slot;
    duk_hobject *h;
    duk_idx_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(prototype_bidx == -1 ||
               (prototype_bidx >= 0 && prototype_bidx < DUK_NUM_BUILTINS));
 
    /* check stack first */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
 
    h = duk_hobject_alloc(thr->heap, hobject_flags_and_class);
    if (!h) {
        DUK_ERROR_ALLOC_DEFMSG(thr);
    }
 
    DUK_DDD(DUK_DDDPRINT("created object with flags: 0x%08lx", (unsigned long) h->hdr.h_flags));
 
    tv_slot = thr->valstack_top;
    DUK_TVAL_SET_OBJECT(tv_slot, h);
    DUK_HOBJECT_INCREF(thr, h);  /* no side effects */
    ret = (duk_idx_t) (thr->valstack_top - thr->valstack_bottom);
    thr->valstack_top++;
 
    /* object is now reachable */
 
    if (prototype_bidx >= 0) {
        DUK_HOBJECT_SET_PROTOTYPE_UPDREF(thr, h, thr->builtins[prototype_bidx]);
    } else {
        DUK_ASSERT(prototype_bidx == -1);
        DUK_ASSERT(DUK_HOBJECT_GET_PROTOTYPE(thr->heap, h) == NULL);
    }
 
    return ret;
}
 
DUK_INTERNAL duk_idx_t duk_push_object_helper_proto(duk_context *ctx, duk_uint_t hobject_flags_and_class, duk_hobject *proto) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_idx_t ret;
    duk_hobject *h;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    ret = duk_push_object_helper(ctx, hobject_flags_and_class, -1);
    h = duk_get_hobject(ctx, -1);
    DUK_ASSERT(h != NULL);
    DUK_ASSERT(DUK_HOBJECT_GET_PROTOTYPE(thr->heap, h) == NULL);
    DUK_HOBJECT_SET_PROTOTYPE_UPDREF(thr, h, proto);
    return ret;
}
 
DUK_EXTERNAL duk_idx_t duk_push_object(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    return duk_push_object_helper(ctx,
                                  DUK_HOBJECT_FLAG_EXTENSIBLE |
                                  DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_OBJECT),
                                  DUK_BIDX_OBJECT_PROTOTYPE);
}
 
DUK_EXTERNAL duk_idx_t duk_push_array(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hobject *obj;
    duk_idx_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    ret = duk_push_object_helper(ctx,
                                 DUK_HOBJECT_FLAG_EXTENSIBLE |
                                 DUK_HOBJECT_FLAG_ARRAY_PART |
                                 DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_ARRAY),
                                 DUK_BIDX_ARRAY_PROTOTYPE);
 
    obj = duk_require_hobject(ctx, ret);
 
    /*
     *  An array must have a 'length' property (E5 Section 15.4.5.2).
     *  The special array behavior flag must only be enabled once the
     *  length property has been added.
     *
     *  The internal property must be a number (and preferably a
     *  fastint if fastint support is enabled).
     */
 
    duk_push_int(ctx, 0);
#if defined(DUK_USE_FASTINT)
    DUK_ASSERT(DUK_TVAL_IS_FASTINT(duk_require_tval(ctx, -1)));
#endif
 
    duk_hobject_define_property_internal(thr,
                                         obj,
                                         DUK_HTHREAD_STRING_LENGTH(thr),
                                         DUK_PROPDESC_FLAGS_W);
    DUK_HOBJECT_SET_EXOTIC_ARRAY(obj);
 
    return ret;
}
 
DUK_EXTERNAL duk_idx_t duk_push_thread_raw(duk_context *ctx, duk_uint_t flags) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hthread *obj;
    duk_idx_t ret;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* check stack first */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
 
    obj = duk_hthread_alloc(thr->heap,
                            DUK_HOBJECT_FLAG_EXTENSIBLE |
                            DUK_HOBJECT_FLAG_THREAD |
                            DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_THREAD));
    if (!obj) {
        DUK_ERROR_ALLOC_DEFMSG(thr);
    }
    obj->state = DUK_HTHREAD_STATE_INACTIVE;
#if defined(DUK_USE_ROM_STRINGS)
    /* Nothing to initialize, strs[] is in ROM. */
#else
#if defined(DUK_USE_HEAPPTR16)
    obj->strs16 = thr->strs16;
#else
    obj->strs = thr->strs;
#endif
#endif
    DUK_DDD(DUK_DDDPRINT("created thread object with flags: 0x%08lx", (unsigned long) obj->obj.hdr.h_flags));
 
    /* make the new thread reachable */
    tv_slot = thr->valstack_top;
    DUK_TVAL_SET_OBJECT(tv_slot, (duk_hobject *) obj);
    DUK_HTHREAD_INCREF(thr, obj);
    ret = (duk_idx_t) (thr->valstack_top - thr->valstack_bottom);
    thr->valstack_top++;
 
    /* important to do this *after* pushing, to make the thread reachable for gc */
    if (!duk_hthread_init_stacks(thr->heap, obj)) {
        DUK_ERROR_ALLOC_DEFMSG(thr);
    }
 
    /* initialize built-ins - either by copying or creating new ones */
    if (flags & DUK_THREAD_NEW_GLOBAL_ENV) {
        duk_hthread_create_builtin_objects(obj);
    } else {
        duk_hthread_copy_builtin_objects(thr, obj);
    }
 
    /* default prototype (Note: 'obj' must be reachable) */
    DUK_HOBJECT_SET_PROTOTYPE_UPDREF(thr, (duk_hobject *) obj, obj->builtins[DUK_BIDX_THREAD_PROTOTYPE]);
 
