Add a "shim" to allow use of Clang 5's __builtin_available everywhere

This is mostly relevant for Apple platforms, where we can use the new
unguarded availability warnings to guarantee that proper version checks
are present when using APIs that are not necessarily available on the
deployment target.

Change-Id: Ie408704b2924e1220491a9ea30f0141dfa4867d9
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry-picked from 70422449ef892d7cc3086d88e5e9e43c771e2bc3)

7 files changed, 147 insertions, 9 deletions

diff --git a/src/corelib/global/global.pri b/src/corelib/global/global.pri
index a3c1c4d65e..eee01341a5 100644
--- a/src/corelib/global/global.pri
+++ b/src/corelib/global/global.pri
@@ -38,7 +38,10 @@ SOURCES += \
 VERSIONTAGGING_SOURCES = global/qversiontagging.cpp
 
 darwin: SOURCES += global/qoperatingsystemversion_darwin.mm
-win32: SOURCES += global/qoperatingsystemversion_win.cpp
+win32 {
+    SOURCES += global/qoperatingsystemversion_win.cpp
+    HEADERS += global/qoperatingsystemversion_win_p.h
+}
 
 # qlibraryinfo.cpp includes qconfig.cpp
 INCLUDEPATH += $$QT_BUILD_TREE/src/corelib/global
diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index 8d614b4f91..d609f6a30a 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -47,6 +47,9 @@
 #include "qdatetime.h"
 #include "qoperatingsystemversion.h"
 #include "qoperatingsystemversion_p.h"
+#if defined(Q_OS_WIN) || defined(Q_OS_CYGWIN) || defined(Q_OS_WINRT)
+#include "qoperatingsystemversion_win_p.h"
+#endif
 #include <private/qlocale_tools_p.h>
 
 #include <qmutex.h>
diff --git a/src/corelib/global/qglobal_p.h b/src/corelib/global/qglobal_p.h
index b1d2836783..5f5891bcff 100644
--- a/src/corelib/global/qglobal_p.h
+++ b/src/corelib/global/qglobal_p.h
@@ -1,5 +1,6 @@
 /****************************************************************************
 **
+** Copyright (C) 2017 The Qt Company Ltd.
 ** Copyright (C) 2015 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
@@ -59,5 +60,77 @@
 #include <QtCore/private/qtcore-config_p.h>
 #endif
 
+#if defined(__cplusplus)
+#if !QT_HAS_BUILTIN(__builtin_available)
+#include <initializer_list>
+#include <QtCore/private/qoperatingsystemversion_p.h>
+#include <QtCore/qversionnumber.h>
+
+QT_BEGIN_NAMESPACE
+
+struct qt_clang_builtin_available_os_version_data {
+    QOperatingSystemVersion::OSType type;
+    const char *version;
+};
+
+static inline bool qt_clang_builtin_available(
+    const std::initializer_list<qt_clang_builtin_available_os_version_data> &versions)
+{
+    for (auto it = versions.begin(); it != versions.end(); ++it) {
+        if (currentType() == it->type) {
+            const auto current = QOperatingSystemVersion::current();
+            return QVersionNumber(
+                current.majorVersion(),
+                current.minorVersion(),
+                current.microVersion()) >= QVersionNumber::fromString(
+                    QString::fromLatin1(it->version));
+        }
+    }
+
+    // Result is true if the platform is not any of the checked ones; this matches behavior of
+    // LLVM __builtin_available and @available constructs
+    return true;
+}
+
+QT_END_NAMESPACE
+
+#define QT_AVAILABLE_OS_VER(os, ver) \
+    QT_PREPEND_NAMESPACE(qt_clang_builtin_available_os_version_data){\
+        QT_PREPEND_NAMESPACE(QOperatingSystemVersion)::os, #ver}
+#define QT_AVAILABLE_CAT(L, R) QT_AVAILABLE_CAT_(L, R)
+#define QT_AVAILABLE_CAT_(L, R) L ## R
+#define QT_AVAILABLE_EXPAND(...) QT_AVAILABLE_OS_VER(__VA_ARGS__)
+#define QT_AVAILABLE_SPLIT(os_ver) QT_AVAILABLE_EXPAND(QT_AVAILABLE_CAT(QT_AVAILABLE_SPLIT_, os_ver))
+#define QT_AVAILABLE_SPLIT_macOS MacOS,
+#define QT_AVAILABLE_SPLIT_iOS IOS,
+#define QT_AVAILABLE_SPLIT_tvOS TvOS,
+#define QT_AVAILABLE_SPLIT_watchOS WatchOS,
+#define QT_BUILTIN_AVAILABLE0(e) \
+    QT_PREPEND_NAMESPACE(qt_clang_builtin_available)({})
+#define QT_BUILTIN_AVAILABLE1(a, e) \
+    QT_PREPEND_NAMESPACE(qt_clang_builtin_available)({QT_AVAILABLE_SPLIT(a)})
+#define QT_BUILTIN_AVAILABLE2(a, b, e) \
+    QT_PREPEND_NAMESPACE(qt_clang_builtin_available)({QT_AVAILABLE_SPLIT(a), \
+                                                      QT_AVAILABLE_SPLIT(b)})
+#define QT_BUILTIN_AVAILABLE3(a, b, c, e) \
+    QT_PREPEND_NAMESPACE(qt_clang_builtin_available)({QT_AVAILABLE_SPLIT(a), \
+                                                      QT_AVAILABLE_SPLIT(b), \
+                                                      QT_AVAILABLE_SPLIT(c)})
+#define QT_BUILTIN_AVAILABLE4(a, b, c, d, e) \
+    QT_PREPEND_NAMESPACE(qt_clang_builtin_available)({QT_AVAILABLE_SPLIT(a), \
+                                                      QT_AVAILABLE_SPLIT(b), \
+                                                      QT_AVAILABLE_SPLIT(c), \
+                                                      QT_AVAILABLE_SPLIT(d)})
+#define QT_BUILTIN_AVAILABLE_ARG(arg0, arg1, arg2, arg3, arg4, arg5, ...) arg5
+#define QT_BUILTIN_AVAILABLE_CHOOSER(...) QT_BUILTIN_AVAILABLE_ARG(__VA_ARGS__, \
+    QT_BUILTIN_AVAILABLE4, \
+    QT_BUILTIN_AVAILABLE3, \
+    QT_BUILTIN_AVAILABLE2, \
+    QT_BUILTIN_AVAILABLE1, \
+    QT_BUILTIN_AVAILABLE0, )
+#define __builtin_available(...) QT_BUILTIN_AVAILABLE_CHOOSER(__VA_ARGS__)(__VA_ARGS__)
+#endif // !QT_HAS_BUILTIN(__builtin_available)
+#endif // defined(__cplusplus)
+
 #endif // QGLOBAL_P_H
 
