Build Qt libraries with -fapplication-extension

This ensures at compile-time that Qt libraries do not use any APIs that
are not safe for use in application extensions, and fixes warning
messages that appear when linking to Qt libraries that are not built
with this flag, when used in an application extension.

This is especially important on watchOS where *all* "applications" are
actually application extensions, and on other Apple platforms if
application extensions are developed using Qt.

Task-number: QTBUG-40101
Change-Id: I022046f2584e0222253d33052b0abc221d7c93d6
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

mkspecs/features/mac/default_post.prf

@@ -38,6 +38,13 @@ qt {
 
 !bitcode: QMAKE_LFLAGS += $$QMAKE_LFLAGS_HEADERPAD
 
+app_extension_api_only {
+    QMAKE_CFLAGS              += -fapplication-extension
+    QMAKE_CXXFLAGS            += -fapplication-extension
+    QMAKE_CXXFLAGS_PRECOMPILE += -fapplication-extension
+    QMAKE_LFLAGS              += -fapplication-extension
+}
+
 macx-xcode {
     !isEmpty(QMAKE_XCODE_DEBUG_INFORMATION_FORMAT) {
         debug_information_format.name = DEBUG_INFORMATION_FORMAT

mkspecs/features/qml_plugin.prf

@@ -21,6 +21,9 @@ if(win32|mac):!macx-xcode {
 
 CONFIG += relative_qt_rpath  # Qt's QML plugins should be relocatable
 
+# Qt libraries should only use Application Extension safe APIs
+darwin:!no_app_extension_api_only: CONFIG += app_extension_api_only
+
 !no_cxx_module:isEmpty(CXX_MODULE) {
     CXX_MODULE = $$TARGET
     TARGET = declarative_$${TARGET}

mkspecs/features/qt_module.prf

@@ -46,6 +46,9 @@ CONFIG(shared, static|shared):qtConfig(framework): \
 
 CONFIG += relative_qt_rpath  # Qt libraries should be relocatable
 
+# Qt libraries should only use Application Extension safe APIs
+darwin:!no_app_extension_api_only: CONFIG += app_extension_api_only
+
 ucmodule = $$upper($$MODULE)
 
 isEmpty(MODULE_INCNAME): MODULE_INCNAME = $$TARGET

mkspecs/features/qt_plugin.prf

@@ -32,6 +32,9 @@ tool_plugin {
 
 CONFIG += relative_qt_rpath  # Qt's plugins should be relocatable
 
+# Qt libraries should only use Application Extension safe APIs
+darwin:!no_app_extension_api_only: CONFIG += app_extension_api_only
+
 CONFIG(static, static|shared)|prefix_build {
     isEmpty(MODULE): MODULE = $$basename(TARGET)
 

qmake/generators/mac/pbuilder_pbx.cpp

@@ -1485,6 +1485,7 @@ ProjectBuilderMakefileGenerator::writeMakeParts(QTextStream &t)
             }
         }
         settings.insert("COPY_PHASE_STRIP", (as_release ? "YES" : "NO"));
+        settings.insert("APPLICATION_EXTENSION_API_ONLY", project->isActiveConfig("app_extension_api_only") ? "YES" : "NO");
         // required for tvOS (and watchos), optional on iOS (deployment target >= iOS 6.0)
         settings.insert("ENABLE_BITCODE", project->isActiveConfig("bitcode") ? "YES" : "NO");
         settings.insert("GCC_GENERATE_DEBUGGING_SYMBOLS", as_release ? "NO" : "YES");

src/corelib/kernel/qeventdispatcher_cf.mm

@@ -80,7 +80,8 @@ QT_USE_NAMESPACE
 #elif defined(Q_OS_WATCHOS)
             object:[WKExtension sharedExtension]];
 #else
-            object:[UIApplication sharedApplication]];
+            // Use performSelector so this can work in an App Extension
+            object:[[UIApplication class] performSelector:@selector(sharedApplication)]];
 #endif
     }
 

src/plugins/platforms/cocoa/cocoa.pro

@@ -86,6 +86,8 @@ QT += \
     accessibility_support-private clipboard_support-private theme_support-private \
     fontdatabase_support-private graphics_support-private cgl_support-private
 
+CONFIG += no_app_extension_api_only
+
 qtHaveModule(widgets) {
     OBJECTIVE_SOURCES += \
         qpaintengine_mac.mm \

src/plugins/platforms/ios/kernel.pro

@@ -5,6 +5,8 @@ TARGET = qios
 # application's main() when the plugin is a shared library.
 qtConfig(shared): CONFIG += static
 
+CONFIG += no_app_extension_api_only
+
 QT += \
     core-private gui-private \
     clipboard_support-private fontdatabase_support-private graphics_support-private