Support C++17 fallthrough attribute

Replaces our mix of comments for annotating intended absence of break
in switches with the C++17 attribute [[fallthrough]], or its earlier
a clang extension counterpart.

Change-Id: I4b2d0b9b5e4425819c7f1bf01608093c536b6d14
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

69 files changed, 187 insertions, 158 deletions

diff --git a/src/corelib/codecs/qiconvcodec.cpp b/src/corelib/codecs/qiconvcodec.cpp
index 96f1ee16ac..845155dce0 100644
--- a/src/corelib/codecs/qiconvcodec.cpp
+++ b/src/corelib/codecs/qiconvcodec.cpp
@@ -411,7 +411,7 @@ QByteArray QIconvCodec::convertFromUnicode(const QChar *uc, int len, ConverterSt
             switch (errno) {
             case EILSEQ:
                 ++invalidCount;
-                // fall through
+                Q_FALLTHROUGH();
             case EINVAL:
                 {
                     inBytes += sizeof(QChar);
diff --git a/src/corelib/codecs/qjiscodec.cpp b/src/corelib/codecs/qjiscodec.cpp
index 9c628c6012..a8625db054 100644
--- a/src/corelib/codecs/qjiscodec.cpp
+++ b/src/corelib/codecs/qjiscodec.cpp
@@ -288,7 +288,7 @@ QString QJisCodec::convertToUnicode(const char* chars, int len, ConverterState *
                             result += QLatin1Char(ch);
                             break;
                         }
-                        /* fall through */
+                        Q_FALLTHROUGH();
                     case JISX0201_Latin:
                         u = conv->jisx0201ToUnicode(ch);
                         result += QValidChar(u);
diff --git a/src/corelib/global/qcompilerdetection.h b/src/corelib/global/qcompilerdetection.h
index 70c9e97c13..085e3063b4 100644
--- a/src/corelib/global/qcompilerdetection.h
+++ b/src/corelib/global/qcompilerdetection.h
@@ -1341,6 +1341,18 @@
         Q_ASSUME_IMPL(valueOfExpression);\
     } while (0)
 
+#if QT_HAS_CPP_ATTRIBUTE(fallthrough)
+#  define Q_FALLTHROUGH() [[fallthrough]]
+#elif defined(__cplusplus)
+/* Clang can not parse namespaced attributes in C mode, but defines __has_cpp_attribute */
+#  if QT_HAS_CPP_ATTRIBUTE(clang::fallthrough)
+#    define Q_FALLTHROUGH() [[clang::fallthrough]]
+#  endif
+#endif
+#ifndef Q_FALLTHROUGH
+#  define Q_FALLTHROUGH() (void)0
+#endif
+
 
 /*
     Sanitize compiler feature availability
diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index 03216358aa..170dd757d3 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -2950,6 +2950,20 @@ QString QSysInfo::machineHostName()
 */
 
 /*!
+    \macro void Q_FALLTHROUGH()
+    \relates <QtGlobal>
+    \since 5.8
+
+    Can be used in switch statements at the end of case block to tell the compiler
+    and other developers that that the lack of a break statement is intentional.
+
+    This is useful since a missing break statement is often a bug, and some
+    compilers can be configured to emit warnings when one is not found.
+
+    \sa Q_UNREACHABLE()
+*/
+
+/*!
     \macro void Q_CHECK_PTR(void *pointer)
     \relates <QtGlobal>
 
diff --git a/src/corelib/io/qsettings.cpp b/src/corelib/io/qsettings.cpp
index 856108e417..11f201344e 100644
--- a/src/corelib/io/qsettings.cpp
+++ b/src/corelib/io/qsettings.cpp
@@ -813,7 +813,7 @@ StNormal:
                 ++i;
                 goto StSkipSpaces;
             }
-            // fallthrough
+            Q_FALLTHROUGH();
         default: {
             int j = i + 1;
             while (j < to) {
diff --git a/src/corelib/io/qsettings_win.cpp b/src/corelib/io/qsettings_win.cpp
index 7c6b782acd..3f06ab7043 100644
--- a/src/corelib/io/qsettings_win.cpp
+++ b/src/corelib/io/qsettings_win.cpp
@@ -742,7 +742,7 @@ void QWinSettingsPrivate::set(const QString &uKey, const QVariant &value)
         }
 
         case QVariant::ByteArray:
-            // fallthrough intended
+            Q_FALLTHROUGH();
 
