Internal Program Version: source-highlight  3.1.9

Source-highlight reads source language specifications dynamically, thus it can
be easily extended (without recompiling the sources) for handling new
languages. It also reads output format specifications dynamically, and thus it
can be easily extended (without recompiling the sources) for handling new
output formats. The syntax for these specifications is quite easy (take a look
at the manual).

libsource-highlight is a C++ library that provides the features of
Source-highlight.

https://www.gnu.org/software/src-highlite