duktape-1.8.0/src-separate/duk_js_call.c

Go to the documentation of this file.

/*
 *  Call handling.
 *
 *  Main functions are:
 *
 *    - duk_handle_call_unprotected(): unprotected call to Ecmascript or
 *      Duktape/C function
 *    - duk_handle_call_protected(): protected call to Ecmascript or
 *      Duktape/C function
 *    - duk_handle_safe_call(): make a protected C call within current
 *      activation
 *    - duk_handle_ecma_call_setup(): Ecmascript-to-Ecmascript calls
 *      (not always possible), including tail calls and coroutine resume
 *
 *  See 'execution.rst'.
 *
 *  Note: setjmp() and local variables have a nasty interaction,
 *  see execution.rst; non-volatile locals modified after setjmp()
 *  call are not guaranteed to keep their value.
 */
 
#include "duk_internal.h"
 
/*
 *  Forward declarations.
 */
 
DUK_LOCAL void duk__handle_call_inner(duk_hthread *thr,
                                      duk_idx_t num_stack_args,
                                      duk_small_uint_t call_flags,
                                      duk_idx_t idx_func);
DUK_LOCAL void duk__handle_call_error(duk_hthread *thr,
                                      duk_size_t entry_valstack_bottom_index,
                                      duk_size_t entry_valstack_end,
                                      duk_size_t entry_catchstack_top,
                                      duk_size_t entry_callstack_top,
                                      duk_int_t entry_call_recursion_depth,
                                      duk_hthread *entry_curr_thread,
                                      duk_uint_fast8_t entry_thread_state,
                                      duk_instr_t **entry_ptr_curr_pc,
                                      duk_idx_t idx_func,
                                      duk_jmpbuf *old_jmpbuf_ptr);
DUK_LOCAL void duk__handle_safe_call_inner(duk_hthread *thr,
                                           duk_safe_call_function func,
                                           duk_idx_t idx_retbase,
                                           duk_idx_t num_stack_rets,
                                           duk_size_t entry_valstack_bottom_index,
                                           duk_size_t entry_callstack_top,
                                           duk_size_t entry_catchstack_top);
DUK_LOCAL void duk__handle_safe_call_error(duk_hthread *thr,
                                           duk_idx_t idx_retbase,
                                           duk_idx_t num_stack_rets,
                                           duk_size_t entry_valstack_bottom_index,
                                           duk_size_t entry_callstack_top,
                                           duk_size_t entry_catchstack_top,
                                           duk_jmpbuf *old_jmpbuf_ptr);
DUK_LOCAL void duk__handle_safe_call_shared(duk_hthread *thr,
                                            duk_idx_t idx_retbase,
                                            duk_idx_t num_stack_rets,
                                            duk_int_t entry_call_recursion_depth,
                                            duk_hthread *entry_curr_thread,
                                            duk_uint_fast8_t entry_thread_state,
                                            duk_instr_t **entry_ptr_curr_pc);
 
/*
 *  Interrupt counter fixup (for development only).
 */
 
#if defined(DUK_USE_INTERRUPT_COUNTER) && defined(DUK_USE_DEBUG)
DUK_LOCAL void duk__interrupt_fixup(duk_hthread *thr, duk_hthread *entry_curr_thread) {
    /* Currently the bytecode executor and executor interrupt
     * instruction counts are off because we don't execute the
     * interrupt handler when we're about to exit from the initial
     * user call into Duktape.
     *
     * If we were to execute the interrupt handler here, the counts
     * would match.  You can enable this block manually to check
     * that this is the case.
     */
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(thr->heap != NULL);
 
#if defined(DUK_USE_INTERRUPT_DEBUG_FIXUP)
    if (entry_curr_thread == NULL) {
        thr->interrupt_init = thr->interrupt_init - thr->interrupt_counter;
        thr->heap->inst_count_interrupt += thr->interrupt_init;
        DUK_DD(DUK_DDPRINT("debug test: updated interrupt count on exit to "
                           "user code, instruction counts: executor=%ld, interrupt=%ld",
                           (long) thr->heap->inst_count_exec, (long) thr->heap->inst_count_interrupt));
        DUK_ASSERT(thr->heap->inst_count_exec == thr->heap->inst_count_interrupt);
    }
#else
    DUK_UNREF(thr);
    DUK_UNREF(entry_curr_thread);
#endif
}
#endif
 
/*
 *  Arguments object creation.
 *
 *  Creating arguments objects involves many small details, see E5 Section
 *  10.6 for the specific requirements.  Much of the arguments object exotic
 *  behavior is implemented in duk_hobject_props.c, and is enabled by the
 *  object flag DUK_HOBJECT_FLAG_EXOTIC_ARGUMENTS.
 */
 
DUK_LOCAL void duk__create_arguments_object(duk_hthread *thr,
                                            duk_hobject *func,
                                            duk_hobject *varenv,
                                            duk_idx_t idx_argbase,        /* idx of first argument on stack */
                                            duk_idx_t num_stack_args) {   /* num args starting from idx_argbase */
    duk_context *ctx = (duk_context *) thr;
    duk_hobject *arg;          /* 'arguments' */
    duk_hobject *formals;      /* formals for 'func' (may be NULL if func is a C function) */
    duk_idx_t i_arg;
    duk_idx_t i_map;
    duk_idx_t i_mappednames;
    duk_idx_t i_formals;
    duk_idx_t i_argbase;
    duk_idx_t n_formals;
    duk_idx_t idx;
    duk_bool_t need_map;
 
    DUK_DDD(DUK_DDDPRINT("creating arguments object for func=%!iO, varenv=%!iO, "
                         "idx_argbase=%ld, num_stack_args=%ld",
                         (duk_heaphdr *) func, (duk_heaphdr *) varenv,
                         (long) idx_argbase, (long) num_stack_args));
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(func != NULL);
    DUK_ASSERT(DUK_HOBJECT_IS_NONBOUND_FUNCTION(func));
    DUK_ASSERT(varenv != NULL);
    DUK_ASSERT(idx_argbase >= 0);  /* assumed to bottom relative */
    DUK_ASSERT(num_stack_args >= 0);
 
    need_map = 0;
 
    i_argbase = idx_argbase;
    DUK_ASSERT(i_argbase >= 0);
 
    duk_push_hobject(ctx, func);
    duk_get_prop_stridx(ctx, -1, DUK_STRIDX_INT_FORMALS);
    formals = duk_get_hobject(ctx, -1);
    n_formals = 0;
    if (formals) {
        duk_get_prop_stridx(ctx, -1, DUK_STRIDX_LENGTH);
        n_formals = (duk_idx_t) duk_require_int(ctx, -1);
        duk_pop(ctx);
    }
    duk_remove(ctx, -2);  /* leave formals on stack for later use */
    i_formals = duk_require_top_index(ctx);
 
    DUK_ASSERT(n_formals >= 0);
    DUK_ASSERT(formals != NULL || n_formals == 0);
 
    DUK_DDD(DUK_DDDPRINT("func=%!O, formals=%!O, n_formals=%ld",
                         (duk_heaphdr *) func, (duk_heaphdr *) formals,
                         (long) n_formals));
 
    /* [ ... formals ] */
 
    /*
     *  Create required objects:
     *    - 'arguments' object: array-like, but not an array
     *    - 'map' object: internal object, tied to 'arguments'
     *    - 'mappedNames' object: temporary value used during construction
     */
 
    i_arg = duk_push_object_helper(ctx,
                                   DUK_HOBJECT_FLAG_EXTENSIBLE |
                                   DUK_HOBJECT_FLAG_ARRAY_PART |
                                   DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_ARGUMENTS),
                                   DUK_BIDX_OBJECT_PROTOTYPE);
    DUK_ASSERT(i_arg >= 0);
    arg = duk_require_hobject(ctx, -1);
    DUK_ASSERT(arg != NULL);
 
    i_map = duk_push_object_helper(ctx,
                                   DUK_HOBJECT_FLAG_EXTENSIBLE |
                                   DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_OBJECT),
                                   -1);  /* no prototype */
    DUK_ASSERT(i_map >= 0);
 
    i_mappednames = duk_push_object_helper(ctx,
                                           DUK_HOBJECT_FLAG_EXTENSIBLE |
                                           DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_OBJECT),
                                           -1);  /* no prototype */
    DUK_ASSERT(i_mappednames >= 0);
 
    /* [ ... formals arguments map mappedNames ] */
 
    DUK_DDD(DUK_DDDPRINT("created arguments related objects: "
                         "arguments at index %ld -> %!O "
                         "map at index %ld -> %!O "
                         "mappednames at index %ld -> %!O",
                         (long) i_arg, (duk_heaphdr *) duk_get_hobject(ctx, i_arg),
                         (long) i_map, (duk_heaphdr *) duk_get_hobject(ctx, i_map),
                         (long) i_mappednames, (duk_heaphdr *) duk_get_hobject(ctx, i_mappednames)));
 
    /*
     *  Init arguments properties, map, etc.
     */
 
    duk_push_int(ctx, num_stack_args);
    duk_xdef_prop_stridx(ctx, i_arg, DUK_STRIDX_LENGTH, DUK_PROPDESC_FLAGS_WC);
 
    /*
     *  Init argument related properties
     */
 
    /* step 11 */
    idx = num_stack_args - 1;
    while (idx >= 0) {
        DUK_DDD(DUK_DDDPRINT("arg idx %ld, argbase=%ld, argidx=%ld",
                             (long) idx, (long) i_argbase, (long) (i_argbase + idx)));
 
        DUK_DDD(DUK_DDDPRINT("define arguments[%ld]=arg", (long) idx));
        duk_dup(ctx, i_argbase + idx);
        duk_xdef_prop_index_wec(ctx, i_arg, (duk_uarridx_t) idx);
        DUK_DDD(DUK_DDDPRINT("defined arguments[%ld]=arg", (long) idx));
 
        /* step 11.c is relevant only if non-strict (checked in 11.c.ii) */
        if (!DUK_HOBJECT_HAS_STRICT(func) && idx < n_formals) {
            DUK_ASSERT(formals != NULL);
 
            DUK_DDD(DUK_DDDPRINT("strict function, index within formals (%ld < %ld)",
                                 (long) idx, (long) n_formals));
 
            duk_get_prop_index(ctx, i_formals, idx);
            DUK_ASSERT(duk_is_string(ctx, -1));
 
            duk_dup(ctx, -1);  /* [ ... name name ] */
 
            if (!duk_has_prop(ctx, i_mappednames)) {
                /* steps 11.c.ii.1 - 11.c.ii.4, but our internal book-keeping
                 * differs from the reference model
                 */
 
                /* [ ... name ] */
 
                need_map = 1;
 
                DUK_DDD(DUK_DDDPRINT("set mappednames[%s]=%ld",
                                     (const char *) duk_get_string(ctx, -1),
                                     (long) idx));
                duk_dup(ctx, -1);                      /* name */
                duk_push_uint(ctx, (duk_uint_t) idx);  /* index */
                duk_to_string(ctx, -1);
                duk_xdef_prop_wec(ctx, i_mappednames);  /* out of spec, must be configurable */
 
                DUK_DDD(DUK_DDDPRINT("set map[%ld]=%s",
                                     (long) idx,
                                     duk_get_string(ctx, -1)));
                duk_dup(ctx, -1);         /* name */
                duk_xdef_prop_index_wec(ctx, i_map, (duk_uarridx_t) idx);  /* out of spec, must be configurable */
            } else {
                /* duk_has_prop() popped the second 'name' */
            }
 
            /* [ ... name ] */
            duk_pop(ctx);  /* pop 'name' */
        }
 
        idx--;
    }
 
    DUK_DDD(DUK_DDDPRINT("actual arguments processed"));
 
    /* step 12 */
    if (need_map) {
        DUK_DDD(DUK_DDDPRINT("adding 'map' and 'varenv' to arguments object"));
 
        /* should never happen for a strict callee */
        DUK_ASSERT(!DUK_HOBJECT_HAS_STRICT(func));
 
        duk_dup(ctx, i_map);
        duk_xdef_prop_stridx(ctx, i_arg, DUK_STRIDX_INT_MAP, DUK_PROPDESC_FLAGS_NONE);  /* out of spec, don't care */
 
        /* The variable environment for magic variable bindings needs to be
         * given by the caller and recorded in the arguments object.
         *
         * See E5 Section 10.6, the creation of setters/getters.
         *
         * The variable environment also provides access to the callee, so
         * an explicit (internal) callee property is not needed.
         */
 
        duk_push_hobject(ctx, varenv);
        duk_xdef_prop_stridx(ctx, i_arg, DUK_STRIDX_INT_VARENV, DUK_PROPDESC_FLAGS_NONE);  /* out of spec, don't care */
    }
 
    /* steps 13-14 */
    if (DUK_HOBJECT_HAS_STRICT(func)) {
        /* Callee/caller are throwers and are not deletable etc.  They
         * could be implemented as virtual properties, but currently
         * there is no support for virtual properties which are accessors
         * (only plain virtual properties).  This would not be difficult
         * to change in duk_hobject_props, but we can make the throwers
         * normal, concrete properties just as easily.
         *
         * Note that the specification requires that the *same* thrower
         * built-in object is used here!  See E5 Section 10.6 main
         * algoritm, step 14, and Section 13.2.3 which describes the
         * thrower.  See test case test-arguments-throwers.js.
         */
 
        DUK_DDD(DUK_DDDPRINT("strict function, setting caller/callee to throwers"));
 
        duk_xdef_prop_stridx_thrower(ctx, i_arg, DUK_STRIDX_CALLER, DUK_PROPDESC_FLAGS_NONE);
        duk_xdef_prop_stridx_thrower(ctx, i_arg, DUK_STRIDX_CALLEE, DUK_PROPDESC_FLAGS_NONE);
    } else {
        DUK_DDD(DUK_DDDPRINT("non-strict function, setting callee to actual value"));
        duk_push_hobject(ctx, func);
        duk_xdef_prop_stridx(ctx, i_arg, DUK_STRIDX_CALLEE, DUK_PROPDESC_FLAGS_WC);
    }
 
    /* set exotic behavior only after we're done */
    if (need_map) {
        /* Exotic behaviors are only enabled for arguments objects
         * which have a parameter map (see E5 Section 10.6 main
         * algorithm, step 12).
         *
         * In particular, a non-strict arguments object with no
         * mapped formals does *NOT* get exotic behavior, even
         * for e.g. "caller" property.  This seems counterintuitive
         * but seems to be the case.
         */
 
        /* cannot be strict (never mapped variables) */
        DUK_ASSERT(!DUK_HOBJECT_HAS_STRICT(func));
 
        DUK_DDD(DUK_DDDPRINT("enabling exotic behavior for arguments object"));
        DUK_HOBJECT_SET_EXOTIC_ARGUMENTS(arg);
    } else {
        DUK_DDD(DUK_DDDPRINT("not enabling exotic behavior for arguments object"));
    }
 
