malloc in core.memory.GC

[Steven Schveighoffer]

On Sun, 08 Apr 2012 16:33:01 -0400, Alex Rønne Petersen  
<xtzgzorex at gmail.com> wrote:

> APPENDABLE is, IIRC, mostly an internal attribute used for the array  
> append cache. You can ignore it entirely (we should document this).

It's used to flag that the block of GC data is actually an appendable  
array.  If this flag is missing, and you attempt to append data that  
points at the block, it will always reallocate.  If this flag is present,  
it assumes it has a valid the "used" length in the block, and proceed.  Do  
NOT set this flag unless you know what you are doing.  Let the runtime do  
it.

> FINALIZE is only relevant if the type allocated in the block has a  
> destructor (it simply specifies that finalization is then desired).

I'll add that it not only identifies the type stored has a dtor, the GC  
expects that the layout of the block is of type Object.  This is an  
important distinction, because it will use that information to traverse  
the vtable looking for dtors.  For example, just setting this flag for a  
struct that has a dtor will not work, because a struct has no vtable.

-Steve