    /* Initial stack size satisfies the stack spare constraints so there
     * is no need to require stack here.
     */
    DUK_ASSERT(DUK_VALSTACK_INITIAL_SIZE >=
               DUK_VALSTACK_API_ENTRY_MINIMUM + DUK_VALSTACK_INTERNAL_EXTRA);
 
    return ret;
}
 
DUK_INTERNAL duk_idx_t duk_push_compiledfunction(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hcompiledfunction *obj;
    duk_idx_t ret;
    duk_tval *tv_slot;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* check stack first */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
 
    /* Template functions are not strictly constructable (they don't
     * have a "prototype" property for instance), so leave the
     * DUK_HOBJECT_FLAG_CONSRUCTABLE flag cleared here.
     */
 
    obj = duk_hcompiledfunction_alloc(thr->heap,
                                      DUK_HOBJECT_FLAG_EXTENSIBLE |
                                      DUK_HOBJECT_FLAG_COMPILEDFUNCTION |
                                      DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_FUNCTION));
    if (!obj) {
        DUK_ERROR_ALLOC_DEFMSG(thr);
    }
 
    DUK_DDD(DUK_DDDPRINT("created compiled function object with flags: 0x%08lx", (unsigned long) obj->obj.hdr.h_flags));
 
    tv_slot = thr->valstack_top;
    DUK_TVAL_SET_OBJECT(tv_slot, (duk_hobject *) obj);
    DUK_HOBJECT_INCREF(thr, obj);
    ret = (duk_idx_t) (thr->valstack_top - thr->valstack_bottom);
    thr->valstack_top++;
 
    /* default prototype (Note: 'obj' must be reachable) */
    DUK_HOBJECT_SET_PROTOTYPE_UPDREF(thr, (duk_hobject *) obj, thr->builtins[DUK_BIDX_FUNCTION_PROTOTYPE]);
 
    return ret;
}
 
DUK_LOCAL duk_idx_t duk__push_c_function_raw(duk_context *ctx, duk_c_function func, duk_idx_t nargs, duk_uint_t flags) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hnativefunction *obj;
    duk_idx_t ret;
    duk_tval *tv_slot;
    duk_int16_t func_nargs;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* check stack first */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
    if (func == NULL) {
        goto api_error;
    }
    if (nargs >= 0 && nargs < DUK_HNATIVEFUNCTION_NARGS_MAX) {
        func_nargs = (duk_int16_t) nargs;
    } else if (nargs == DUK_VARARGS) {
        func_nargs = DUK_HNATIVEFUNCTION_NARGS_VARARGS;
    } else {
        goto api_error;
    }
 
    obj = duk_hnativefunction_alloc(thr->heap, flags);
    if (!obj) {
        DUK_ERROR_ALLOC_DEFMSG(thr);
    }
 
    obj->func = func;
    obj->nargs = func_nargs;
 
    DUK_DDD(DUK_DDDPRINT("created native function object with flags: 0x%08lx, nargs=%ld",
                         (unsigned long) obj->obj.hdr.h_flags, (long) obj->nargs));
 
    tv_slot = thr->valstack_top;
    DUK_TVAL_SET_OBJECT(tv_slot, (duk_hobject *) obj);
    DUK_HOBJECT_INCREF(thr, obj);
    ret = (duk_idx_t) (thr->valstack_top - thr->valstack_bottom);
    thr->valstack_top++;
 
    /* default prototype (Note: 'obj' must be reachable) */
    DUK_HOBJECT_SET_PROTOTYPE_UPDREF(thr, (duk_hobject *) obj, thr->builtins[DUK_BIDX_FUNCTION_PROTOTYPE]);
 
    return ret;
 
 api_error:
    DUK_ERROR_API(thr, DUK_STR_INVALID_CALL_ARGS);
    return 0;  /* not reached */
}
 
DUK_EXTERNAL duk_idx_t duk_push_c_function(duk_context *ctx, duk_c_function func, duk_int_t nargs) {
    duk_uint_t flags;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
            DUK_HOBJECT_FLAG_CONSTRUCTABLE |
            DUK_HOBJECT_FLAG_NATIVEFUNCTION |
            DUK_HOBJECT_FLAG_NEWENV |
            DUK_HOBJECT_FLAG_STRICT |
            DUK_HOBJECT_FLAG_NOTAIL |
            DUK_HOBJECT_FLAG_EXOTIC_DUKFUNC |
            DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_FUNCTION);
 
    return duk__push_c_function_raw(ctx, func, nargs, flags);
}
 
DUK_INTERNAL void duk_push_c_function_noexotic(duk_context *ctx, duk_c_function func, duk_int_t nargs) {
    duk_uint_t flags;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
            DUK_HOBJECT_FLAG_CONSTRUCTABLE |
            DUK_HOBJECT_FLAG_NATIVEFUNCTION |
            DUK_HOBJECT_FLAG_NEWENV |
            DUK_HOBJECT_FLAG_STRICT |
            DUK_HOBJECT_FLAG_NOTAIL |
            DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_FUNCTION);
 
    (void) duk__push_c_function_raw(ctx, func, nargs, flags);
}
 
DUK_INTERNAL void duk_push_c_function_noconstruct_noexotic(duk_context *ctx, duk_c_function func, duk_int_t nargs) {
    duk_uint_t flags;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    flags = DUK_HOBJECT_FLAG_EXTENSIBLE |
            DUK_HOBJECT_FLAG_NATIVEFUNCTION |
            DUK_HOBJECT_FLAG_NEWENV |
            DUK_HOBJECT_FLAG_STRICT |
            DUK_HOBJECT_FLAG_NOTAIL |
            DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_FUNCTION);
 