    DUK_DDD(DUK_DDDPRINT("final arguments related objects: "
                         "arguments at index %ld -> %!O "
                         "map at index %ld -> %!O "
                         "mappednames at index %ld -> %!O",
                         (long) i_arg, (duk_heaphdr *) duk_get_hobject(ctx, i_arg),
                         (long) i_map, (duk_heaphdr *) duk_get_hobject(ctx, i_map),
                         (long) i_mappednames, (duk_heaphdr *) duk_get_hobject(ctx, i_mappednames)));
 
    /* [ args(n) [crud] formals arguments map mappednames ] */
 
    duk_pop_2(ctx);
    duk_remove(ctx, -2);
 
    /* [ args [crud] arguments ] */
}
 
/* Helper for creating the arguments object and adding it to the env record
 * on top of the value stack.  This helper has a very strict dependency on
 * the shape of the input stack.
 */
DUK_LOCAL void duk__handle_createargs_for_call(duk_hthread *thr,
                                               duk_hobject *func,
                                               duk_hobject *env,
                                               duk_idx_t num_stack_args) {
    duk_context *ctx = (duk_context *) thr;
 
    DUK_DDD(DUK_DDDPRINT("creating arguments object for function call"));
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(func != NULL);
    DUK_ASSERT(env != NULL);
    DUK_ASSERT(DUK_HOBJECT_HAS_CREATEARGS(func));
    DUK_ASSERT(duk_get_top(ctx) >= num_stack_args + 1);
 
    /* [ ... arg1 ... argN envobj ] */
 
    duk__create_arguments_object(thr,
                                 func,
                                 env,
                                 duk_get_top(ctx) - num_stack_args - 1,    /* idx_argbase */
                                 num_stack_args);
 
    /* [ ... arg1 ... argN envobj argobj ] */
 
    duk_xdef_prop_stridx(ctx,
                         -2,
                         DUK_STRIDX_LC_ARGUMENTS,
                         DUK_HOBJECT_HAS_STRICT(func) ? DUK_PROPDESC_FLAGS_E :   /* strict: non-deletable, non-writable */
                                                        DUK_PROPDESC_FLAGS_WE);  /* non-strict: non-deletable, writable */
    /* [ ... arg1 ... argN envobj ] */
}
 
/*
 *  Helper for handling a "bound function" chain when a call is being made.
 *
 *  Follows the bound function chain until a non-bound function is found.
 *  Prepends the bound arguments to the value stack (at idx_func + 2),
 *  updating 'num_stack_args' in the process.  The 'this' binding is also
 *  updated if necessary (at idx_func + 1).  Note that for constructor calls
 *  the 'this' binding is never updated by [[BoundThis]].
 *
 *  XXX: bound function chains could be collapsed at bound function creation
 *  time so that each bound function would point directly to a non-bound
 *  function.  This would make call time handling much easier.
 */
 
DUK_LOCAL void duk__handle_bound_chain_for_call(duk_hthread *thr,
                                                duk_idx_t idx_func,
                                                duk_idx_t *p_num_stack_args,   /* may be changed by call */
                                                duk_bool_t is_constructor_call) {
    duk_context *ctx = (duk_context *) thr;
    duk_idx_t num_stack_args;
    duk_tval *tv_func;
    duk_hobject *func;
    duk_uint_t sanity;
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(p_num_stack_args != NULL);
 
    /* On entry, item at idx_func is a bound, non-lightweight function,
     * but we don't rely on that below.
     */
 
    num_stack_args = *p_num_stack_args;
 
    sanity = DUK_HOBJECT_BOUND_CHAIN_SANITY;
    do {
        duk_idx_t i, len;
 
        tv_func = duk_require_tval(ctx, idx_func);
        DUK_ASSERT(tv_func != NULL);
 
        if (DUK_TVAL_IS_LIGHTFUNC(tv_func)) {
            /* Lightweight function: never bound, so terminate. */
            break;
        } else if (DUK_TVAL_IS_OBJECT(tv_func)) {
            func = DUK_TVAL_GET_OBJECT(tv_func);
            if (!DUK_HOBJECT_HAS_BOUND(func)) {
                /* Normal non-bound function. */
                break;
            }
        } else {
            /* Function.prototype.bind() should never let this happen,
             * ugly error message is enough.
             */
            DUK_ERROR_INTERNAL_DEFMSG(thr);
        }
        DUK_ASSERT(DUK_TVAL_GET_OBJECT(tv_func) != NULL);
 
        /* XXX: this could be more compact by accessing the internal properties
         * directly as own properties (they cannot be inherited, and are not
         * externally visible).
         */
 
        DUK_DDD(DUK_DDDPRINT("bound function encountered, ptr=%p, num_stack_args=%ld: %!T",
                             (void *) DUK_TVAL_GET_OBJECT(tv_func), (long) num_stack_args, tv_func));
 
        /* [ ... func this arg1 ... argN ] */
 
        if (is_constructor_call) {
            /* See: tests/ecmascript/test-spec-bound-constructor.js */
            DUK_DDD(DUK_DDDPRINT("constructor call: don't update this binding"));
        } else {
            duk_get_prop_stridx(ctx, idx_func, DUK_STRIDX_INT_THIS);
            duk_replace(ctx, idx_func + 1);  /* idx_this = idx_func + 1 */
        }
 
        /* [ ... func this arg1 ... argN ] */
 
        /* XXX: duk_get_length? */
        duk_get_prop_stridx(ctx, idx_func, DUK_STRIDX_INT_ARGS);  /* -> [ ... func this arg1 ... argN _Args ] */
        duk_get_prop_stridx(ctx, -1, DUK_STRIDX_LENGTH);          /* -> [ ... func this arg1 ... argN _Args length ] */
        len = (duk_idx_t) duk_require_int(ctx, -1);
        duk_pop(ctx);
 
        duk_require_stack(ctx, len);
        for (i = 0; i < len; i++) {
            /* XXX: very slow - better to bulk allocate a gap, and copy
             * from args_array directly (we know it has a compact array
             * part, etc).
             */
 
            /* [ ... func this <some bound args> arg1 ... argN _Args ] */
            duk_get_prop_index(ctx, -1, i);
            duk_insert(ctx, idx_func + 2 + i);  /* idx_args = idx_func + 2 */
        }
        num_stack_args += len;  /* must be updated to work properly (e.g. creation of 'arguments') */
        duk_pop(ctx);
 
        /* [ ... func this <bound args> arg1 ... argN ] */
 
        duk_get_prop_stridx(ctx, idx_func, DUK_STRIDX_INT_TARGET);
        duk_replace(ctx, idx_func);  /* replace in stack */
 
        DUK_DDD(DUK_DDDPRINT("bound function handled, num_stack_args=%ld, idx_func=%ld, curr func=%!T",
                             (long) num_stack_args, (long) idx_func, duk_get_tval(ctx, idx_func)));
    } while (--sanity > 0);
 
    if (sanity == 0) {
        DUK_ERROR_RANGE(thr, DUK_STR_BOUND_CHAIN_LIMIT);
    }
 
    DUK_DDD(DUK_DDDPRINT("final non-bound function is: %!T", duk_get_tval(ctx, idx_func)));
 
#if defined(DUK_USE_ASSERTIONS)
    tv_func = duk_require_tval(ctx, idx_func);
    DUK_ASSERT(DUK_TVAL_IS_LIGHTFUNC(tv_func) || DUK_TVAL_IS_OBJECT(tv_func));
    if (DUK_TVAL_IS_OBJECT(tv_func)) {
        func = DUK_TVAL_GET_OBJECT(tv_func);
        DUK_ASSERT(func != NULL);
        DUK_ASSERT(!DUK_HOBJECT_HAS_BOUND(func));
        DUK_ASSERT(DUK_HOBJECT_HAS_COMPILEDFUNCTION(func) ||
                   DUK_HOBJECT_HAS_NATIVEFUNCTION(func));
    }
#endif
 
    /* write back */
    *p_num_stack_args = num_stack_args;
}
 
/*
 *  Helper for setting up var_env and lex_env of an activation,
 *  assuming it does NOT have the DUK_HOBJECT_FLAG_NEWENV flag.
 */
 
DUK_LOCAL void duk__handle_oldenv_for_call(duk_hthread *thr,
                                           duk_hobject *func,
                                           duk_activation *act) {
    duk_tval *tv;
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(func != NULL);
    DUK_ASSERT(act != NULL);
    DUK_ASSERT(!DUK_HOBJECT_HAS_NEWENV(func));
    DUK_ASSERT(!DUK_HOBJECT_HAS_CREATEARGS(func));
 
    tv = duk_hobject_find_existing_entry_tval_ptr(thr->heap, func, DUK_HTHREAD_STRING_INT_LEXENV(thr));
    if (tv) {
        DUK_ASSERT(DUK_TVAL_IS_OBJECT(tv));
        DUK_ASSERT(DUK_HOBJECT_IS_ENV(DUK_TVAL_GET_OBJECT(tv)));
        act->lex_env = DUK_TVAL_GET_OBJECT(tv);
 
        tv = duk_hobject_find_existing_entry_tval_ptr(thr->heap, func, DUK_HTHREAD_STRING_INT_VARENV(thr));
        if (tv) {
            DUK_ASSERT(DUK_TVAL_IS_OBJECT(tv));
            DUK_ASSERT(DUK_HOBJECT_IS_ENV(DUK_TVAL_GET_OBJECT(tv)));
            act->var_env = DUK_TVAL_GET_OBJECT(tv);
        } else {
            act->var_env = act->lex_env;
        }
    } else {
        act->lex_env = thr->builtins[DUK_BIDX_GLOBAL_ENV];
        act->var_env = act->lex_env;
    }
 
    DUK_HOBJECT_INCREF_ALLOWNULL(thr, act->lex_env);
    DUK_HOBJECT_INCREF_ALLOWNULL(thr, act->var_env);
}
 
/*
 *  Helper for updating callee 'caller' property.
 */
 
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
DUK_LOCAL void duk__update_func_caller_prop(duk_hthread *thr, duk_hobject *func) {
    duk_tval *tv_caller;
    duk_hobject *h_tmp;
    duk_activation *act_callee;
    duk_activation *act_caller;
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(func != NULL);
    DUK_ASSERT(!DUK_HOBJECT_HAS_BOUND(func));  /* bound chain resolved */
    DUK_ASSERT(thr->callstack_top >= 1);
 
    if (DUK_HOBJECT_HAS_STRICT(func)) {
        /* Strict functions don't get their 'caller' updated. */
        return;
    }
 
    act_callee = thr->callstack + thr->callstack_top - 1;
    act_caller = (thr->callstack_top >= 2 ? act_callee - 1 : NULL);
 
    /* XXX: check .caller writability? */
 
    /* Backup 'caller' property and update its value. */
    tv_caller = duk_hobject_find_existing_entry_tval_ptr(thr->heap, func, DUK_HTHREAD_STRING_CALLER(thr));
    if (tv_caller) {
        /* If caller is global/eval code, 'caller' should be set to
         * 'null'.
         *
         * XXX: there is no exotic flag to infer this correctly now.
         * The NEWENV flag is used now which works as intended for
         * everything (global code, non-strict eval code, and functions)
         * except strict eval code.  Bound functions are never an issue
         * because 'func' has been resolved to a non-bound function.
         */
 
        if (act_caller) {
            /* act_caller->func may be NULL in some finalization cases,
             * just treat like we don't know the caller.
             */
            if (act_caller->func && !DUK_HOBJECT_HAS_NEWENV(act_caller->func)) {
                /* Setting to NULL causes 'caller' to be set to
                 * 'null' as desired.
                 */
                act_caller = NULL;
            }
        }
 
        if (DUK_TVAL_IS_OBJECT(tv_caller)) {
            h_tmp = DUK_TVAL_GET_OBJECT(tv_caller);
            DUK_ASSERT(h_tmp != NULL);
            act_callee->prev_caller = h_tmp;
 
            /* Previous value doesn't need refcount changes because its ownership
             * is transferred to prev_caller.
             */
 
            if (act_caller) {
                DUK_ASSERT(act_caller->func != NULL);
                DUK_TVAL_SET_OBJECT(tv_caller, act_caller->func);
                DUK_TVAL_INCREF(thr, tv_caller);
            } else {
                DUK_TVAL_SET_NULL(tv_caller);  /* no incref */
            }
        } else {
            /* 'caller' must only take on 'null' or function value */
            DUK_ASSERT(!DUK_TVAL_IS_HEAP_ALLOCATED(tv_caller));
            DUK_ASSERT(act_callee->prev_caller == NULL);
            if (act_caller && act_caller->func) {
                /* Tolerate act_caller->func == NULL which happens in
                 * some finalization cases; treat like unknown caller.
                 */
                DUK_TVAL_SET_OBJECT(tv_caller, act_caller->func);
                DUK_TVAL_INCREF(thr, tv_caller);
            } else {
                DUK_TVAL_SET_NULL(tv_caller);  /* no incref */
            }
        }
    }
}
#endif  /* DUK_USE_NONSTD_FUNC_CALLER_PROPERTY */
 
/*
 *  Determine the effective 'this' binding and coerce the current value
 *  on the valstack to the effective one (in-place, at idx_this).
 *
 *  The current this value in the valstack (at idx_this) represents either:
 *    - the caller's requested 'this' binding; or
 *    - a 'this' binding accumulated from the bound function chain
 *
 *  The final 'this' binding for the target function may still be
 *  different, and is determined as described in E5 Section 10.4.3.
 *
 *  For global and eval code (E5 Sections 10.4.1 and 10.4.2), we assume
 *  that the caller has provided the correct 'this' binding explicitly
 *  when calling, i.e.:
 *
 *    - global code: this=global object
 *    - direct eval: this=copy from eval() caller's this binding
 *    - other eval:  this=global object
 *
 *  Note: this function may cause a recursive function call with arbitrary
 *  side effects, because ToObject() may be called.
 */
 
DUK_LOCAL void duk__coerce_effective_this_binding(duk_hthread *thr,
                                                  duk_hobject *func,
                                                  duk_idx_t idx_this) {
    duk_context *ctx = (duk_context *) thr;
    duk_tval *tv_this;
    duk_hobject *obj_global;
 
    if (func == NULL || DUK_HOBJECT_HAS_STRICT(func)) {
        /* Lightfuncs are always considered strict. */
        DUK_DDD(DUK_DDDPRINT("this binding: strict -> use directly"));
        return;
    }
 
