Bug #22516: Emacs-Mule accepts a code point whose first byte is below 0x80 in format("%c")

• Status: Open
• Assignee: -
• Target version: -
• Backport: 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED

[mame (Yusuke Endoh)]

format("%c") in Emacs-Mule accepts a code point that Integer#chr rejects, and writes more bytes than it allocated.

fmt = ("a" * 100 + "%c").force_encoding("Emacs-Mule")

p format(fmt, 0x01018000)
# expected: ArgumentError (invalid character)
# actual:   "aaa...aaa\x01\x01" (the other 2 bytes "\x80\x00" of the character are written past the buffer)

p 0x01018000.chr("Emacs-Mule") #=> #<RangeError: invalid codepoint 0x1018000 in Emacs-Mule> (as expected)

[mame (Yusuke Endoh)]

https://github.com/ruby/ruby/pull/19792