This file was previously overhauled to call strtod() and strtof(), fixing long-standing correctness and performance issues:

For binary compatibility, the new-ish machinery is activated by a sentinel value:

In vNext, we need to:

1. Eliminate the _ENABLE_V2_BEHAVIOR sentinel value and make it unconditional.
2. Eliminate lots of dead code (whole functions and source files).
3. Eliminate other dead logic; e.g. _Val *= _CSTD pow(10.0, static_cast<double>(_Pten)); is almost certainly dead (which is good, because it would be incorrect - anything that wants to multiply by a power of ten is highly suspicious) incorrect, see <xlocnum>: "multiply by power of 10" logic is imprecise #1582.

It may be possible to go further. Using charconv for iostreams floating-point would result in dramatic performance wins, but we'd have to solve issues like:

• Locale sensitivity
• Differing formats (e.g. 0x prefixes)
• Runtime rounding modes

vNext note: Resolving this issue will require breaking binary compatibility. We won't be able to accept pull requests for this issue until the vNext branch is available. See #169 for more information.