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)

7 files changed, 204 insertions, 3 deletions

diff --git a/lib/libc/stdlib/Makefile.inc b/lib/libc/stdlib/Makefile.inc
index 3627294..7db0f60 100644
--- a/lib/libc/stdlib/Makefile.inc
+++ b/lib/libc/stdlib/Makefile.inc
@@ -8,8 +8,8 @@ MISRCS+=_Exit.c a64l.c abort.c abs.c atexit.c atof.c atoi.c atol.c atoll.c \
 	bsearch.c div.c exit.c getenv.c getopt.c getopt_long.c \
 	getsubopt.c hcreate.c heapsort.c imaxabs.c imaxdiv.c \
 	insque.c l64a.c labs.c ldiv.c llabs.c lldiv.c lsearch.c malloc.c \
-	merge.c ptsname.c qsort.c qsort_r.c radixsort.c rand.c random.c \
-	reallocf.c realpath.c remque.c strfmon.c strtoimax.c \
+	merge.c ptsname.c qsort.c qsort_r.c quick_exit.c radixsort.c rand.c \
+	random.c reallocf.c realpath.c remque.c strfmon.c strtoimax.c \
 	strtol.c strtoll.c strtoq.c strtoul.c strtonum.c strtoull.c \
         strtoumax.c strtouq.c system.c tdelete.c tfind.c tsearch.c twalk.c
 
@@ -18,10 +18,12 @@ SYM_MAPS+= ${.CURDIR}/stdlib/Symbol.map
 # machine-dependent stdlib sources
 .sinclude "${.CURDIR}/${LIBC_ARCH}/stdlib/Makefile.inc"
 
-MAN+=	a64l.3 abort.3 abs.3 alloca.3 atexit.3 atof.3 atoi.3 atol.3 bsearch.3 \
+MAN+=	a64l.3 abort.3 abs.3 alloca.3 atexit.3 atof.3 atoi.3 atol.3 \
+	at_quick_exit.3 bsearch.3 \
 	div.3 exit.3 getenv.3 getopt.3 getopt_long.3 getsubopt.3 \
 	hcreate.3 imaxabs.3 imaxdiv.3 insque.3 labs.3 ldiv.3 llabs.3 lldiv.3 \
 	lsearch.3 malloc.3 memory.3 posix_memalign.3 ptsname.3 qsort.3 \
+	quick_exit.3 \
 	radixsort.3 rand.3 random.3 \
 	realpath.3 strfmon.3 strtod.3 strtol.3 strtonum.3 strtoul.3 system.3 \
 	tsearch.3
diff --git a/lib/libc/stdlib/Symbol.map b/lib/libc/stdlib/Symbol.map
index c268ab9..897bccd 100644
--- a/lib/libc/stdlib/Symbol.map
+++ b/lib/libc/stdlib/Symbol.map
@@ -97,6 +97,8 @@ FBSD_1.3 {
 	atoi_l;
 	atol_l;
 	atoll_l;
+	at_quick_exit;
+	quick_exit;
 	strtod_l;
 	strtol_l;
 	strtoll_l;
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.
diff --git a/lib/libc/stdlib/atexit.3 b/lib/libc/stdlib/atexit.3
index 3c44b8d..3a514b9 100644
--- a/lib/libc/stdlib/atexit.3
+++ b/lib/libc/stdlib/atexit.3
@@ -79,6 +79,7 @@ No memory was available to add the function to the list.
 The existing list of functions is unmodified.
 .El
 .Sh SEE ALSO
+.Xr at_quick_exit 3
 .Xr exit 3
 .Sh STANDARDS
 The
diff --git a/lib/libc/stdlib/exit.3 b/lib/libc/stdlib/exit.3
index a864ccb..4547efe 100644
--- a/lib/libc/stdlib/exit.3
+++ b/lib/libc/stdlib/exit.3
@@ -118,7 +118,9 @@ never return.
 .Xr _exit 2 ,
 .Xr wait 2 ,
 .Xr atexit 3 ,
+.Xr at_quick_exit 3 ,
 .Xr intro 3 ,
+.Xr quick_exit 3 ,
 .Xr sysexits 3 ,
 .Xr tmpfile 3
 .Sh STANDARDS
diff --git a/lib/libc/stdlib/quick_exit.3 b/lib/libc/stdlib/quick_exit.3
new file mode 100644
index 0000000..e29112f
--- /dev/null
+++ b/lib/libc/stdlib/quick_exit.3
@@ -0,0 +1,55 @@
+.\"  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 QUICK_EXIT 3
+.Os
+.Sh NAME
+.Nm quick_exit
+.Nd Exits a program quickly, running minimal cleanup
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In stdlib.h
+.Ft _Noreturn void
+.Fn quick_exit "void"
+.Sh DESCRIPTION
+The
+.Fn quick_exit
+function exits the program quickly calling any cleanup functions registered
+with
+.Xr at_quick_exit 3
+but not any C++ destructors or cleanup code registered with
+.Xr atexit 3 .
+.El
+.Sh SEE ALSO
+.Xr exit 3 ,
+.Xr at_quick_exit 3
+.Sh STANDARDS
+The
+.Fn quick_exit
+function conforms to the C1x draft specification.
+
diff --git a/lib/libc/stdlib/quick_exit.c b/lib/libc/stdlib/quick_exit.c
new file mode 100644
index 0000000..11e22da
--- /dev/null
+++ b/lib/libc/stdlib/quick_exit.c
@@ -0,0 +1,81 @@
+/*-
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#include <stdlib.h>
+#include <pthread.h>
+
+/**
+ * Linked list of quick exit handlers.  This is simpler than the atexit()
+ * version, because it is not required to support C++ destructors or
+ * DSO-specific cleanups.
+ */
+struct quick_exit_handler {
+	struct quick_exit_handler *next;
+	void (*cleanup)(void);
+};
+
+__attribute((weak))
+void _ZSt9terminatev(void);
+
+/**
+ * Lock protecting the handlers list.
+ */
+static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
+/**
+ * Stack of cleanup handlers.  These will be invoked in reverse order when 
+ */
+static struct quick_exit_handler *handlers;
+
+int
+at_quick_exit(void (*func)(void))
+{
+	struct quick_exit_handler *h = malloc(sizeof(struct quick_exit_handler));
+
+	if (0 == h) {
+		return 1;
+	}
+	h->cleanup = func;
+	pthread_mutex_lock(&atexit_mutex);
+	h->next = handlers;
+	handlers = h;
+	pthread_mutex_unlock(&atexit_mutex);
+	return 0;
+}
+
+void quick_exit(int status)
+{
+	/*
+	 * XXX: The C++ spec requires us to call std::terminate if there is an
+	 * exception here.
+	 */
+	for (struct quick_exit_handler *h = handlers ; NULL != h ; h = h->next)
+	{
+		h->cleanup();
+	}
+	_Exit(status);
+}