    /* XXX: byte offset */
    tv_this = thr->valstack_bottom + idx_this;
    switch (DUK_TVAL_GET_TAG(tv_this)) {
    case DUK_TAG_OBJECT:
    case DUK_TAG_LIGHTFUNC:  /* lightfuncs are treated like objects and not coerced */
        DUK_DDD(DUK_DDDPRINT("this binding: non-strict, object -> use directly"));
        break;
    case DUK_TAG_UNDEFINED:
    case DUK_TAG_NULL:
        DUK_DDD(DUK_DDDPRINT("this binding: non-strict, undefined/null -> use global object"));
        obj_global = thr->builtins[DUK_BIDX_GLOBAL];
        /* XXX: avoid this check somehow */
        if (DUK_LIKELY(obj_global != NULL)) {
            DUK_ASSERT(!DUK_TVAL_IS_HEAP_ALLOCATED(tv_this));  /* no need to decref previous value */
            DUK_TVAL_SET_OBJECT(tv_this, obj_global);
            DUK_HOBJECT_INCREF(thr, obj_global);
        } else {
            /* This may only happen if built-ins are being "torn down".
             * This behavior is out of specification scope.
             */
            DUK_D(DUK_DPRINT("this binding: wanted to use global object, but it is NULL -> using undefined instead"));
            DUK_ASSERT(!DUK_TVAL_IS_HEAP_ALLOCATED(tv_this));  /* no need to decref previous value */
            DUK_TVAL_SET_UNDEFINED(tv_this);  /* nothing to incref */
        }
        break;
    default:
        DUK_ASSERT(!DUK_TVAL_IS_UNUSED(tv_this));
        DUK_DDD(DUK_DDDPRINT("this binding: non-strict, not object/undefined/null -> use ToObject(value)"));
        duk_to_object(ctx, idx_this);  /* may have side effects */
        break;
    }
}
 
/*
 *  Shared helper for non-bound func lookup.
 *
 *  Returns duk_hobject * to the final non-bound function (NULL for lightfunc).
 */
 
DUK_LOCAL duk_hobject *duk__nonbound_func_lookup(duk_context *ctx,
                                                 duk_idx_t idx_func,
                                                 duk_idx_t *out_num_stack_args,
                                                 duk_tval **out_tv_func,
                                                 duk_small_uint_t call_flags) {
    duk_hthread *thr = (duk_hthread *) ctx;
    duk_tval *tv_func;
    duk_hobject *func;
 
    for (;;) {
        /* Use loop to minimize code size of relookup after bound function case */
        tv_func = DUK_GET_TVAL_POSIDX(ctx, idx_func);
        DUK_ASSERT(tv_func != NULL);
 
        if (DUK_TVAL_IS_OBJECT(tv_func)) {
            func = DUK_TVAL_GET_OBJECT(tv_func);
            if (!DUK_HOBJECT_IS_CALLABLE(func)) {
                goto not_callable_error;
            }
            if (DUK_HOBJECT_HAS_BOUND(func)) {
                duk__handle_bound_chain_for_call(thr, idx_func, out_num_stack_args, call_flags & DUK_CALL_FLAG_CONSTRUCTOR_CALL);
 
                /* The final object may be a normal function or a lightfunc.
                 * We need to re-lookup tv_func because it may have changed
                 * (also value stack may have been resized).  Loop again to
                 * do that; we're guaranteed not to come here again.
                 */
                DUK_ASSERT(DUK_TVAL_IS_OBJECT(duk_require_tval(ctx, idx_func)) ||
                           DUK_TVAL_IS_LIGHTFUNC(duk_require_tval(ctx, idx_func)));
                continue;
            }
        } else if (DUK_TVAL_IS_LIGHTFUNC(tv_func)) {
            func = NULL;
        } else {
            goto not_callable_error;
        }
        break;
    }
 
    DUK_ASSERT((DUK_TVAL_IS_OBJECT(tv_func) && DUK_HOBJECT_IS_CALLABLE(DUK_TVAL_GET_OBJECT(tv_func))) ||
               DUK_TVAL_IS_LIGHTFUNC(tv_func));
    DUK_ASSERT(func == NULL || !DUK_HOBJECT_HAS_BOUND(func));
    DUK_ASSERT(func == NULL || (DUK_HOBJECT_IS_COMPILEDFUNCTION(func) ||
                                DUK_HOBJECT_IS_NATIVEFUNCTION(func)));
 
    *out_tv_func = tv_func;
    return func;
 
 not_callable_error:
    DUK_ASSERT(tv_func != NULL);
#if defined(DUK_USE_PARANOID_ERRORS)
    DUK_ERROR_TYPE(thr, DUK_STR_NOT_CALLABLE);
#else
    DUK_ERROR_FMT1(thr, DUK_ERR_TYPE_ERROR, "%s not callable", duk_push_string_tval_readable(ctx, tv_func));
#endif
    DUK_UNREACHABLE();
    return NULL;  /* never executed */
}
 
/*
 *  Value stack resize and stack top adjustment helper.
 *
 *  XXX: This should all be merged to duk_valstack_resize_raw().
 */
 
DUK_LOCAL void duk__adjust_valstack_and_top(duk_hthread *thr,
                                            duk_idx_t num_stack_args,
                                            duk_idx_t idx_args,
                                            duk_idx_t nregs,
                                            duk_idx_t nargs,
                                            duk_hobject *func) {
    duk_context *ctx = (duk_context *) thr;
    duk_size_t vs_min_size;
    duk_bool_t adjusted_top = 0;
 
    vs_min_size = (thr->valstack_bottom - thr->valstack) +  /* bottom of current func */
                  idx_args;                                 /* bottom of new func */
 
    if (nregs >= 0) {
        DUK_ASSERT(nargs >= 0);
        DUK_ASSERT(nregs >= nargs);
        vs_min_size += nregs;
    } else {
        /* 'func' wants stack "as is" */
        vs_min_size += num_stack_args;  /* num entries of new func at entry */
    }
    if (func == NULL || DUK_HOBJECT_IS_NATIVEFUNCTION(func)) {
        vs_min_size += DUK_VALSTACK_API_ENTRY_MINIMUM;  /* Duktape/C API guaranteed entries (on top of args) */
    }
    vs_min_size += DUK_VALSTACK_INTERNAL_EXTRA;             /* + spare */
 
    /* XXX: We can't resize the value stack to a size smaller than the
     * current top, so the order of the resize and adjusting the stack
     * top depends on the current vs. final size of the value stack.
     * The operations could be combined to avoid this, but the proper
     * fix is to only grow the value stack on a function call, and only
     * shrink it (without throwing if the shrink fails) on function
     * return.
     */
 
    if (vs_min_size < (duk_size_t) (thr->valstack_top  - thr->valstack)) {
        DUK_DDD(DUK_DDDPRINT(("final size smaller, set top before resize")));
 
        DUK_ASSERT(nregs >= 0);  /* can't happen when keeping current stack size */
        duk_set_top(ctx, idx_args + nargs);  /* clamp anything above nargs */
        duk_set_top(ctx, idx_args + nregs);  /* extend with undefined */
        adjusted_top = 1;
    }
 
    (void) duk_valstack_resize_raw((duk_context *) thr,
                                   vs_min_size,
                                   DUK_VSRESIZE_FLAG_SHRINK |      /* flags */
                                   0 /* no compact */ |
                                   DUK_VSRESIZE_FLAG_THROW);
 
    if (!adjusted_top) {
        if (nregs >= 0) {
            DUK_ASSERT(nregs >= nargs);
            duk_set_top(ctx, idx_args + nargs);  /* clamp anything above nargs */
            duk_set_top(ctx, idx_args + nregs);  /* extend with undefined */
        }
    }
}
 
/*
 *  Manipulate value stack so that exactly 'num_stack_rets' return
 *  values are at 'idx_retbase' in every case, assuming there are
 *  'rc' return values on top of stack.
 *
 *  This is a bit tricky, because the called C function operates in
 *  the same activation record and may have e.g. popped the stack
 *  empty (below idx_retbase).
 */
 
DUK_LOCAL void duk__safe_call_adjust_valstack(duk_hthread *thr, duk_idx_t idx_retbase, duk_idx_t num_stack_rets, duk_idx_t num_actual_rets) {
    duk_context *ctx = (duk_context *) thr;
    duk_idx_t idx_rcbase;
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(idx_retbase >= 0);
    DUK_ASSERT(num_stack_rets >= 0);
    DUK_ASSERT(num_actual_rets >= 0);
 
    idx_rcbase = duk_get_top(ctx) - num_actual_rets;  /* base of known return values */
 
    DUK_DDD(DUK_DDDPRINT("adjust valstack after func call: "
                         "num_stack_rets=%ld, num_actual_rets=%ld, stack_top=%ld, idx_retbase=%ld, idx_rcbase=%ld",
                         (long) num_stack_rets, (long) num_actual_rets, (long) duk_get_top(ctx),
                         (long) idx_retbase, (long) idx_rcbase));
 
    DUK_ASSERT(idx_rcbase >= 0);  /* caller must check */
 
    /* Ensure space for final configuration (idx_retbase + num_stack_rets)
     * and intermediate configurations.
     */
    duk_require_stack_top(ctx,
                          (idx_rcbase > idx_retbase ? idx_rcbase : idx_retbase) +
                          num_stack_rets);
 
    /* Chop extra retvals away / extend with undefined. */
    duk_set_top(ctx, idx_rcbase + num_stack_rets);
 
    if (idx_rcbase >= idx_retbase) {
        duk_idx_t count = idx_rcbase - idx_retbase;
        duk_idx_t i;
 
        DUK_DDD(DUK_DDDPRINT("elements at/after idx_retbase have enough to cover func retvals "
                             "(idx_retbase=%ld, idx_rcbase=%ld)", (long) idx_retbase, (long) idx_rcbase));
 
        /* nuke values at idx_retbase to get the first retval (initially
         * at idx_rcbase) to idx_retbase
         */
 
        DUK_ASSERT(count >= 0);
 
        for (i = 0; i < count; i++) {
            /* XXX: inefficient; block remove primitive */
            duk_remove(ctx, idx_retbase);
        }
    } else {
        duk_idx_t count = idx_retbase - idx_rcbase;
        duk_idx_t i;
 
        DUK_DDD(DUK_DDDPRINT("not enough elements at/after idx_retbase to cover func retvals "
                             "(idx_retbase=%ld, idx_rcbase=%ld)", (long) idx_retbase, (long) idx_rcbase));
 
        /* insert 'undefined' values at idx_rcbase to get the
         * return values to idx_retbase
         */
 
        DUK_ASSERT(count > 0);
 
        for (i = 0; i < count; i++) {
            /* XXX: inefficient; block insert primitive */
            duk_push_undefined(ctx);
            duk_insert(ctx, idx_rcbase);
        }
    }
}
 
/*
 *  Misc shared helpers.
 */
 
/* Get valstack index for the func argument or throw if insane stack. */
DUK_LOCAL duk_idx_t duk__get_idx_func(duk_hthread *thr, duk_idx_t num_stack_args) {
    duk_size_t off_stack_top;
    duk_size_t off_stack_args;
    duk_size_t off_stack_all;
    duk_idx_t idx_func;         /* valstack index of 'func' and retval (relative to entry valstack_bottom) */
 
    /* Argument validation and func/args offset. */
    off_stack_top = (duk_size_t) ((duk_uint8_t *) thr->valstack_top - (duk_uint8_t *) thr->valstack_bottom);
    off_stack_args = (duk_size_t) ((duk_size_t) num_stack_args * sizeof(duk_tval));
    off_stack_all = off_stack_args + 2 * sizeof(duk_tval);
    if (DUK_UNLIKELY(off_stack_all > off_stack_top)) {
        /* Since stack indices are not reliable, we can't do anything useful
         * here.  Invoke the existing setjmp catcher, or if it doesn't exist,
         * call the fatal error handler.
         */
        DUK_ERROR_API(thr, DUK_STR_INVALID_CALL_ARGS);
        return 0;
    }
    idx_func = (duk_idx_t) ((off_stack_top - off_stack_all) / sizeof(duk_tval));
    return idx_func;
}
 
/*
 *  duk_handle_call_protected() and duk_handle_call_unprotected():
 *  call into a Duktape/C or an Ecmascript function from any state.
 *
 *  Input stack (thr):
 *
 *    [ func this arg1 ... argN ]
 *
 *  Output stack (thr):
 *
 *    [ retval ]         (DUK_EXEC_SUCCESS)
 *    [ errobj ]         (DUK_EXEC_ERROR (normal error), protected call)
 *
 *  Even when executing a protected call an error may be thrown in rare cases
 *  such as an insane num_stack_args argument.  If there is no catchpoint for
 *  such errors, the fatal error handler is called.
 *
 *  The error handling path should be error free, even for out-of-memory
 *  errors, to ensure safe sandboxing.  (As of Duktape 1.4.0 this is not
 *  yet the case, see XXX notes below.)
 */
 
DUK_INTERNAL duk_int_t duk_handle_call_protected(duk_hthread *thr,
                                                 duk_idx_t num_stack_args,
                                                 duk_small_uint_t call_flags) {
    duk_context *ctx;
    duk_size_t entry_valstack_bottom_index;
    duk_size_t entry_valstack_end;
    duk_size_t entry_callstack_top;
    duk_size_t entry_catchstack_top;
    duk_int_t entry_call_recursion_depth;
    duk_hthread *entry_curr_thread;
    duk_uint_fast8_t entry_thread_state;
    duk_instr_t **entry_ptr_curr_pc;
    duk_jmpbuf *old_jmpbuf_ptr = NULL;
    duk_jmpbuf our_jmpbuf;
    duk_idx_t idx_func;  /* valstack index of 'func' and retval (relative to entry valstack_bottom) */
 
    /* XXX: Multiple tv_func lookups are now avoided by making a local
     * copy of tv_func.  Another approach would be to compute an offset
     * for tv_func from valstack bottom and recomputing the tv_func
     * pointer quickly as valstack + offset instead of calling duk_get_tval().
     */
 
    ctx = (duk_context *) thr;
    DUK_UNREF(ctx);
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(num_stack_args >= 0);
    /* XXX: currently NULL allocations are not supported; remove if later allowed */
    DUK_ASSERT(thr->valstack != NULL);
    DUK_ASSERT(thr->callstack != NULL);
    DUK_ASSERT(thr->catchstack != NULL);
 
    /* Argument validation and func/args offset. */
    idx_func = duk__get_idx_func(thr, num_stack_args);
 
    /* Preliminaries, required by setjmp() handler.  Must be careful not
     * to throw an unintended error here.
     */
 
    entry_valstack_bottom_index = (duk_size_t) (thr->valstack_bottom - thr->valstack);
#if defined(DUK_USE_PREFER_SIZE)
    entry_valstack_end = (duk_size_t) (thr->valstack_end - thr->valstack);
#else
    DUK_ASSERT((duk_size_t) (thr->valstack_end - thr->valstack) == thr->valstack_size);
    entry_valstack_end = thr->valstack_size;
#endif
    entry_callstack_top = thr->callstack_top;
    entry_catchstack_top = thr->catchstack_top;
    entry_call_recursion_depth = thr->heap->call_recursion_depth;
    entry_curr_thread = thr->heap->curr_thread;  /* Note: may be NULL if first call */
    entry_thread_state = thr->state;
    entry_ptr_curr_pc = thr->ptr_curr_pc;  /* may be NULL */
 
