io.c: fix 7bit coderange condition

* io.c (io_getc): fix 7bit coderange condition, check if ascii read
  data instead of read length. [ruby-core:55444] [Bug #8516]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41250 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 1 deletions

diff --git a/io.c b/io.c
index aef0e4609d..aef5ab2236 100644
--- a/io.c
+++ b/io.c
@@ -3411,7 +3411,11 @@ io_getc(rb_io_t *fptr, rb_encoding *enc)
 	}
 	else {
 	    io_shift_cbuf(fptr, MBCLEN_CHARFOUND_LEN(r), &str);
-	    cr = ISASCII(r) ? ENC_CODERANGE_7BIT : ENC_CODERANGE_VALID;
+	    cr = ENC_CODERANGE_VALID;
+	    if (MBCLEN_CHARFOUND_LEN(r) == 1 && rb_enc_asciicompat(read_enc) &&
+		ISASCII(RSTRING_PTR(str)[0])) {
+		cr = ENC_CODERANGE_7BIT;
+	    }
 	}
 	str = io_enc_str(str, fptr);
 	ENC_CODERANGE_SET(str, cr);