mbsrtowcs
=========

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/mbsrtowcs.html

Gnulib module: mbsrtowcs

Portability problems fixed by Gnulib:

  * This function is missing on some platforms: Minix 3.1.8, HP-UX 11.00, IRIX 6.5, mingw.

  * This function does not work on some platforms: HP-UX 11, Solaris 11 2010-11.

  * In the C or POSIX locales, this function can return (size_t) -1 and set errno to EILSEQ: glibc 2.35.

  * This function does not work when the first argument is NULL on some platforms: mingw.

Portability problems not fixed by Gnulib:

  * On Windows and 32-bit AIX platforms, wchar_t is a 16-bit type and therefore cannot accommodate all Unicode characters. However, the Gnulib function mbsrtoc32s, provided by Gnulib module mbsrtoc32s, operates on 32-bit wide characters and therefore does not have this limitation.

  * The specification is not clear about whether this function should update the conversion state when the first argument (the destination pointer) is NULL. The glibc implementation does not update the state in this case; the macOS and FreeBSD implementations do. For portability, when passing a NULL destination argument, it is best to pass a pointer to a temporary copy of the conversion state.