1597925 - Moving a HeapPtr asserts the contents are not gray

Status: RESOLVED FIXED

(Core :: JavaScript: GC, defect, P1)

Description

[Jon Coppeard (:jonco)]

This is showing up with the debugger changes in bug 1592116:

https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=276383216&repo=try&lineNumber=25499

We want to assert that we don't assign a HeapPtr with a pointer to a gray GC thing, but I think that moving a HeapPtr should not check this. Also, it shouldn't trigger barriers which it looks like this will do.

Comment 1

[Jon Coppeard (:jonco)]

(In reply to Jon Coppeard (:jonco) from comment #0)

Also, it shouldn't trigger barriers which it looks like this will do.

It's triggering barriers on the destination of the move, which is correct.

Comment 2

[Jon Coppeard (:jonco)]

Attachment: Bug 1597925 - Refactor GC wrapper comparison tests a little r?sfink

Comment 3

[Jon Coppeard (:jonco)]

Attachment: Bug 1597925 - Allow moving wrapped pointer types without triggering pre-barriers or asserting that their contents are not gray r?sfink

More use is being made of C++ move semantics recently and this imporves support for moving our GC wrapper types. In this case we don't want to trigger the pre-barrier on the source of the move because we are not modifying the object graph. We also do not want to check that wrapper contents are non gray, because this is valid (it's not valid to create a new heap pointer to a GC thing).

The patch adds a release() method to wrappers that returns the original contents of the wrapper after clearing it, without triggering a pre-barrier. Also it adds setUnchecked() methods to set wrapper contents without the gray marking check.

Depends on D54304

Comment 4

[Jon Coppeard (:jonco)]

Attachment: Bug 1597925 - Add post barrier tests for wrapper types which support move construction and move assignement r?sfink

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2607f7ba81ba
Refactor GC wrapper comparison tests a little r=sfink
https://hg.mozilla.org/integration/autoland/rev/d3e369f6977c
Allow moving wrapped pointer types without triggering pre-barriers or asserting that their contents are not gray r=sfink
https://hg.mozilla.org/integration/autoland/rev/f4a33a4dbfa7
Add post barrier tests for wrapper types which support move construction and move assignement r=sfink

Comment 6

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/2607f7ba81ba
https://hg.mozilla.org/mozilla-central/rev/d3e369f6977c
https://hg.mozilla.org/mozilla-central/rev/f4a33a4dbfa7