From a4a19b114ba94b8f28d5a91aee5d595a516006d5 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Thu, 1 Aug 2019 14:41:21 -0400
Subject: [PATCH] Allow non-finalizable objects in ObjectSpace::WeakMap

[feature #16035]

This goes one step farther than what nobu did in [feature #13498]

With this patch, special objects such as static symbols, integers, etc can be used as either key or values inside WeakMap. They simply don't have a finalizer defined on them.

This is useful if you need to deduplicate value objects
---
 gc.c                      | 20 +++++++++-----------
 test/ruby/test_weakmap.rb | 31 +++++++++++++++++++++----------
 2 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/gc.c b/gc.c
index 18ae189421..c083fbb297 100644
--- a/gc.c
+++ b/gc.c
@@ -2986,18 +2986,12 @@ should_be_callable(VALUE block)
 }
 
 static void
-should_be_finalizable_internal(VALUE obj)
+should_be_finalizable(VALUE obj)
 {
     if (!FL_ABLE(obj)) {
 	rb_raise(rb_eArgError, "cannot define finalizer for %s",
 		 rb_obj_classname(obj));
     }
-}
-
-static void
-should_be_finalizable(VALUE obj)
-{
-    should_be_finalizable_internal(obj);
     rb_check_frozen(obj);
 }
 
@@ -10253,6 +10247,7 @@ wmap_allocate(VALUE klass)
 static int
 wmap_live_p(rb_objspace_t *objspace, VALUE obj)
 {
+    if (!FL_ABLE(obj)) return TRUE;
     if (!is_id_value(objspace, obj)) return FALSE;
     if (!is_live_object(objspace, obj)) return FALSE;
     return TRUE;
@@ -10510,10 +10505,13 @@ wmap_aset(VALUE self, VALUE wmap, VALUE orig)
     struct weakmap *w;
 
     TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
-    should_be_finalizable_internal(orig);
-    should_be_finalizable_internal(wmap);
-    define_final0(orig, w->final);
-    define_final0(wmap, w->final);
+    if (FL_ABLE(orig)) {
+        define_final0(orig, w->final);
+    }
+    if (FL_ABLE(wmap)) {
+        define_final0(wmap, w->final);
+    }
+
     st_update(w->obj2wmap, (st_data_t)orig, wmap_aset_update, wmap);
     st_insert(w->wmap2obj, (st_data_t)wmap, (st_data_t)orig);
     return nonspecial_obj_id(orig);
diff --git a/test/ruby/test_weakmap.rb b/test/ruby/test_weakmap.rb
index 8eb32b574f..3b9eef770a 100644
--- a/test/ruby/test_weakmap.rb
+++ b/test/ruby/test_weakmap.rb
@@ -16,16 +16,27 @@ class TestWeakMap < Test::Unit::TestCase
 
   def test_aset_const
     x = Object.new
-    assert_raise(ArgumentError) {@wm[true] = x}
-    assert_raise(ArgumentError) {@wm[false] = x}
-    assert_raise(ArgumentError) {@wm[nil] = x}
-    assert_raise(ArgumentError) {@wm[42] = x}
-    assert_raise(ArgumentError) {@wm[:foo] = x}
-    assert_raise(ArgumentError) {@wm[x] = true}
-    assert_raise(ArgumentError) {@wm[x] = false}
-    assert_raise(ArgumentError) {@wm[x] = nil}
-    assert_raise(ArgumentError) {@wm[x] = 42}
-    assert_raise(ArgumentError) {@wm[x] = :foo}
+    @wm[true] = x
+    assert_same(x, @wm[true])
+    @wm[false] = x
+    assert_same(x, @wm[false])
+    @wm[nil] = x
+    assert_same(x, @wm[nil])
+    @wm[42] = x
+    assert_same(x, @wm[42])
+    @wm[:foo] = x
+    assert_same(x, @wm[:foo])
+
+    @wm[x] = true
+    assert_same(true, @wm[x])
+    @wm[x] = false
+    assert_same(false, @wm[x])
+    @wm[x] = nil
+    assert_same(nil, @wm[x])
+    @wm[x] = 42
+    assert_same(42, @wm[x])
+    @wm[x] = :foo
+    assert_same(:foo, @wm[x])
   end
 
   def assert_weak_include(m, k, n = 100)