    DUK_DD(DUK_DDPRINT("duk_handle_call_protected: thr=%p, num_stack_args=%ld, "
                       "call_flags=0x%08lx (ignorerec=%ld, constructor=%ld), "
                       "valstack_top=%ld, idx_func=%ld, idx_args=%ld, rec_depth=%ld/%ld, "
                       "entry_valstack_bottom_index=%ld, entry_callstack_top=%ld, entry_catchstack_top=%ld, "
                       "entry_call_recursion_depth=%ld, entry_curr_thread=%p, entry_thread_state=%ld",
                       (void *) thr,
                       (long) num_stack_args,
                       (unsigned long) call_flags,
                       (long) ((call_flags & DUK_CALL_FLAG_IGNORE_RECLIMIT) != 0 ? 1 : 0),
                       (long) ((call_flags & DUK_CALL_FLAG_CONSTRUCTOR_CALL) != 0 ? 1 : 0),
                       (long) duk_get_top(ctx),
                       (long) idx_func,
                       (long) (idx_func + 2),
                       (long) thr->heap->call_recursion_depth,
                       (long) thr->heap->call_recursion_limit,
                       (long) entry_valstack_bottom_index,
                       (long) entry_callstack_top,
                       (long) entry_catchstack_top,
                       (long) entry_call_recursion_depth,
                       (void *) entry_curr_thread,
                       (long) entry_thread_state));
 
    old_jmpbuf_ptr = thr->heap->lj.jmpbuf_ptr;
    thr->heap->lj.jmpbuf_ptr = &our_jmpbuf;
 
#if defined(DUK_USE_CPP_EXCEPTIONS)
    try {
#else
    DUK_ASSERT(thr->heap->lj.jmpbuf_ptr == &our_jmpbuf);
    if (DUK_SETJMP(our_jmpbuf.jb) == 0) {
#endif
        /* Call handling and success path.  Success path exit cleans
         * up almost all state.
         */
        duk__handle_call_inner(thr, num_stack_args, call_flags, idx_func);
 
        /* Success path handles */
        DUK_ASSERT(thr->heap->call_recursion_depth == entry_call_recursion_depth);
        DUK_ASSERT(thr->ptr_curr_pc == entry_ptr_curr_pc);
 
        /* Longjmp state is kept clean in success path */
        DUK_ASSERT(thr->heap->lj.type == DUK_LJ_TYPE_UNKNOWN);
        DUK_ASSERT(thr->heap->lj.iserror == 0);
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value1));
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value2));
 
        thr->heap->lj.jmpbuf_ptr = old_jmpbuf_ptr;
 
        return DUK_EXEC_SUCCESS;
#if defined(DUK_USE_CPP_EXCEPTIONS)
    } catch (duk_internal_exception &exc) {
#else
    } else {
#endif
        /* Error; error value is in heap->lj.value1. */
 
#if defined(DUK_USE_CPP_EXCEPTIONS)
        DUK_UNREF(exc);
#endif
 
        duk__handle_call_error(thr,
                               entry_valstack_bottom_index,
                               entry_valstack_end,
                               entry_catchstack_top,
                               entry_callstack_top,
                               entry_call_recursion_depth,
                               entry_curr_thread,
                               entry_thread_state,
                               entry_ptr_curr_pc,
                               idx_func,
                               old_jmpbuf_ptr);
 
        /* Longjmp state is cleaned up by error handling */
        DUK_ASSERT(thr->heap->lj.type == DUK_LJ_TYPE_UNKNOWN);
        DUK_ASSERT(thr->heap->lj.iserror == 0);
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value1));
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value2));
        return DUK_EXEC_ERROR;
    }
#if defined(DUK_USE_CPP_EXCEPTIONS)
    catch (std::exception &exc) {
        const char *what = exc.what();
        if (!what) {
            what = "unknown";
        }
        DUK_D(DUK_DPRINT("unexpected c++ std::exception (perhaps thrown by user code)"));
        try {
            DUK_ERROR_FMT1(thr, DUK_ERR_API_ERROR, "caught invalid c++ std::exception '%s' (perhaps thrown by user code)", what);
        } catch (duk_internal_exception exc) {
            DUK_D(DUK_DPRINT("caught api error thrown from unexpected c++ std::exception"));
            DUK_UNREF(exc);
            duk__handle_call_error(thr,
                                   entry_valstack_bottom_index,
                                   entry_valstack_end,
                                   entry_catchstack_top,
                                   entry_callstack_top,
                                   entry_call_recursion_depth,
                                   entry_curr_thread,
                                   entry_thread_state,
                                   entry_ptr_curr_pc,
                                   idx_func,
                                   old_jmpbuf_ptr);
            return DUK_EXEC_ERROR;
        }
    } catch (...) {
        DUK_D(DUK_DPRINT("unexpected c++ exception (perhaps thrown by user code)"));
        try {
            DUK_ERROR_API(thr, "caught invalid c++ exception (perhaps thrown by user code)");
        } catch (duk_internal_exception exc) {
            DUK_D(DUK_DPRINT("caught api error thrown from unexpected c++ exception"));
            DUK_UNREF(exc);
            duk__handle_call_error(thr,
                                   entry_valstack_bottom_index,
                                   entry_valstack_end,
                                   entry_catchstack_top,
                                   entry_callstack_top,
                                   entry_call_recursion_depth,
                                   entry_curr_thread,
                                   entry_thread_state,
                                   entry_ptr_curr_pc,
                                   idx_func,
                                   old_jmpbuf_ptr);
            return DUK_EXEC_ERROR;
        }
    }
#endif
}
 
DUK_INTERNAL void duk_handle_call_unprotected(duk_hthread *thr,
                                              duk_idx_t num_stack_args,
                                              duk_small_uint_t call_flags) {
    duk_idx_t idx_func;         /* valstack index of 'func' and retval (relative to entry valstack_bottom) */
 
    /* Argument validation and func/args offset. */
    idx_func = duk__get_idx_func(thr, num_stack_args);
 
    duk__handle_call_inner(thr, num_stack_args, call_flags, idx_func);
}
 
DUK_LOCAL void duk__handle_call_inner(duk_hthread *thr,
                                      duk_idx_t num_stack_args,
                                      duk_small_uint_t call_flags,
                                      duk_idx_t idx_func) {
    duk_context *ctx;
    duk_size_t entry_valstack_bottom_index;
    duk_size_t entry_valstack_end;
    duk_size_t entry_callstack_top;
    duk_size_t entry_catchstack_top;
    duk_int_t entry_call_recursion_depth;
    duk_hthread *entry_curr_thread;
    duk_uint_fast8_t entry_thread_state;
    duk_instr_t **entry_ptr_curr_pc;
    duk_idx_t nargs;            /* # argument registers target function wants (< 0 => "as is") */
    duk_idx_t nregs;            /* # total registers target function wants on entry (< 0 => "as is") */
    duk_hobject *func;          /* 'func' on stack (borrowed reference) */
    duk_tval *tv_func;          /* duk_tval ptr for 'func' on stack (borrowed reference) or tv_func_copy */
    duk_tval tv_func_copy;      /* to avoid relookups */
    duk_activation *act;
    duk_hobject *env;
    duk_ret_t rc;
 
    ctx = (duk_context *) thr;
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_ASSERT(ctx != NULL);
    DUK_ASSERT(num_stack_args >= 0);
    /* XXX: currently NULL allocations are not supported; remove if later allowed */
    DUK_ASSERT(thr->valstack != NULL);
    DUK_ASSERT(thr->callstack != NULL);
    DUK_ASSERT(thr->catchstack != NULL);
 
    DUK_DD(DUK_DDPRINT("duk__handle_call_inner: num_stack_args=%ld, call_flags=0x%08lx, top=%ld",
                       (long) num_stack_args, (long) call_flags, (long) duk_get_top(ctx)));
 
    /*
     *  Store entry state.
     */
 
    entry_valstack_bottom_index = (duk_size_t) (thr->valstack_bottom - thr->valstack);
#if defined(DUK_USE_PREFER_SIZE)
    entry_valstack_end = (duk_size_t) (thr->valstack_end - thr->valstack);
#else
    DUK_ASSERT((duk_size_t) (thr->valstack_end - thr->valstack) == thr->valstack_size);
    entry_valstack_end = thr->valstack_size;
#endif
    entry_callstack_top = thr->callstack_top;
    entry_catchstack_top = thr->catchstack_top;
    entry_call_recursion_depth = thr->heap->call_recursion_depth;
    entry_curr_thread = thr->heap->curr_thread;  /* Note: may be NULL if first call */
    entry_thread_state = thr->state;
    entry_ptr_curr_pc = thr->ptr_curr_pc;  /* may be NULL */
 
    /* If thr->ptr_curr_pc is set, sync curr_pc to act->pc.  Then NULL
     * thr->ptr_curr_pc so that it's not accidentally used with an incorrect
     * activation when side effects occur.
     */
    duk_hthread_sync_and_null_currpc(thr);
 
    DUK_DD(DUK_DDPRINT("duk__handle_call_inner: thr=%p, num_stack_args=%ld, "
                       "call_flags=0x%08lx (ignorerec=%ld, constructor=%ld), "
                       "valstack_top=%ld, idx_func=%ld, idx_args=%ld, rec_depth=%ld/%ld, "
                       "entry_valstack_bottom_index=%ld, entry_callstack_top=%ld, entry_catchstack_top=%ld, "
                       "entry_call_recursion_depth=%ld, entry_curr_thread=%p, entry_thread_state=%ld",
                       (void *) thr,
                       (long) num_stack_args,
                       (unsigned long) call_flags,
                       (long) ((call_flags & DUK_CALL_FLAG_IGNORE_RECLIMIT) != 0 ? 1 : 0),
                       (long) ((call_flags & DUK_CALL_FLAG_CONSTRUCTOR_CALL) != 0 ? 1 : 0),
                       (long) duk_get_top(ctx),
                       (long) idx_func,
                       (long) (idx_func + 2),
                       (long) thr->heap->call_recursion_depth,
                       (long) thr->heap->call_recursion_limit,
                       (long) entry_valstack_bottom_index,
                       (long) entry_callstack_top,
                       (long) entry_catchstack_top,
                       (long) entry_call_recursion_depth,
                       (void *) entry_curr_thread,
                       (long) entry_thread_state));
 
 
    /*
     *  Thread state check and book-keeping.
     */
 
    if (thr == thr->heap->curr_thread) {
        /* same thread */
        if (thr->state != DUK_HTHREAD_STATE_RUNNING) {
            /* should actually never happen, but check anyway */
            goto thread_state_error;
        }
    } else {
        /* different thread */
        DUK_ASSERT(thr->heap->curr_thread == NULL ||
                   thr->heap->curr_thread->state == DUK_HTHREAD_STATE_RUNNING);
        if (thr->state != DUK_HTHREAD_STATE_INACTIVE) {
            goto thread_state_error;
        }
        DUK_HEAP_SWITCH_THREAD(thr->heap, thr);
        thr->state = DUK_HTHREAD_STATE_RUNNING;
 
        /* Note: multiple threads may be simultaneously in the RUNNING
         * state, but not in the same "resume chain".
         */
    }
    DUK_ASSERT(thr->heap->curr_thread == thr);
    DUK_ASSERT(thr->state == DUK_HTHREAD_STATE_RUNNING);
 
    /*
     *  C call recursion depth check, which provides a reasonable upper
     *  bound on maximum C stack size (arbitrary C stack growth is only
     *  possible by recursive handle_call / handle_safe_call calls).
     */
 
    /* XXX: remove DUK_CALL_FLAG_IGNORE_RECLIMIT flag: there's now the
     * reclimit bump?
     */
 
    DUK_ASSERT(thr->heap->call_recursion_depth >= 0);
    DUK_ASSERT(thr->heap->call_recursion_depth <= thr->heap->call_recursion_limit);
    if (call_flags & DUK_CALL_FLAG_IGNORE_RECLIMIT) {
        DUK_DD(DUK_DDPRINT("ignoring reclimit for this call (probably an errhandler call)"));
    } else {
        if (thr->heap->call_recursion_depth >= thr->heap->call_recursion_limit) {
            /* XXX: error message is a bit misleading: we reached a recursion
             * limit which is also essentially the same as a C callstack limit
             * (except perhaps with some relaxed threading assumptions).
             */
            DUK_ERROR_RANGE(thr, DUK_STR_C_CALLSTACK_LIMIT);
        }
        thr->heap->call_recursion_depth++;
    }
 
    /*
     *  Check the function type, handle bound function chains, and prepare
     *  parameters for the rest of the call handling.  Also figure out the
     *  effective 'this' binding, which replaces the current value at
     *  idx_func + 1.
     *
     *  If the target function is a 'bound' one, follow the chain of 'bound'
     *  functions until a non-bound function is found.  During this process,
     *  bound arguments are 'prepended' to existing ones, and the "this"
     *  binding is overridden.  See E5 Section 15.3.4.5.1.
     *
     *  Lightfunc detection happens here too.  Note that lightweight functions
     *  can be wrapped by (non-lightweight) bound functions so we must resolve
     *  the bound function chain first.
     */
 
    func = duk__nonbound_func_lookup(ctx, idx_func, &num_stack_args, &tv_func, call_flags);
    DUK_TVAL_SET_TVAL(&tv_func_copy, tv_func);
    tv_func = &tv_func_copy;  /* local copy to avoid relookups */
 
    DUK_ASSERT(func == NULL || !DUK_HOBJECT_HAS_BOUND(func));
    DUK_ASSERT(func == NULL || (DUK_HOBJECT_IS_COMPILEDFUNCTION(func) ||
                                DUK_HOBJECT_IS_NATIVEFUNCTION(func)));
 
    duk__coerce_effective_this_binding(thr, func, idx_func + 1);
    DUK_DDD(DUK_DDDPRINT("effective 'this' binding is: %!T",
                         (duk_tval *) duk_get_tval(ctx, idx_func + 1)));
 
    /* [ ... func this arg1 ... argN ] */
 
    /*
     *  Setup a preliminary activation and figure out nargs/nregs.
     *
     *  Don't touch valstack_bottom or valstack_top yet so that Duktape API
     *  calls work normally.
     */
 
    duk_hthread_callstack_grow(thr);
 
    if (thr->callstack_top > 0) {
        /*
         *  Update idx_retval of current activation.
         *
         *  Although it might seem this is not necessary (bytecode executor
         *  does this for Ecmascript-to-Ecmascript calls; other calls are
         *  handled here), this turns out to be necessary for handling yield
         *  and resume.  For them, an Ecmascript-to-native call happens, and
         *  the Ecmascript call's idx_retval must be set for things to work.
         */
 
        (thr->callstack + thr->callstack_top - 1)->idx_retval = entry_valstack_bottom_index + idx_func;
    }
 
    DUK_ASSERT(thr->callstack_top < thr->callstack_size);
    act = thr->callstack + thr->callstack_top;
    thr->callstack_top++;
    DUK_ASSERT(thr->callstack_top <= thr->callstack_size);
    DUK_ASSERT(thr->valstack_top > thr->valstack_bottom);  /* at least effective 'this' */
    DUK_ASSERT(func == NULL || !DUK_HOBJECT_HAS_BOUND(func));
 
    act->flags = 0;
 
    /* For now all calls except Ecma-to-Ecma calls prevent a yield. */
    act->flags |= DUK_ACT_FLAG_PREVENT_YIELD;
    if (call_flags & DUK_CALL_FLAG_CONSTRUCTOR_CALL) {
        act->flags |= DUK_ACT_FLAG_CONSTRUCT;
    }
    if (call_flags & DUK_CALL_FLAG_DIRECT_EVAL) {
        act->flags |= DUK_ACT_FLAG_DIRECT_EVAL;
    }
 
