C would really need some serious overhaul as it still can’t be used to implement even the most basics of zero-cost abstractions, like sane strings or a vector. So I’m not sure it’s a great example.
It's certainly possible to build a compiler in C for a language that provides zero cost abstractions.
The same way it is possible in Brainfuck or powerpoint — that’s just Turing-completeness and outputting a binary file.
Sure, but your statement about C remains false.
Being pedantic, it is either true and completely useless, xor false. Feel free to believe any of the options, it won’t make a sane vector implementation in the language possible for generic datatypes.
Your statement that C cannot be used to implement zero cost abstractions is factually false. There are no other options here. You said something that is incorrect.