Final_tag and garbage collection

[Robbert VanRenesse <rvr@cs.cornell.edu>]

The system that I'm building uses a mixture of C and CAML.  Sometimes it is
necessary to have references from CAML objects to C objects.  When CAML
cleans up its objects, the C objects need to be cleaned up as well.  I'm
using the finalization functionality of CAML for that.  However, it only
appears to work reliably in combination with alloc_shr(), not with alloc().
Here's the code:

	value link;

	link = alloc_shr(3, Final_tag);
	Field(link, 0) = (value) link_final;
	...

Very reliably, the function link_final is automatically invoked when the
system is garbage collecting.  However, if I use alloc() instead, it
sometimes happens, but lots of blocks appear to not get finalized.  I
used all of gc__minor, gc__major, and gc__fullmajor to try to provoke
finalization, but only a subset of what I allocated this way gets
finalized.

Any ideas?

				Robbert