Ractor.make_shareable(obj)

Introduce new method Ractor.make_shareable(obj) which tries to make
obj shareable object. Protocol is here.

(1) If obj is shareable, it is shareable.
(2) If obj is not a shareable object and if obj can be shareable
    object if it is frozen, then freeze obj. If obj has reachable
    objects (rs), do rs.each{|o| Ractor.make_shareable(o)}
    recursively (recursion is not Ruby-level, but C-level).
(3) Otherwise, raise Ractor::Error. Now T_DATA is not a shareable
    object even if the object is frozen.

If the method finished without error, given obj is marked as
a sharable object.

To allow makng a shareable frozen T_DATA object, then set
`RUBY_TYPED_FROZEN_SHAREABLE` as type->flags. On default,
this flag is not set. It means user defined T_DATA objects are
not allowed to become shareable objects when it is frozen.

You can make any object  shareable by setting FL_SHAREABLE flag,
so if you know that the T_DATA object is shareable (== thread-safe),
set this flag, at creation time for example. `Ractor` object is one
example, which is not a frozen, but a shareable object.

bootstraptest/test_ractor.rb

@@ -832,6 +832,80 @@ class C
   }.take
 }
 
+# Ractor.make_shareable(obj)
+assert_equal 'true', %q{
+  class C
+    def initialize
+      @a = 'foo'
+      @b = 'bar'
+    end
+    attr_reader :a, :b
+  end
+  S = Struct.new(:s1, :s2)
+  str = "hello"
+  str.instance_variable_set("@iv", "hello")
+  /a/ =~ 'a'
+  m = $~
+  class N < Numeric
+    def /(other)
+      1
+    end
+  end
+  ary = []; ary << ary
+
+  a = [[1, ['2', '3']],
+       {Object.new => "hello"},
+       C.new,
+       S.new("x", "y"),
+       ("a".."b"),
+       str,
+       ary,             # cycle
+       /regexp/,
+       /#{'r'.upcase}/,
+       m,
+       Complex(N.new,0),
+       Rational(N.new,0),
+       true,
+       false,
+       nil,
+       1, 1.2, 1+3r, 1+4i, # Numeric
+  ]
+  Ractor.make_shareable(a)
+
+  # check all frozen
+  a.each{|o|
+    raise o.inspect unless o.frozen?
+
+    case o
+    when C
+      raise o.a.inspect unless o.a.frozen?
+      raise o.b.inspect unless o.b.frozen?
+    when Rational
+      raise o.numerator.inspect unless o.numerator.frozen?
+    when Complex
+      raise o.real.inspect unless o.real.frozen?
+    when Array
+      if o[0] == 1
+        raise o[1][1].inspect unless o[1][1].frozen?
+      end
+    when Hash
+      o.each{|k, v|
+        raise k.inspect unless k.frozen?
+        raise v.inspect unless v.frozen?
+      }
+    end
+  }
+
+  Ractor.shareable?(a)
+}
+
+# Ractor.make_shareable(obj) doesn't freeze shareable objects
+assert_equal 'true', %q{
+  r = Ractor.new{}
+  Ractor.make_shareable(a = [r])
+  [a.frozen?, a[0].frozen?] == [true, false]
+}
+
 ###
 ### Synchronization tests
 ###

