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, 81 insertions, 0 deletions

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);
+}