DUK_INTERNAL duk_ret_t duk_bi_error_constructor_shared(duk_context *ctx) {
/* Behavior for constructor and non-constructor call is
* the same except for augmenting the created error. When
* called as a constructor, the caller (duk_new()) will handle
* augmentation; when called as normal function, we need to do
* it here.
*/
duk_hthread *thr = (duk_hthread *) ctx;
duk_small_int_t bidx_prototype = duk_get_current_magic(ctx);
/* same for both error and each subclass like TypeError */
duk_uint_t flags_and_class = DUK_HOBJECT_FLAG_EXTENSIBLE |
DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_ERROR);
DUK_UNREF(thr);
duk_push_object_helper(ctx, flags_and_class, bidx_prototype);
/* If message is undefined, the own property 'message' is not set at
* all to save property space. An empty message is inherited anyway.
*/
if (!duk_is_undefined(ctx, 0)) {
duk_to_string(ctx, 0);
duk_dup_0(ctx); /* [ message error message ] */
duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_MESSAGE, DUK_PROPDESC_FLAGS_WC);
}
/* Augment the error if called as a normal function. __FILE__ and __LINE__
* are not desirable in this case.
*/
#ifdef DUK_USE_AUGMENT_ERROR_CREATE
if (!duk_is_constructor_call(ctx)) {
duk_err_augment_error_create(thr, thr, NULL, 0, 1 /*noblame_fileline*/);
}
#endif
return 1;
}
DUK_EXTERNAL void duk_new(duk_context *ctx, duk_idx_t nargs) {
/*
* There are two [[Construct]] operations in the specification:
*
* - E5 Section 13.2.2: for Function objects
* - E5 Section 15.3.4.5.2: for "bound" Function objects
*
* The chain of bound functions is resolved in Section 15.3.4.5.2,
* with arguments "piling up" until the [[Construct]] internal
* method is called on the final, actual Function object. Note
* that the "prototype" property is looked up *only* from the
* final object, *before* calling the constructor.
*
* Currently we follow the bound function chain here to get the
* "prototype" property value from the final, non-bound function.
* However, we let duk_handle_call() handle the argument "piling"
* when the constructor is called. The bound function chain is
* thus now processed twice.
*
* When constructing new Array instances, an unnecessary object is
* created and discarded now: the standard [[Construct]] creates an
* object, and calls the Array constructor. The Array constructor
* returns an Array instance, which is used as the result value for
* the "new" operation; the object created before the Array constructor
* call is discarded.
*
* This would be easy to fix, e.g. by knowing that the Array constructor
* will always create a replacement object and skip creating the fallback
* object in that case.
*
* Note: functions called via "new" need to know they are called as a
* constructor. For instance, built-in constructors behave differently
* depending on how they are called.
*/
/* XXX: merge this with duk_js_call.c, as this function implements
* core semantics (or perhaps merge the two files altogether).
*/
duk_hthread *thr = (duk_hthread *) ctx;
duk_hobject *proto;
duk_hobject *cons;
duk_hobject *fallback;
duk_idx_t idx_cons;
duk_small_uint_t call_flags;
DUK_ASSERT_CTX_VALID(ctx);
/* [... constructor arg1 ... argN] */
idx_cons = duk_require_normalize_index(ctx, -nargs - 1);
DUK_DDD(DUK_DDDPRINT("top=%ld, nargs=%ld, idx_cons=%ld",
(long) duk_get_top(ctx), (long) nargs, (long) idx_cons));
/* XXX: code duplication */
/*
* Figure out the final, non-bound constructor, to get "prototype"
* property.
*/
duk_dup(ctx, idx_cons);
for (;;) {
cons = duk_get_hobject(ctx, -1);
if (cons == NULL || !DUK_HOBJECT_HAS_CONSTRUCTABLE(cons)) {
/* Checking constructability from anything else than the
* initial constructor is not strictly necessary, but a
* nice sanity check.
