You got me thinking about C/C++ style guides of my youth...

I think Indian Hill (C, not C++) was the first one I ever read: https://www2.cs.arizona.edu/~mccann/cstyle.html

Looks like there is an updated version (1997) here: https://www.cs.cornell.edu/people/egs/comp303/tutorials/csty...

Paul Haeberli's "The SGI C Source Compliance Requirements" is hard to forget: https://www.graficaobscura.com/ccode/index.html

I wonder whether there is a centralised historical archive of C/C++ style guides?

The modern staples are covered here, I guess:

https://github.com/kciter/awesome-style-guide#cpp