    (void) duk__push_c_function_raw(ctx, func, nargs, flags);
}
 
DUK_EXTERNAL duk_idx_t duk_push_c_lightfunc(duk_context *ctx, duk_c_function func, duk_idx_t nargs, duk_idx_t length, duk_int_t magic) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval tv_tmp;
    duk_small_uint_t lf_flags;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* check stack first */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
 
    if (nargs >= DUK_LFUNC_NARGS_MIN && nargs <= DUK_LFUNC_NARGS_MAX) {
        /* as is */
    } else if (nargs == DUK_VARARGS) {
        nargs = DUK_LFUNC_NARGS_VARARGS;
    } else {
        goto api_error;
    }
    if (!(length >= DUK_LFUNC_LENGTH_MIN && length <= DUK_LFUNC_LENGTH_MAX)) {
        goto api_error;
    }
    if (!(magic >= DUK_LFUNC_MAGIC_MIN && magic <= DUK_LFUNC_MAGIC_MAX)) {
        goto api_error;
    }
 
    lf_flags = DUK_LFUNC_FLAGS_PACK(magic, length, nargs);
    DUK_TVAL_SET_LIGHTFUNC(&tv_tmp, func, lf_flags);
    duk_push_tval(ctx, &tv_tmp);  /* XXX: direct valstack write */
    DUK_ASSERT(thr->valstack_top != thr->valstack_bottom);
    return ((duk_idx_t) (thr->valstack_top - thr->valstack_bottom)) - 1;
 
 api_error:
    DUK_ERROR_API(thr, DUK_STR_INVALID_CALL_ARGS);
    return 0;  /* not reached */
}
 
DUK_INTERNAL duk_hbufferobject *duk_push_bufferobject_raw(duk_context *ctx, duk_uint_t hobject_flags_and_class, duk_small_int_t prototype_bidx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_hbufferobject *obj;
    duk_tval *tv_slot;
 
    DUK_ASSERT(ctx != NULL);
    DUK_ASSERT(prototype_bidx >= 0);
 
    /* check stack first */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
 
    obj = duk_hbufferobject_alloc(thr->heap, hobject_flags_and_class);
    if (!obj) {
        DUK_ERROR_ALLOC_DEFMSG(thr);
    }
 
    DUK_HOBJECT_SET_PROTOTYPE_UPDREF(thr, (duk_hobject *) obj, thr->builtins[prototype_bidx]);
    DUK_ASSERT_HBUFFEROBJECT_VALID(obj);
 
    tv_slot = thr->valstack_top;
    DUK_TVAL_SET_OBJECT(tv_slot, (duk_hobject *) obj);
    DUK_HOBJECT_INCREF(thr, obj);
    thr->valstack_top++;
 
    return obj;
}
 
/* XXX: There's quite a bit of overlap with buffer creation handling in
 * duk_bi_buffer.c.  Look for overlap and refactor.
 */
#define DUK__PACK_ARGS(classnum,protobidx,elemtype,elemshift,isview) \
    (((classnum) << 24) | ((protobidx) << 16) | ((elemtype) << 8) | ((elemshift) << 4) | (isview))
 
#if defined(DUK_USE_BUFFEROBJECT_SUPPORT)
static const duk_uint32_t duk__bufobj_flags_lookup[] = {
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_BUFFER,            DUK_BIDX_BUFFER_PROTOTYPE,            DUK_HBUFFEROBJECT_ELEM_UINT8,        0, 0),  /* DUK_BUFOBJ_DUKTAPE_BUFFER */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_BUFFER,            DUK_BIDX_NODEJS_BUFFER_PROTOTYPE,     DUK_HBUFFEROBJECT_ELEM_UINT8,        0, 0),  /* DUK_BUFOBJ_NODEJS_BUFFER */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_ARRAYBUFFER,       DUK_BIDX_ARRAYBUFFER_PROTOTYPE,       DUK_HBUFFEROBJECT_ELEM_UINT8,        0, 0),  /* DUK_BUFOBJ_ARRAYBUFFER */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_DATAVIEW,          DUK_BIDX_DATAVIEW_PROTOTYPE,          DUK_HBUFFEROBJECT_ELEM_UINT8,        0, 1),  /* DUK_BUFOBJ_DATAVIEW */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_INT8ARRAY,         DUK_BIDX_INT8ARRAY_PROTOTYPE,         DUK_HBUFFEROBJECT_ELEM_INT8,         0, 1),  /* DUK_BUFOBJ_INT8ARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_UINT8ARRAY,        DUK_BIDX_UINT8ARRAY_PROTOTYPE,        DUK_HBUFFEROBJECT_ELEM_UINT8,        0, 1),  /* DUK_BUFOBJ_UINT8ARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_UINT8CLAMPEDARRAY, DUK_BIDX_UINT8CLAMPEDARRAY_PROTOTYPE, DUK_HBUFFEROBJECT_ELEM_UINT8CLAMPED, 0, 1),  /* DUK_BUFOBJ_UINT8CLAMPEDARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_INT16ARRAY,        DUK_BIDX_INT16ARRAY_PROTOTYPE,        DUK_HBUFFEROBJECT_ELEM_INT16,        1, 1),  /* DUK_BUFOBJ_INT16ARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_UINT16ARRAY,       DUK_BIDX_UINT16ARRAY_PROTOTYPE,       DUK_HBUFFEROBJECT_ELEM_UINT16,       1, 1),  /* DUK_BUFOBJ_UINT16ARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_INT32ARRAY,        DUK_BIDX_INT32ARRAY_PROTOTYPE,        DUK_HBUFFEROBJECT_ELEM_INT32,        2, 1),  /* DUK_BUFOBJ_INT32ARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_UINT32ARRAY,       DUK_BIDX_UINT32ARRAY_PROTOTYPE,       DUK_HBUFFEROBJECT_ELEM_UINT32,       2, 1),  /* DUK_BUFOBJ_UINT32ARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_FLOAT32ARRAY,      DUK_BIDX_FLOAT32ARRAY_PROTOTYPE,      DUK_HBUFFEROBJECT_ELEM_FLOAT32,      2, 1),  /* DUK_BUFOBJ_FLOAT32ARRAY */
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_FLOAT64ARRAY,      DUK_BIDX_FLOAT64ARRAY_PROTOTYPE,      DUK_HBUFFEROBJECT_ELEM_FLOAT64,      3, 1)   /* DUK_BUFOBJ_FLOAT64ARRAY */
};
#else  /* DUK_USE_BUFFEROBJECT_SUPPORT */
/* Only allow Duktape.Buffer when support disabled. */
static const duk_uint32_t duk__bufobj_flags_lookup[] = {
    DUK__PACK_ARGS(DUK_HOBJECT_CLASS_BUFFER,            DUK_BIDX_BUFFER_PROTOTYPE,            DUK_HBUFFEROBJECT_ELEM_UINT8,        0, 0)   /* DUK_BUFOBJ_DUKTAPE_BUFFER */
};
#endif  /* DUK_USE_BUFFEROBJECT_SUPPORT */
#undef DUK__PACK_ARGS
 