    /* These base values are never used, but if the compiler doesn't know
     * that DUK_ERROR() won't return, these are needed to silence warnings.
     * On the other hand, scan-build will warn about the values not being
     * used, so add a DUK_UNREF.
     */
    nargs = 0; DUK_UNREF(nargs);
    nregs = 0; DUK_UNREF(nregs);
 
    if (DUK_LIKELY(func != NULL)) {
        if (DUK_HOBJECT_HAS_STRICT(func)) {
            act->flags |= DUK_ACT_FLAG_STRICT;
        }
        if (DUK_HOBJECT_IS_COMPILEDFUNCTION(func)) {
            nargs = ((duk_hcompiledfunction *) func)->nargs;
            nregs = ((duk_hcompiledfunction *) func)->nregs;
            DUK_ASSERT(nregs >= nargs);
        } else if (DUK_HOBJECT_IS_NATIVEFUNCTION(func)) {
            /* Note: nargs (and nregs) may be negative for a native,
             * function, which indicates that the function wants the
             * input stack "as is" (i.e. handles "vararg" arguments).
             */
            nargs = ((duk_hnativefunction *) func)->nargs;
            nregs = nargs;
        } else {
            /* XXX: this should be an assert */
            DUK_ERROR_TYPE(thr, DUK_STR_NOT_CALLABLE);
        }
    } else {
        duk_small_uint_t lf_flags;
 
        DUK_ASSERT(DUK_TVAL_IS_LIGHTFUNC(tv_func));
        lf_flags = DUK_TVAL_GET_LIGHTFUNC_FLAGS(tv_func);
        nargs = DUK_LFUNC_FLAGS_GET_NARGS(lf_flags);
        if (nargs == DUK_LFUNC_NARGS_VARARGS) {
            nargs = -1;  /* vararg */
        }
        nregs = nargs;
 
        act->flags |= DUK_ACT_FLAG_STRICT;
    }
 
    act->func = func;  /* NULL for lightfunc */
    act->var_env = NULL;
    act->lex_env = NULL;
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
    act->prev_caller = NULL;
#endif
    act->curr_pc = NULL;
#if defined(DUK_USE_DEBUGGER_SUPPORT)
    act->prev_line = 0;
#endif
    act->idx_bottom = entry_valstack_bottom_index + idx_func + 2;
#if 0  /* topmost activation idx_retval is considered garbage, no need to init */
    act->idx_retval = 0;
#endif
    DUK_TVAL_SET_TVAL(&act->tv_func, tv_func);  /* borrowed, no refcount */
 
    /* XXX: remove the preventcount and make yield walk the callstack?
     * Or perhaps just use a single flag, not a counter, faster to just
     * set and restore?
     */
    if (act->flags & DUK_ACT_FLAG_PREVENT_YIELD) {
        /* duk_hthread_callstack_unwind() will decrease this on unwind */
        thr->callstack_preventcount++;
    }
 
    /* XXX: Is this INCREF necessary? 'func' is always a borrowed
     * reference reachable through the value stack?  If changed, stack
     * unwind code also needs to be fixed to match.
     */
    DUK_HOBJECT_INCREF_ALLOWNULL(thr, func);  /* act->func */
 
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
    if (func) {
        duk__update_func_caller_prop(thr, func);
        act = thr->callstack + thr->callstack_top - 1;
    }
#endif
 
    /* [ ... func this arg1 ... argN ] */
 
    /*
     *  Environment record creation and 'arguments' object creation.
     *  Named function expression name binding is handled by the
     *  compiler; the compiled function's parent env will contain
     *  the (immutable) binding already.
     *
     *  This handling is now identical for C and Ecmascript functions.
     *  C functions always have the 'NEWENV' flag set, so their
     *  environment record initialization is delayed (which is good).
     *
     *  Delayed creation (on demand) is handled in duk_js_var.c.
     */
 
    DUK_ASSERT(func == NULL || !DUK_HOBJECT_HAS_BOUND(func));  /* bound function chain has already been resolved */
 
    if (DUK_LIKELY(func != NULL)) {
        if (DUK_LIKELY(DUK_HOBJECT_HAS_NEWENV(func))) {
            if (DUK_LIKELY(!DUK_HOBJECT_HAS_CREATEARGS(func))) {
                /* Use a new environment but there's no 'arguments' object;
                 * delayed environment initialization.  This is the most
                 * common case.
                 */
                DUK_ASSERT(act->lex_env == NULL);
                DUK_ASSERT(act->var_env == NULL);
            } else {
                /* Use a new environment and there's an 'arguments' object.
                 * We need to initialize it right now.
                 */
 
                /* third arg: absolute index (to entire valstack) of idx_bottom of new activation */
                env = duk_create_activation_environment_record(thr, func, act->idx_bottom);
                DUK_ASSERT(env != NULL);
 
                /* [ ... func this arg1 ... argN envobj ] */
 
                DUK_ASSERT(DUK_HOBJECT_HAS_CREATEARGS(func));
                duk__handle_createargs_for_call(thr, func, env, num_stack_args);
 
                /* [ ... func this arg1 ... argN envobj ] */
 
                act = thr->callstack + thr->callstack_top - 1;
                act->lex_env = env;
                act->var_env = env;
                DUK_HOBJECT_INCREF(thr, env);
                DUK_HOBJECT_INCREF(thr, env);  /* XXX: incref by count (2) directly */
                duk_pop(ctx);
            }
        } else {
            /* Use existing env (e.g. for non-strict eval); cannot have
             * an own 'arguments' object (but can refer to an existing one).
             */
 
            DUK_ASSERT(!DUK_HOBJECT_HAS_CREATEARGS(func));
 
            duk__handle_oldenv_for_call(thr, func, act);
            /* No need to re-lookup 'act' at present: no side effects. */
 
            DUK_ASSERT(act->lex_env != NULL);
            DUK_ASSERT(act->var_env != NULL);
        }
    } else {
        /* Lightfuncs are always native functions and have "newenv". */
        DUK_ASSERT(act->lex_env == NULL);
        DUK_ASSERT(act->var_env == NULL);
    }
 
    /* [ ... func this arg1 ... argN ] */
 
    /*
     *  Setup value stack: clamp to 'nargs', fill up to 'nregs'
     *
     *  Value stack may either grow or shrink, depending on the
     *  number of func registers and the number of actual arguments.
     *  If nregs >= 0, func wants args clamped to 'nargs'; else it
     *  wants all args (= 'num_stack_args').
     */
 
    /* XXX: optimize value stack operation */
    /* XXX: don't want to shrink allocation here */
 
    duk__adjust_valstack_and_top(thr,
                                 num_stack_args,
                                 idx_func + 2,
                                 nregs,
                                 nargs,
                                 func);
 
    /*
     *  Determine call type, then finalize activation, shift to
     *  new value stack bottom, and call the target.
     */
 
    act = thr->callstack + thr->callstack_top - 1;
    if (func != NULL && DUK_HOBJECT_IS_COMPILEDFUNCTION(func)) {
        /*
         *  Ecmascript call
         */
 
        duk_tval *tv_ret;
        duk_tval *tv_funret;
 
        DUK_ASSERT(func != NULL);
        DUK_ASSERT(DUK_HOBJECT_HAS_COMPILEDFUNCTION(func));
        act->curr_pc = DUK_HCOMPILEDFUNCTION_GET_CODE_BASE(thr->heap, (duk_hcompiledfunction *) func);
 
        thr->valstack_bottom = thr->valstack_bottom + idx_func + 2;
        /* keep current valstack_top */
        DUK_ASSERT(thr->valstack_bottom >= thr->valstack);
        DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
        DUK_ASSERT(thr->valstack_end >= thr->valstack_top);
 
        /* [ ... func this | arg1 ... argN ] ('this' must precede new bottom) */
 
        /*
         *  Bytecode executor call.
         *
         *  Execute bytecode, handling any recursive function calls and
         *  thread resumptions.  Returns when execution would return from
         *  the entry level activation.  When the executor returns, a
         *  single return value is left on the stack top.
         *
         *  The only possible longjmp() is an error (DUK_LJ_TYPE_THROW),
         *  other types are handled internally by the executor.
         */
 
        /* thr->ptr_curr_pc is set by bytecode executor early on entry */
        DUK_ASSERT(thr->ptr_curr_pc == NULL);
        DUK_DDD(DUK_DDDPRINT("entering bytecode execution"));
        duk_js_execute_bytecode(thr);
        DUK_DDD(DUK_DDDPRINT("returned from bytecode execution"));
 
        /* Unwind. */
 
        DUK_ASSERT(thr->catchstack_top >= entry_catchstack_top);  /* may need unwind */
        DUK_ASSERT(thr->callstack_top == entry_callstack_top + 1);
        DUK_ASSERT(thr->callstack_top == entry_callstack_top + 1);
        duk_hthread_catchstack_unwind(thr, entry_catchstack_top);
        duk_hthread_catchstack_shrink_check(thr);
        duk_hthread_callstack_unwind(thr, entry_callstack_top);
        duk_hthread_callstack_shrink_check(thr);
 
        thr->valstack_bottom = thr->valstack + entry_valstack_bottom_index;
        /* keep current valstack_top */
        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(thr->valstack_top - thr->valstack_bottom >= idx_func + 1);
 
        /* Return value handling. */
 
        /* [ ... func this (crud) retval ] */
 
        tv_ret = thr->valstack_bottom + idx_func;
        tv_funret = thr->valstack_top - 1;
#if defined(DUK_USE_FASTINT)
        /* Explicit check for fastint downgrade. */
        DUK_TVAL_CHKFAST_INPLACE(tv_funret);
#endif
        DUK_TVAL_SET_TVAL_UPDREF(thr, tv_ret, tv_funret);  /* side effects */
    } else {
        /*
         *  Native call.
         */
 
        duk_tval *tv_ret;
        duk_tval *tv_funret;
 
        thr->valstack_bottom = thr->valstack_bottom + idx_func + 2;
        /* keep current valstack_top */
        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(func == NULL || ((duk_hnativefunction *) func)->func != NULL);
 
        /* [ ... func this | arg1 ... argN ] ('this' must precede new bottom) */
 
        /* For native calls must be NULL so we don't sync back */
        DUK_ASSERT(thr->ptr_curr_pc == NULL);
 
        if (func) {
            rc = ((duk_hnativefunction *) func)->func((duk_context *) thr);
        } else {
            duk_c_function funcptr = DUK_TVAL_GET_LIGHTFUNC_FUNCPTR(tv_func);
            rc = funcptr((duk_context *) thr);
        }
 
        /* Automatic error throwing, retval check. */
 
        if (rc < 0) {
            duk_error_throw_from_negative_rc(thr, rc);
            DUK_UNREACHABLE();
        } else if (rc > 1) {
            DUK_ERROR_API(thr, "c function returned invalid rc");
        }
        DUK_ASSERT(rc == 0 || rc == 1);
 
        /* Unwind. */
 
        DUK_ASSERT(thr->catchstack_top == entry_catchstack_top);  /* no need to unwind */
        DUK_ASSERT(thr->callstack_top == entry_callstack_top + 1);
        duk_hthread_callstack_unwind(thr, entry_callstack_top);
        duk_hthread_callstack_shrink_check(thr);
 
        thr->valstack_bottom = thr->valstack + entry_valstack_bottom_index;
        /* keep current valstack_top */
        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(thr->valstack_top - thr->valstack_bottom >= idx_func + 1);
 
        /* Return value handling. */
 
        /* XXX: should this happen in the callee's activation or after unwinding? */
        tv_ret = thr->valstack_bottom + idx_func;
        if (rc == 0) {
            DUK_TVAL_SET_UNDEFINED_UPDREF(thr, tv_ret);  /* side effects */
        } else {
            /* [ ... func this (crud) retval ] */
            tv_funret = thr->valstack_top - 1;
#if defined(DUK_USE_FASTINT)
            /* Explicit check for fastint downgrade. */
            DUK_TVAL_CHKFAST_INPLACE(tv_funret);
#endif
            DUK_TVAL_SET_TVAL_UPDREF(thr, tv_ret, tv_funret);  /* side effects */
        }
    }
 
    duk_set_top(ctx, idx_func + 1);  /* XXX: unnecessary, handle in adjust */
 
    /* [ ... retval ] */
 
    /* Ensure there is internal valstack spare before we exit; this may
     * throw an alloc error.  The same guaranteed size must be available
     * as before the call.  This is not optimal now: we store the valstack
     * allocated size during entry; this value may be higher than the
     * minimal guarantee for an application.
     */
 
    /* XXX: we should never shrink here; when we error out later, we'd
     * need to potentially grow the value stack in error unwind which could
     * cause another error.
     */
 
    (void) duk_valstack_resize_raw((duk_context *) thr,
                                   entry_valstack_end,                    /* same as during entry */
                                   DUK_VSRESIZE_FLAG_SHRINK |             /* flags */
                                   DUK_VSRESIZE_FLAG_COMPACT |
                                   DUK_VSRESIZE_FLAG_THROW);
 
    /* Restore entry thread executor curr_pc stack frame pointer. */
    thr->ptr_curr_pc = entry_ptr_curr_pc;
 
    DUK_HEAP_SWITCH_THREAD(thr->heap, entry_curr_thread);  /* may be NULL */
    thr->state = (duk_uint8_t) entry_thread_state;
 
    DUK_ASSERT((thr->state == DUK_HTHREAD_STATE_INACTIVE && thr->heap->curr_thread == NULL) ||  /* first call */
               (thr->state == DUK_HTHREAD_STATE_INACTIVE && thr->heap->curr_thread != NULL) ||  /* other call */
               (thr->state == DUK_HTHREAD_STATE_RUNNING && thr->heap->curr_thread == thr));     /* current thread */
 
    thr->heap->call_recursion_depth = entry_call_recursion_depth;
 
    /* If the debugger is active we need to force an interrupt so that
     * debugger breakpoints are rechecked.  This is important for function
     * calls caused by side effects (e.g. when doing a DUK_OP_GETPROP), see
     * GH-303.  Only needed for success path, error path always causes a
     * breakpoint recheck in the executor.  It would be enough to set this
     * only when returning to an Ecmascript activation, but setting the flag
     * on every return should have no ill effect.
     */
#if defined(DUK_USE_DEBUGGER_SUPPORT)
    if (DUK_HEAP_IS_DEBUGGER_ATTACHED(thr->heap)) {
        DUK_DD(DUK_DDPRINT("returning with debugger enabled, force interrupt"));
        DUK_ASSERT(thr->interrupt_counter <= thr->interrupt_init);
        thr->interrupt_init -= thr->interrupt_counter;
        thr->interrupt_counter = 0;
        thr->heap->dbg_force_restart = 1;
    }
#endif
 
#if defined(DUK_USE_INTERRUPT_COUNTER) && defined(DUK_USE_DEBUG)
    duk__interrupt_fixup(thr, entry_curr_thread);
#endif
 
    return;
 
 thread_state_error:
    DUK_ERROR_FMT1(thr, DUK_ERR_TYPE_ERROR, "invalid thread state for call (%ld)", (long) thr->state);
    DUK_UNREACHABLE();
    return;  /* never executed */
}
 
