`\u00{80..ff}` characters in string literals are translated incorrectly in some languages

[generalmimon]

For example, if you parse a UTF-8 string with the U+00A3 POUND SIGN (£) character and test it for equality with the "£" string literal (or equivalently "\u00a3"), you'll get false in some target languages.

Below is a reproducible .ksy snippet that assumes a binary input c2 a3 (this is the pound sign encoded in UTF-8 using Python: "\u00a3".encode('utf-8').hex(' ') == 'c2 a3', "\u00a3" == '£'):

meta:
  id: str_literals_latin1
seq:
  - id: parsed
    size: 2
    type: str
    encoding: UTF-8
instances:
  parsed_eq_literal:
    value: parsed == "\u00a3"

According to my tests, parsed_eq_literal will be false in C++, Go, Lua, Nim, PHP and Ruby. This indicates that in these languages, the string literal "\u00a3" was translated incorrectly, as it apparently doesn't represent a UTF-8 string with the U+00A3 character (i.e. the pound sign):

$ grep -ri 'parsed_\?eq_\?literal.* =' -B1 | grep -F '\'
cpp_stl_11/str_literals_latin1.cpp:    m_parsed_eq_literal = parsed() == (std::string("\243"));
cpp_stl_98/str_literals_latin1.cpp:    m_parsed_eq_literal = parsed() == (std::string("\243"));
go/src/test_formats/str_literals_latin1.go:     this.parsedEqLiteral = bool(this.Parsed == "\243")
graphviz/str_literals_latin1.dot:                       <TR><TD>parsed_eq_literal</TD><TD>parsed == &quot;\243&quot;</TD></TR>
lua/str_literals_latin1.lua:  self._m_parsed_eq_literal = self.parsed == "\243"
nim/str_literals_latin1.nim:  let parsedEqLiteralInstExpr = bool(this.parsed == "\243")
php/StrLiteralsLatin1.php:            $this->_m_parsedEqLiteral = $this->parsed() == "\243";
ruby/str_literals_latin1.rb:    @parsed_eq_literal = parsed == "\243"

In contrast, in C#, Java, JavaScript, Perl, Python and Rust, the parsed_eq_literal instance evaluates to true, so we can say that "\u00a3" was translated correctly for these target languages:

construct/str_literals_latin1.py:       'parsed_eq_literal' / Computed(lambda this: this.parsed == u"\243"),
csharp/StrLiteralsLatin1.cs:                _parsedEqLiteral = (bool) (Parsed == "\u00a3");
java/src/io/kaitai/struct/testformats/StrLiteralsLatin1.java-        boolean _tmp = (boolean) (parsed().equals("\243"));
javascript/StrLiteralsLatin1.js:      this._m_parsedEqLiteral = this.parsed == "\xa3";
perl/StrLiteralsLatin1.pm:    $self->{parsed_eq_literal} = $self->parsed() eq "\243";
python/str_literals_latin1.py:        self._m_parsed_eq_literal = self.parsed == u"\243"
rust/str_literals_latin1.rs:        *self.parsed_eq_literal.borrow_mut() = (*self.parsed() == "\u{a3}".to_string()) as bool;

[generalmimon]

To see which characters are affected, see the C1 Controls and Latin-1 Supplement table at https://en.wikibooks.org/wiki/Unicode/Character_reference/0000-0FFF