On heap segregation, GC optimization and @nogc relaxing

[via Digitalmars-d]

On Thursday, 13 November 2014 at 22:12:22 UTC, deadalnix wrote:
> You need a set of root from the TL heap. The trick being to
> consider everything that is allocated AFTER you get the roots as
> automatically alive (you'll collect this in the next collection
> cycle).
>
> That way, new allocated chunk that have reference in the TL heap
> will be kept alive, even if you don't know about the roots.
>
> You'll find plenty of information about the details if look into
> GC for ML family languages.

Consider this:

     auto i = new immutable(int);
     immutable(int)* a, b;
     b = i;
     // GC kicks in here, scans `a` (== null)
     a = b;
     b = null;
     // GC goes on, scans `b` (== null)
     // => whoops, no reference to *i

Here, a and b are on the stack or in registers. They could also 
be on the TL heap.