         default: {
             // If the string does not contain '\0', we can use REG_SZ, the native registry
diff --git a/src/corelib/json/qjson.cpp b/src/corelib/json/qjson.cpp
index 4b98ef076c..e9a1366af0 100644
--- a/src/corelib/json/qjson.cpp
+++ b/src/corelib/json/qjson.cpp
@@ -339,7 +339,7 @@ bool Value::isValid(const Base *b) const
     case QJsonValue::Double:
         if (latinOrIntValue)
             break;
-        // fall through
+        Q_FALLTHROUGH();
     case QJsonValue::String:
     case QJsonValue::Array:
     case QJsonValue::Object:
@@ -418,7 +418,7 @@ uint Value::valueToStore(const QJsonValue &v, uint offset)
         if (c != INT_MAX)
             return c;
     }
-        // fall through
+        Q_FALLTHROUGH();
     case QJsonValue::String:
     case QJsonValue::Array:
     case QJsonValue::Object:
diff --git a/src/corelib/kernel/qmimedata.cpp b/src/corelib/kernel/qmimedata.cpp
index 95153f8fa9..a550ca6ca1 100644
--- a/src/corelib/kernel/qmimedata.cpp
+++ b/src/corelib/kernel/qmimedata.cpp
@@ -167,7 +167,7 @@ QVariant QMimeDataPrivate::retrieveTypedData(const QString &format, QVariant::Ty
         case QVariant::List: {
             if (format != QLatin1String("text/uri-list"))
                 break;
-            // fall through
+            Q_FALLTHROUGH();
         }
         case QVariant::Url: {
             QByteArray ba = data.toByteArray();
diff --git a/src/corelib/kernel/qsystemerror.cpp b/src/corelib/kernel/qsystemerror.cpp
index f38daec4f8..3899f24d3b 100644
--- a/src/corelib/kernel/qsystemerror.cpp
+++ b/src/corelib/kernel/qsystemerror.cpp
@@ -149,12 +149,13 @@ QString QSystemError::toString() const
         return windowsErrorString(errorCode);
 #else
         //unix: fall through as native and standard library are the same
+        Q_FALLTHROUGH();
 #endif
     case StandardLibraryError:
         return standardLibraryErrorString(errorCode);
     default:
         qWarning("invalid error scope");
-        //fall through
+        Q_FALLTHROUGH();
     case NoError:
         return QLatin1String("No error");
     }
diff --git a/src/corelib/kernel/qtimerinfo_unix.cpp b/src/corelib/kernel/qtimerinfo_unix.cpp
index 56337bdb45..c3b8c86063 100644
--- a/src/corelib/kernel/qtimerinfo_unix.cpp
+++ b/src/corelib/kernel/qtimerinfo_unix.cpp
@@ -468,7 +468,6 @@ void QTimerInfoList::registerTimer(int timerId, int interval, Qt::TimerType time
         // above 20 s, 5% inaccuracy is above 1 s, so we convert to VeryCoarseTimer
         if (interval >= 20000) {
             t->timerType = Qt::VeryCoarseTimer;
-            // fall through
         } else {
             t->timeout = expected;
             if (interval <= 20) {
@@ -479,7 +478,7 @@ void QTimerInfoList::registerTimer(int timerId, int interval, Qt::TimerType time
             }
             break;
         }
-        // fall through
+        Q_FALLTHROUGH();
     case Qt::VeryCoarseTimer:
         // the very coarse timer is based on full second precision,
         // so we keep the interval in seconds (round to closest second)
diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index f1d38db96c..d21529d124 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -203,7 +203,7 @@ static qlonglong qConvertToNumber(const QVariant::Private *d, bool *ok)
     case QMetaType::QJsonValue:
         if (!v_cast<QJsonValue>(d)->isDouble())
             break;
-        // no break
+        Q_FALLTHROUGH();
 #endif
     case QVariant::Double:
     case QVariant::Int:
@@ -278,7 +278,7 @@ static qulonglong qConvertToUnsignedNumber(const QVariant::Private *d, bool *ok)
     case QMetaType::QJsonValue:
         if (!v_cast<QJsonValue>(d)->isDouble())
             break;
-        // no break
+        Q_FALLTHROUGH();
 #endif
     case QVariant::Double:
     case QVariant::Int:
@@ -3119,7 +3119,7 @@ bool QVariant::canConvert(int targetTypeId) const
         case QVariant::Int:
             if (currentType == QVariant::KeySequence)
                 return true;
-            // fall through
+            Q_FALLTHROUGH();
         case QVariant::UInt:
         case QVariant::LongLong:
         case QVariant::ULongLong:
diff --git a/src/corelib/tools/qdatetime.cpp b/src/corelib/tools/qdatetime.cpp
index ee5ee5c362..a2c92835fe 100644
--- a/src/corelib/tools/qdatetime.cpp