*/
goto not_constructable;
}
if (!DUK_HOBJECT_HAS_BOUNDFUNC(cons)) {
break;
}
duk_get_prop_stridx(ctx, -1, DUK_STRIDX_INT_TARGET); /* -> [... cons target] */
duk_remove(ctx, -2); /* -> [... target] */
}
DUK_ASSERT(cons != NULL && !DUK_HOBJECT_HAS_BOUNDFUNC(cons));
/* [... constructor arg1 ... argN final_cons] */
/*
* Create "fallback" object to be used as the object instance,
* unless the constructor returns a replacement value.
* Its internal prototype needs to be set based on "prototype"
* property of the constructor.
*/
duk_push_object(ctx); /* class Object, extensible */
/* [... constructor arg1 ... argN final_cons fallback] */
duk_get_prop_stridx(ctx, -2, DUK_STRIDX_PROTOTYPE);
proto = duk_get_hobject(ctx, -1);
if (!proto) {
DUK_DDD(DUK_DDDPRINT("constructor has no 'prototype' property, or value not an object "
"-> leave standard Object prototype as fallback prototype"));
} else {
DUK_DDD(DUK_DDDPRINT("constructor has 'prototype' property with object value "
"-> set fallback prototype to that value: %!iO", (duk_heaphdr *) proto));
fallback = duk_get_hobject(ctx, -2);
DUK_ASSERT(fallback != NULL);
DUK_HOBJECT_SET_PROTOTYPE_UPDREF(thr, fallback, proto);
}
duk_pop(ctx);
/* [... constructor arg1 ... argN final_cons fallback] */
/*
* Manipulate callstack for the call.
*/
duk_dup_top(ctx);
duk_insert(ctx, idx_cons + 1); /* use fallback as 'this' value */
duk_insert(ctx, idx_cons); /* also stash it before constructor,
* in case we need it (as the fallback value)
*/
duk_pop(ctx); /* pop final_cons */
/* [... fallback constructor fallback(this) arg1 ... argN];
* Note: idx_cons points to first 'fallback', not 'constructor'.
*/
DUK_DDD(DUK_DDDPRINT("before call, idx_cons+1 (constructor) -> %!T, idx_cons+2 (fallback/this) -> %!T, "
"nargs=%ld, top=%ld",
(duk_tval *) duk_get_tval(ctx, idx_cons + 1),
(duk_tval *) duk_get_tval(ctx, idx_cons + 2),
(long) nargs,
(long) duk_get_top(ctx)));
/*
* Call the constructor function (called in "constructor mode").
*/
call_flags = DUK_CALL_FLAG_CONSTRUCTOR_CALL; /* not protected, respect reclimit, is a constructor call */
duk_handle_call_unprotected(thr, /* thread */
nargs, /* num_stack_args */
call_flags); /* call_flags */
/* [... fallback retval] */
DUK_DDD(DUK_DDDPRINT("constructor call finished, fallback=%!iT, retval=%!iT",
(duk_tval *) duk_get_tval(ctx, -2),
(duk_tval *) duk_get_tval(ctx, -1)));
/*
* Determine whether to use the constructor return value as the created
* object instance or not.
*/
if (duk_is_object(ctx, -1)) {
duk_remove(ctx, -2);
} else {
duk_pop(ctx);
}
/*
* Augment created errors upon creation (not when they are thrown or
* rethrown). __FILE__ and __LINE__ are not desirable here; the call
* stack reflects the caller which is correct.
*/
#ifdef DUK_USE_AUGMENT_ERROR_CREATE
duk_hthread_sync_currpc(thr);
duk_err_augment_error_create(thr, thr, NULL, 0, 1 /*noblame_fileline*/);
#endif
/* [... retval] */
return;
not_constructable:
#if defined(DUK_USE_VERBOSE_ERRORS)
#if defined(DUK_USE_PARANOID_ERRORS)
DUK_ERROR_FMT1(thr, DUK_ERR_TYPE_ERROR, "%s not constructable", duk_get_type_name(ctx, -1));
#else
DUK_ERROR_FMT1(thr, DUK_ERR_TYPE_ERROR, "%s not constructable", duk_push_string_readable(ctx, -1));
#endif
#else
DUK_ERROR_TYPE(thr, "not constructable");
#endif
}
