string.c: fix memsize of frozen shared string

* string.c (str_new4): copy the original capacity so that memsize of
  frozen shared string returns correct size.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43862 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 0 deletions

diff --git a/test/objspace/test_objspace.rb b/test/objspace/test_objspace.rb
index f3bb3cd8c6..83cd6d3ca0 100644
--- a/test/objspace/test_objspace.rb
+++ b/test/objspace/test_objspace.rb
@@ -24,6 +24,14 @@ class TestObjSpace < Test::Unit::TestCase
                     ObjectSpace.memsize_of(//.match("")))
   end
 
+  def test_memsize_of_root_shared_string
+    a = "hello" * 5
+    b = a.dup
+    c = nil
+    ObjectSpace.each_object(String) {|x| break c = x if x == a and x.frozen?}
+    assert_equal([0, 0, 26], [a, b, c].map {|x| ObjectSpace.memsize_of(x)})
+  end
+
   def test_argf_memsize
     size = ObjectSpace.memsize_of(ARGF)
     assert_kind_of(Integer, size)