From: "tompng (tomoya ishida) via ruby-core" <ruby-core@...>
Date: 2024-01-16T13:31:24+00:00
Subject: [ruby-core:116228] [Ruby master Bug#20189] `rb_str_resize` does not clear coderange when expanding

Issue #20189 has been updated by tompng (tomoya ishida).





I think so. sjis char does not end with null bytes, other encoding seems same too.



~~~ruby

Encoding.list.select {|e|

  256.times.any? do |first_byte|

    a = first_byte.chr

    b = a + "\0";

    # only one of \x??\x00 and \x?? is valid

    a.force_encoding(e).valid_encoding? != b.force_encoding(e).valid_encoding?

  end

}

# => [#<Encoding:UTF-16BE>, #<Encoding:UTF-16LE>]

~~~



It looks like there is no string like ("���"(sjis)=="\x95\x5c") that satisfies "\x??\x00" is valid and "\x??" is not.



I opened a pull request https://github.com/ruby/ruby/pull/9552



----------------------------------------

Bug #20189: `rb_str_resize` does not clear coderange when expanding

https://bugs.ruby-lang.org/issues/20189#change-106247



* Author: tompng (tomoya ishida)

* Status: Open

* Priority: Normal

* ruby -v: ruby 3.4.0dev (2024-01-09T07:07:19Z master db476cc71c) [x86_64-linux]

* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN

----------------------------------------

Expanding string in some encoding (utf16 utf32) can change coderange to either valid or broken, but rb_str_resize does not clear coderange.





This will cause a bug in c-extension libraries that use rb_str_resize.

~~~ruby

# Example for stringio

s = StringIO.new("\0".encode('UTF-16LE'))



s.truncate(1); s.truncate(2); s.string.valid_encoding?

#=> true

s.truncate(1); s.string.valid_encoding?; s.truncate(2); s.string.valid_encoding?

#=> false (expect to be true)

~~~









-- 

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