From 70422449ef892d7cc3086d88e5e9e43c771e2bc3 Mon Sep 17 00:00:00 2001
From: Jake Petroules <jake.petroules@qt.io>
Date: Fri, 22 Sep 2017 00:35:24 -0700
Subject: 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>
---
 src/corelib/global/qglobal_p.h    | 73 +++++++++++++++++++++++++++++++++++++++
 src/tools/bootstrap/bootstrap.pro |  1 +
 2 files changed, 74 insertions(+)

diff --git a/src/corelib/global/qglobal_p.h b/src/corelib/global/qglobal_p.h
index b1d2836783..0f092e9006 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/qoperatingsystemversion.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 (QOperatingSystemVersion::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/tools/bootstrap/bootstrap.pro b/src/tools/bootstrap/bootstrap.pro
index dedb4ff138..042ad7adb9 100644
--- a/src/tools/bootstrap/bootstrap.pro
+++ b/src/tools/bootstrap/bootstrap.pro
@@ -81,6 +81,7 @@ 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 \
-- 
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