diff --git a/src/corelib/global/qoperatingsystemversion_p.h b/src/corelib/global/qoperatingsystemversion_p.h
index 78d0daf0c6..77f19d27c5 100644
--- a/src/corelib/global/qoperatingsystemversion_p.h
+++ b/src/corelib/global/qoperatingsystemversion_p.h
@@ -53,16 +53,8 @@
 
 #include "qoperatingsystemversion.h"
 
-#ifdef Q_OS_WIN
-#include <qt_windows.h>
-#endif
-
 QT_BEGIN_NAMESPACE
 
-#ifdef Q_OS_WIN
-OSVERSIONINFOEX qWindowsVersionInfo();
-#endif
-
 static inline QOperatingSystemVersion::OSType currentType()
 {
 #if defined(Q_OS_WIN)
diff --git a/src/corelib/global/qoperatingsystemversion_win.cpp b/src/corelib/global/qoperatingsystemversion_win.cpp
index 060ca2f7da..f3662ae1f9 100644
--- a/src/corelib/global/qoperatingsystemversion_win.cpp
+++ b/src/corelib/global/qoperatingsystemversion_win.cpp
@@ -37,7 +37,10 @@
 **
 ****************************************************************************/
 
+#include "qoperatingsystemversion_win_p.h"
+
 #include "qoperatingsystemversion_p.h"
+
 #include <qt_windows.h>
 #include <qbytearray.h>
 
diff --git a/src/corelib/global/qoperatingsystemversion_win_p.h b/src/corelib/global/qoperatingsystemversion_win_p.h
new file mode 100644
index 0000000000..446bd286fc
--- /dev/null
+++ b/src/corelib/global/qoperatingsystemversion_win_p.h
@@ -0,0 +1,63 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QOPERATINGSYSTEMVERSION_WIN_P_H
+#define QOPERATINGSYSTEMVERSION_WIN_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API. It exists purely as an
+// implementation detail. This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/qglobal.h>
+#include <qt_windows.h>
+
+QT_BEGIN_NAMESPACE
+
+OSVERSIONINFOEX qWindowsVersionInfo();
+
+QT_END_NAMESPACE
+
+#endif // QOPERATINGSYSTEMVERSION_WIN_P_H
diff --git a/src/tools/bootstrap/bootstrap.pro b/src/tools/bootstrap/bootstrap.pro
index 521dd5f0f2..50f669cd23 100644
--- a/src/tools/bootstrap/bootstrap.pro
+++ b/src/tools/bootstrap/bootstrap.pro
@@ -80,6 +80,7 @@ SOURCES += \
            ../../corelib/tools/qstringbuilder.cpp \
            ../../corelib/tools/qstring_compat.cpp \
            ../../corelib/tools/qstringlist.cpp \
+           ../../corelib/tools/qversionnumber.cpp \
            ../../corelib/tools/qvsnprintf.cpp \
            ../../corelib/xml/qxmlutils.cpp \
            ../../corelib/xml/qxmlstream.cpp \