610306 - MarkStackRangeConservatively in jsgc.cpp marked wrong objects on big endian system.

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Leon Sha]

"jsvals" have different layout on big endian system. We need to provide the real payload to scan.

Comment 1

[Leon Sha]

Attachment: patch

Comment 2

[Boris Zbarsky [:bzbarsky]]

It really feels to me like this should somehow live in Value...

Comment 3

[Andreas Gal :gal]

Probably not a bad idea. Luke, want to do some magic here?

Comment 4

[Luke Wagner [:luke]]

Whoa, this code has been 'optimized' since I touched it.  Skipping every other word is only valid if every jsval on the stack is 64-bit aligned.  I had an assert in js::Value accessors that 'this' was aligned, but I had to take it out since the compiler was misaligning jsvals (parameters in MSVC and temporaries in GCC, IIRC).  jsvals aren't even declared to be aligned on MSVC.  Thus, unless I'm missing something, I think the real fix is to mark every word.

Comment 5

[Andreas Gal :gal]

I think this was intended for scanning the JIT stack, which is guaranteed to be aligned. At the very least there should always be a version that scans aligned memory.

Comment 6

[Luke Wagner [:luke]]

(In reply to comment #5)
> I think this was intended for scanning the JIT stack

D'oh!  I assumed this was in the C-stack scanner.

Comment 7

[Luke Wagner [:luke]]

Attachment: patch

This encapsulates the value representation a bit more.

Comment 8

[Luke Wagner [:luke]]

http://hg.mozilla.org/tracemonkey/rev/18d56745c3e6

Comment 9

[Robert Sayre]

http://hg.mozilla.org/mozilla-central/rev/18d56745c3e6