It would have been bootstrapped in assembly (or B/BCPL?) and then once you can compile enough C to write a C compiler you rewrite your compiler in C.

I remember a Computerphile video where prof. Brailsford said something along the lines of "nobody knew who wrote the first C compiler, everybody just kinda had it and passed it around the office" which I think is funny. There's some sort of analogy to life and things emerging from the primordial soup there, if you squint hard enough.

yes. the Q you're asking is: "how was this bootstrapped?"

the page that's referenced from GitHub doesn't describe that

http://cm.bell-labs.co/who/dmr/primevalC.html

however there probably was a running c compiler (written in assembly) and an assembler and a linker available, hand bootstrapped from machine code, then assembler, linker, then B, NB and then C...

We can't tell but that would make sense...

The first B compiler was written in BCPL on the GE 635 mainframe. Thompson wrote a B compiler in BCPL which they used to cross-compile for PDP-7. Then Thompson rewrote B in B, using the BCPL compiler to bootstrap. AFAIK this is the only clean "bootstrap" step involved in the birth of C (BCPL -> B -> self-compiled B)

Then they tweaked the compiler and called it NB (New B), then eventually tweaked it enough they decided to call it C.

The compiler continuously evolved by compiling new versions of itself through the B -> New B -> C transition. There was no clean cutoff to say "ah this was the first C compiler written in New B".

You can see evidence of this in the "pre-struct" version of the compiler after Ritchie had added structure support but before the compiler itself actually used structs. They compiled that version of the compiler then modified the compiler source to use structs, thus all older versions of the compiler could no longer compile the compiler: https://web.archive.org/web/20140708222735/http://thechangel...

Primeval C: https://web.archive.org/web/20140910102704/http://cm.bell-la...

A modern bootstrapping compiler usually keeps around one or more "simplified" versions of the compiler's source. The simplest one either starts with C or assembly. Phase 0 is compiled or assembled then is used to compile Phase 1, which is used to compile Phase 2.

(Technically if you parsed through all the backup tapes and restored the right versions of old compilers and compiler source you'd have the bootstrap chain for C but no one bothered to do that until decades later).