[ruby-core:109655] [Ruby master Bug#18973] Kernel#sprintf: %c allows codepoints above 127 for 7-bits ASCII encoding

Issue #18973 has been updated by nobu (Nobuyoshi Nakada).


Sorry, this.
```diff
diff --git a/enc/us_ascii.c b/enc/us_ascii.c
index 08f9072c435..9d854b12245 100644
--- a/enc/us_ascii.c
+++ b/enc/us_ascii.c
@@ -7,6 +7,12 @@
 # define ENCINDEX_US_ASCII 0
 #endif
 
+static int
+us_ascii_code_to_mbclen(OnigCodePoint code ARG_UNUSED, OnigEncoding enc ARG_UNUSED)
+{
+  return !(code & 0x80);
+}
+
 static int
 us_ascii_mbc_enc_len(const UChar* p, const UChar* e, OnigEncoding enc)
 {
@@ -22,7 +28,7 @@ OnigEncodingDefine(us_ascii, US_ASCII) = {
   1,           /* min byte length */
   onigenc_is_mbc_newline_0x0a,
   onigenc_single_byte_mbc_to_code,
-  onigenc_single_byte_code_to_mbclen,
+  us_ascii_code_to_mbclen,
   onigenc_single_byte_code_to_mbc,
   onigenc_ascii_mbc_case_fold,
   onigenc_ascii_apply_all_case_fold,
```

----------------------------------------
Bug #18973: Kernel#sprintf: %c allows codepoints above 127 for 7-bits ASCII encoding
https://bugs.ruby-lang.org/issues/18973#change-98878

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* Priority: Normal
* ruby -v: 3.0.3
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
I've noticed the following behavior:

```ruby
sprintf("%c".encode("US-ASCII"), 128)
=> "\x80"

sprintf("%c".encode("US-ASCII"), 128).valid_encoding?
=> false
```

Specifying codepoints 128-255 for ASCII encoded formatting sequence leads to a broken string.

```ruby
sprintf("%c".encode("US-ASCII"), 255)
=> "\xFF"
sprintf("%c".encode("US-ASCII"), 256)
(irb):17:in `sprintf': 256 out of char range (RangeError)
```

Specifying codepoint greater that 255 causes the expected exception `out of char range`.

I suppose this exception should be raised for codepoints 128-255 as well (for ASCII encoding).



-- 
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