merge revision(s) 496591de96b261b8789332c7f8b2bfbd17658955: [Backport #18578]

	st.c: Do not clear entries_bound when calling Hash#shift for empty
	 hash

	tab->entries_bound is used to check if the bins are full in
	rebuild_table_if_necessary.

	Hash#shift against an empty hash assigned 0 to tab->entries_bound, but
	didn't clear the bins. Thus, the table is not rebuilt even when the bins
	are full. Attempting to add a new element into full-bin hash gets stuck.

	This change stops clearing tab->entries_bound in Hash#shift.
	[Bug #18578]
	---
	 st.c                   |  1 -
	 test/ruby/test_hash.rb | 13 +++++++++++++
	 2 files changed, 13 insertions(+), 1 deletion(-)

1 files changed, 13 insertions, 0 deletions

diff --git a/test/ruby/test_hash.rb b/test/ruby/test_hash.rb
index f79879c20a..eaff09d434 100644
--- a/test/ruby/test_hash.rb
+++ b/test/ruby/test_hash.rb
@@ -1069,6 +1069,19 @@ class TestHash < Test::Unit::TestCase
     assert_equal("FOO", h.shift)
   end
 
+  def test_shift_for_empty_hash
+    # [ruby-dev:51159]
+    h = @cls[]
+    100.times{|n|
+      while h.size < n
+        k = Random.rand 0..1<<30
+        h[k] = 1
+      end
+      0 while h.shift
+      assert_equal({}, h)
+    }
+  end
+
   def test_reject_bang2
     assert_equal({1=>2}, @cls[1=>2,3=>4].reject! {|k, v| k + v == 7 })
     assert_nil(@cls[1=>2,3=>4].reject! {|k, v| k == 5 })