Handle only stop parameter set, but not start.

If start is not specified, the value given for stop will be injected
into start's position; it is wise to safeguard against this.
(via @yaauie)

Author: badboy

lib/redis.rb

@@ -909,12 +909,16 @@ def bitop(operation, destkey, *keys)
   # Return the position of the first bit set to 1 or 0 in a string.
   #
   # @param [String] key
-  # @param [Fixnum] bit wether to look for the first 1 or 0 bit
+  # @param [Fixnum] bit whether to look for the first 1 or 0 bit
   # @param [Fixnum] start start index
   # @param [Fixnum] stop stop index
   # @return [Fixnum] the position of the first 1/0 bit.
   #                  -1 if looking for 1 and it is not found or start and stop are given.
   def bitpos(key, bit, start=nil, stop=nil)
+    if stop and not start
+      raise(ArgumentError, 'stop parameter specified without start parameter')
+    end
+
     synchronize do |client|
       command = [:bitpos, key, bit]
       command << start if start

test/bitpos_test.rb

@@ -58,4 +58,12 @@ def test_bitpos_one_intervals
     end
   end
 
+  def test_bitpos_raise_exception_if_stop_not_start
+    target_version "2.9.11" do
+      assert_raises(ArgumentError) do
+        r.bitpos("foo", 0, nil, 2)
+      end
+    end
+  end
+
 end