gistfile1.diff

diff --git a/core/src/main/java/org/jruby/util/io/EncodingUtils.java b/core/src/main/java/org/jruby/util/io/EncodingUtils.java
index c057e8a..16cd559 100644
--- a/core/src/main/java/org/jruby/util/io/EncodingUtils.java
+++ b/core/src/main/java/org/jruby/util/io/EncodingUtils.java
@@ -15,6 +15,7 @@ import org.jcodings.transcode.EConvResult;
 import org.jcodings.transcode.Transcoder;
 import org.jcodings.transcode.TranscoderDB;
 import org.jcodings.transcode.Transcoding;
+import org.jcodings.unicode.UnicodeEncoding;
 import org.jcodings.util.CaseInsensitiveBytesHash;
 import org.jruby.Ruby;
 import org.jruby.RubyArray;
@@ -1830,35 +1831,40 @@ public class EncodingUtils {
         return getActualEncoding(str.getEncoding(), str);
     }
 
+    private static final Encoding UTF16Dummy = EncodingDB.getEncodings().get("UTF-16".getBytes()).getEncoding();
+    private static final Encoding UTF32Dummy = EncodingDB.getEncodings().get("UTF-32".getBytes()).getEncoding();
+
     // MRI: get_actual_encoding
     public static Encoding getActualEncoding(Encoding enc, ByteList byteList) {
-        byte[] bytes = byteList.unsafeBytes();
-        int p = byteList.begin();
-        int end = p + byteList.getRealSize();
-
-        CaseInsensitiveBytesHash<EncodingDB.Entry> encodings = EncodingDB.getEncodings();
-        if (enc == encodings.get("UTF-16".getBytes()).getEncoding() && end - p >= 2) {
-            int c0 = bytes[p] & 0xff;
-            int c1 = bytes[p + 1] & 0xff;
-
-            if (c0 == 0xFE && c1 == 0xFF) {
-                return UTF16BEEncoding.INSTANCE;
-            } else if (c0 == 0xFF && c1 == 0xFE) {
-                return UTF16LEEncoding.INSTANCE;
-            }
-            return ASCIIEncoding.INSTANCE;
-        } else if (enc == encodings.get("UTF-32".getBytes()).getEncoding() && end - p >= 4) {
-            int c0 = bytes[p] & 0xff;
-            int c1 = bytes[p + 1] & 0xff;
-            int c2 = bytes[p + 2] & 0xff;
-            int c3 = bytes[p + 3] & 0xff;
-
-            if (c0 == 0 && c1 == 0 && c2 == 0xFE && c3 == 0xFF) {
-                return UTF32BEEncoding.INSTANCE;
-            } else if (c3 == 0 && c2 == 0 && c1 == 0xFE && c0 == 0xFF) {
-                return UTF32LEEncoding.INSTANCE;
+        if (enc.isDummy() && enc instanceof UnicodeEncoding) {
+            // handle dummy UTF-16 and UTF-32 by scanning for BOM, as in MRI
+            byte[] bytes = byteList.unsafeBytes();
+            int p = byteList.begin();
+            int end = p + byteList.getRealSize();
+
+            if (enc == UTF16Dummy && end - p >= 2) {
+                int c0 = bytes[p] & 0xff;
+                int c1 = bytes[p + 1] & 0xff;
+
+                if (c0 == 0xFE && c1 == 0xFF) {
+                    return UTF16BEEncoding.INSTANCE;
+                } else if (c0 == 0xFF && c1 == 0xFE) {
+                    return UTF16LEEncoding.INSTANCE;
+                }
+                return ASCIIEncoding.INSTANCE;
+            } else if (enc == UTF32Dummy && end - p >= 4) {
+                int c0 = bytes[p] & 0xff;
+                int c1 = bytes[p + 1] & 0xff;
+                int c2 = bytes[p + 2] & 0xff;
+                int c3 = bytes[p + 3] & 0xff;
+
+                if (c0 == 0 && c1 == 0 && c2 == 0xFE && c3 == 0xFF) {
+                    return UTF32BEEncoding.INSTANCE;
+                } else if (c3 == 0 && c2 == 0 && c1 == 0xFE && c0 == 0xFF) {
+                    return UTF32LEEncoding.INSTANCE;
+                }
+                return ASCIIEncoding.INSTANCE;
             }
-            return ASCIIEncoding.INSTANCE;
         }
         return enc;
     }
diff --git a/lib/ruby/stdlib/pty.rb b/lib/ruby/stdlib/pty.rb
index 9f5e096..a68e2b9 100644
--- a/lib/ruby/stdlib/pty.rb
+++ b/lib/ruby/stdlib/pty.rb
@@ -5,8 +5,8 @@ module PTY
   module LibUtil
     extend FFI::Library
     ffi_lib FFI::Library::LIBC
-    # forkpty(3) is in libutil on linux, libc on MacOS/BSD
-    if FFI::Platform.linux?
+    # forkpty(3) is in libutil on linux and BSD, libc on MacOS
+    if FFI::Platform.linux? || (FFI::Platform.bsd? && !FFI::Platform.mac?)
       ffi_lib 'libutil'
     end
     attach_function :forkpty, [ :buffer_out, :buffer_out, :buffer_in, :buffer_in ], :pid_t