Perhaps better than a book, can anyone authoritatively point to a few small-and-readable but best-in-class open-source C projects to use as a reference?

Crypto library in the size of a hundred tweets [ https://twitter.com/tweetnacl ] by the only person with a genuine claim to being able to write safe C & company.

* https://github.com/mit-pdos/xv6-public

&

* https://github.com/mit-pdos/xv6-riscv

UNIX v6 clone in ANSI C by influential Plan 9-era Bell Laboratories employee and now influential Google employee Russ Cox, along with influential computer virus author and son of one of the original UNIX authors Robert T. Morrison; entire source code fits in under a hundred pages of well-typeset documents [ warning, old copy, you should generate a modern one: https://pdos.csail.mit.edu/6.828/2011/xv6/xv6-rev6.pdf ].