[rab/gsab] Return false in [[PreventExtensions]] for variable-length TAs

This is a spec normative change: tc39/ecma262#3453

Fixed: 374310073
Change-Id: I085260fea077bc27cf1e4f06d4389519e12c4e14
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6014979
Commit-Queue: Shu-yu Guo <[email protected]>
Auto-Submit: Shu-yu Guo <[email protected]>
Commit-Queue: Rezvan Mahdavi Hezaveh <[email protected]>
Reviewed-by: Rezvan Mahdavi Hezaveh <[email protected]>
Cr-Commit-Position: refs/heads/main@{#97166}

test/staging/built-ins/Object/preventExtensions/preventExtensions-variable-length-typed-arrays.js

@@ -0,0 +1,49 @@
+// Copyright (C) 2024 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-object.preventExtensions
+description: Can't preventExtensions variable length TypedArrays
+features: [SharedArrayBuffer, ArrayBuffer, resizable-arraybuffer]
+includes: [resizableArrayBufferUtils.js]
+---*/
+
+for (let ctor of ctors) {
+  const rab = new ArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, { maxByteLength: 8 * ctor.BYTES_PER_ELEMENT });
+  const fixedLength = new ctor(rab, 0, 4);
+  const fixedLengthWithOffset = new ctor(rab, 2 * ctor.BYTES_PER_ELEMENT, 2);
+  const lengthTracking = new ctor(rab);
+  const lengthTrackingWithOffset = new ctor(rab, 2 * ctor.BYTES_PER_ELEMENT);
+
+  // "Fixed length" TAs backed by RABs can shrink then re-grow.
+  assert.throws(TypeError, function() {
+    Object.preventExtensions(fixedLength);
+  });
+  assert.throws(TypeError, function() {
+    Object.preventExtensions(fixedLengthWithOffset);
+  });
+  assert.throws(TypeError, function() {
+    Object.preventExtensions(lengthTracking);
+  });
+  assert.throws(TypeError, function() {
+    Object.preventExtensions(lengthTrackingWithOffset);
+  });
+}
+
+for (let ctor of ctors) {
+  const gsab = new SharedArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, { maxByteLength: 8 * ctor.BYTES_PER_ELEMENT });
+  const fixedLength = new ctor(gsab, 0, 4);
+  const fixedLengthWithOffset = new ctor(gsab, 2 * ctor.BYTES_PER_ELEMENT, 2);
+  const lengthTracking = new ctor(gsab);
+  const lengthTrackingWithOffset = new ctor(gsab, 2 * ctor.BYTES_PER_ELEMENT);
+
+  // Fixed length TAs backed by GSABs can't shrink, and so are allowed.
+  Object.preventExtensions(fixedLength);
+  Object.preventExtensions(fixedLengthWithOffset);
+  assert.throws(TypeError, function() {
+    Object.preventExtensions(lengthTracking);
+  });
+  assert.throws(TypeError, function() {
+    Object.preventExtensions(lengthTrackingWithOffset);
+  });
+}

test/staging/built-ins/Object/seal/seal-variable-length-typed-arrays.js

@@ -0,0 +1,49 @@
+// Copyright (C) 2024 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-object.seal
+description: Can't seal variable length TypedArrays
+features: [SharedArrayBuffer, ArrayBuffer, resizable-arraybuffer]
+includes: [resizableArrayBufferUtils.js]
+---*/
+
+for (let ctor of ctors) {
+  const rab = new ArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, { maxByteLength: 8 * ctor.BYTES_PER_ELEMENT });
+  const fixedLength = new ctor(rab, 0, 4);
+  const fixedLengthWithOffset = new ctor(rab, 2 * ctor.BYTES_PER_ELEMENT, 2);
+  const lengthTracking = new ctor(rab);
+  const lengthTrackingWithOffset = new ctor(rab, 2 * ctor.BYTES_PER_ELEMENT);
+
+  // "Fixed length" TAs backed by RABs can shrink then re-grow.
+  assert.throws(TypeError, function() {
+    Object.seal(fixedLength);
+  });
+  assert.throws(TypeError, function() {
+    Object.seal(fixedLengthWithOffset);
+  });
+  assert.throws(TypeError, function() {
+    Object.seal(lengthTracking);
+  });
+  assert.throws(TypeError, function() {
+    Object.seal(lengthTrackingWithOffset);
+  });
+}
+
+for (let ctor of ctors) {
+  const gsab = new SharedArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, { maxByteLength: 8 * ctor.BYTES_PER_ELEMENT });
+  const fixedLength = new ctor(gsab, 0, 4);
+  const fixedLengthWithOffset = new ctor(gsab, 2 * ctor.BYTES_PER_ELEMENT, 2);
+  const lengthTracking = new ctor(gsab);
+  const lengthTrackingWithOffset = new ctor(gsab, 2 * ctor.BYTES_PER_ELEMENT);
+
+  // Fixed length TAs backed by GSABs can't shrink, and so are allowed.
+  Object.seal(fixedLength);
+  Object.seal(fixedLengthWithOffset);
+  assert.throws(TypeError, function() {
+    Object.seal(lengthTracking);
+  });
+  assert.throws(TypeError, function() {
+    Object.seal(lengthTrackingWithOffset);
+  });
+}

test/staging/built-ins/Reflect/preventExtensions/preventExtensions-variable-length-typed-arrays.js

@@ -0,0 +1,37 @@
+// Copyright (C) 2024 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Reflect.preventExtensions
+description: Can't preventExtensions variable length TypedArrays
+features: [SharedArrayBuffer, ArrayBuffer, resizable-arraybuffer]
+includes: [resizableArrayBufferUtils.js]
+---*/
+
+for (let ctor of ctors) {
+  const rab = new ArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, { maxByteLength: 8 * ctor.BYTES_PER_ELEMENT });
+  const fixedLength = new ctor(rab, 0, 4);
+  const fixedLengthWithOffset = new ctor(rab, 2 * ctor.BYTES_PER_ELEMENT, 2);
+  const lengthTracking = new ctor(rab);
+  const lengthTrackingWithOffset = new ctor(rab, 2 * ctor.BYTES_PER_ELEMENT);
+
+  // "Fixed length" TAs backed by RABs can shrink then re-grow.
+  assert.sameValue(Reflect.preventExtensions(fixedLength), false);
+  assert.sameValue(Reflect.preventExtensions(fixedLengthWithOffset), false);
+  assert.sameValue(Reflect.preventExtensions(lengthTracking), false);
+  assert.sameValue(Reflect.preventExtensions(lengthTrackingWithOffset), false);
+}
+
+for (let ctor of ctors) {
+  const gsab = new SharedArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, { maxByteLength: 8 * ctor.BYTES_PER_ELEMENT });
+  const fixedLength = new ctor(gsab, 0, 4);
+  const fixedLengthWithOffset = new ctor(gsab, 2 * ctor.BYTES_PER_ELEMENT, 2);
+  const lengthTracking = new ctor(gsab);
+  const lengthTrackingWithOffset = new ctor(gsab, 2 * ctor.BYTES_PER_ELEMENT);
+
+  // Fixed length TAs backed by GSABs can't shrink, and so are allowed.
+  assert.sameValue(Reflect.preventExtensions(fixedLength), true);
+  assert.sameValue(Reflect.preventExtensions(fixedLengthWithOffset), true);
+  assert.sameValue(Reflect.preventExtensions(lengthTracking), false);
+  assert.sameValue(Reflect.preventExtensions(lengthTrackingWithOffset), false);
+}