510522 - Firefox crashes on startup on Linux x86_64 [@ JSScope::create]

Status: RESOLVED DUPLICATE of bug 510449

(Core :: JavaScript Engine, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: stack of the crash

Today's Linux x86_64 nightly and my own debug build both crash on startup.

Yesterday's Linux x86_64 nightly works fine.

I think the previous revision from which I'd updated my debug build gives a regression range of:
http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=c95ef80a5f20&tochange=e6034ded61fd

Comment 1

[Andreas Gal :gal]

We really, really, really need x86_64 test coverage if we are serious about supporting that platform.

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(In reply to comment #1)
> We really, really, really need x86_64 test coverage if we are serious about
> supporting that platform.

I already complained on bug 464027 once today, if that's what you're asking. :-)

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

I think the problem is that this (JSObject::getClass):
        return (JSClass *) (classword & ~JSSLOT_CLASS_MASK_BITS);
is masking off the upper 32 bits because JSSLOT_CLASS_MASK_BITS is a constant of type that defaults to 32-bit, so ~-ing it doesn't set the high bits.

Testing a fix shortly.