For an example of what Greg Maxwell might consider "adequate testing", see https://www.ietf.org/proceedings/82/slides/codec-4.pdf (he is the one responsible for all of the testing described in that presentation).

Slide 20 lists no less than 8 toolchain bugs found with a codebase of less than 50k lines of C code (no C++), using only thoroughly trodden language features, without "massive functions" or anything else. Admittedly 4 of those bugs were in pre-release versions of gcc, but the rest weren't.