Re: [Caml-list] concurrent gc?

[Goswin von Brederlow <goswin-v-b@web.de>]

On Tue, Jul 29, 2014 at 12:49:19PM +0800, ygrek wrote:
> Hello,
> 
>  See also the pros and cons in http://caml.inria.fr/mantis/view.php?id=5010

"pros and cons"?

The issue talks about arrays and xleroy mentioned that the magic that
is used to tag float arrays as such does not extend to e.g int arrays
and therefore, since it needs to be a runtime thing, special tagging
won't work there. Seems ther is only one big con.


But that doesn't hold for records. The type of a record is known at
compile time and the compiler knows it if can contain any pointer or
not. This gets a bit tricky with polymorphic records, e.g.:

type 'a t = { x : 'a }

Then "int t" has no pointers but "int list t" does. Since 'a t records
can be created in polymorphic functions that means even "int t" can
not be tagged no-scan or you would end up with different tags
depending on who created the record.

Tagging records without pointer would only be for records without
polymorphic members (more specific for !E 'a . 'a t contains pointer),
e.g.

type 'a x = int
type 'a t = { x: 'a x; y: int; }

That somewhat limits the use case but avoids the problem of runtime
detection of the type.

MfG
	Goswin