@node stdnoreturn.h
@section @file{stdnoreturn.h}

POSIX specification:@* Not in POSIX yet, but we expect it will be.
ISO C11 (latest free draft
@url{http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf})
sections 7.23.

Gnulib module: stdnoreturn

Portability problems fixed by Gnulib:
@itemize
@item
This header file is missing on many platforms:
FreeBSD 6.4, NetBSD 7.1, OpenBSD 6.7, Minix 3.3.0, AIX 7.1, HP-UX 11.31, IRIX 6.5, Solaris 11.3, Cygwin 2.9.0, mingw, MSVC 14, Android 9.0.
@item
This file conflicts with some system header files, such as @code{<stdlib.h>} and
@code{<process.h>}, on some platforms:
MSVC/clang.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
@code{<stdnoreturn.h>} and the @code{noreturn} macro are obsolescent in C23.
@item
@code{<stdnoreturn.h>} cannot be #included in C++ mode on some platforms:
FreeBSD 13.1.
@item
@code{<stdnoreturn.h>} should be #included before @samp{_Noreturn} is used.
@item
You cannot assume that @code{_Noreturn} is a reserved word;
it might be a macro.
@item
When the macro @code{lint} is defined, standard headers define
@code{_Noreturn} (and therefore @code{noreturn}) to be a macro that
expands to the empty token sequence on some platforms:
Cygwin 2.5.1, FreeBSD 10.3.
@item
On Cygwin 1.7.30 and MSVC 14, @code{noreturn} expands to the empty token
sequence, to avoid problems with standard headers that use @code{noreturn}
in combination with @code{__attribute__} or @code{__declspec}.  Although
the resulting code operates correctly, the compiler is not informed whether
@code{noreturn} functions do not return, so it may generate incorrect
warnings at compile-time, or code that is slightly less optimized.  This
problem does not occur with @code{_Noreturn}.
@item
Circa 2012 bleeding-edge GCC with @code{-Werror=old-style-declaration}
requires @code{_Noreturn} or @code{noreturn} before the returned type
in a declaration, and therefore rejects valid but unusually-worded
declarations such as @code{void _Noreturn foo (void);}.
@end itemize