Implement quick_exit() / at_quick_exit() from C++11 / C1x. Also add a

__noreturn macro and modify the other exiting functions to use it.

The __noreturn macro, unlike __dead2, must be used BEFORE the function.
This is in line with the C and C++ specifications that place _Noreturn (c1x)
and [[noreturn]] (C++11) in front of the functions.  As with __dead2, this
macro falls back to using the GCC attribute.

Unfortunately, clang currently sets the same value for the C version macro
in C99 and C1x modes, so these functions are hidden by default.  At some
point before 10.0, I need to go through the headers and clean up the C1x /
C++11 visibility.

Reviewed by:	brooks (mentor)

1 files changed, 58 insertions, 0 deletions

diff --git a/lib/libc/stdlib/at_quick_exit.3 b/lib/libc/stdlib/at_quick_exit.3
new file mode 100644
index 0000000..241553f
--- /dev/null
+++ b/lib/libc/stdlib/at_quick_exit.3
@@ -0,0 +1,58 @@
+.\"  Copyright (c) 2011 David Chisnall
+.\"  All rights reserved.
+.\" 
+.\"  Redistribution and use in source and binary forms, with or without
+.\"  modification, are permitted provided that the following conditions
+.\"  are met:
+.\"  1. Redistributions of source code must retain the above copyright
+.\"     notice, this list of conditions and the following disclaimer.
+.\"  2. Redistributions in binary form must reproduce the above copyright
+.\"     notice, this list of conditions and the following disclaimer in the
+.\"     documentation and/or other materials provided with the distribution.
+.\" 
+.\"  THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\"  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\"  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\"  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\"  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\"  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\"  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\"  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\"  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\"  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\"  SUCH DAMAGE.
+.\" 
+.\"  $FreeBSD$
+.\" /
+.Dd December 7, 2011o.Dt ATEXIT 3
+.Dt AT_QUICK_EXIT 3
+.Os
+.Sh NAME
+.Nm at_quick_exit
+.Nd Registers a cleanup function to run on quick exit.
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In stdlib.h
+.Ft int
+.Fn at_quick_exit "void (*func)(void)"
+.Sh DESCRIPTION
+The
+.Fn at_quick_exit
+function registers a cleanup function to be called when the program exits as a
+result of calling 
+.Xr quick_exit 3 .
+The cleanup functions are called in the reverse order and will not be called if
+the program exits by calling 
+.Xr exit 3 ,
+.Xr _Exit 3 ,
+or
+.Xr abort 3 .
+.El
+.Sh SEE ALSO
+.Xr exit 3 ,
+.Xr at_quick_exit 3
+.Sh STANDARDS
+The
+.Fn at_quick_exit
+function conforms to the C1x draft specification.