tenderlove	2018-11-30 05:39:51 +0900 (Fri, 30 Nov 2018)

  New Revision: 66095

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=66095

  Log:
    Use a shared array for the `duparray` instruction
    
    In this example code:
    
    ```ruby
    def foo
      [1, 2, 3, 4]
    end
    ```
    
    The array literal uses a `duparray` instruction. Before this patch,
    `rb_ary_resurrect` would malloc and memcpy a new array buffer.  This
    patch changes `rb_ary_resurrect` to use `ary_make_partial` so that the
    new array object shares the underlying buffer with the array stored in
    the instruction sequences.
    
    Before this patch, the new array object is not shared:
    
    ```
    $ ruby -r objspace -e'p ObjectSpace.dump([1, 2, 3, 4])'
    "{\"address\":\"0x7fa2718372d0\", \"type\":\"ARRAY\", \"class\":\"0x7fa26f8b0010\", \"length\":4, \"memsize\":72, \"flags\":{\"wb_protected\":true}}\n"
    ```
    
    After this patch:
    
    ```
    $ ./ruby -r objspace -e'p ObjectSpace.dump([1, 2, 3, 4])'
    "{\"address\":\"0x7f9a76883638\", \"type\":\"ARRAY\", \"class\":\"0x7f9a758af900\", \"length\":4, \"shared\":true, \"references\":[\"0x7f9a768837c8\"], \"memsize\":40, \"flags\":{\"wb_protected\":true}}\n"
    ```
    
    [Feature #15289] [ruby-core:90097]

  Modified files:
    trunk/array.c
Index: array.c
===================================================================
--- array.c	(revision 66094)
+++ array.c	(revision 66095)
@@ -2191,7 +2191,7 @@ rb_ary_dup(VALUE ary) https://github.com/ruby/ruby/blob/trunk/array.c#L2191
 VALUE
 rb_ary_resurrect(VALUE ary)
 {
-    return rb_ary_new4(RARRAY_LEN(ary), RARRAY_CONST_PTR_TRANSIENT(ary));
+    return ary_make_partial(ary, rb_cArray, 0, RARRAY_LEN(ary));
 }
 
 extern VALUE rb_output_fs;

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