On Thu, 19 Jun 2025, 12:34 Mathieu Malaterre via Gcc-help, < gcc-help@xxxxxxxxxxx> wrote: > Dear all, > > I am reading the following note taken from url (*) > > [...] > The guarantee that std::from_chars can recover every floating-point > value formatted by std::to_chars exactly is only provided if both > functions are from the same implementation. > [...] > > Could some gurus please confirm my understanding of the above note for > *finite* and/or *normal* numbers (not interested in the special > nan/inf case) ? > > My understanding is that: GCC and MSVC may output a different ASCII > text given the same inupt floating-point value (bitwise identical). > Or in other words, you're assuming that the note refers to formatting bitwise identical values. It doesn't. The point is that a 'double' on one implementation is not required to be bitwise identical to a 'double' on a different implementation. C++ does not require IEEE representations, and so there's no guarantee of identical bit patterns for any given value. >
