Except it is not a loop[1], but a non-tail recursive function (with dual calls), if the compiler can optimise that to a loop that is actually impressive.

Most likely function call overhead (and in the slower cases, interpreter overhead) is probably what is being measured in the best case.

[1] In that it won't be a jump and check style loop.

> Most likely function call overhead

Quite likely: https://godbolt.org/g/xGkCyA although it really depends on the compiler (gcc is smarter here). He also seems to be benchmarking printing more than anything else (hence the difference between C and C++).

Without versions of the compilers and explained methods of measurement, the results posted on the blog are more anecdotal knowledge than any kind of benchmark.