From 22ca1336dcfb663d86a6892dbe1e48eee20bb6db Mon Sep 17 00:00:00 2001
From: dim <dim@FreeBSD.org>
Date: Wed, 5 Mar 2014 19:30:36 +0000
Subject: MFC r261283:

Import libc++ 3.4 release.  This contains a lot of bugfixes, and some
preliminary support for C++1y.

MFC r261604:

HEAD is not buildable for the past day.  Commit a 'quick fix' in order to permit
buildworld to complete.

Reviewed by:	theraven

MFC r261608:

Apply a cleaner solution for the sign warnings that can occur when
compiling libc++'s <locale> header with -Wsystem-headers on.

This has also been submitted upstream.

Reported by:	asomers

MFC r261801:

An ABI incompatibility crept into the libc++ 3.4 import in r261283.  It
was caused by upstream libc++ commit r194536, which aimed to make the
headers more standards-compliant, by making std::pair's copy constructor
trivial.  Unfortunately, this could cause certain C++ applications using
shared libraries built against the previous version of libc++ to crash.

Fix the ABI incompatibility by making std::pair's copy constructor
non-trivial again.

Please note: Any C++ applications or shared libraries built with libc++
between r261283 and this revision should be recompiled.

Reported by:	stefanf
---
 contrib/libc++/src/shared_mutex.cpp | 101 ++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 contrib/libc++/src/shared_mutex.cpp

(limited to 'contrib/libc++/src/shared_mutex.cpp')

diff --git a/contrib/libc++/src/shared_mutex.cpp b/contrib/libc++/src/shared_mutex.cpp
new file mode 100644
index 0000000..5fb22e4
--- /dev/null
+++ b/contrib/libc++/src/shared_mutex.cpp
@@ -0,0 +1,101 @@
+//===---------------------- shared_mutex.cpp ------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#define _LIBCPP_BUILDING_SHARED_MUTEX
+#include "shared_mutex"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+shared_mutex::shared_mutex()
+    : __state_(0)
+{
+}
+
+// Exclusive ownership
+
+void
+shared_mutex::lock()
+{
+    unique_lock<mutex> lk(__mut_);
+    while (__state_ & __write_entered_)
+        __gate1_.wait(lk);
+    __state_ |= __write_entered_;
+    while (__state_ & __n_readers_)
+        __gate2_.wait(lk);
+}
+
+bool
+shared_mutex::try_lock()
+{
+    unique_lock<mutex> lk(__mut_);
+    if (__state_ == 0)
+    {
+        __state_ = __write_entered_;
+        return true;
+    }
+    return false;
+}
+
+void
+shared_mutex::unlock()
+{
+    lock_guard<mutex> _(__mut_);
+    __state_ = 0;
+    __gate1_.notify_all();
+}
+
+// Shared ownership
+
+void
+shared_mutex::lock_shared()
+{
+    unique_lock<mutex> lk(__mut_);
+    while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
+        __gate1_.wait(lk);
+    unsigned num_readers = (__state_ & __n_readers_) + 1;
+    __state_ &= ~__n_readers_;
+    __state_ |= num_readers;
+}
+
+bool
+shared_mutex::try_lock_shared()
+{
+    unique_lock<mutex> lk(__mut_);
+    unsigned num_readers = __state_ & __n_readers_;
+    if (!(__state_ & __write_entered_) && num_readers != __n_readers_)
+    {
+        ++num_readers;
+        __state_ &= ~__n_readers_;
+        __state_ |= num_readers;
+        return true;
+    }
+    return false;
+}
+
+void
+shared_mutex::unlock_shared()
+{
+    lock_guard<mutex> _(__mut_);
+    unsigned num_readers = (__state_ & __n_readers_) - 1;
+    __state_ &= ~__n_readers_;
+    __state_ |= num_readers;
+    if (__state_ & __write_entered_)
+    {
+        if (num_readers == 0)
+            __gate2_.notify_one();
+    }
+    else
+    {
+        if (num_readers == __n_readers_ - 1)
+            __gate1_.notify_one();
+    }
+}
+
+
+_LIBCPP_END_NAMESPACE_STD
-- 
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