Document: N1373
Title: Wording improvements for mblen, mbtowc, and c16rtomb
Date: 2009-03-24
Author: P.J. Plauger

it is equivalent to
mbtowc((wchar_t *)0, (const char *)0, 0); // ADDED
mbtowc((wchar_t *)0, s, n);
ADD to description:
If multibyte characters have a state-dependent encoding, the function stores the initial conversion state in an internal static-duration object at program startup. It updates this object on each call to reflect the current conversion state. If s is a null pointer, the resulting conversion state is the initial conversion state.
ADD after "(including any shift sequences)" in Description:
using the conversion state stored at *ps,
ADD after "(including any shift sequences)" in Returns:
and stores the resulting conversion state at *ps