Add Q_FALLTHROUGH for Qt < 5.8

... and make use of it.
With gcc 7, the new option -Wimplicit-fallthrough is introduced and
added to the -Wextra set, triggering dozens of warnings in our sources.
Therefore, we annotate all obviously intended fall-throughs. The ones
that are still left are unclear and need to be checked by the respective
maintainer.

Change-Id: I44ead33cd42a4b41c28ee5fcb5a31db272710bbc
Reviewed-by: Nikita Baryshnikov <nib952051@gmail.com>
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/3rdparty/cplusplus/Parser.cpp

@@ -27,6 +27,8 @@
 #include "ObjectiveCTypeQualifiers.h"
 #include "QtContextKeywords.h"
 
+#include <utils/qtcfallthrough.h>
+
 #include <unordered_map>
 #include <utility>
 
@@ -442,7 +444,7 @@ bool Parser::skipUntilStatement()
             case T_AT_THROW:
                 if (_languageFeatures.objCEnabled)
                     return true;
-
+                Q_FALLTHROUGH();
             default:
                 consumeToken();
         }

src/libs/utils/qtcfallthrough.h

@@ -0,0 +1,54 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** 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 General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** 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-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <QtGlobal>
+
+#ifndef Q_FALLTHROUGH
+#ifndef QT_HAS_CPP_ATTRIBUTE
+#ifdef __has_cpp_attribute
+#  define QT_HAS_CPP_ATTRIBUTE(x)       __has_cpp_attribute(x)
+#else
+#  define QT_HAS_CPP_ATTRIBUTE(x)       0
+#endif
+#endif
+#if defined(__cplusplus)
+#if QT_HAS_CPP_ATTRIBUTE(fallthrough)
+#  define Q_FALLTHROUGH() [[fallthrough]]
+#elif QT_HAS_CPP_ATTRIBUTE(clang::fallthrough)
+#    define Q_FALLTHROUGH() [[clang::fallthrough]]
+#elif QT_HAS_CPP_ATTRIBUTE(gnu::fallthrough)
+#    define Q_FALLTHROUGH() [[gnu::fallthrough]]
+#endif
+#endif
+#ifndef Q_FALLTHROUGH
+#  if (defined(Q_CC_GNU) && Q_CC_GNU >= 700) && !defined(Q_CC_INTEL)
+#    define Q_FALLTHROUGH() __attribute__((fallthrough))
+#  else
+#    define Q_FALLTHROUGH() (void)0
+#endif
+#endif
+#endif

src/libs/utils/utils-lib.pri

@@ -239,6 +239,7 @@ HEADERS += \
     $$PWD/asconst.h \
     $$PWD/smallstringfwd.h \
     $$PWD/optional.h \
+    $$PWD/qtcfallthrough.h \
     $$PWD/../3rdparty/optional/optional.hpp
 
 FORMS += $$PWD/filewizardpage.ui \

src/libs/utils/utils.qbs

@@ -175,6 +175,7 @@ Project {
             "proxycredentialsdialog.cpp",
             "proxycredentialsdialog.h",
             "proxycredentialsdialog.ui",
+            "qtcfallthrough.h",
             "qtcassert.cpp",
             "qtcassert.h",
             "qtcolorbutton.cpp",

src/plugins/cppeditor/cppquickfixes.cpp

@@ -56,6 +56,7 @@
 
 #include <utils/fancylineedit.h>
 #include <utils/qtcassert.h>
+#include <utils/qtcfallthrough.h>
 
 #include <QApplication>
 #include <QComboBox>
@@ -4119,7 +4120,7 @@ public:
             break;
         case FromReference:
             removeReferenceOperator(changes);
-            // fallthrough intended
+            Q_FALLTHROUGH();
         case FromVariable:
             convertToPointer(changes);
             break;

src/plugins/cpptools/compileroptionsbuilder.cpp

@@ -26,6 +26,7 @@
 #include "compileroptionsbuilder.h"
 
 #include <projectexplorer/projectexplorerconstants.h>
+#include <utils/qtcfallthrough.h>
 