DUK_EXTERNAL void duk_push_buffer_object(duk_context *ctx, duk_idx_t idx_buffer, duk_size_t byte_offset, duk_size_t byte_length, duk_uint_t flags) {
    duk_hthread *thr;
    duk_hbufferobject *h_bufobj;
    duk_hbuffer *h_val;
    duk_uint32_t tmp;
    duk_uint_t classnum;
    duk_uint_t protobidx;
    duk_uint_t lookupidx;
    duk_uint_t uint_offset, uint_length, uint_added;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK_UNREF(thr);
 
    /* The underlying types for offset/length in duk_hbufferobject is
     * duk_uint_t; make sure argument values fit and that offset + length
     * does not wrap.
     */
    uint_offset = (duk_uint_t) byte_offset;
    uint_length = (duk_uint_t) byte_length;
    if (sizeof(duk_size_t) != sizeof(duk_uint_t)) {
        if ((duk_size_t) uint_offset != byte_offset || (duk_size_t) uint_length != byte_length) {
            goto range_error;
        }
    }
    uint_added = uint_offset + uint_length;
    if (uint_added < uint_offset) {
        goto range_error;
    }
    DUK_ASSERT(uint_added >= uint_offset && uint_added >= uint_length);
 
    DUK_ASSERT_DISABLE(flags >= 0);  /* flags is unsigned */
    lookupidx = flags & 0x0f;  /* 4 low bits */
    if (lookupidx >= sizeof(duk__bufobj_flags_lookup) / sizeof(duk_uint32_t)) {
        goto arg_error;
    }
    tmp = duk__bufobj_flags_lookup[lookupidx];
    classnum = tmp >> 24;
    protobidx = (tmp >> 16) & 0xff;
 
    h_val = duk_require_hbuffer(ctx, idx_buffer);
    DUK_ASSERT(h_val != NULL);
 
    h_bufobj = duk_push_bufferobject_raw(ctx,
                                         DUK_HOBJECT_FLAG_EXTENSIBLE |
                                         DUK_HOBJECT_FLAG_BUFFEROBJECT |
                                         DUK_HOBJECT_CLASS_AS_FLAGS(classnum),
                                         protobidx);
    DUK_ASSERT(h_bufobj != NULL);
 
    h_bufobj->buf = h_val;
    DUK_HBUFFER_INCREF(thr, h_val);
    h_bufobj->offset = uint_offset;
    h_bufobj->length = uint_length;
    h_bufobj->shift = (tmp >> 4) & 0x0f;
    h_bufobj->elem_type = (tmp >> 8) & 0xff;
    h_bufobj->is_view = tmp & 0x0f;
    DUK_ASSERT_HBUFFEROBJECT_VALID(h_bufobj);
 
#if defined(DUK_USE_BUFFEROBJECT_SUPPORT)
    /* TypedArray views need an automatic ArrayBuffer which must be
     * provided as .buffer property of the view.  Just create a new
     * ArrayBuffer sharing the same underlying buffer.
     */
    if (flags & DUK_BUFOBJ_CREATE_ARRBUF) {
        h_bufobj = duk_push_bufferobject_raw(ctx,
                                             DUK_HOBJECT_FLAG_EXTENSIBLE |
                                             DUK_HOBJECT_FLAG_BUFFEROBJECT |
                                             DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_ARRAYBUFFER),
                                             DUK_BIDX_ARRAYBUFFER_PROTOTYPE);
 
        DUK_ASSERT(h_bufobj != NULL);
 
        h_bufobj->buf = h_val;
        DUK_HBUFFER_INCREF(thr, h_val);
        h_bufobj->offset = uint_offset;
        h_bufobj->length = uint_length;
        DUK_ASSERT(h_bufobj->shift == 0);
        h_bufobj->elem_type = DUK_HBUFFEROBJECT_ELEM_UINT8;
        DUK_ASSERT(h_bufobj->is_view == 0);
        DUK_ASSERT_HBUFFEROBJECT_VALID(h_bufobj);
 
        duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_LC_BUFFER, DUK_PROPDESC_FLAGS_NONE);
        duk_compact(ctx, -1);
    }
#endif  /* DUK_USE_BUFFEROBJECT_SUPPORT */
 
    return;
 
 range_error:
    DUK_ERROR_RANGE(thr, DUK_STR_INVALID_CALL_ARGS);
    return;  /* not reached */
 
 arg_error:
    DUK_ERROR_TYPE(thr, DUK_STR_INVALID_CALL_ARGS);
    return;  /* not reached */
}
 
DUK_EXTERNAL duk_idx_t duk_push_error_object_va_raw(duk_context *ctx, duk_errcode_t err_code, const char *filename, duk_int_t line, const char *fmt, va_list ap) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_idx_t ret;
    duk_hobject *proto;
#ifdef DUK_USE_AUGMENT_ERROR_CREATE
    duk_bool_t noblame_fileline;
#endif
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
    DUK_UNREF(filename);
    DUK_UNREF(line);
 
