check for self-assignment in bitfield operator=

include/libtorrent/bitfield.hpp

@@ -145,6 +145,7 @@ namespace libtorrent {
 		// assignment operator
 		bitfield& operator=(bitfield const& rhs)
 		{
+			if (&rhs == this) return *this;
 			assign(rhs.data(), rhs.size());
 			return *this;
 		}

test/test_bitfield.cpp

@@ -387,6 +387,14 @@ TORRENT_TEST(not_initialized)
 	// get_bit, clear_bit, set_bit
 }
 
+TORRENT_TEST(self_assign)
+{
+	bitfield test1(123, false);
+	test1 = test1;
+	TEST_EQUAL(test1.size(), 123);
+	TEST_EQUAL(test1.count(), 0);
+}
+
 TORRENT_TEST(not_initialized_assign)
 {
 	// check a not initialized empty bitfield