+++ b/src/corelib/tools/qdatetime.cpp
@@ -2656,7 +2656,7 @@ static void setTimeSpec(QDateTimeData &d, Qt::TimeSpec spec, int offsetSeconds)
     case Qt::TimeZone:
         // Use system time zone instead
         spec = Qt::LocalTime;
-        // fallthrough
+        Q_FALLTHROUGH();
     case Qt::UTC:
     case Qt::LocalTime:
         offsetSeconds = 0;
diff --git a/src/corelib/tools/qdatetimeparser.cpp b/src/corelib/tools/qdatetimeparser.cpp
index 9c9009d636..ac973b047f 100644
--- a/src/corelib/tools/qdatetimeparser.cpp
+++ b/src/corelib/tools/qdatetimeparser.cpp
@@ -602,7 +602,7 @@ int QDateTimeParser::sectionMaxSize(Section s, int count) const
         return 2;
 #else
         mcount = 7;
-        // fall through
+        Q_FALLTHROUGH();
 #endif
     case MonthSection:
 #ifdef QT_NO_TEXTDATE
@@ -770,7 +770,8 @@ int QDateTimeParser::parseSection(const QDateTime &currentValue, int sectionInde
                 state = Intermediate;
             }
             break;
-        } // else: fall through
+        }
+        Q_FALLTHROUGH();
     case DaySection:
     case YearSection:
     case YearSection2Digits:
@@ -1155,7 +1156,7 @@ end:
                             done = true;
                             break;
                         }
-                        // fallthrough
+                        Q_FALLTHROUGH();
                     default: {
                         int toMin;
                         int toMax;
@@ -1489,7 +1490,7 @@ QDateTimeParser::FieldInfo QDateTimeParser::fieldInfo(int index) const
     switch (sn.type) {
     case MSecSection:
         ret |= Fraction;
-        // fallthrough
+        Q_FALLTHROUGH();
     case SecondSection:
     case MinuteSection:
     case Hour24Section:
@@ -1509,7 +1510,7 @@ QDateTimeParser::FieldInfo QDateTimeParser::fieldInfo(int index) const
         switch (sn.count) {
         case 2:
             ret |= FixedWidth;
-            // fallthrough
+            Q_FALLTHROUGH();
         case 1:
             ret |= (Numeric|AllowPartial);
             break;
diff --git a/src/corelib/tools/qregexp.cpp b/src/corelib/tools/qregexp.cpp
index f8f3347786..96ddca56af 100644
--- a/src/corelib/tools/qregexp.cpp
+++ b/src/corelib/tools/qregexp.cpp
@@ -3011,7 +3011,7 @@ int QRegExpEngine::getEscape()
     case 'I':
         if (xmlSchemaExtensions) {
             yyCharClass->setNegative(!yyCharClass->negative());
-            // fall through
+            Q_FALLTHROUGH();
         } else {
             break;
         }
@@ -3051,7 +3051,7 @@ int QRegExpEngine::getEscape()
     case 'C':
         if (xmlSchemaExtensions) {
             yyCharClass->setNegative(!yyCharClass->negative());
-            // fall through
+            Q_FALLTHROUGH();
         } else {
             break;
         }
@@ -3097,7 +3097,7 @@ int QRegExpEngine::getEscape()
     case 'P':
         if (xmlSchemaExtensions) {
             yyCharClass->setNegative(!yyCharClass->negative());
-            // fall through
+            Q_FALLTHROUGH();
         } else {
             break;
         }
diff --git a/src/corelib/tools/qunicodetools.cpp b/src/corelib/tools/qunicodetools.cpp
index fad4267edc..be1d88e260 100644
--- a/src/corelib/tools/qunicodetools.cpp
+++ b/src/corelib/tools/qunicodetools.cpp
@@ -522,13 +522,13 @@ static void getLineBreaks(const ushort *string, quint32 len, QCharAttributes *at
                 // do not change breaks before and after the expression
                 for (quint32 j = nestart + 1; j < pos; ++j)
                     attributes[j].lineBreak = false;
-                // fall through
+                Q_FALLTHROUGH();
             case LB::NS::None:
                 nelast = LB::NS::XX; // reset state
                 break;
             case LB::NS::Start:
                 nestart = i;
-                // fall through
+                Q_FALLTHROUGH();
             default:
                 nelast = necur;
                 break;
diff --git a/src/corelib/xml/qxmlstream.cpp b/src/corelib/xml/qxmlstream.cpp
index 83b26d50ab..1ffaeca852 100644
--- a/src/corelib/xml/qxmlstream.cpp
+++ b/src/corelib/xml/qxmlstream.cpp
@@ -976,11 +976,11 @@ bool QXmlStreamReaderPrivate::scanUntil(const char *str, short tokenToInject)
         case '\r':
             if ((c = filterCarriageReturn()) == 0)
