Editorial: Don't allow writing NaN to frozen properties #3404
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If an implementation can produce distinguishable NaN values, then writing NaN values to a frozen (non-configurable and non-writable) property can be detectable.
michaelficarra
approved these changes
Aug 26, 2024
syg
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Aug 26, 2024
| @@ -12748,7 +12748,7 @@ <h1> | |||
| 1. If _Desc_ has a [[Set]] field and SameValue(_Desc_.[[Set]], _current_.[[Set]]) is *false*, return *false*. | |||
| 1. Else if _current_.[[Writable]] is *false*, then | |||
| 1. If _Desc_ has a [[Writable]] field and _Desc_.[[Writable]] is *true*, return *false*. | |||
| 1. If _Desc_ has a [[Value]] field and SameValue(_Desc_.[[Value]], _current_.[[Value]]) is *false*, return *false*. | |||
| 1. If _Desc_ has a [[Value]] field, return SameValue(_Desc_.[[Value]], _current_.[[Value]]). | |||
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Maybe a note to discourage future would-be refactorings?
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Unless you have a concrete suggestion on hand, I'd rather not delay this indefinitely. We could always add the note in a follow-up, right?
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NOTE: The following is not equivalent to returning false when SameValue returns false in the case of NaN.
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Nah, I don't like that wording. I'd say something like "the following step must not fall through to the property configuration steps below, even when SameValue returns true, because NaN values may be distinguishable".
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Suggested change
| 1. If _Desc_ has a [[Value]] field, return SameValue(_Desc_.[[Value]], _current_.[[Value]]). | |
| 1. NOTE: SameValue returns true for *NaN* values which may be distinguishable by other means. Returning here ensures that any existing property of _O_ remains unmodified. | |
| 1. If _Desc_ has a [[Value]] field, return SameValue(_Desc_.[[Value]], _current_.[[Value]]). |
gibson042
approved these changes
Aug 26, 2024
| @@ -12748,7 +12748,7 @@ <h1> | |||
| 1. If _Desc_ has a [[Set]] field and SameValue(_Desc_.[[Set]], _current_.[[Set]]) is *false*, return *false*. | |||
| 1. Else if _current_.[[Writable]] is *false*, then | |||
| 1. If _Desc_ has a [[Writable]] field and _Desc_.[[Writable]] is *true*, return *false*. | |||
| 1. If _Desc_ has a [[Value]] field and SameValue(_Desc_.[[Value]], _current_.[[Value]]) is *false*, return *false*. | |||
| 1. If _Desc_ has a [[Value]] field, return SameValue(_Desc_.[[Value]], _current_.[[Value]]). | |||
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Suggested change
| 1. If _Desc_ has a [[Value]] field, return SameValue(_Desc_.[[Value]], _current_.[[Value]]). | |
| 1. NOTE: SameValue returns true for *NaN* values which may be distinguishable by other means. Returning here ensures that any existing property of _O_ remains unmodified. | |
| 1. If _Desc_ has a [[Value]] field, return SameValue(_Desc_.[[Value]], _current_.[[Value]]). |
moz-v2v-gh
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Aug 27, 2024
…spidermonkey-reviewers,jandem `ValidateAndApplyPropertyDescriptor` was refactored in <tc39/ecma262#2468>, make sure our implementation follows the current spec text more closely. But also include the fix from <tc39/ecma262#3404>. Differential Revision: https://phabricator.services.mozilla.com/D220231
ErichDonGubler
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Aug 28, 2024
…spidermonkey-reviewers,jandem `ValidateAndApplyPropertyDescriptor` was refactored in <tc39/ecma262#2468>, make sure our implementation follows the current spec text more closely. But also include the fix from <tc39/ecma262#3404>. Differential Revision: https://phabricator.services.mozilla.com/D220231
i3roly
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Aug 29, 2024
…spidermonkey-reviewers,jandem `ValidateAndApplyPropertyDescriptor` was refactored in <tc39/ecma262#2468>, make sure our implementation follows the current spec text more closely. But also include the fix from <tc39/ecma262#3404>. Differential Revision: https://phabricator.services.mozilla.com/D220231
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If an implementation can produce distinguishable NaN values, then writing NaN values to a frozen (non-configurable and non-writable) property can be detectable.
This is a regression from #2468.