    /* Error code also packs a tracedata related flag. */
#ifdef DUK_USE_AUGMENT_ERROR_CREATE
    noblame_fileline = err_code & DUK_ERRCODE_FLAG_NOBLAME_FILELINE;
#endif
    err_code = err_code & (~DUK_ERRCODE_FLAG_NOBLAME_FILELINE);
 
    /* error gets its 'name' from the prototype */
    proto = duk_error_prototype_from_code(thr, err_code);
    ret = duk_push_object_helper_proto(ctx,
                                       DUK_HOBJECT_FLAG_EXTENSIBLE |
                                       DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_ERROR),
                                       proto);
 
    /* ... and its 'message' from an instance property */
    if (fmt) {
        duk_push_vsprintf(ctx, fmt, ap);
        duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_MESSAGE, DUK_PROPDESC_FLAGS_WC);
    } else {
        /* If no explicit message given, put error code into message field
         * (as a number).  This is not fully in keeping with the Ecmascript
         * error model because messages are supposed to be strings (Error
         * constructors use ToString() on their argument).  However, it's
         * probably more useful than having a separate 'code' property.
         */
        duk_push_int(ctx, err_code);
        duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_MESSAGE, DUK_PROPDESC_FLAGS_WC);
    }
 
    /* XXX: .code = err_code disabled, not sure if useful */
 
    /* Creation time error augmentation */
#ifdef DUK_USE_AUGMENT_ERROR_CREATE
    /* filename may be NULL in which case file/line is not recorded */
    duk_err_augment_error_create(thr, thr, filename, line, noblame_fileline);  /* may throw an error */
#endif
 
    return ret;
}
 
DUK_EXTERNAL duk_idx_t duk_push_error_object_raw(duk_context *ctx, duk_errcode_t err_code, const char *filename, duk_int_t line, const char *fmt, ...) {
    va_list ap;
    duk_idx_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    va_start(ap, fmt);
    ret = duk_push_error_object_va_raw(ctx, err_code, filename, line, fmt, ap);
    va_end(ap);
    return ret;
}
 
#if !defined(DUK_USE_VARIADIC_MACROS)
DUK_EXTERNAL duk_idx_t duk_push_error_object_stash(duk_context *ctx, duk_errcode_t err_code, const char *fmt, ...) {
    const char *filename = duk_api_global_filename;
    duk_int_t line = duk_api_global_line;
    va_list ap;
    duk_idx_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk_api_global_filename = NULL;
    duk_api_global_line = 0;
    va_start(ap, fmt);
    ret = duk_push_error_object_va_raw(ctx, err_code, filename, line, fmt, ap);
    va_end(ap);
    return ret;
}
#endif  /* DUK_USE_VARIADIC_MACROS */
 
DUK_EXTERNAL void *duk_push_buffer_raw(duk_context *ctx, duk_size_t size, duk_small_uint_t flags) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv_slot;
    duk_hbuffer *h;
    void *buf_data;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* check stack first */
    if (thr->valstack_top >= thr->valstack_end) {
        DUK_ERROR_API(thr, DUK_STR_PUSH_BEYOND_ALLOC_STACK);
    }
 
    /* Check for maximum buffer length. */
    if (size > DUK_HBUFFER_MAX_BYTELEN) {
        DUK_ERROR_RANGE(thr, DUK_STR_BUFFER_TOO_LONG);
    }
 
    h = duk_hbuffer_alloc(thr->heap, size, flags, &buf_data);
    if (!h) {
        DUK_ERROR_ALLOC_DEFMSG(thr);
    }
 
    tv_slot = thr->valstack_top;
    DUK_TVAL_SET_BUFFER(tv_slot, h);
    DUK_HBUFFER_INCREF(thr, h);
    thr->valstack_top++;
 
    return (void *) buf_data;
}
 
DUK_EXTERNAL duk_idx_t duk_push_heapptr(duk_context *ctx, void *ptr) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_idx_t ret;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    ret = (duk_idx_t) (thr->valstack_top - thr->valstack_bottom);
 
    if (ptr == NULL) {
        goto push_undefined;
    }
 
    switch ((int) DUK_HEAPHDR_GET_TYPE((duk_heaphdr *) ptr)) {
    case DUK_HTYPE_STRING:
        duk_push_hstring(ctx, (duk_hstring *) ptr);
        break;
    case DUK_HTYPE_OBJECT:
        duk_push_hobject(ctx, (duk_hobject *) ptr);
        break;
    case DUK_HTYPE_BUFFER:
        duk_push_hbuffer(ctx, (duk_hbuffer *) ptr);
        break;
    default:
        goto push_undefined;
    }
    return ret;
 
 push_undefined:
    duk_push_undefined(ctx);
    return ret;
}
 
DUK_INTERNAL duk_idx_t duk_push_object_internal(duk_context *ctx) {
    return duk_push_object_helper(ctx,
                                  DUK_HOBJECT_FLAG_EXTENSIBLE |
                                  DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_OBJECT),
                                  -1);  /* no prototype */
}
 
DUK_INTERNAL void duk_push_hstring(duk_context *ctx, duk_hstring *h) {
    duk_tval tv;
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(h != NULL);
    DUK_TVAL_SET_STRING(&tv, h);
    duk_push_tval(ctx, &tv);
}
 
DUK_INTERNAL void duk_push_hstring_stridx(duk_context *ctx, duk_small_int_t stridx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    DUK_UNREF(thr);
    DUK_ASSERT(stridx >= 0 && stridx < DUK_HEAP_NUM_STRINGS);
    duk_push_hstring(ctx, DUK_HTHREAD_GET_STRING(thr, stridx));
}
 
DUK_INTERNAL void duk_push_hobject(duk_context *ctx, duk_hobject *h) {
    duk_tval tv;
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(h != NULL);
    DUK_TVAL_SET_OBJECT(&tv, h);
    duk_push_tval(ctx, &tv);
}
 
