642806 - List add crashes with GCInlineObject inheritance

Status: RESOLVED FIXED

(Tamarin Graveyard :: Garbage Collection (mmGC), defect, P1)

Comment 1

[Tommy Reilly]

Attachment: demonstrates the crash

Comment 2

[Tommy Reilly]

Attachment: fixes the problem

Comment 3

[Tommy Reilly]

I can't explain why this fixes it, the *()&m_that construction just stopped working when the list picked up a base class, don't know why.  Anyway this seems cleaner.

Comment 4

[Steven Johnson]

I hate to delay fixing a crash, but I'd really like to know *why* this fixes it before I R+... disassembler?

Comment 5

[Tommy Reilly]

I can do that but I'm not sure it will be very informative, I think what's needed here is an understanding of C++ here (assuming that what GCC is doing is correct, haven't tried a different compiler yet).   Hmm, maybe this is a good excuse to download the shiny new xcode 4 and see what clang does.

Do you happen to remember why the code wasn't written this way in the first place?

Comment 6

[Steven Johnson]

(In reply to comment #5)
> Do you happen to remember why the code wasn't written this way in the first
> place?

Nope. I guess *removing* a cast is safer than adding one...

Comment 7

[Tommy Reilly]

And quite a dubious cast at that.   Crash doesn't repro with gcc-4.0.  I smell a compiler bug.

Comment 8

[Tommy Reilly]

Okay I'm done, no assembler for me, it only crashes on GCC 4.2 x86 so  Its a compiler bug that I have no interest in knowing more about.   At least its a good fix that stands on its own and not some odd ball bug workaround hack.

Comment 9

[Tommy Reilly]

This is blocking the landing of the exact tracing safety net in the player.

Comment 10

[Tamarin Bot]

changeset: 6117:3b45d4b79183
user:      Tommy Reilly <[e-mail]>
summary:   Bug 642806 - List add crashes with GCInlineObject inheritance (r=stejohns,sr=edwsmith)

http://hg.mozilla.org/tamarin-redux/rev/3b45d4b79183