 #include <QDir>
 #include <QRegularExpression>
@@ -201,7 +202,8 @@ static QStringList createLanguageOptionGcc(ProjectFile::Kind fileKind, bool objc
         if (!objcExt) {
             opts += QLatin1String("c++-header");
             break;
-        } // else: fall-through!
+        }
+        Q_FALLTHROUGH();
     case ProjectFile::ObjCHeader:
     case ProjectFile::ObjCXXHeader:
         opts += QLatin1String("objective-c++-header");
@@ -211,7 +213,8 @@ static QStringList createLanguageOptionGcc(ProjectFile::Kind fileKind, bool objc
         if (!objcExt) {
             opts += QLatin1String("c");
             break;
-        } // else: fall-through!
+        }
+        Q_FALLTHROUGH();
     case ProjectFile::ObjCSource:
         opts += QLatin1String("objective-c");
         break;
@@ -220,7 +223,8 @@ static QStringList createLanguageOptionGcc(ProjectFile::Kind fileKind, bool objc
         if (!objcExt) {
             opts += QLatin1String("c++");
             break;
-        } // else: fall-through!
+        }
+        Q_FALLTHROUGH();
     case ProjectFile::ObjCXXSource:
         opts += QLatin1String("objective-c++");
         break;

src/plugins/debugger/gdb/attachgdbadapter.cpp

@@ -31,6 +31,7 @@
 #include <debugger/debuggerstartparameters.h>
 
 #include <utils/qtcassert.h>
+#include <utils/qtcfallthrough.h>
 
 namespace Debugger {
 namespace Internal {
@@ -102,7 +103,7 @@ void GdbAttachEngine::handleAttach(const DebuggerResponse &response)
             notifyEngineIll();
             break;
         }
-        // if msg != "ptrace: ..." fall through
+        Q_FALLTHROUGH(); // if msg != "ptrace: ..."
     default:
         showStatusMessage(tr("Failed to attach to application: %1")
                           .arg(QString(response.data["msg"].data())));

src/plugins/debugger/gdb/remotegdbserveradapter.cpp

@@ -34,6 +34,7 @@
 #include <coreplugin/messagebox.h>
 
 #include <utils/hostosinfo.h>
+#include <utils/qtcfallthrough.h>
 #include <utils/qtcassert.h>
 #include <utils/qtcprocess.h>
 
@@ -367,7 +368,7 @@ void GdbRemoteServerEngine::handleAttach(const DebuggerResponse &response)
             notifyInferiorSetupFailed(msgPtraceError(runParameters().startMode));
             break;
         }
-        // if msg != "ptrace: ..." fall through
+        Q_FALLTHROUGH(); // if msg != "ptrace: ..."
     default:
         notifyInferiorSetupFailed(response.data["msg"].data());
     }

src/plugins/debugger/qml/qmlengine.cpp

@@ -60,6 +60,7 @@
 #include <utils/treemodel.h>
 #include <utils/basetreeview.h>
 #include <utils/qtcassert.h>
+#include <utils/qtcfallthrough.h>
 
 #include <QDebug>
 #include <QDir>
@@ -505,7 +506,7 @@ void QmlEngine::errorMessageBoxFinished(int result)
     }
     case QMessageBox::Help: {
         HelpManager::handleHelpRequest("qthelp://org.qt-project.qtcreator/doc/creator-debugging-qml.html");
-        // fall through
+        Q_FALLTHROUGH();
     }
     default:
         if (state() == InferiorRunOk) {

src/plugins/debugger/watchutils.cpp

@@ -29,6 +29,8 @@
 #include "watchutils.h"
 #include "watchdata.h"
 
+#include <utils/qtcfallthrough.h>
+
 #include <QDebug>
 
 #include <string.h>
@@ -231,8 +233,10 @@ QString formatToolTipAddress(quint64 a)
         switch (rc.size()) {
         case 16:
             rc.insert(12, colon);
+            Q_FALLTHROUGH();
         case 12:
             rc.insert(8, colon);
+            Q_FALLTHROUGH();
         case 8:
             rc.insert(4, colon);
         }

src/plugins/ios/iostoolhandler.cpp

@@ -33,6 +33,7 @@
 #include <coreplugin/icore.h>
 #include <utils/qtcassert.h>
 #include <utils/fileutils.h>
+#include <utils/qtcfallthrough.h>
 #include "utils/runextensions.h"
 #include "utils/synchronousprocess.h"
 
