C++11 introduced the c16rtomb()/c32rtomb() conversion functions, along with the inverse (mbrtoc16()/mbrtoc32()). c16rtomb() clearly states in the reference documentation here:
The multibyte encoding used by this function is specified by the currently active C locale
The documentation for c32rtomb() states the same. Both the C and C++ versions agree that these are locale-dependent conversions (as they should be, according to the naming convention of the functions themselves).
However, MSVC seems to have taken a different approach and made them locale-independent (not using the current C locale) according to this document. These conversion functions are specified under the heading Locale-independent multibyte routines.
C++20 adds to the confusion by including the c8rtomb()/mbrtoc8() functions, which if locale-independent would basically do nothing, converting UTF-8 input to UTF-8 output.
Two questions arise from this:
- Do any other compilers actually follow the standard and implement locale-dependent Unicode multibyte conversion routines? I couldn't find any concrete information after extensive searching.
- Is this a bug in MSVC's implementation?