DUK_INTERNAL void duk_push_hbuffer(duk_context *ctx, duk_hbuffer *h) {
    duk_tval tv;
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(h != NULL);
    DUK_TVAL_SET_BUFFER(&tv, h);
    duk_push_tval(ctx, &tv);
}
 
DUK_INTERNAL void duk_push_hobject_bidx(duk_context *ctx, duk_small_int_t builtin_idx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(builtin_idx >= 0 && builtin_idx < DUK_NUM_BUILTINS);
    DUK_ASSERT(thr->builtins[builtin_idx] != NULL);
    duk_push_hobject(ctx, thr->builtins[builtin_idx]);
}
 
/*
 *  Poppers
 */
 
DUK_EXTERNAL void duk_pop_n(duk_context *ctx, duk_idx_t count) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    if (DUK_UNLIKELY(count < 0)) {
        DUK_ERROR_API(thr, DUK_STR_INVALID_COUNT);
        return;
    }
 
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    if (DUK_UNLIKELY((duk_size_t) (thr->valstack_top - thr->valstack_bottom) < (duk_size_t) count)) {
        DUK_ERROR_API(thr, DUK_STR_POP_TOO_MANY);
    }
 
    /*
     *  Must be very careful here, every DECREF may cause reallocation
     *  of our valstack.
     */
 
    /* XXX: inlined DECREF macro would be nice here: no NULL check,
     * refzero queueing but no refzero algorithm run (= no pointer
     * instability), inline code.
     */
 
    /* XXX: optimize loops */
 
#if defined(DUK_USE_REFERENCE_COUNTING)
    while (count > 0) {
        count--;
        tv = --thr->valstack_top;  /* tv points to element just below prev top */
        DUK_ASSERT(tv >= thr->valstack_bottom);
        DUK_TVAL_SET_UNDEFINED_UPDREF(thr, tv);  /* side effects */
    }
#else
    tv = thr->valstack_top;
    while (count > 0) {
        count--;
        tv--;
        DUK_ASSERT(tv >= thr->valstack_bottom);
        DUK_TVAL_SET_UNDEFINED(tv);
    }
    thr->valstack_top = tv;
#endif
 
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
}
 
/* Popping one element is called so often that when footprint is not an issue,
 * compile a specialized function for it.
 */
#if defined(DUK_USE_PREFER_SIZE)
DUK_EXTERNAL void duk_pop(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
    duk_pop_n(ctx, 1);
}
#else
DUK_EXTERNAL void duk_pop(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv;
    DUK_ASSERT_CTX_VALID(ctx);
 
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    if (DUK_UNLIKELY(thr->valstack_top == thr->valstack_bottom)) {
        DUK_ERROR_API(thr, DUK_STR_POP_TOO_MANY);
    }
 
    tv = --thr->valstack_top;  /* tv points to element just below prev top */
    DUK_ASSERT(tv >= thr->valstack_bottom);
#ifdef DUK_USE_REFERENCE_COUNTING
    DUK_TVAL_SET_UNDEFINED_UPDREF(thr, tv);  /* side effects */
#else
    DUK_TVAL_SET_UNDEFINED(tv);
#endif
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
}
#endif  /* !DUK_USE_PREFER_SIZE */
 
DUK_EXTERNAL void duk_pop_2(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
    duk_pop_n(ctx, 2);
}
 
DUK_EXTERNAL void duk_pop_3(duk_context *ctx) {
    DUK_ASSERT_CTX_VALID(ctx);
    duk_pop_n(ctx, 3);
}
 
/*
 *  Error throwing
 */
 
DUK_EXTERNAL void duk_throw(duk_context *ctx) {
    duk_hthread *thr = (duk_hthread *) ctx;
 
    DUK_ASSERT(thr->valstack_bottom >= thr->valstack);
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    DUK_ASSERT(thr->valstack_end >= thr->valstack_top);
 
    if (thr->valstack_top == thr->valstack_bottom) {
        DUK_ERROR_API(thr, DUK_STR_INVALID_CALL_ARGS);
    }
 
    /* Errors are augmented when they are created, not when they are
     * thrown or re-thrown.  The current error handler, however, runs
     * just before an error is thrown.
     */
 
    /* Sync so that augmentation sees up-to-date activations, NULL
     * thr->ptr_curr_pc so that it's not used if side effects occur
     * in augmentation or longjmp handling.
     */
    duk_hthread_sync_and_null_currpc(thr);
 
#if defined(DUK_USE_AUGMENT_ERROR_THROW)
    DUK_DDD(DUK_DDDPRINT("THROW ERROR (API): %!dT (before throw augment)", (duk_tval *) duk_get_tval(ctx, -1)));
    duk_err_augment_error_throw(thr);
#endif
    DUK_DDD(DUK_DDDPRINT("THROW ERROR (API): %!dT (after throw augment)", (duk_tval *) duk_get_tval(ctx, -1)));
 
    duk_err_setup_heap_ljstate(thr, DUK_LJ_TYPE_THROW);
 
    /* thr->heap->lj.jmpbuf_ptr is checked by duk_err_longjmp() so we don't
     * need to check that here.  If the value is NULL, a panic occurs because
     * we can't return.
     */
 
    duk_err_longjmp(thr);
    DUK_UNREACHABLE();
}
 
DUK_EXTERNAL void duk_fatal(duk_context *ctx, duk_errcode_t err_code, const char *err_msg) {
    duk_hthread *thr = (duk_hthread *) ctx;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(thr->heap != NULL);
    DUK_ASSERT(thr->heap->fatal_func != NULL);
 
    DUK_D(DUK_DPRINT("fatal error occurred, code %ld, message %s",
                     (long) err_code, (const char *) err_msg));
 
