Fix coderange calculation in String#b

Leave the new coderange unknown if the original encoding is not
ASCII-compatible. Non-ASCII-compatible encoding strings with valid or
broken coderange can end up as ascii-only.

Fixes 9a8f6e392fbd ("Cheaply derive code range for String#b return
value", 2022-07-25).

1 files changed, 16 insertions, 14 deletions

diff --git a/string.c b/string.c
index c5711bcfe3..b455c8b7d9 100644
--- a/string.c
+++ b/string.c
@@ -10771,20 +10771,22 @@ rb_str_b(VALUE str)
     }
     str_replace_shared_without_enc(str2, str);
 
-    // BINARY strings can never be broken; they're either 7-bit ASCII or VALID.
-    // If we know the receiver's code range then we know the result's code range.
-    int cr = ENC_CODERANGE(str);
-    switch (cr) {
-      case ENC_CODERANGE_7BIT:
-        ENC_CODERANGE_SET(str2, ENC_CODERANGE_7BIT);
-        break;
-      case ENC_CODERANGE_BROKEN:
-      case ENC_CODERANGE_VALID:
-        ENC_CODERANGE_SET(str2, ENC_CODERANGE_VALID);
-        break;
-      default:
-        ENC_CODERANGE_CLEAR(str2);
-        break;
+    if (rb_enc_asciicompat(STR_ENC_GET(str))) {
+        // BINARY strings can never be broken; they're either 7-bit ASCII or VALID.
+        // If we know the receiver's code range then we know the result's code range.
+        int cr = ENC_CODERANGE(str);
+        switch (cr) {
+          case ENC_CODERANGE_7BIT:
+            ENC_CODERANGE_SET(str2, ENC_CODERANGE_7BIT);
+            break;
+          case ENC_CODERANGE_BROKEN:
+          case ENC_CODERANGE_VALID:
+            ENC_CODERANGE_SET(str2, ENC_CODERANGE_VALID);
+            break;
+          default:
+            ENC_CODERANGE_CLEAR(str2);
+            break;
+        }
     }
 
     return str2;