[Webkit-unassigned] [Bug 163417] New: ES6: Make Array.prototype.splice implement step 8 of its spec.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=163417

            Bug ID: 163417
           Summary: ES6: Make Array.prototype.splice implement step 8 of
                    its spec.
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: mark.lam at apple.com

Step 8 of the Array.prototype.splice spec (https://tc39.github.io/ecma262/#sec-array.prototype.splice) states that we should throw a TypeError if the spliced array's length will exceed 2^53-1.  This is gated on the JSArray getLength() convenience function being updated to return a length value that is greater than 32-bits.  This issue is only a compliance issue in a contrived example, e.g.

    var maxLength = (2 ** 53) - 1;
    Array.prototype.splice.call({ length: maxLength }, maxLength, 0, 1, 2, 3);

In real world code, the JSC runtime prevents us from creating arrays with a length that exceeds UINT_MAX.  We're also bounded on the number of args that we pass to Array.prototype.splice.  As a result, we can never splice together an array that gets anywhere near 2^53-1.  We'll get an OutOfMemoryError long before then.

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