DUK_LOCAL void duk__handle_call_error(duk_hthread *thr,
                                      duk_size_t entry_valstack_bottom_index,
                                      duk_size_t entry_valstack_end,
                                      duk_size_t entry_catchstack_top,
                                      duk_size_t entry_callstack_top,
                                      duk_int_t entry_call_recursion_depth,
                                      duk_hthread *entry_curr_thread,
                                      duk_uint_fast8_t entry_thread_state,
                                      duk_instr_t **entry_ptr_curr_pc,
                                      duk_idx_t idx_func,
                                      duk_jmpbuf *old_jmpbuf_ptr) {
    duk_context *ctx;
    duk_tval *tv_ret;
 
    ctx = (duk_context *) thr;
 
    DUK_DDD(DUK_DDDPRINT("error caught during duk__handle_call_inner(): %!T",
                         (duk_tval *) &thr->heap->lj.value1));
 
    /* Other longjmp types are handled by executor before propagating
     * the error here.
     */
    DUK_ASSERT(thr->heap->lj.type == DUK_LJ_TYPE_THROW);
    DUK_ASSERT(thr->callstack_top >= entry_callstack_top);
    DUK_ASSERT(thr->catchstack_top >= entry_catchstack_top);
 
    /* We don't need to sync back thr->ptr_curr_pc here because
     * the bytecode executor always has a setjmp catchpoint which
     * does that before errors propagate to here.
     */
    DUK_ASSERT(thr->ptr_curr_pc == NULL);
 
    /* Restore the previous setjmp catcher so that any error in
     * error handling will propagate outwards rather than re-enter
     * the same handler.  However, the error handling path must be
     * designed to be error free so that sandboxing guarantees are
     * reliable, see e.g. https://github.com/svaarala/duktape/issues/476.
     */
    thr->heap->lj.jmpbuf_ptr = old_jmpbuf_ptr;
 
    /* XXX: callstack unwind may now throw an error when closing
     * scopes; this is a sandboxing issue, described in:
     * https://github.com/svaarala/duktape/issues/476
     */
    duk_hthread_catchstack_unwind(thr, entry_catchstack_top);
    duk_hthread_catchstack_shrink_check(thr);
    duk_hthread_callstack_unwind(thr, entry_callstack_top);
    duk_hthread_callstack_shrink_check(thr);
 
    thr->valstack_bottom = thr->valstack + entry_valstack_bottom_index;
    tv_ret = thr->valstack_bottom + idx_func;  /* XXX: byte offset? */
    DUK_TVAL_SET_TVAL_UPDREF(thr, tv_ret, &thr->heap->lj.value1);  /* side effects */
#if defined(DUK_USE_FASTINT)
    /* Explicit check for fastint downgrade. */
    DUK_TVAL_CHKFAST_INPLACE(tv_ret);
#endif
    duk_set_top(ctx, idx_func + 1);  /* XXX: could be eliminated with valstack adjust */
 
    /* [ ... errobj ] */
 
    /* Ensure there is internal valstack spare before we exit; this may
     * throw an alloc error.  The same guaranteed size must be available
     * as before the call.  This is not optimal now: we store the valstack
     * allocated size during entry; this value may be higher than the
     * minimal guarantee for an application.
     */
 
    /* XXX: this needs to be reworked so that we never shrink the value
     * stack on function entry so that we never need to grow it here.
     * Needing to grow here is a sandboxing issue because we need to
     * allocate which may cause an error in the error handling path
     * and thus propagate an error out of a protected call.
     */
 
    (void) duk_valstack_resize_raw((duk_context *) thr,
                                   entry_valstack_end,                    /* same as during entry */
                                   DUK_VSRESIZE_FLAG_SHRINK |             /* flags */
                                   DUK_VSRESIZE_FLAG_COMPACT |
                                   DUK_VSRESIZE_FLAG_THROW);
 
 
    /* These are just convenience "wiping" of state.  Side effects should
     * not be an issue here: thr->heap and thr->heap->lj have a stable
     * pointer.  Finalizer runs etc capture even out-of-memory errors so
     * nothing should throw here.
     */
    thr->heap->lj.type = DUK_LJ_TYPE_UNKNOWN;
    thr->heap->lj.iserror = 0;
    DUK_TVAL_SET_UNDEFINED_UPDREF(thr, &thr->heap->lj.value1);  /* side effects */
    DUK_TVAL_SET_UNDEFINED_UPDREF(thr, &thr->heap->lj.value2);  /* side effects */
 
    /* Restore entry thread executor curr_pc stack frame pointer. */
    thr->ptr_curr_pc = entry_ptr_curr_pc;
 
    DUK_HEAP_SWITCH_THREAD(thr->heap, entry_curr_thread);  /* may be NULL */
    thr->state = (duk_uint8_t) entry_thread_state;
 
    DUK_ASSERT((thr->state == DUK_HTHREAD_STATE_INACTIVE && thr->heap->curr_thread == NULL) ||  /* first call */
               (thr->state == DUK_HTHREAD_STATE_INACTIVE && thr->heap->curr_thread != NULL) ||  /* other call */
               (thr->state == DUK_HTHREAD_STATE_RUNNING && thr->heap->curr_thread == thr));     /* current thread */
 
    thr->heap->call_recursion_depth = entry_call_recursion_depth;
 
    /* If the debugger is active we need to force an interrupt so that
     * debugger breakpoints are rechecked.  This is important for function
     * calls caused by side effects (e.g. when doing a DUK_OP_GETPROP), see
     * GH-303.  Only needed for success path, error path always causes a
     * breakpoint recheck in the executor.  It would be enough to set this
     * only when returning to an Ecmascript activation, but setting the flag
     * on every return should have no ill effect.
     */
#if defined(DUK_USE_DEBUGGER_SUPPORT)
    if (DUK_HEAP_IS_DEBUGGER_ATTACHED(thr->heap)) {
        DUK_DD(DUK_DDPRINT("returning with debugger enabled, force interrupt"));
        DUK_ASSERT(thr->interrupt_counter <= thr->interrupt_init);
        thr->interrupt_init -= thr->interrupt_counter;
        thr->interrupt_counter = 0;
        thr->heap->dbg_force_restart = 1;
    }
#endif
 
#if defined(DUK_USE_INTERRUPT_COUNTER) && defined(DUK_USE_DEBUG)
    duk__interrupt_fixup(thr, entry_curr_thread);
#endif
}
 
/*
 *  duk_handle_safe_call(): make a "C protected call" within the
 *  current activation.
 *
 *  The allowed thread states for making a call are the same as for
 *  duk_handle_call_xxx().
 *
 *  Error handling is similar to duk_handle_call_xxx(); errors may be thrown
 *  (and result in a fatal error) for insane arguments.
 */
 
/* XXX: bump preventcount by one for the duration of this call? */
 
DUK_INTERNAL duk_int_t duk_handle_safe_call(duk_hthread *thr,
                                            duk_safe_call_function func,
                                            duk_idx_t num_stack_args,
                                            duk_idx_t num_stack_rets) {
    duk_context *ctx = (duk_context *) thr;
    duk_size_t entry_valstack_bottom_index;
    duk_size_t entry_callstack_top;
    duk_size_t entry_catchstack_top;
    duk_int_t entry_call_recursion_depth;
    duk_hthread *entry_curr_thread;
    duk_uint_fast8_t entry_thread_state;
    duk_instr_t **entry_ptr_curr_pc;
    duk_jmpbuf *old_jmpbuf_ptr = NULL;
    duk_jmpbuf our_jmpbuf;
    duk_idx_t idx_retbase;
    duk_int_t retval;
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(ctx != NULL);
 
    /* Note: careful with indices like '-x'; if 'x' is zero, it refers to bottom */
    entry_valstack_bottom_index = (duk_size_t) (thr->valstack_bottom - thr->valstack);
    entry_callstack_top = thr->callstack_top;
    entry_catchstack_top = thr->catchstack_top;
    entry_call_recursion_depth = thr->heap->call_recursion_depth;
    entry_curr_thread = thr->heap->curr_thread;  /* Note: may be NULL if first call */
    entry_thread_state = thr->state;
    entry_ptr_curr_pc = thr->ptr_curr_pc;  /* may be NULL */
    idx_retbase = duk_get_top(ctx) - num_stack_args;  /* Note: not a valid stack index if num_stack_args == 0 */
 
    /* Note: cannot portably debug print a function pointer, hence 'func' not printed! */
    DUK_DD(DUK_DDPRINT("duk_handle_safe_call: thr=%p, num_stack_args=%ld, num_stack_rets=%ld, "
                       "valstack_top=%ld, idx_retbase=%ld, rec_depth=%ld/%ld, "
                       "entry_valstack_bottom_index=%ld, entry_callstack_top=%ld, entry_catchstack_top=%ld, "
                       "entry_call_recursion_depth=%ld, entry_curr_thread=%p, entry_thread_state=%ld",
                       (void *) thr,
                       (long) num_stack_args,
                       (long) num_stack_rets,
                       (long) duk_get_top(ctx),
                       (long) idx_retbase,
                       (long) thr->heap->call_recursion_depth,
                       (long) thr->heap->call_recursion_limit,
                       (long) entry_valstack_bottom_index,
                       (long) entry_callstack_top,
                       (long) entry_catchstack_top,
                       (long) entry_call_recursion_depth,
                       (void *) entry_curr_thread,
                       (long) entry_thread_state));
 
    if (idx_retbase < 0) {
        /* Since stack indices are not reliable, we can't do anything useful
         * here.  Invoke the existing setjmp catcher, or if it doesn't exist,
         * call the fatal error handler.
         */
 
        DUK_ERROR_API(thr, DUK_STR_INVALID_CALL_ARGS);
    }
 
    /* setjmp catchpoint setup */
 
    old_jmpbuf_ptr = thr->heap->lj.jmpbuf_ptr;
    thr->heap->lj.jmpbuf_ptr = &our_jmpbuf;
 
#if defined(DUK_USE_CPP_EXCEPTIONS)
    try {
#else
    DUK_ASSERT(thr->heap->lj.jmpbuf_ptr == &our_jmpbuf);
    if (DUK_SETJMP(our_jmpbuf.jb) == 0) {
        /* Success path. */
#endif
        DUK_DDD(DUK_DDDPRINT("safe_call setjmp catchpoint setup complete"));
 
        duk__handle_safe_call_inner(thr,
                                    func,
                                    idx_retbase,
                                    num_stack_rets,
                                    entry_valstack_bottom_index,
                                    entry_callstack_top,
                                    entry_catchstack_top);
 
        /* Longjmp state is kept clean in success path */
        DUK_ASSERT(thr->heap->lj.type == DUK_LJ_TYPE_UNKNOWN);
        DUK_ASSERT(thr->heap->lj.iserror == 0);
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value1));
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value2));
 
        /* Note: either pointer may be NULL (at entry), so don't assert */
        thr->heap->lj.jmpbuf_ptr = old_jmpbuf_ptr;
 
        retval = DUK_EXEC_SUCCESS;
#if defined(DUK_USE_CPP_EXCEPTIONS)
    } catch (duk_internal_exception &exc) {
        DUK_UNREF(exc);
#else
    } else {
        /* Error path. */
#endif
        duk__handle_safe_call_error(thr,
                                    idx_retbase,
                                    num_stack_rets,
                                    entry_valstack_bottom_index,
                                    entry_callstack_top,
                                    entry_catchstack_top,
                                    old_jmpbuf_ptr);
 
        /* Longjmp state is cleaned up by error handling */
        DUK_ASSERT(thr->heap->lj.type == DUK_LJ_TYPE_UNKNOWN);
        DUK_ASSERT(thr->heap->lj.iserror == 0);
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value1));
        DUK_ASSERT(DUK_TVAL_IS_UNDEFINED(&thr->heap->lj.value2));
 
        retval = DUK_EXEC_ERROR;
    }
#if defined(DUK_USE_CPP_EXCEPTIONS)
    catch (std::exception &exc) {
        const char *what = exc.what();
        if (!what) {
            what = "unknown";
        }
        DUK_D(DUK_DPRINT("unexpected c++ std::exception (perhaps thrown by user code)"));
        try {
            DUK_ERROR_FMT1(thr, DUK_ERR_API_ERROR, "caught invalid c++ std::exception '%s' (perhaps thrown by user code)", what);
        } catch (duk_internal_exception exc) {
            DUK_D(DUK_DPRINT("caught api error thrown from unexpected c++ std::exception"));
            DUK_UNREF(exc);
            duk__handle_safe_call_error(thr,
                                        idx_retbase,
                                        num_stack_rets,
                                        entry_valstack_bottom_index,
                                        entry_callstack_top,
                                        entry_catchstack_top,
                                        old_jmpbuf_ptr);
            retval = DUK_EXEC_ERROR;
        }
    } catch (...) {
        DUK_D(DUK_DPRINT("unexpected c++ exception (perhaps thrown by user code)"));
        try {
            DUK_ERROR_API(thr, "caught invalid c++ exception (perhaps thrown by user code)");
        } catch (duk_internal_exception exc) {
            DUK_D(DUK_DPRINT("caught api error thrown from unexpected c++ exception"));
            DUK_UNREF(exc);
            duk__handle_safe_call_error(thr,
                                        idx_retbase,
                                        num_stack_rets,
                                        entry_valstack_bottom_index,
                                        entry_callstack_top,
                                        entry_catchstack_top,
                                        old_jmpbuf_ptr);
            retval = DUK_EXEC_ERROR;
        }
    }
#endif
 
    DUK_ASSERT(thr->heap->lj.jmpbuf_ptr == old_jmpbuf_ptr);  /* success/error path both do this */
 
    duk__handle_safe_call_shared(thr,
                                 idx_retbase,
                                 num_stack_rets,
                                 entry_call_recursion_depth,
                                 entry_curr_thread,
                                 entry_thread_state,
                                 entry_ptr_curr_pc);
 
    return retval;
}
 
DUK_LOCAL void duk__handle_safe_call_inner(duk_hthread *thr,
                                           duk_safe_call_function func,
                                           duk_idx_t idx_retbase,
                                           duk_idx_t num_stack_rets,
                                           duk_size_t entry_valstack_bottom_index,
                                           duk_size_t entry_callstack_top,
                                           duk_size_t entry_catchstack_top) {
    duk_context *ctx;
    duk_ret_t rc;
 
    DUK_ASSERT(thr != NULL);
    ctx = (duk_context *) thr;
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(entry_valstack_bottom_index);
    DUK_UNREF(entry_callstack_top);
    DUK_UNREF(entry_catchstack_top);
 