    /* fatal_func should be noreturn, but noreturn declarations on function
     * pointers has a very spotty support apparently so it's not currently
     * done.
     */
    thr->heap->fatal_func(ctx, err_code, err_msg);
 
    DUK_PANIC(DUK_ERR_API_ERROR, "fatal handler returned");
}
 
DUK_EXTERNAL void duk_error_va_raw(duk_context *ctx, duk_errcode_t err_code, const char *filename, duk_int_t line, const char *fmt, va_list ap) {
    DUK_ASSERT_CTX_VALID(ctx);
 
    duk_push_error_object_va_raw(ctx, err_code, filename, line, fmt, ap);
    duk_throw(ctx);
}
 
DUK_EXTERNAL void duk_error_raw(duk_context *ctx, duk_errcode_t err_code, const char *filename, duk_int_t line, const char *fmt, ...) {
    va_list ap;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    va_start(ap, fmt);
    duk_push_error_object_va_raw(ctx, err_code, filename, line, fmt, ap);
    va_end(ap);
    duk_throw(ctx);
}
 
#if !defined(DUK_USE_VARIADIC_MACROS)
DUK_EXTERNAL void duk_error_stash(duk_context *ctx, duk_errcode_t err_code, const char *fmt, ...) {
    const char *filename;
    duk_int_t line;
    va_list ap;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    filename = duk_api_global_filename;
    line = duk_api_global_line;
    duk_api_global_filename = NULL;
    duk_api_global_line = 0;
 
    va_start(ap, fmt);
    duk_push_error_object_va_raw(ctx, err_code, filename, line, fmt, ap);
    va_end(ap);
    duk_throw(ctx);
}
#endif  /* DUK_USE_VARIADIC_MACROS */
 
/*
 *  Comparison
 */
 
DUK_EXTERNAL duk_bool_t duk_equals(duk_context *ctx, duk_idx_t index1, duk_idx_t index2) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv1, *tv2;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv1 = duk_get_tval(ctx, index1);
    tv2 = duk_get_tval(ctx, index2);
    if ((tv1 == NULL) || (tv2 == NULL)) {
        return 0;
    }
 
    /* Coercion may be needed, the helper handles that by pushing the
     * tagged values to the stack.
     */
    return duk_js_equals(thr, tv1, tv2);
}
 
DUK_EXTERNAL duk_bool_t duk_strict_equals(duk_context *ctx, duk_idx_t index1, duk_idx_t index2) {
    duk_tval *tv1, *tv2;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    tv1 = duk_get_tval(ctx, index1);
    tv2 = duk_get_tval(ctx, index2);
    if ((tv1 == NULL) || (tv2 == NULL)) {
        return 0;
    }
 
    /* No coercions or other side effects, so safe */
    return duk_js_strict_equals(tv1, tv2);
}
 
/*
 *  instanceof
 */
 
DUK_EXTERNAL duk_bool_t duk_instanceof(duk_context *ctx, duk_idx_t index1, duk_idx_t index2) {
    duk_tval *tv1, *tv2;
 
    DUK_ASSERT_CTX_VALID(ctx);
 
    /* Index validation is strict, which differs from duk_equals().
     * The strict behavior mimics how instanceof itself works, e.g.
     * it is a TypeError if rval is not a -callable- object.  It would
     * be somewhat inconsistent if rval would be allowed to be
     * non-existent without a TypeError.
     */
    tv1 = duk_require_tval(ctx, index1);
    DUK_ASSERT(tv1 != NULL);
    tv2 = duk_require_tval(ctx, index2);
    DUK_ASSERT(tv2 != NULL);
 
    return duk_js_instanceof((duk_hthread *) ctx, tv1, tv2);
}
 
/*
 *  Lightfunc
 */
 
DUK_INTERNAL void duk_push_lightfunc_name(duk_context *ctx, duk_tval *tv) {
    duk_c_function func;
 
    DUK_ASSERT(DUK_TVAL_IS_LIGHTFUNC(tv));
 
    /* Lightfunc name, includes Duktape/C native function pointer, which
     * can often be used to locate the function from a symbol table.
     * The name also includes the 16-bit duk_tval flags field because it
     * includes the magic value.  Because a single native function often
     * provides different functionality depending on the magic value, it
     * seems reasonably to include it in the name.
     *
     * On the other hand, a complicated name increases string table
     * pressure in low memory environments (but only when function name
     * is accessed).
     */
 
    func = DUK_TVAL_GET_LIGHTFUNC_FUNCPTR(tv);
    duk_push_sprintf(ctx, "light_");
    duk_push_string_funcptr(ctx, (duk_uint8_t *) &func, sizeof(func));
    duk_push_sprintf(ctx, "_%04x", (unsigned int) DUK_TVAL_GET_LIGHTFUNC_FLAGS(tv));
    duk_concat(ctx, 3);
}
 
DUK_INTERNAL void duk_push_lightfunc_tostring(duk_context *ctx, duk_tval *tv) {
    DUK_ASSERT(DUK_TVAL_IS_LIGHTFUNC(tv));
 
    duk_push_string(ctx, "function ");
    duk_push_lightfunc_name(ctx, tv);
    duk_push_string(ctx, "() {\"light\"}");
    duk_concat(ctx, 3);
}
 
/*
 *  Function pointers
 *
 *  Printing function pointers is non-portable, so we do that by hex printing
 *  bytes from memory.
 */
 
DUK_INTERNAL void duk_push_string_funcptr(duk_context *ctx, duk_uint8_t *ptr, duk_size_t sz) {
    duk_uint8_t buf[32 * 2];
    duk_uint8_t *p, *q;
    duk_small_uint_t i;
    duk_small_uint_t t;
 
