Coverage counters

I recently encountered an error containing some output something along the lines of

undefined reference to `__stop___llvm_prf_cnts' ... undefined reference to `__stop___llvm_prf_names' ... undefined reference to `__start___llvm_prf_names' ... undefined reference to `__stop___llvm_prf_data'

To solve this (and this solution only works for Rust programs) one thing which is very likely to fix the error is to add -C instrument-coverage to your RUSTFLAGS, for example

RUSTFLAGS -C instrument-coverage cargo <the rest of the command>