From: Stanislav Sedov <stas@...>
Date: 2009-06-18T18:30:35+09:00
Subject: [ruby-core:23913] Broken finalizers in ruby 1.8

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Hi!

It looks like r21435 of ruby_1_8_7 broke ObjectSpace finalizers.
I don't entirely understand the code envolved, but it seems that
the following fragment is responsible for this:

% mark_tbl(finalizer_table, 0);
% st_foreach(finalizer_table, chain_finalized_object,
%     (st_data_t)&deferred_final_list);

Here, all objects in the finalizer table get marked, and the
chain_finalized_object function is called for each object in
the table.  However, chain_finalized_object immediately
returns if the object passes is marked:

% static int
% chain_finalized_object(st_data_t key, st_data_t val, st_data_t arg)
% {
%     RVALUE *p =3D (RVALUE *)key, **final_list =3D (RVALUE **)arg;
%     if ((p->as.basic.flags & (FL_FINALIZE|FL_MARK)) =3D=3D FL_FINALIZE) {
%        if (BUILTIN_TYPE(p) !=3D T_DEFERRED) {
%            p->as.free.flags =3D FL_MARK | T_DEFERRED; /* remain marked */
%           RDATA(p)->dfree =3D 0;
%        }
%        p->as.free.next =3D *final_list;
%        *final_list =3D p;
%     }
%     return ST_CONTINUE;
% }

Changing the test from '(p->as.basic.flags & (FL_FINALIZE|FL_MARK))' to
simple '(p->as.basic.flags & (FL_FINALIZE))' as before fixes the problem
for me, but I'm not sure this is the right solution.

The problem can be verified using the following simple snipplet:

% obj =3D "Test"
% handler =3D Proc.new { puts "Finalized!" }
% ObjectSpace.define_finalizer(obj, handler)

If you run this code in ruby 1.8.7 before r21435 it prints 'Finalized!'.
In newer version it is never called.

Thanks!

--=20
Stanislav Sedov
ST4096-RIPE

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