Skip to content

Add immutable array buffer awareness to structuredClone #11033

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 6 commits into
base: main
Choose a base branch
from
Open

Add immutable array buffer awareness to structuredClone #11033

Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
06282ff
Prevent structuredClone transfer of immutable array buffers (which ar…
gibson042 Feb 15, 2025
2f4d3cb
Preserve ArrayBuffer immutability in Structured{Serialize,Deserialize}
gibson042 Feb 17, 2025
a48c69a
Comment on StructuredSerializeInternal for an immutable ArrayBuffer w…
gibson042 Feb 18, 2025
1c0cf64
fixup! Comment on StructuredSerializeInternal for an immutable ArrayB…
gibson042 Feb 18, 2025
88b5fdf
fixup! Prevent structuredClone transfer of immutable array buffers (w…
gibson042 Feb 18, 2025
56c3332
fixup! Preserve ArrayBuffer immutability in Structured{Serialize,Dese…
gibson042 Feb 18, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 37 additions & 3 deletions source
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3047,6 +3047,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
<li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-isconstructor">IsConstructor</dfn> abstract operation</li>
<li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-isdatadescriptor">IsDataDescriptor</dfn> abstract operation</li>
<li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-isdetachedbuffer">IsDetachedBuffer</dfn> abstract operation</li>
<li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-isimmutablebuffer">IsImmutableBuffer</dfn> abstract operation</li>
<li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-issharedarraybuffer">IsSharedArrayBuffer</dfn> abstract operation</li>
<li>The <dfn data-x="js-NewObjectEnvironment" data-x-href="https://tc39.es/ecma262/#sec-newobjectenvironment">NewObjectEnvironment</dfn> abstract operation</li>
<li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-normalcompletion">NormalCompletion</dfn> abstract operation</li>
Expand Down Expand Up @@ -9744,6 +9745,23 @@ interface <dfn interface>DOMStringList</dfn> {
</ol>
</li>

<li>
<p>Otherwise, if <span>IsImmutableBuffer</span>(<var>value</var>) is true, then:</p>

<ol>
<li>
<p>Set <var>serialized</var> to { [[Type]]: "ImmutableArrayBuffer", [[ArrayBufferData]]:
<var>value</var>.[[ArrayBufferData]], [[ArrayBufferByteLength]]:
<var>value</var>.[[ArrayBufferByteLength]] }.</p>

<p class="note">To support deserialization by independent processes at arbitrary points in
the future, the <em>contents</em> of <var>value</var>.[[ArrayBufferData]] need to be
preserved when <var>forStorage</var> is true. But otherwise, a pointer <em>referencing</em>
<var>value</var>.[[ArrayBufferData]] is expected to suffice.</p>
</li>
</ol>
</li>

<li>
<p>Otherwise:</p>

Expand Down Expand Up @@ -9791,7 +9809,8 @@ interface <dfn interface>DOMStringList</dfn> {
<var>memory</var>).</p></li>

<li><p><span>Assert</span>: <var>bufferSerialized</var>.[[Type]] is "ArrayBuffer",
"ResizableArrayBuffer", "SharedArrayBuffer", or "GrowableSharedArrayBuffer".</p></li>
"ImmutableArrayBuffer", "ResizableArrayBuffer", "SharedArrayBuffer", or
"GrowableSharedArrayBuffer".</p></li>

<li><p>If <var>value</var> has a [[DataView]] internal slot, then set <var>serialized</var> to
{ [[Type]]: "ArrayBufferView", [[Constructor]]: "DataView", [[ArrayBufferSerialized]]:
Expand Down Expand Up @@ -10186,6 +10205,20 @@ o.myself = o;</code></pre>
</ol>
</li>

<li>
<p>Otherwise, if <var>serialized</var>.[[Type]] is "ImmutableArrayBuffer", then:</p>

<ol>
<li><p>Set <var>value</var> to a new ArrayBuffer object in <var>targetRealm</var> whose
[[ArrayBufferData]] internal slot value is <var>serialized</var>.[[ArrayBufferData]], whose
[[ArrayBufferByteLength]] internal slot value is
<var>serialized</var>.[[ArrayBufferByteLength]], and whose [[ArrayBufferIsImmutable]] internal
slot value is undefined.</p></li>

Copy link
Member

@domenic domenic Feb 18, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is it possible for a slot to not have a value in this way?

Copy link
Contributor Author

@gibson042 gibson042 Feb 18, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Technically yes, but it's obviously not great and I see now that things are moving away from it. I've updated accordingly.

Copy link
Contributor Author

@gibson042 gibson042 Feb 18, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

But for the record, the document.all HTMLAllCollection seems to be another example—it has an [[IsHTMLDDA]] internal slot for which no value is ever specified AFAICT.

Copy link
Contributor Author

@gibson042 gibson042 Feb 18, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

And in ECMAScript, Object Internal Methods and Internal Slots defines the initial value of an internal slot to be undefined.

Copy link
Contributor

@bakkot bakkot Feb 18, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

True although see also tc39/ecma262#3399

<li><p><span>Assert</span>: <span>IsImmutableBuffer</span>(<var>value</var>) is true.</p></li>
</ol>
</li>

<li>
<p>Otherwise, if <var>serialized</var>.[[Type]] is "ArrayBuffer", then set <var>value</var> to a
new ArrayBuffer object in <var>targetRealm</var> whose [[ArrayBufferData]] internal slot value
Expand Down Expand Up @@ -10462,8 +10495,9 @@ o.myself = o;</code></pre>
<span>[[Detached]]</span> internal slot, then throw a
<span>"<code>DataCloneError</code>"</span> <code>DOMException</code>.</p></li>

<li><p>If <var>transferable</var> has an [[ArrayBufferData]] internal slot and
<span>IsSharedArrayBuffer</span>(<var>transferable</var>) is true, then throw a
<li><p>If <var>transferable</var> has an [[ArrayBufferData]] internal slot and either
<span>IsSharedArrayBuffer</span>(<var>transferable</var>) is true or
<span>IsImmutableBuffer</span>(<var>transferable</var>) is true, then throw a
<span>"<code>DataCloneError</code>"</span> <code>DOMException</code>.</p></li>

<li><p>If <var>memory</var>[<var>transferable</var>] <span data-x="map exists">exists</span>,
Expand Down