common.mk

@@ -10193,10 +10193,17 @@ ractor.$(OBJEXT): $(CCAN_DIR)/list/list.h
 ractor.$(OBJEXT): $(CCAN_DIR)/str/str.h
 ractor.$(OBJEXT): $(hdrdir)/ruby/ruby.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/array.h
+ractor.$(OBJEXT): $(top_srcdir)/internal/bignum.h
+ractor.$(OBJEXT): $(top_srcdir)/internal/bits.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/compilers.h
+ractor.$(OBJEXT): $(top_srcdir)/internal/complex.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/error.h
+ractor.$(OBJEXT): $(top_srcdir)/internal/fixnum.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/gc.h
+ractor.$(OBJEXT): $(top_srcdir)/internal/hash.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/imemo.h
+ractor.$(OBJEXT): $(top_srcdir)/internal/numeric.h
+ractor.$(OBJEXT): $(top_srcdir)/internal/rational.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/serial.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/static_assert.h
 ractor.$(OBJEXT): $(top_srcdir)/internal/string.h
@@ -10220,6 +10227,7 @@ ractor.$(OBJEXT): {$(VPATH)}debug.h
 ractor.$(OBJEXT): {$(VPATH)}debug_counter.h
 ractor.$(OBJEXT): {$(VPATH)}defines.h
 ractor.$(OBJEXT): {$(VPATH)}encoding.h
+ractor.$(OBJEXT): {$(VPATH)}gc.h
 ractor.$(OBJEXT): {$(VPATH)}id.h
 ractor.$(OBJEXT): {$(VPATH)}id_table.h
 ractor.$(OBJEXT): {$(VPATH)}intern.h
@@ -10381,6 +10389,7 @@ ractor.$(OBJEXT): {$(VPATH)}subst.h
 ractor.$(OBJEXT): {$(VPATH)}thread.h
 ractor.$(OBJEXT): {$(VPATH)}thread_$(THREAD_MODEL).h
 ractor.$(OBJEXT): {$(VPATH)}thread_native.h
+ractor.$(OBJEXT): {$(VPATH)}variable.h
 ractor.$(OBJEXT): {$(VPATH)}vm_core.h
 ractor.$(OBJEXT): {$(VPATH)}vm_debug.h
 ractor.$(OBJEXT): {$(VPATH)}vm_opts.h

include/ruby/internal/core/rtypeddata.h

@@ -52,13 +52,15 @@
 #define RTYPEDDATA_P                 RTYPEDDATA_P
 #define RTYPEDDATA_TYPE              RTYPEDDATA_TYPE
 #define RUBY_TYPED_FREE_IMMEDIATELY  RUBY_TYPED_FREE_IMMEDIATELY
+#define RUBY_TYPED_FROZEN_SHAREABLE  RUBY_TYPED_FROZEN_SHAREABLE
 #define RUBY_TYPED_WB_PROTECTED      RUBY_TYPED_WB_PROTECTED
 #define RUBY_TYPED_PROMOTED1         RUBY_TYPED_PROMOTED1
 /** @endcond */
 
 /* bits for rb_data_type_struct::flags */
 enum rbimpl_typeddata_flags {
     RUBY_TYPED_FREE_IMMEDIATELY = 1,
+    RUBY_TYPED_FROZEN_SHAREABLE = RUBY_FL_SHAREABLE,
     RUBY_TYPED_WB_PROTECTED     = RUBY_FL_WB_PROTECTED, /* THIS FLAG DEPENDS ON Ruby version */
     RUBY_TYPED_PROMOTED1        = RUBY_FL_PROMOTED1     /* THIS FLAG DEPENDS ON Ruby version */
 };

internal/hash.h

@@ -83,6 +83,8 @@ VALUE rb_hash_set_pair(VALUE hash, VALUE pair);
 int rb_hash_stlike_delete(VALUE hash, st_data_t *pkey, st_data_t *pval);
 int rb_hash_stlike_foreach_with_replace(VALUE hash, st_foreach_check_callback_func *func, st_update_callback_func *replace, st_data_t arg);
 int rb_hash_stlike_update(VALUE hash, st_data_t key, st_update_callback_func *func, st_data_t arg);
+extern st_table *rb_hash_st_table(VALUE hash);
+
 static inline unsigned RHASH_AR_TABLE_SIZE_RAW(VALUE h);
 static inline VALUE RHASH_IFNONE(VALUE h);
 static inline size_t RHASH_SIZE(VALUE h);
@@ -135,7 +137,6 @@ RHASH_AR_TABLE(VALUE h)
 static inline st_table *
 RHASH_ST_TABLE(VALUE h)
 {
-    extern st_table *rb_hash_st_table(VALUE hash);
     return rb_hash_st_table(h)
 }