C++ Runtime: Signed/unsigned comparison in UnbufferedCharStream.cpp

[jm-mikkelsen]

In UnbufferedCharStream.cpp, there is a comparison between char_traits<char32_t>::eof and char_traits<wchar_t>::eof, leading to the following error with Clang 13.

C++ obj-FREEBSD/clang13/release/notpic/antlr4/runtime/Cpp/runtime/src/UnbufferedCharStream.o 
antlr4/runtime/Cpp/runtime/src/UnbufferedCharStream.cpp:101:41: error: comparison of integers of different signs: 'std::basic_string<char32_t>::value_type' (aka 'char32_t') and 'std::char_traits<wchar_t>::int_type' (aka 'int') [-Werror,-Wsign-compare]
  if (_data[static_cast<size_t>(index)] == std::char_traits<wchar_t>::eof()) {
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

The type of _data is std::u32string, which is defined as having a data type of char32_t.

The correct comparison should be:

  if (_data[static_cast<size_t>(index)] == std::char_traits<char32_t>::eof()) {