[jk-jeon]

A way to achieve perfect round-tripping was proposed back in 1990, by Steele and White (and likely they are not the first ones who came up with a similar idea). I guess their proposal probably wasn't extremely popular at least until 2000's, compared to more classical `printf`-like rounding methods, but it seems many languages and platforms these days do provide such round-tripping formatting algorithms as the default option. So, I guess nowadays roundtripping isn't that hard, unless people do something sophisticated without really understanding what they're doing.

[ape4]

"How to print floating-point numbers accurately" by Steele & White https://dl.acm.org/doi/10.1145/93548.93559

[lifthrasiir]

I do think the OP was worrying about such people. Now a performant and correctly rounded JSON library is reasonably common, but it was not the case a decade ago (I think).

[kccqzy]

Interesting! I didn't know about Steele and White's 1990 method. I did however remember the Burger and Dybvig's method from 1996.