Also see Templates in C by David Priver - https://www.davidpriver.com/ctemplates.html

He also has other interesting C techniques, namely;

Adding reflection to C - https://news.ycombinator.com/item?id=49964525

_Generic for Type Reification in C - https://www.davidpriver.com/creification.html

See also his C2y interpreter with REPL named "DrC" for the upcoming C29 standard (https://en.wikipedia.org/wiki/C29_(C_standard_revision)) - https://github.com/drpriver/drc

PS: I really like his style of writing and presentation; concise and precise without unnecessary fluff and page beautifying.