To be clear, David Gay's dtoa is not a modern implementation of decimal-to-float conversion. There had been several much simpler and performant alternatives, including:

- Google's double-conversion [1], which is best known for introducing the Grisu family of new float-to-decimal algorithms but also has a much less documented float-to-decimal algorithm via successive approximations AFAIK.

- The Eisel-Lemire algorithm [2], which is a Grisu3-like algorithm and returns either correct digits or a much rare fallback signal and currently in the standard libraries of Go and Rust.

- I believe Microsoft's own C Runtime (msvcrt, later ucrt) also has a completely separate code which algorithm is roughly similar to one of above.

These implementations also clearly demonstrate that such conversion only needs a bigint support of the bounded size (~3 KB) and can be done in much smaller code than dtoa.

[1] https://github.com/google/double-conversion

[1] https://lemire.me/blog/2020/03/10/fast-float-parsing-in-prac...