519998 - Make FixedMalloc optional if MMGC_USE_SYSTEM_MALLOC is specified

Status: RESOLVED WONTFIX

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

Description

[Lars T Hansen]

Attachment: Preliminary patch

I'm attaching a preliminary patch, which gets rid of FixedMalloc and its subtypes throughout the entire system except in one place: one of the GCRoot constructors depends on FixedMalloc to compute the size of the instance.  But this size could be passed explicitly to the other constructor (there would be some ripple effects in the code base), so it's conceivable that FixedMalloc really could be made optional in the sense that if one wished to use the system malloc and not have more than one fixed allocator, we could provide it.

This bug is about making that possible by resolving the outstanding issue (mostly figuring out what the consequences would be) and discussing the value of the change.

Comment 1

[Lars T Hansen]

The point may be somewhat moot because I understand the Flash Player uses instances of FixedAlloc for fast allocation; still, getting rid of FixedMalloc seems useful.

Comment 2

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

I don't think we can do this without getting rid of GCRoot or at least eliminating GCRoot abuse.

See Bug 663159 for why we need to track allocation of GCRoot instances ourselves.

See Bug 599820 for thoughts for why (and how) we might get rid of GCRoot.