@node mbrtoc16
@subsection @code{mbrtoc16}
@findex mbrtoc16

ISO C23 specification:@* @url{https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf} section 7.30.1.3.

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9799919799/functions/mbrtoc16.html}

Gnulib module: mbrtoc16
@mindex mbrtoc16

Portability problems fixed by Gnulib:
@itemize
@item
This function is missing on most non-glibc platforms:
glibc 2.15, macOS 14, FreeBSD 6.4, NetBSD 10.0, OpenBSD 7.3, Minix 3.1.8, AIX 7.1, HP-UX 11.31, Solaris 11.3, Cygwin 3.4.x, mingw, MSVC 9, Android 4.4.
@item
This function may crash when the first argument is NULL on some platforms:
@c https://sourceware.org/bugzilla/show_bug.cgi?id=28898
glibc 2.36.
@item
In the C or POSIX locales, this function can return @code{(size_t) -1}
and set @code{errno} to @code{EILSEQ}:
@c https://sourceware.org/bugzilla/show_bug.cgi?id=19932
@c https://sourceware.org/bugzilla/show_bug.cgi?id=29511
glibc 2.36.
@item
This function returns 0 instead of @code{(size_t) -2} when the input
is empty:
@c https://sourceware.org/bugzilla/show_bug.cgi?id=16950
glibc 2.19,
@c https://issuetracker.google.com/issues/289419880
Android 11.
@item
This function returns the total number of bytes that make up the multibyte
character, not the number of bytes that were needed to complete the multibyte
character, on some platforms:
mingw.
@item
This function returns @code{(size_t) -3} instead of a byte count when it
has stored a high surrogate, and returns a byte count instead of
@code{(size_t) -3} when it has stored a low surrogate, on some platforms:
@c https://issuetracker.google.com/issues/289419882
Android.
@item
This function does not recognize multibyte sequences that @code{mbrtowc}
recognizes on some platforms:
@c https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=272293
FreeBSD 13.2,
Solaris 11.4, MSVC 14.
@c For MSVC this is because it assumes that the input is always UTF-8 encoded.
@c See https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/mbrtoc16-mbrtoc323
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
@c https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=272218
After @code{mbrtoc16} returns a @code{char16_t} value, @code{mbsinit}
cannot be used to determine whether the function is ready to return
another @code{char16_t} value.  To do so, instead call @code{mbrtoc16}
again, with an appropriately incremented @code{const char *} argument
and an appropriately decremented @code{size_t} argument.
@end itemize