@@ -606,7 +607,7 @@ void IosDeviceToolHandlerPrivate::subprocessHasData()
         switch (state) {
         case NonStarted:
             qCWarning(toolHandlerLog) << "IosToolHandler unexpected state in subprocessHasData: NonStarted";
-            // pass
+            Q_FALLTHROUGH();
         case Starting:
         case StartedInferior:
             // read some data
@@ -771,7 +772,7 @@ void IosDeviceToolHandlerPrivate::stop(int errorCode)
     switch (oldState) {
     case NonStarted:
         qCWarning(toolHandlerLog) << "IosToolHandler::stop() when state was NonStarted";
-        // pass
+        Q_FALLTHROUGH();
     case Starting:
         switch (op){
         case OpNone:
@@ -786,7 +787,7 @@ void IosDeviceToolHandlerPrivate::stop(int errorCode)
         case OpDeviceInfo:
             break;
         }
-        // pass
+        Q_FALLTHROUGH();
     case StartedInferior:
     case XmlEndProcessed:
         toolExited(errorCode);

src/plugins/qmldesigner/components/formeditor/formeditorscene.cpp

@@ -44,6 +44,7 @@
 
 #include <utils/algorithm.h>
 #include <utils/qtcassert.h>
+#include <utils/qtcfallthrough.h>
 
 namespace QmlDesigner {
 
@@ -358,6 +359,7 @@ bool FormEditorScene::event(QEvent * event)
                 currentTool()->keyPressEvent(static_cast<QKeyEvent*>(event));
                 return true;
             }
+            Q_FALLTHROUGH();
         default: return QGraphicsScene::event(event);
     }
 

src/plugins/qmlprofiler/qmlprofilertool.cpp

@@ -69,6 +69,8 @@
 
 #include <qtsupport/qtkitinformation.h>
 
+#include <utils/qtcfallthrough.h>
+
 #include <QApplication>
 #include <QDockWidget>
 #include <QFileDialog>
@@ -387,6 +389,7 @@ void QmlProfilerTool::finalizeRunControl(QmlProfilerRunner *runWorker)
             case QMessageBox::Help:
                 HelpManager::handleHelpRequest(
                             "qthelp://org.qt-project.qtcreator/doc/creator-debugging-qml.html");
+                Q_FALLTHROUGH();
             case QMessageBox::Cancel:
                 // The actual error message has already been logged.
                 logState(tr("Failed to connect."));

src/plugins/qmlprofiler/qmlprofilertraceview.cpp

@@ -53,6 +53,7 @@
 // Needed for the load&save actions in the context menu
 #include <debugger/analyzer/analyzermanager.h>
 #include <coreplugin/findplaceholder.h>
+#include <utils/qtcfallthrough.h>
 #include <utils/styledbar.h>
 #include <utils/algorithm.h>
 
@@ -103,7 +104,7 @@ QmlProfilerTraceView::QmlProfilerTraceView(QWidget *parent, QmlProfilerViewManag
             qint64 end = modelManager->traceTime()->endTime();
             d->m_zoomControl->setTrace(start, end);
             d->m_zoomControl->setRange(start, start + (end - start) / 10);
-            // Fall through
+            Q_FALLTHROUGH();
         }
         case QmlProfilerModelManager::Empty:
             d->m_modelProxy->setModels(d->m_suspendedModels);
@@ -116,7 +117,7 @@ QmlProfilerTraceView::QmlProfilerTraceView(QWidget *parent, QmlProfilerViewManag
             d->m_zoomControl->clear();
             if (!d->m_suspendedModels.isEmpty())
                 break; // Models are suspended already. AcquiringData was aborted.
-            // Fall through
+            Q_FALLTHROUGH();
         case QmlProfilerModelManager::AcquiringData:
             // Temporarily remove the models, while we're changing them
             d->m_suspendedModels = d->m_modelProxy->models();

src/plugins/scxmleditor/common/structuremodel.cpp

@@ -27,6 +27,8 @@
 #include "scxmldocument.h"
 #include "scxmltag.h"
 
+#include <utils/qtcfallthrough.h>
+
 #include <QMimeData>
 #include <QUndoStack>
 
@@ -245,6 +247,7 @@ Qt::ItemFlags StructureModel::flags(const QModelIndex &index) const
         case Final:
         case History:
             defaultFlags |= Qt::ItemIsDragEnabled;
+            Q_FALLTHROUGH();
         case Scxml:
             defaultFlags |= Qt::ItemIsDropEnabled;
             break;

src/plugins/vcsbase/vcsbaseclientsettings.cpp

@@ -29,6 +29,7 @@
 #include <utils/fileutils.h>
 #include <utils/hostosinfo.h>
 #include <utils/qtcassert.h>
+#include <utils/qtcfallthrough.h>
 
 #include <QSettings>
 #include <QVariant>
@@ -56,6 +57,7 @@ public:
         switch (v.type()) {
         case QVariant::UInt:
             m_type = QVariant::Int;
+            Q_FALLTHROUGH();
         case QVariant::Int:
             m_comp.intValue = v.toInt();
             break;