No compatibility check in US-ASCII case

ruby · Jul 19, 2020 · 59df1c8 · 59df1c8
1 parent 1d28e5c
commit 59df1c8
Show file tree

Hide file tree

Showing 2 changed files with 9 additions and 2 deletions.
diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
@@ -1429,14 +1429,15 @@ strio_write(VALUE self, VALUE str)
     long len, olen;
     rb_encoding *enc, *enc2;
     rb_encoding *const ascii8bit = rb_ascii8bit_encoding();
+    rb_encoding *usascii = 0;
 
     if (!RB_TYPE_P(str, T_STRING))
 	str = rb_obj_as_string(str);
     enc = get_enc(ptr);
     enc2 = rb_enc_get(str);
-    if (enc != enc2 && enc != ascii8bit) {
+    if (enc != enc2 && enc != ascii8bit && enc != (usascii = rb_usascii_encoding())) {
 	VALUE converted = rb_str_conv_enc(str, enc2, enc);
-	if (converted == str && enc2 != ascii8bit) { /* conversion failed */
+	if (converted == str && enc2 != ascii8bit && enc2 != usascii) { /* conversion failed */
 	    rb_enc_check(rb_enc_from_encoding(enc), str);
 	}
 	str = converted;

diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
@@ -195,9 +195,15 @@ def test_write_encoding_conversion
     s = StringIO.new.set_encoding(conversion_encoding)
     s.write(convertible)
     assert_equal(conversion_encoding, s.string.encoding)
+
     s = StringIO.new.set_encoding(Encoding::UTF_8)
     s.write("foo".force_encoding("ISO-8859-1"), convertible)
     assert_equal(Encoding::UTF_8, s.string.encoding)
+
+    s = StringIO.new.set_encoding(Encoding::US_ASCII)
+    s.write("foo".force_encoding("US-ASCII"), convertible)
+    assert_equal(Encoding::UTF_8, s.string.encoding)
+
     all_assertions do |a|
       [
         inconvertible,