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Tricky fix to allow non-ECMA Function.prototype extensions to be readonly except when delegated to from other classes (320119, r/sr=mrbkap/shaver).

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brendan%mozilla.org 2005-12-16 19:32:44 +00:00
parent b91b76b673
commit f548d87078
1 changed files with 39 additions and 8 deletions
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47
js/src/jsfun.c
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@ -893,15 +893,25 @@ JSClass js_CallClass = {
#endif /* JS_HAS_CALL_OBJECT */
/* SHARED because fun_getProperty always computes a new value. */
#define FUNCTION_PROP_ATTRS (JSPROP_READONLY|JSPROP_PERMANENT|JSPROP_SHARED)
/*
* ECMCA-262 specifies that length is a property of function object instances,
* but we can avoid that space cost by delegating to a prototype property that
* is JSPROP_PERMANENT and JSPROP_SHARED. Each fun_getProperty call computes
* a fresh length value based on the arity of the individual function object's
* private data.
*
* The extensions below other than length, i.e., the ones not in ECMA-262,
* are neither JSPROP_READONLY nor JSPROP_SHARED, because for compatibility
* with ECMA we must allow a delegating object to override them.
*/
#define LENGTH_PROP_ATTRS (JSPROP_READONLY|JSPROP_PERMANENT|JSPROP_SHARED)
static JSPropertySpec function_props[] = {
{js_arguments_str, CALL_ARGUMENTS, FUNCTION_PROP_ATTRS,0,0},
{js_arity_str, FUN_ARITY, FUNCTION_PROP_ATTRS,0,0},
{js_length_str, ARGS_LENGTH, FUNCTION_PROP_ATTRS,0,0},
{js_name_str, FUN_NAME, FUNCTION_PROP_ATTRS,0,0},
{js_caller_str, FUN_CALLER, FUNCTION_PROP_ATTRS,0,0},
{js_arguments_str, CALL_ARGUMENTS, JSPROP_PERMANENT, 0,0},
{js_arity_str, FUN_ARITY, JSPROP_PERMANENT, 0,0},
{js_caller_str, FUN_CALLER, JSPROP_PERMANENT, 0,0},
{js_length_str, ARGS_LENGTH, LENGTH_PROP_ATTRS, 0,0},
{js_name_str, FUN_NAME, JSPROP_PERMANENT, 0,0},
{0,0,0,0,0}
};
@ -916,9 +926,30 @@ fun_getProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
return JS_TRUE;
slot = JSVAL_TO_INT(id);
/* Loop because getter and setter can be delegated from another class. */
/*
* Loop because getter and setter can be delegated from another class,
* but loop only for ARGS_LENGTH because we must pretend that f.length
* is in each function instance f, per ECMA-262, instead of only in the
* Function.prototype object (we use JSPROP_PERMANENT with JSPROP_SHARED
* to make it appear so).
*
* This code couples tightly to the attributes for the function_props[]
* initializers above, and to js_SetProperty and js_HasOwnPropertyHelper.
*
* It's important to allow delegating objects, even though they inherit
* this getter (fun_getProperty), to override arguments, arity, caller,
* and name. If we didn't return early for slot != ARGS_LENGTH, we would
* clobber *vp with the native property value, instead of letting script
* override that value in delegating objects.
*
* Note how that clobbering is what simulates JSPROP_READONLY for all of
* the non-standard properties when the directly addressed object (obj)
* is a function object (i.e., when this loop does not iterate).
*/
while (!(fun = (JSFunction *)
JS_GetInstancePrivate(cx, obj, &js_FunctionClass, NULL))) {
if (slot != ARGS_LENGTH)
return JS_TRUE;
obj = OBJ_GET_PROTO(cx, obj);
if (!obj)
return JS_TRUE;