After reading this and the related issue (https://github.com/cppalliance/charconv/issues/110) I actually strongly oppose the existing macro BOOST_CHARCONV_STD_ERANGE.
It doesn't change the behavior of the users application but that of the compiled (Boost) library. And if given a compiled library there is a) no way to know the actual behavior of `from_chars` and b) there could be(?) ODR violations when using the library statically.
As it seems to be only about whether the pass-by-reference value is modified it seems to be trivial to implement a wrapper around `boost::charconv::from_chars`, that is basically https://github.com/cppalliance/charconv/pull/111/files#diff-de4e106c65731933... I would even go as far as prodiving that function in Boost::CharConv, e.g. as `from_chars_strict` which could probably even be a template.
To reiterate: Having the BOOST_CHARCONV_STD_ERANGE macro (and similar ones) makes the behavior of from_chars unpredictable which to me would be a reason to reject the library. To me it would be better to have "wrong" behavior than unknown behavior.
Alex
Originally I was not keen on adding additional functions, but you're right this macro could make things non-deterministic. I'll revert the change, and add `from_chars_strict` instead. Matt