664137 - GCRoot: derive object's beginning via FixedMalloc::FindBeginning(this).

Status: RESOLVED FIXED

(Tamarin Graveyard :: Garbage Collection (mmGC), defect, P3)

Description

[Felix S. Klock II [:pnkfelix, :fklock]]

Bug 663159 points out a serious issue with multiple-inheritance of GCRoot (or subclasses of GCRoot).

In Bug 663159, comment 1, Steven suggested the approach of adding FixedMalloc::FindBeginning and then utilizing it to derive the object's true beginning (which may fall before 'this').

Felix had argued that this was too risky and explored other options (Bug 663177, Bug 663491) but Tommy countered in Bug 663491, comment 7 (a response to Bug 663491, comment 5) that Steven's suggestion was our best option.

Comment 1

[Felix S. Klock II [:pnkfelix, :fklock]]

Attachment: GCRoot: proper derivation of beginning

Comment 2

[Felix S. Klock II [:pnkfelix, :fklock]]

(In reply to comment #1)
> Created attachment 539548 [details] [diff] [review] [review]
> GCRoot: proper derivation of beginning

Pushed to Serrano.

  tamarin-redux-serrano
  changeset: 6322:7fc6e10cdc24
  user:      Felix S Klock II <[e-mail]>
  summary:   Bug 664137: GCRoot: proper derivation of object beginning via FixedMalloc::FindBeginning (r=treilly, sr pending lhansen).
  http://asteam.corp.adobe.com/hg/tamarin-redux-serrano/rev/7fc6e10cdc24

Comment 3

[Lars T Hansen]

Comment on attachment 539548 [details] [diff] [review]
GCRoot: proper derivation of beginning

GCAssertMsg might be more desirable, in order for the asserts to provide more diagnostic value right off the bat.

Comment 4

[Tamarin Bot]

changeset: 6540:0bdd7ace90ff
user:      Felix S Klock II <[e-mail]>
summary:   Bug 663508: FixedMalloc::FindBeginning code; it is slow (r=treilly, sr=lhansen).

http://hg.mozilla.org/tamarin-redux/rev/0bdd7ace90ff

Comment 5

[Tamarin Bot]

changeset: 6544:e0ed1665d4f8
user:      Felix S Klock II <[e-mail]>
summary:   Bug 664137: derive GCRoot's true beginning via FixedMalloc (r=treilly, sr=lhansen).

http://hg.mozilla.org/tamarin-redux/rev/e0ed1665d4f8

Comment 6

[Tamarin Bot]

changeset: 6550:0632cf3ccf4e
user:      Felix S Klock II <[e-mail]>
summary:   Bug 664137: use GCAssertMsg to provide better/faster diagnostic value (r=fklockii).

http://hg.mozilla.org/tamarin-redux/rev/0632cf3ccf4e