                 break;
-            // fall through
+            Q_FALLTHROUGH();
         case '\n':
             ++lineNumber;
             lastLineStart = characterOffset + readBufferPos;
-            // fall through
+            Q_FALLTHROUGH();
         case '\t':
             textBuffer += QChar(c);
             continue;
@@ -1158,11 +1158,11 @@ inline int QXmlStreamReaderPrivate::fastScanLiteralContent()
         case '\r':
             if (filterCarriageReturn() == 0)
                 return n;
-            // fall through
+            Q_FALLTHROUGH();
         case '\n':
             ++lineNumber;
             lastLineStart = characterOffset + readBufferPos;
-            // fall through
+            Q_FALLTHROUGH();
         case ' ':
         case '\t':
             if (normalizeLiterals)
@@ -1179,7 +1179,7 @@ inline int QXmlStreamReaderPrivate::fastScanLiteralContent()
                 putChar(c);
                 return n;
             }
-            // fall through
+            Q_FALLTHROUGH();
         default:
             if (c < 0x20) {
                 putChar(c);
@@ -1201,11 +1201,11 @@ inline int QXmlStreamReaderPrivate::fastScanSpace()
         case '\r':
             if ((c = filterCarriageReturn()) == 0)
                 return n;
-            // fall through
+            Q_FALLTHROUGH();
         case '\n':
             ++lineNumber;
             lastLineStart = characterOffset + readBufferPos;
-            // fall through
+            Q_FALLTHROUGH();
         case ' ':
         case '\t':
             textBuffer += QChar(c);
@@ -1259,11 +1259,11 @@ inline int QXmlStreamReaderPrivate::fastScanContentCharList()
         case '\r':
             if ((c = filterCarriageReturn()) == 0)
                 return n;
-            // fall through
+            Q_FALLTHROUGH();
         case '\n':
             ++lineNumber;
             lastLineStart = characterOffset + readBufferPos;
-            // fall through
+            Q_FALLTHROUGH();
         case ' ':
         case '\t':
             textBuffer += QChar(ushort(c));
@@ -1275,7 +1275,7 @@ inline int QXmlStreamReaderPrivate::fastScanContentCharList()
                 putChar(c);
                 return n;
             }
-            // fall through
+            Q_FALLTHROUGH();
         default:
             if (c < 0x20) {
                 putChar(c);
@@ -1339,7 +1339,7 @@ inline int QXmlStreamReaderPrivate::fastScanName(int *prefix)
                 putChar(c);
                 return n;
             }
-            // fall through
+            Q_FALLTHROUGH();
         default:
             textBuffer += QChar(c);
             ++n;
@@ -2123,7 +2123,7 @@ QString QXmlStreamReader::readElementText(ReadElementTextBehaviour behaviour)
                     result += readElementText(behaviour);
                     break;
                 }
-                // Fall through (for ErrorOnUnexpectedElement)
+                Q_FALLTHROUGH();
             default:
                 if (d->error || behaviour == ErrorOnUnexpectedElement) {
                     if (!d->error)
diff --git a/src/corelib/xml/qxmlstream_p.h b/src/corelib/xml/qxmlstream_p.h
index c68d6f0f53..b62cc9ac39 100644
--- a/src/corelib/xml/qxmlstream_p.h
+++ b/src/corelib/xml/qxmlstream_p.h
@@ -1048,7 +1048,7 @@ bool QXmlStreamReaderPrivate::parse()
         dtdName.clear();
         dtdPublicId.clear();
         dtdSystemId.clear();
-        // fall through
+        Q_FALLTHROUGH();
     case QXmlStreamReader::Comment:
     case QXmlStreamReader::Characters:
         isCDATA = false;
@@ -1080,7 +1080,7 @@ bool QXmlStreamReaderPrivate::parse()
             return false;
         }
 #endif
-        // fall through
+        Q_FALLTHROUGH();
     default:
         clearTextBuffer();
         ;
@@ -1124,7 +1124,7 @@ bool QXmlStreamReaderPrivate::parse()
                 } else {
                     break;
                 }
-                // fall through
+                Q_FALLTHROUGH();
             case ~0U: {
                 token = EOF_SYMBOL;
                 if (!tagsDone && !inParseEntity) {
@@ -1338,7 +1338,7 @@ bool QXmlStreamReaderPrivate::parse()
         case 17:
         case 18:
             dtdName = symString(3);
-            // fall through
+            Q_FALLTHROUGH();
 
