563305 - jsgc.cpp: replace handcrafted GC chunk layout with a real struct

Status: ASSIGNED

(Core :: JavaScript Engine, defect)

Description

[Julian Seward [:jseward]]

In jsgc.cpp, the basic representation of the heap centers around 'gc
chunks', which contain a number of JSGCArenas and supporting data.
This is described in a bit comment at jsgc.cpp:142.  For unclear
reasons, although every other data structure has a real C++
definition, this one doesn't.  Consequently the code that manipulates
it is hard to follow and contains by-hand address arithmetic and bit
twiddling that we'd normally expect the compiler to do for us.

Hence: give a proper struct definition, GCChunk, and use its fields
in the obvious way, rather than manual address arithmetic, where possible.

A possible followup tidying is would be to change JSRuntime::gcChunks
from a vector of JSGCChunkInfo*s to a vector of GCChunk*s.

Comment 1

[Julian Seward [:jseward]]

Attachment: patch, v1

Comment 2

[Nicholas Nethercote [inactive]]

In C++ you can use just "GCChunk" rather than "struct GCChunk" when referring to it, AIUI.