I was going to post his list of system languages that came before C (and were better/safer) but can't find his post. Notable examples, before or after C, are:
Burroughs' ALGOL's their safer OS was written in
https://en.wikipedia.org/wiki/Burroughs_large_systems#ALGOL
Modula-2 with its better readability and safety invented in Lilith homebrew system:
http://www.cfbsoftware.com/modula2/Lilith.pdf
Hansen's Concurrent Pascal was concurrency-safe in tiny runtime; Edison was C minimalism on same PDP-11 with cleaner, safer design
http://brinch-hansen.net/papers/
Modula-3 had many C++ advantages, Modula-style safety, and without C's BS:
https://en.wikipedia.org/wiki/Modula-3
Note: SPIN OS was written in it. Supported type-safe compilation and linking of code into running kernel for acceleration.
PL/I was one of predominant languages. IBM's mainframe OS's were written in a version of it (PL/S).
https://en.wikipedia.org/wiki/PL/I
Ada was systematically and cleverly designed for safety against most issues. Still is:
http://www.adacore.com/knowledge/technical-papers/safe-secur...
Note: Army Secure OS (ASOS), MarteOS, and Muen kernel were written in Ada leveraging its safety properties.
That should cover the ones that have been around since the 60's-80's. Doesn't even count functional-oriented languages like Common LISP, Schemes, or Standard ML. LISP had both OS's and CPU's made in it and for it. SML & Ocaml kicked ass in app correctness and compiler writing. Also ignored niche-specific ones like COBOL or Fortran that I thought weren't suitable for a C comparison.
Safe, C variants were even made to address its problems:
https://www.cs.uic.edu/pub/Main/PhDQualifyingExam/Sample4.pd...
Note: Cyclone concepts got rolled into Rust. So some benefit there.
There's also modern attempts like D, Go, and Rust that try to replace it to various degrees. Wirth's Modula work lives on in Active Oberon System and Go language. Almost all are moving in a direction with ALGOL68's features being the baseline. That there was better stuff before C on 1960's hardware suggests that people should've ditched it or fixed it up a long time ago when hardware limitations weren't holding it back anymore.
And let it be known that those are the only reason C was designed how it was. BCPL author actually wanted an ALGOL variant but hardware didn't work well enough. Rest was accidents of history. More detail that stretches further back than OP in this link:
http://pastebin.com/UAQaWuWG