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ToString(Object) sometimes returns [object Null] #12411

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Sebmaster opened this issue Apr 14, 2017 · 11 comments
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ToString(Object) sometimes returns [object Null] #12411

Sebmaster opened this issue Apr 14, 2017 · 11 comments
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v8 engine Issues and PRs related to the V8 dependency.

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@Sebmaster
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Sebmaster commented Apr 14, 2017

  • Version: 7.7.1
  • Platform: Linux web 4.4.0-18-generic #34~14.04.1-Ubuntu SMP Thu Apr 7 18:31:54 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
  • Subsystem: v8

I think we're encountering this bug in our staging and prod environments under heavy load. It does not occur in node v6, but only v7.

I can't reproduce this in the node console (with the v8 repro), but it seems like the v8 code is the same in node.

Is it possible to somehow verify this also applies to node and backport that v8 fix into node v7?

@mscdex mscdex added v7.x v8 engine Issues and PRs related to the V8 dependency. question Issues that look for answers. labels Apr 14, 2017
@mscdex
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mscdex commented Apr 14, 2017

I don't think it's out of the ordinary, seeing as how null is considered an object type in Javascript. For example:

> Object.prototype.toString.call(null)
'[object Null]'

It could be a bug though whose fix didn't get backported to 5.5 though.

@Sebmaster
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Sebmaster commented Apr 14, 2017

This is not about what happens when you stringify null.[object Null] is returned when you stringify an ordinary object. See also this Stackoverflow, which has a great log of the behaviour of the object.

Also see in the linked v8 issue where an array is stringified, but [object Null] gets returned (in full codegen, seems to be fixed in ignition).

@bnoordhuis
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The V8 in v7.x has the same bug. I'll prepare a back-port.

@bnoordhuis
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#12412

@holm
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holm commented Apr 14, 2017

This has been troubling us for months! So happy the issue has been found. Getting the fix out in a patch release soon would be great for us. Thanks.

@addaleax
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@holm I would assume we do another v7.x patch release next week, as usual.

@holm
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holm commented Apr 15, 2017

Great, thanks a lot for the quick work (as usual)!

bnoordhuis added a commit to bnoordhuis/io.js that referenced this issue Apr 19, 2017
This is a chery-pick if you consider reducing the context to -C2
a cherry-pick; WordIsSmi has been renamed to TaggedIsSmi upstream.

Original commit message:

    [builtins] Fix pointer comparison in ToString builtin.

    This fixes the bogus {Word32Equal} comparison in the ToString
    builtin implementing Object.prototype.toString to be a pointer-size
    {WordEqual} comparison instead. Comparing just the lower half-word
    is insufficient on 64-bit architectures.

    [email protected]
    TEST=mjsunit/regress/regress-crbug-664506
    BUG=chromium:664506

    Review-Url: https://codereview.chromium.org/2496043003
    Cr-Commit-Position: refs/heads/master@{nodejs#40963}

Fixes: nodejs#12411
PR-URL: nodejs#12412
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>
@bnoordhuis
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Fixed in f882f47, should be in the next v7.x release.

@holm
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holm commented Apr 27, 2017

Any idea when the next v7.x release might be? This bug is hurting us quite a bit, and a new release would be wonderful. Thanks as always.

@bnoordhuis
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Next Tuesday, I think. I'm not on the release team though.

@evanlucas
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Ben is correct. I have a release almost ready but decided to hold off due to #12663

evanlucas pushed a commit that referenced this issue May 1, 2017
This is a chery-pick if you consider reducing the context to -C2
a cherry-pick; WordIsSmi has been renamed to TaggedIsSmi upstream.

Original commit message:

    [builtins] Fix pointer comparison in ToString builtin.

    This fixes the bogus {Word32Equal} comparison in the ToString
    builtin implementing Object.prototype.toString to be a pointer-size
    {WordEqual} comparison instead. Comparing just the lower half-word
    is insufficient on 64-bit architectures.

    [email protected]
    TEST=mjsunit/regress/regress-crbug-664506
    BUG=chromium:664506

    Review-Url: https://codereview.chromium.org/2496043003
    Cr-Commit-Position: refs/heads/master@{#40963}

Fixes: #12411
PR-URL: #12412
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>
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