* io.c (io_encoding_set): handle nil for v1.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@14975 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -3,6 +3,8 @@ Thu Jan 10 10:15:03 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 	* io.c (io_encoding_set): IO.pipe("euc-jp", nil) should work as
 	  IO.pipe("euc-jp", nil).  [ruby-dev:33000]
 
+	* io.c (io_encoding_set): handle nil for v1.
+
 Thu Jan 10 02:41:22 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* io.c (rb_io_binmode): should not alter encoding.  [ruby-dev:32918]

io.c

@@ -5627,6 +5627,10 @@ io_encoding_set(rb_io_t *fptr, int argc, VALUE v1, VALUE v2)
 	fptr->enc = rb_to_encoding(v2);
     }
     else if (argc == 1) {
+	if if (NIL_P(v1)) {
+	    fptr->enc = 0;
+	}
+	else {
 	    VALUE tmp = rb_check_string_type(v1);
 	    if (!NIL_P(tmp)) {
 		mode_enc(fptr, StringValueCStr(tmp));
@@ -5635,6 +5639,7 @@ io_encoding_set(rb_io_t *fptr, int argc, VALUE v1, VALUE v2)
 		fptr->enc = rb_to_encoding(v1);
 	    }
 	}
+    }
 }
 
 /*