    DUK_ASSERT(sz <= 32);  /* sanity limit for function pointer size */
 
    p = buf;
#if defined(DUK_USE_INTEGER_LE)
    q = ptr + sz;
#else
    q = ptr;
#endif
    for (i = 0; i < sz; i++) {
#if defined(DUK_USE_INTEGER_LE)
        t = *(--q);
#else
        t = *(q++);
#endif
        *p++ = duk_lc_digits[t >> 4];
        *p++ = duk_lc_digits[t & 0x0f];
    }
 
    duk_push_lstring(ctx, (const char *) buf, sz * 2);
}
 
#if !defined(DUK_USE_PARANOID_ERRORS)
/*
 *  Push readable string summarizing duk_tval.  The operation is side effect
 *  free and will only throw from internal errors (e.g. out of memory).
 *  This is used by e.g. property access code to summarize a key/base safely,
 *  and is not intended to be fast (but small and safe).
 */
 
#define DUK__READABLE_STRING_MAXCHARS 32
 
/* String sanitizer which escapes ASCII control characters and a few other
 * ASCII characters, passes Unicode as is, and replaces invalid UTF-8 with
 * question marks.  No errors are thrown for any input string, except in out
 * of memory situations.
 */
DUK_LOCAL void duk__push_hstring_readable_unicode(duk_context *ctx, duk_hstring *h_input) {
    duk_hthread *thr;
    const duk_uint8_t *p, *p_start, *p_end;
    duk_uint8_t buf[DUK_UNICODE_MAX_XUTF8_LENGTH * DUK__READABLE_STRING_MAXCHARS +
                    2 /*quotes*/ + 3 /*periods*/];
    duk_uint8_t *q;
    duk_ucodepoint_t cp;
    duk_small_uint_t nchars;
 
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(h_input != NULL);
    thr = (duk_hthread *) ctx;
 
    p_start = (const duk_uint8_t *) DUK_HSTRING_GET_DATA(h_input);
    p_end = p_start + DUK_HSTRING_GET_BYTELEN(h_input);
    p = p_start;
    q = buf;
 
    nchars = 0;
    *q++ = (duk_uint8_t) DUK_ASC_SINGLEQUOTE;
    for (;;) {
        if (p >= p_end) {
            break;
        }
        if (nchars == DUK__READABLE_STRING_MAXCHARS) {
            *q++ = (duk_uint8_t) DUK_ASC_PERIOD;
            *q++ = (duk_uint8_t) DUK_ASC_PERIOD;
            *q++ = (duk_uint8_t) DUK_ASC_PERIOD;
            break;
        }
        if (duk_unicode_decode_xutf8(thr, &p, p_start, p_end, &cp)) {
            if (cp < 0x20 || cp == 0x7f || cp == DUK_ASC_SINGLEQUOTE || cp == DUK_ASC_BACKSLASH) {
                DUK_ASSERT(DUK_UNICODE_MAX_XUTF8_LENGTH >= 4);  /* estimate is valid */
                DUK_ASSERT((cp >> 4) <= 0x0f);
                *q++ = (duk_uint8_t) DUK_ASC_BACKSLASH;
                *q++ = (duk_uint8_t) DUK_ASC_LC_X;
                *q++ = (duk_uint8_t) duk_lc_digits[cp >> 4];
                *q++ = (duk_uint8_t) duk_lc_digits[cp & 0x0f];
            } else {
                q += duk_unicode_encode_xutf8(cp, q);
            }
        } else {
            p++;  /* advance manually */
            *q++ = (duk_uint8_t) DUK_ASC_QUESTION;
        }
        nchars++;
    }
    *q++ = (duk_uint8_t) DUK_ASC_SINGLEQUOTE;
 
    duk_push_lstring(ctx, (const char *) buf, (duk_size_t) (q - buf));
}
 
DUK_INTERNAL const char *duk_push_string_tval_readable(duk_context *ctx, duk_tval *tv) {
    duk_hthread *thr;
 
    DUK_ASSERT_CTX_VALID(ctx);
    thr = (duk_hthread *) ctx;
    DUK_UNREF(thr);
 
    if (tv == NULL) {
        duk_push_string(ctx, "none");
    } else {
        switch (DUK_TVAL_GET_TAG(tv)) {
        case DUK_TAG_STRING: {
            duk__push_hstring_readable_unicode(ctx, DUK_TVAL_GET_STRING(tv));
            break;
        }
        case DUK_TAG_OBJECT: {
            duk_hobject *h = DUK_TVAL_GET_OBJECT(tv);
            DUK_ASSERT(h != NULL);
            duk_push_hobject_class_string(ctx, h);
            break;
        }
        case DUK_TAG_BUFFER: {
            /* XXX: Hex encoded, length limited buffer summary here? */
            duk_hbuffer *h = DUK_TVAL_GET_BUFFER(tv);
            DUK_ASSERT(h != NULL);
            duk_push_sprintf(ctx, "[buffer:%ld]", (long) DUK_HBUFFER_GET_SIZE(h));
            break;
        }
        case DUK_TAG_POINTER: {
            /* Surround with parentheses like in JX, ensures NULL pointer
             * is distinguishable from null value ("(null)" vs "null").
             */
            duk_push_tval(ctx, tv);
            duk_push_sprintf(ctx, "(%s)", duk_to_string(ctx, -1));
            duk_remove(ctx, -2);
            break;
        }
        default: {
            duk_push_tval(ctx, tv);
            break;
        }
        }
    }
 
    return duk_to_string(ctx, -1);
}
 
DUK_INTERNAL const char *duk_push_string_readable(duk_context *ctx, duk_idx_t index) {
    DUK_ASSERT_CTX_VALID(ctx);
    return duk_push_string_tval_readable(ctx, duk_get_tval(ctx, index));
}
#endif  /* !DUK_USE_PARANOID_ERRORS */
 
#undef DUK__CHECK_SPACE
#undef DUK__PACK_ARGS
#undef DUK__READABLE_STRING_MAXCHARS