    /*
     *  Thread state check and book-keeping.
     */
 
    if (thr == thr->heap->curr_thread) {
        /* same thread */
        if (thr->state != DUK_HTHREAD_STATE_RUNNING) {
            /* should actually never happen, but check anyway */
            goto thread_state_error;
        }
    } else {
        /* different thread */
        DUK_ASSERT(thr->heap->curr_thread == NULL ||
                   thr->heap->curr_thread->state == DUK_HTHREAD_STATE_RUNNING);
        if (thr->state != DUK_HTHREAD_STATE_INACTIVE) {
            goto thread_state_error;
        }
        DUK_HEAP_SWITCH_THREAD(thr->heap, thr);
        thr->state = DUK_HTHREAD_STATE_RUNNING;
 
        /* Note: multiple threads may be simultaneously in the RUNNING
         * state, but not in the same "resume chain".
         */
    }
 
    DUK_ASSERT(thr->heap->curr_thread == thr);
    DUK_ASSERT(thr->state == DUK_HTHREAD_STATE_RUNNING);
 
    /*
     *  Recursion limit check.
     *
     *  Note: there is no need for an "ignore recursion limit" flag
     *  for duk_handle_safe_call now.
     */
 
    DUK_ASSERT(thr->heap->call_recursion_depth >= 0);
    DUK_ASSERT(thr->heap->call_recursion_depth <= thr->heap->call_recursion_limit);
    if (thr->heap->call_recursion_depth >= thr->heap->call_recursion_limit) {
        /* XXX: error message is a bit misleading: we reached a recursion
         * limit which is also essentially the same as a C callstack limit
         * (except perhaps with some relaxed threading assumptions).
         */
        DUK_ERROR_RANGE(thr, DUK_STR_C_CALLSTACK_LIMIT);
    }
    thr->heap->call_recursion_depth++;
 
    /*
     *  Valstack spare check
     */
 
    duk_require_stack(ctx, 0);  /* internal spare */
 
    /*
     *  Make the C call
     */
 
    rc = func(ctx);
 
    DUK_DDD(DUK_DDDPRINT("safe_call, func rc=%ld", (long) rc));
 
    /*
     *  Valstack manipulation for results.
     */
 
    /* we're running inside the caller's activation, so no change in call/catch stack or valstack bottom */
    DUK_ASSERT(thr->callstack_top == entry_callstack_top);
    DUK_ASSERT(thr->catchstack_top == entry_catchstack_top);
    DUK_ASSERT(thr->valstack_bottom >= thr->valstack);
    DUK_ASSERT((duk_size_t) (thr->valstack_bottom - thr->valstack) == entry_valstack_bottom_index);
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    DUK_ASSERT(thr->valstack_end >= thr->valstack_top);
 
    if (rc < 0) {
        duk_error_throw_from_negative_rc(thr, rc);
    }
    DUK_ASSERT(rc >= 0);
 
    if (duk_get_top(ctx) < rc) {
        DUK_ERROR_API(thr, "not enough stack values for safe_call rc");
    }
 
    DUK_ASSERT(thr->catchstack_top == entry_catchstack_top);  /* no need to unwind */
    DUK_ASSERT(thr->callstack_top == entry_callstack_top);
 
    duk__safe_call_adjust_valstack(thr, idx_retbase, num_stack_rets, rc);
    return;
 
 thread_state_error:
    DUK_ERROR_FMT1(thr, DUK_ERR_TYPE_ERROR, "invalid thread state for safe_call (%ld)", (long) thr->state);
    DUK_UNREACHABLE();
}
 
DUK_LOCAL void duk__handle_safe_call_error(duk_hthread *thr,
                                           duk_idx_t idx_retbase,
                                           duk_idx_t num_stack_rets,
                                           duk_size_t entry_valstack_bottom_index,
                                           duk_size_t entry_callstack_top,
                                           duk_size_t entry_catchstack_top,
                                           duk_jmpbuf *old_jmpbuf_ptr) {
    duk_context *ctx;
 
    DUK_ASSERT(thr != NULL);
    ctx = (duk_context *) thr;
    DUK_ASSERT_CTX_VALID(ctx);
 
    /*
     *  Error during call.  The error value is at heap->lj.value1.
     *
     *  The very first thing we do is restore the previous setjmp catcher.
     *  This means that any error in error handling will propagate outwards
     *  instead of causing a setjmp() re-entry above.
     */
 
    DUK_DDD(DUK_DDDPRINT("error caught during protected duk_handle_safe_call()"));
 
    /* Other longjmp types are handled by executor before propagating
     * the error here.
     */
    DUK_ASSERT(thr->heap->lj.type == DUK_LJ_TYPE_THROW);
    DUK_ASSERT(thr->callstack_top >= entry_callstack_top);
    DUK_ASSERT(thr->catchstack_top >= entry_catchstack_top);
 
    /* Note: either pointer may be NULL (at entry), so don't assert. */
    thr->heap->lj.jmpbuf_ptr = old_jmpbuf_ptr;
 
    DUK_ASSERT(thr->catchstack_top >= entry_catchstack_top);
    DUK_ASSERT(thr->callstack_top >= entry_callstack_top);
    duk_hthread_catchstack_unwind(thr, entry_catchstack_top);
    duk_hthread_catchstack_shrink_check(thr);
    duk_hthread_callstack_unwind(thr, entry_callstack_top);
    duk_hthread_callstack_shrink_check(thr);
    thr->valstack_bottom = thr->valstack + entry_valstack_bottom_index;
 
    /* [ ... | (crud) ] */
 
    /* XXX: space in valstack?  see discussion in duk_handle_call_xxx(). */
    duk_push_tval(ctx, &thr->heap->lj.value1);
 
    /* [ ... | (crud) errobj ] */
 
    DUK_ASSERT(duk_get_top(ctx) >= 1);  /* at least errobj must be on stack */
 
    /* check that the valstack has space for the final amount and any
     * intermediate space needed; this is unoptimal but should be safe
     */
    duk_require_stack_top(ctx, idx_retbase + num_stack_rets);  /* final configuration */
    duk_require_stack(ctx, num_stack_rets);
 
    duk__safe_call_adjust_valstack(thr, idx_retbase, num_stack_rets, 1);  /* 1 = num actual 'return values' */
 
    /* [ ... | ] or [ ... | errobj (M * undefined)] where M = num_stack_rets - 1 */
 
    /* These are just convenience "wiping" of state.  Side effects should
     * not be an issue here: thr->heap and thr->heap->lj have a stable
     * pointer.  Finalizer runs etc capture even out-of-memory errors so
     * nothing should throw here.
     */
    thr->heap->lj.type = DUK_LJ_TYPE_UNKNOWN;
    thr->heap->lj.iserror = 0;
    DUK_TVAL_SET_UNDEFINED_UPDREF(thr, &thr->heap->lj.value1);  /* side effects */
    DUK_TVAL_SET_UNDEFINED_UPDREF(thr, &thr->heap->lj.value2);  /* side effects */
}
 
DUK_LOCAL void duk__handle_safe_call_shared(duk_hthread *thr,
                                            duk_idx_t idx_retbase,
                                            duk_idx_t num_stack_rets,
                                            duk_int_t entry_call_recursion_depth,
                                            duk_hthread *entry_curr_thread,
                                            duk_uint_fast8_t entry_thread_state,
                                            duk_instr_t **entry_ptr_curr_pc) {
    duk_context *ctx;
 
    DUK_ASSERT(thr != NULL);
    ctx = (duk_context *) thr;
    DUK_ASSERT_CTX_VALID(ctx);
    DUK_UNREF(ctx);
    DUK_UNREF(idx_retbase);
    DUK_UNREF(num_stack_rets);
 
    /* Restore entry thread executor curr_pc stack frame pointer. */
    thr->ptr_curr_pc = entry_ptr_curr_pc;
 
    /* XXX: because we unwind stacks above, thr->heap->curr_thread is at
     * risk of pointing to an already freed thread.  This was indeed the
     * case in test-bug-multithread-valgrind.c, until duk_handle_call()
     * was fixed to restore thr->heap->curr_thread before rethrowing an
     * uncaught error.
     */
    DUK_HEAP_SWITCH_THREAD(thr->heap, entry_curr_thread);  /* may be NULL */
    thr->state = (duk_uint8_t) entry_thread_state;
 
    DUK_ASSERT((thr->state == DUK_HTHREAD_STATE_INACTIVE && thr->heap->curr_thread == NULL) ||  /* first call */
               (thr->state == DUK_HTHREAD_STATE_INACTIVE && thr->heap->curr_thread != NULL) ||  /* other call */
               (thr->state == DUK_HTHREAD_STATE_RUNNING && thr->heap->curr_thread == thr));     /* current thread */
 
    thr->heap->call_recursion_depth = entry_call_recursion_depth;
 
    /* stack discipline consistency check */
    DUK_ASSERT(duk_get_top(ctx) == idx_retbase + num_stack_rets);
 
    /* A debugger forced interrupt check is not needed here, as
     * problematic safe calls are not caused by side effects.
     */
 
#if defined(DUK_USE_INTERRUPT_COUNTER) && defined(DUK_USE_DEBUG)
    duk__interrupt_fixup(thr, entry_curr_thread);
#endif
}
 
/*
 *  Helper for handling an Ecmascript-to-Ecmascript call or an Ecmascript
 *  function (initial) Duktape.Thread.resume().
 *
 *  Compared to normal calls handled by duk_handle_call(), there are a
 *  bunch of differences:
 *
 *    - the call is never protected
 *    - there is no C recursion depth increase (hence an "ignore recursion
 *      limit" flag is not applicable)
 *    - instead of making the call, this helper just performs the thread
 *      setup and returns; the bytecode executor then restarts execution
 *      internally
 *    - ecmascript functions are never 'vararg' functions (they access
 *      varargs through the 'arguments' object)
 *
 *  The callstack of the target contains an earlier Ecmascript call in case
 *  of an Ecmascript-to-Ecmascript call (whose idx_retval is updated), or
 *  is empty in case of an initial Duktape.Thread.resume().
 *
 *  The first thing to do here is to figure out whether an ecma-to-ecma
 *  call is actually possible.  It's not always the case if the target is
 *  a bound function; the final function may be native.  In that case,
 *  return an error so caller can fall back to a normal call path.
 */
 
DUK_INTERNAL duk_bool_t duk_handle_ecma_call_setup(duk_hthread *thr,
                                                   duk_idx_t num_stack_args,
                                                   duk_small_uint_t call_flags) {
    duk_context *ctx = (duk_context *) thr;
    duk_size_t entry_valstack_bottom_index;
    duk_idx_t idx_func;     /* valstack index of 'func' and retval (relative to entry valstack_bottom) */
    duk_idx_t idx_args;     /* valstack index of start of args (arg1) (relative to entry valstack_bottom) */
    duk_idx_t nargs;        /* # argument registers target function wants (< 0 => never for ecma calls) */
    duk_idx_t nregs;        /* # total registers target function wants on entry (< 0 => never for ecma calls) */
    duk_hobject *func;      /* 'func' on stack (borrowed reference) */
    duk_tval *tv_func;      /* duk_tval ptr for 'func' on stack (borrowed reference) */
    duk_activation *act;
    duk_hobject *env;
    duk_bool_t use_tailcall;
    duk_instr_t **entry_ptr_curr_pc;
 
    DUK_ASSERT(thr != NULL);
    DUK_ASSERT(ctx != NULL);
    DUK_ASSERT(!((call_flags & DUK_CALL_FLAG_IS_RESUME) != 0 && (call_flags & DUK_CALL_FLAG_IS_TAILCALL) != 0));
 
    /* XXX: assume these? */
    DUK_ASSERT(thr->valstack != NULL);
    DUK_ASSERT(thr->callstack != NULL);
    DUK_ASSERT(thr->catchstack != NULL);
 
    /* no need to handle thread state book-keeping here */
    DUK_ASSERT((call_flags & DUK_CALL_FLAG_IS_RESUME) != 0 ||
               (thr->state == DUK_HTHREAD_STATE_RUNNING &&
                thr->heap->curr_thread == thr));
 
    /* If thr->ptr_curr_pc is set, sync curr_pc to act->pc.  Then NULL
     * thr->ptr_curr_pc so that it's not accidentally used with an incorrect
     * activation when side effects occur.  If we end up not making the
     * call we must restore the value.
     */
    entry_ptr_curr_pc = thr->ptr_curr_pc;
    duk_hthread_sync_and_null_currpc(thr);
 
    /* if a tail call:
     *   - an Ecmascript activation must be on top of the callstack
     *   - there cannot be any active catchstack entries
     */
#if defined(DUK_USE_ASSERTIONS)
    if (call_flags & DUK_CALL_FLAG_IS_TAILCALL) {
        duk_size_t our_callstack_index;
        duk_size_t i;
 
        DUK_ASSERT(thr->callstack_top >= 1);
        our_callstack_index = thr->callstack_top - 1;
        DUK_ASSERT_DISABLE(our_callstack_index >= 0);
        DUK_ASSERT(our_callstack_index < thr->callstack_size);
        DUK_ASSERT(DUK_ACT_GET_FUNC(thr->callstack + our_callstack_index) != NULL);
        DUK_ASSERT(DUK_HOBJECT_IS_COMPILEDFUNCTION(DUK_ACT_GET_FUNC(thr->callstack + our_callstack_index)));
 
        /* No entry in the catchstack which would actually catch a
         * throw can refer to the callstack entry being reused.
         * There *can* be catchstack entries referring to the current
         * callstack entry as long as they don't catch (e.g. label sites).
         */
 
        for (i = 0; i < thr->catchstack_top; i++) {
            DUK_ASSERT(thr->catchstack[i].callstack_index < our_callstack_index ||  /* refer to callstack entries below current */
                       DUK_CAT_GET_TYPE(thr->catchstack + i) == DUK_CAT_TYPE_LABEL); /* or a non-catching entry */
        }
    }
#endif  /* DUK_USE_ASSERTIONS */
 
    entry_valstack_bottom_index = (duk_size_t) (thr->valstack_bottom - thr->valstack);
    /* XXX: rework */
    idx_func = duk_normalize_index(thr, -num_stack_args - 2);
    idx_args = idx_func + 2;
 
    DUK_DD(DUK_DDPRINT("handle_ecma_call_setup: thr=%p, "
                       "num_stack_args=%ld, call_flags=0x%08lx (resume=%ld, tailcall=%ld), "
                       "idx_func=%ld, idx_args=%ld, entry_valstack_bottom_index=%ld",
                       (void *) thr,
                       (long) num_stack_args,
                       (unsigned long) call_flags,
                       (long) ((call_flags & DUK_CALL_FLAG_IS_RESUME) != 0 ? 1 : 0),
                       (long) ((call_flags & DUK_CALL_FLAG_IS_TAILCALL) != 0 ? 1 : 0),
                       (long) idx_func,
                       (long) idx_args,
                       (long) entry_valstack_bottom_index));
 
    if (DUK_UNLIKELY(idx_func < 0 || idx_args < 0)) {
        /* XXX: assert? compiler is responsible for this never happening */
        DUK_ERROR_API(thr, DUK_STR_INVALID_CALL_ARGS);
    }
 
