Highlight new C++ keywords introduced in C++11, C++17, and C++20 in the listings package

Question

C++11 added a bunch of new keywords: alignas, alignof, constexpr, etc. But they don't seem to be supported by the listings package.

\documentclass{article}

\usepackage{listings}
\usepackage{xcolor}

\lstset{
  language = [11]C++,
  basicstyle = \ttfamily,
  keywordstyle = \color{blue},
  columns = flexible
}

\begin{document}

\begin{lstlisting}
  constexpr int i = 0;
\end{lstlisting}

\end{document}

The constexpr is not recognized as a keyword:

Expected output:

How can I enable the C++11 keywords? How about C++20 keywords like requires, concept, consteval, etc.?

(Note: This is a self-answer question. I know this question can be closed as a duplicate of many others, such as Extend a language with additional keywords?, but they do not specifically address new C++ keywords. I am frequently asked about this, and I also need this very often, so I decided to write it down for future reference.)

Answer 1

(Reference: https://en.cppreference.com/w/cpp/keyword)

C++11 keywords

The listings package has built in support for C++11. Use language = [11]C++ option to alignas (no pun intended) C++11:

\documentclass{article}

\usepackage{listings}
\usepackage{xcolor}

\lstset{
  language = [11]C++,
  basicstyle = \ttfamily,
  keywordstyle = \color{blue},
  columns = flexible
}

\begin{document}

\begin{lstlisting}
  constexpr int i = 0;
\end{lstlisting}

\end{document}

This yields the desired result:

C++11 identifiers with special meaning

Treated as keywords

C++11 introduces two identifiers with special meaning: override and final. By default, they are not highlighted. You can add them manually to the keyword list:

\lstset{
  morekeywords = {final, override}
}

Minimal example:

\documentclass{article}

\usepackage{listings}
\usepackage{xcolor}

\lstset{
  language = [11]C++,
  basicstyle = \ttfamily,
  keywordstyle = \color{blue},
  columns = flexible
}

\lstset{
  morekeywords = {final, override}
}

\begin{document}

\begin{lstlisting}
  override
  final
\end{lstlisting}

\end{document}

This yields:

Treated specially

If you want differentiate between keywords and identifiers with special meaning, you can override (no pun intended) this by introducing a special emphasis class for them:

\lstset{
  emph = {[11]final, override},
  emphstyle = \color{green}
}

Minimal example:

\documentclass{article}

\usepackage{listings}
\usepackage{xcolor}

\lstset{
  language = [11]C++,
  basicstyle = \ttfamily,
  keywordstyle = \color{blue},
  columns = flexible
}

\lstset{
  emph = {[11]final, override},
  emphstyle = \color{green}
}

\begin{document}

\begin{lstlisting}
  constexpr
  override
  final
\end{lstlisting}

\end{document}

This yields the final (no pun intended) result:

Other

For future reference, here I give the list of C++20 keywords, C++20 identifiers with special meaning, etc. If the maintainer of the listings package sees this, please add the relevant part to language = [20]C++!

C++20 keywords

\lstset{
  morekeywords = {
    char8_t,
    concept,
    co_await,
    co_return,
    co_yield,
    requires
  }
}

C++20 identifiers with special meaning

\lstset{
  emph = {[20]
    import,
    module
  }
}

(Note: the original version included audit and axiom. The Contract TS was later removed from C++20, so audit and axiom are no longer identifiers with special meaning in C++20.)

Transactional Memory Technical Specification (TM TS) keywords

\lstset{
  morekeywords = {
    atomic_cancel,
    atomic_commit,
    atomic_noexcept,
    synchronized
  }
}

Transactional Memory Technical Specification (TM TS) identifiers with special meaning

\lstset{
  emph = {[42]
    transaction_safe,
    transaction_dynamic
  }
}

Reflection TS

\lstset{
  morekeywords = {
    reflexpr
  }
}

---

(Note: all numbers were chosen arbitrarily. Don't forget to adjust them to avoid name clash with existing identifier classes!)