Re: OLD_GC

[Bruno H. <br...@cl...>]

Hi Vladimir,

> I see you've added OLD_GC to revert to pre-MT GC. While adding MT stuff I
> tried hard to keep everything "as is" in single thread builds.

This is good, and I appreciate it. The principle is that any complex feature
should have a simple substitute, so that we can isolate bugs by trying
to reproduce them in various configurations. This is the idea behind
ENABLE_UNICODE, NO_GENERATIONAL_GC, NO_GETTEXT, and so on.

For the GC, there's not only your existing (past) changes. There's also
new algorithm alternatives that we may implement in the future, such as
  - a "1 page per object" model, that may be useful with valgrind,
  - a "1 new generation per thread" structure, that would make the
    allocation of a new object in MT lock-less in most cases,
  - a possible parallel or incremental GC,...
The OLD_GC is meant as a reference point, to make it easier to
distinguish bugs due to new GC changes from bugs outside the GC.
The DEBUG_GCSAFETY instrumentation catches a number of bugs of the
latter category, but not all.

Bruno