    /*
     *  Check the function type, handle bound function chains, and prepare
     *  parameters for the rest of the call handling.  Also figure out the
     *  effective 'this' binding, which replaces the current value at
     *  idx_func + 1.
     *
     *  If the target function is a 'bound' one, follow the chain of 'bound'
     *  functions until a non-bound function is found.  During this process,
     *  bound arguments are 'prepended' to existing ones, and the "this"
     *  binding is overridden.  See E5 Section 15.3.4.5.1.
     *
     *  If the final target function cannot be handled by an ecma-to-ecma
     *  call, return to the caller with a return value indicating this case.
     *  The bound chain is resolved and the caller can resume with a plain
     *  function call.
     */
 
    func = duk__nonbound_func_lookup(ctx, idx_func, &num_stack_args, &tv_func, call_flags);
    if (func == NULL || !DUK_HOBJECT_IS_COMPILEDFUNCTION(func)) {
        DUK_DDD(DUK_DDDPRINT("final target is a lightfunc/nativefunc, cannot do ecma-to-ecma call"));
        thr->ptr_curr_pc = entry_ptr_curr_pc;
        return 0;
    }
    /* XXX: tv_func is not actually needed */
 
    DUK_ASSERT(func != NULL);
    DUK_ASSERT(!DUK_HOBJECT_HAS_BOUND(func));
    DUK_ASSERT(DUK_HOBJECT_IS_COMPILEDFUNCTION(func));
 
    duk__coerce_effective_this_binding(thr, func, idx_func + 1);
    DUK_DDD(DUK_DDDPRINT("effective 'this' binding is: %!T",
                         duk_get_tval(ctx, idx_func + 1)));
 
    nargs = ((duk_hcompiledfunction *) func)->nargs;
    nregs = ((duk_hcompiledfunction *) func)->nregs;
    DUK_ASSERT(nregs >= nargs);
 
    /* [ ... func this arg1 ... argN ] */
 
    /*
     *  Preliminary activation record and valstack manipulation.
     *  The concrete actions depend on whether the we're dealing
     *  with a tail call (reuse an existing activation), a resume,
     *  or a normal call.
     *
     *  The basic actions, in varying order, are:
     *
     *    - Check stack size for call handling
     *    - Grow call stack if necessary (non-tail-calls)
     *    - Update current activation (idx_retval) if necessary
     *      (non-tail, non-resume calls)
     *    - Move start of args (idx_args) to valstack bottom
     *      (tail calls)
     *
     *  Don't touch valstack_bottom or valstack_top yet so that Duktape API
     *  calls work normally.
     */
 
    /* XXX: some overlapping code; cleanup */
    use_tailcall = call_flags & DUK_CALL_FLAG_IS_TAILCALL;
#if !defined(DUK_USE_TAILCALL)
    DUK_ASSERT(use_tailcall == 0);  /* compiler ensures this */
#endif
    if (use_tailcall) {
        /* tailcall cannot be flagged to resume calls, and a
         * previous frame must exist
         */
        DUK_ASSERT(thr->callstack_top >= 1);
        DUK_ASSERT((call_flags & DUK_CALL_FLAG_IS_RESUME) == 0);
 
        act = thr->callstack + thr->callstack_top - 1;
        if (act->flags & DUK_ACT_FLAG_PREVENT_YIELD) {
            /* See: test-bug-tailcall-preventyield-assert.c. */
            DUK_DDD(DUK_DDDPRINT("tail call prevented by current activation having DUK_ACT_FLAG_PREVENTYIELD"));
            use_tailcall = 0;
        } else if (DUK_HOBJECT_HAS_NOTAIL(func)) {
            DUK_D(DUK_DPRINT("tail call prevented by function having a notail flag"));
            use_tailcall = 0;
        }
    }
 
    if (use_tailcall) {
        duk_tval *tv1, *tv2;
        duk_size_t cs_index;
        duk_int_t i_stk;  /* must be signed for loop structure */
        duk_idx_t i_arg;
 
        /*
         *  Tailcall handling
         *
         *  Although the callstack entry is reused, we need to explicitly unwind
         *  the current activation (or simulate an unwind).  In particular, the
         *  current activation must be closed, otherwise something like
         *  test-bug-reduce-judofyr.js results.  Also catchstack needs be unwound
         *  because there may be non-error-catching label entries in valid tail calls.
         */
 
        DUK_DDD(DUK_DDDPRINT("is tail call, reusing activation at callstack top, at index %ld",
                             (long) (thr->callstack_top - 1)));
 
        /* 'act' already set above */
 
        DUK_ASSERT(!DUK_HOBJECT_HAS_BOUND(func));
        DUK_ASSERT(!DUK_HOBJECT_HAS_NATIVEFUNCTION(func));
        DUK_ASSERT(DUK_HOBJECT_HAS_COMPILEDFUNCTION(func));
        DUK_ASSERT((act->flags & DUK_ACT_FLAG_PREVENT_YIELD) == 0);
 
        /* Unwind catchstack entries referring to the callstack entry we're reusing */
        cs_index = thr->callstack_top - 1;
        DUK_ASSERT(thr->catchstack_top <= DUK_INT_MAX);  /* catchstack limits */
        for (i_stk = (duk_int_t) (thr->catchstack_top - 1); i_stk >= 0; i_stk--) {
            duk_catcher *cat = thr->catchstack + i_stk;
            if (cat->callstack_index != cs_index) {
                /* 'i' is the first entry we'll keep */
                break;
            }
        }
        duk_hthread_catchstack_unwind(thr, i_stk + 1);
 
        /* Unwind the topmost callstack entry before reusing it */
        DUK_ASSERT(thr->callstack_top > 0);
        duk_hthread_callstack_unwind(thr, thr->callstack_top - 1);
 
        /* Then reuse the unwound activation; callstack was not shrunk so there is always space */
        thr->callstack_top++;
        DUK_ASSERT(thr->callstack_top <= thr->callstack_size);
        act = thr->callstack + thr->callstack_top - 1;
 
        /* Start filling in the activation */
        act->func = func;  /* don't want an intermediate exposed state with func == NULL */
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
        act->prev_caller = NULL;
#endif
        DUK_ASSERT(func != NULL);
        DUK_ASSERT(DUK_HOBJECT_HAS_COMPILEDFUNCTION(func));
        /* don't want an intermediate exposed state with invalid pc */
        act->curr_pc = DUK_HCOMPILEDFUNCTION_GET_CODE_BASE(thr->heap, (duk_hcompiledfunction *) func);
#if defined(DUK_USE_DEBUGGER_SUPPORT)
        act->prev_line = 0;
#endif
        DUK_TVAL_SET_OBJECT(&act->tv_func, func);  /* borrowed, no refcount */
#if defined(DUK_USE_REFERENCE_COUNTING)
        DUK_HOBJECT_INCREF(thr, func);
        act = thr->callstack + thr->callstack_top - 1;  /* side effects (currently none though) */
#endif
 
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
#if defined(DUK_USE_TAILCALL)
#error incorrect options: tail calls enabled with function caller property
#endif
        /* XXX: this doesn't actually work properly for tail calls, so
         * tail calls are disabled when DUK_USE_NONSTD_FUNC_CALLER_PROPERTY
         * is in use.
         */
        duk__update_func_caller_prop(thr, func);
        act = thr->callstack + thr->callstack_top - 1;
#endif
 
        act->flags = (DUK_HOBJECT_HAS_STRICT(func) ?
                      DUK_ACT_FLAG_STRICT | DUK_ACT_FLAG_TAILCALLED :
                      DUK_ACT_FLAG_TAILCALLED);
 
        DUK_ASSERT(DUK_ACT_GET_FUNC(act) == func);      /* already updated */
        DUK_ASSERT(act->var_env == NULL);   /* already NULLed (by unwind) */
        DUK_ASSERT(act->lex_env == NULL);   /* already NULLed (by unwind) */
        act->idx_bottom = entry_valstack_bottom_index;  /* tail call -> reuse current "frame" */
        DUK_ASSERT(nregs >= 0);
#if 0  /* topmost activation idx_retval is considered garbage, no need to init */
        act->idx_retval = 0;
#endif
 
        /*
         *  Manipulate valstack so that args are on the current bottom and the
         *  previous caller's 'this' binding (which is the value preceding the
         *  current bottom) is replaced with the new 'this' binding:
         *
         *       [ ... this_old | (crud) func this_new arg1 ... argN ]
         *  -->  [ ... this_new | arg1 ... argN ]
         *
         *  For tail calling to work properly, the valstack bottom must not grow
         *  here; otherwise crud would accumulate on the valstack.
         */
 
        tv1 = thr->valstack_bottom - 1;
        tv2 = thr->valstack_bottom + idx_func + 1;
        DUK_ASSERT(tv1 >= thr->valstack && tv1 < thr->valstack_top);  /* tv1 is -below- valstack_bottom */
        DUK_ASSERT(tv2 >= thr->valstack_bottom && tv2 < thr->valstack_top);
        DUK_TVAL_SET_TVAL_UPDREF(thr, tv1, tv2);  /* side effects */
 
        for (i_arg = 0; i_arg < idx_args; i_arg++) {
            /* XXX: block removal API primitive */
            /* Note: 'func' is popped from valstack here, but it is
             * already reachable from the activation.
             */
            duk_remove(ctx, 0);
        }
        idx_func = 0; DUK_UNREF(idx_func);  /* really 'not applicable' anymore, should not be referenced after this */
        idx_args = 0;
 
        /* [ ... this_new | arg1 ... argN ] */
    } else {
        DUK_DDD(DUK_DDDPRINT("not a tail call, pushing a new activation to callstack, to index %ld",
                             (long) (thr->callstack_top)));
 
        duk_hthread_callstack_grow(thr);
 
        if (call_flags & DUK_CALL_FLAG_IS_RESUME) {
            DUK_DDD(DUK_DDDPRINT("is resume -> no update to current activation (may not even exist)"));
        } else {
            DUK_DDD(DUK_DDDPRINT("update to current activation idx_retval"));
            DUK_ASSERT(thr->callstack_top < thr->callstack_size);
            DUK_ASSERT(thr->callstack_top >= 1);
            act = thr->callstack + thr->callstack_top - 1;
            DUK_ASSERT(DUK_ACT_GET_FUNC(act) != NULL);
            DUK_ASSERT(DUK_HOBJECT_IS_COMPILEDFUNCTION(DUK_ACT_GET_FUNC(act)));
            act->idx_retval = entry_valstack_bottom_index + idx_func;
        }
 
        DUK_ASSERT(thr->callstack_top < thr->callstack_size);
        act = thr->callstack + thr->callstack_top;
        thr->callstack_top++;
        DUK_ASSERT(thr->callstack_top <= thr->callstack_size);
 
        DUK_ASSERT(!DUK_HOBJECT_HAS_BOUND(func));
        DUK_ASSERT(!DUK_HOBJECT_HAS_NATIVEFUNCTION(func));
        DUK_ASSERT(DUK_HOBJECT_HAS_COMPILEDFUNCTION(func));
 
        act->flags = (DUK_HOBJECT_HAS_STRICT(func) ?
                      DUK_ACT_FLAG_STRICT :
                      0);
        act->func = func;
        act->var_env = NULL;
        act->lex_env = NULL;
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
        act->prev_caller = NULL;
#endif
        DUK_ASSERT(func != NULL);
        DUK_ASSERT(DUK_HOBJECT_HAS_COMPILEDFUNCTION(func));
        act->curr_pc = DUK_HCOMPILEDFUNCTION_GET_CODE_BASE(thr->heap, (duk_hcompiledfunction *) func);
#if defined(DUK_USE_DEBUGGER_SUPPORT)
        act->prev_line = 0;
#endif
        act->idx_bottom = entry_valstack_bottom_index + idx_args;
        DUK_ASSERT(nregs >= 0);
#if 0  /* topmost activation idx_retval is considered garbage, no need to init */
        act->idx_retval = 0;
#endif
        DUK_TVAL_SET_OBJECT(&act->tv_func, func);  /* borrowed, no refcount */
 
        DUK_HOBJECT_INCREF(thr, func);  /* act->func */
 
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
        duk__update_func_caller_prop(thr, func);
        act = thr->callstack + thr->callstack_top - 1;
#endif
    }
 
    /* [ ... func this arg1 ... argN ]  (not tail call)
     * [ this | arg1 ... argN ]         (tail call)
     *
     * idx_args updated to match
     */
 
    /*
     *  Environment record creation and 'arguments' object creation.
     *  Named function expression name binding is handled by the
     *  compiler; the compiled function's parent env will contain
     *  the (immutable) binding already.
     *
     *  Delayed creation (on demand) is handled in duk_js_var.c.
     */
 
    /* XXX: unify handling with native call. */
 
    DUK_ASSERT(!DUK_HOBJECT_HAS_BOUND(func));  /* bound function chain has already been resolved */
 
    if (!DUK_HOBJECT_HAS_NEWENV(func)) {
        /* use existing env (e.g. for non-strict eval); cannot have
         * an own 'arguments' object (but can refer to the existing one)
         */
 
        duk__handle_oldenv_for_call(thr, func, act);
        /* No need to re-lookup 'act' at present: no side effects. */
 
        DUK_ASSERT(act->lex_env != NULL);
        DUK_ASSERT(act->var_env != NULL);
        goto env_done;
    }
 
    DUK_ASSERT(DUK_HOBJECT_HAS_NEWENV(func));
 
    if (!DUK_HOBJECT_HAS_CREATEARGS(func)) {
        /* no need to create environment record now; leave as NULL */
        DUK_ASSERT(act->lex_env == NULL);
        DUK_ASSERT(act->var_env == NULL);
        goto env_done;
    }
 
    /* third arg: absolute index (to entire valstack) of idx_bottom of new activation */
    env = duk_create_activation_environment_record(thr, func, act->idx_bottom);
    DUK_ASSERT(env != NULL);
 
    /* [ ... arg1 ... argN envobj ] */
 
    /* original input stack before nargs/nregs handling must be
     * intact for 'arguments' object
     */
    DUK_ASSERT(DUK_HOBJECT_HAS_CREATEARGS(func));
    duk__handle_createargs_for_call(thr, func, env, num_stack_args);
 
    /* [ ... arg1 ... argN envobj ] */
 
    act = thr->callstack + thr->callstack_top - 1;
    act->lex_env = env;
    act->var_env = env;
    DUK_HOBJECT_INCREF(thr, act->lex_env);
    DUK_HOBJECT_INCREF(thr, act->var_env);
    duk_pop(ctx);
 
 env_done:
    /* [ ... arg1 ... argN ] */
 
    /*
     *  Setup value stack: clamp to 'nargs', fill up to 'nregs'
     */
 
    duk__adjust_valstack_and_top(thr,
                                 num_stack_args,
                                 idx_args,
                                 nregs,
                                 nargs,
                                 func);
 
    /*
     *  Shift to new valstack_bottom.
     */
 
    thr->valstack_bottom = thr->valstack_bottom + idx_args;
    /* keep current valstack_top */
    DUK_ASSERT(thr->valstack_bottom >= thr->valstack);
    DUK_ASSERT(thr->valstack_top >= thr->valstack_bottom);
    DUK_ASSERT(thr->valstack_end >= thr->valstack_top);
 
    /*
     *  Return to bytecode executor, which will resume execution from
     *  the topmost activation.
     */
 
    return 1;
}