         case 19:
         case 20:
@@ -1480,7 +1480,7 @@ bool QXmlStreamReaderPrivate::parse()
             if (entityDeclaration.parameter)
                 raiseWellFormedError(QXmlStream::tr("NDATA in parameter entity declaration."));
         }
-        //fall through
+        Q_FALLTHROUGH();
 
         case 94:
         case 95: {
@@ -1588,7 +1588,7 @@ bool QXmlStreamReaderPrivate::parse()
 
         case 129:
             isWhitespace = false;
-            // fall through
+            Q_FALLTHROUGH();
 
         case 130:
             sym(1).len += fastScanContentCharList();
@@ -1760,7 +1760,7 @@ bool QXmlStreamReaderPrivate::parse()
 
         case 236:
             isEmptyElement = true;
-        // fall through
+            Q_FALLTHROUGH();
 
         case 237:
             setType(QXmlStreamReader::StartElement);
diff --git a/src/dbus/qdbusmarshaller.cpp b/src/dbus/qdbusmarshaller.cpp
index 7ba7c79808..4ea6cefff6 100644
--- a/src/dbus/qdbusmarshaller.cpp
+++ b/src/dbus/qdbusmarshaller.cpp
@@ -318,7 +318,7 @@ void QDBusMarshaller::open(QDBusMarshaller &sub, int code, const char *signature
             case DBUS_TYPE_ARRAY:
                 *ba += char(code);
                 *ba += signature;
-                // fall through
+                Q_FALLTHROUGH();
 
             case DBUS_TYPE_DICT_ENTRY:
                 sub.closeCode = 0;
@@ -495,9 +495,9 @@ bool QDBusMarshaller::appendVariantInternal(const QVariant &arg)
             return true;
 
         default:
-            ;                   // fall through
+            ;
         }
-        // fall through
+        Q_FALLTHROUGH();
 
     case DBUS_TYPE_STRUCT:
     case DBUS_STRUCT_BEGIN_CHAR:
@@ -513,7 +513,7 @@ bool QDBusMarshaller::appendVariantInternal(const QVariant &arg)
             append(qvariant_cast<QDBusUnixFileDescriptor>(arg));
             return true;
         }
-        // fall through
+        Q_FALLTHROUGH();
 
     default:
         qWarning("QDBusMarshaller::appendVariantInternal: Found unknown D-BUS type '%s'",
diff --git a/src/dbus/qdbusmetatype.cpp b/src/dbus/qdbusmetatype.cpp
index 59a71ade3e..fb2b407997 100644
--- a/src/dbus/qdbusmetatype.cpp
+++ b/src/dbus/qdbusmetatype.cpp
@@ -373,7 +373,7 @@ int QDBusMetaType::signatureToType(const char *signature)
             return qMetaTypeId<QList<QDBusSignature> >();
 
         }
-        // fall through
+        Q_FALLTHROUGH();
     default:
         return QMetaType::UnknownType;
     }
diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index bd32ca7bee..9b14500e7a 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -1888,7 +1888,7 @@ void QImage::invertPixels(InvertMode mode)
         case QImage::Format_RGBA8888:
             if (mode == InvertRgba)
                 break;
-            // no break
+            Q_FALLTHROUGH();
         case QImage::Format_RGBX8888:
 #if Q_BYTE_ORDER == Q_BIG_ENDIAN
             xorbits = 0xffffff00;
@@ -1900,7 +1900,7 @@ void QImage::invertPixels(InvertMode mode)
         case QImage::Format_ARGB32:
             if (mode == InvertRgba)
                 break;
-            // no break
+            Q_FALLTHROUGH();
         case QImage::Format_RGB32:
             xorbits = 0x00ffffff;
             break;
diff --git a/src/gui/image/qimagereader.cpp b/src/gui/image/qimagereader.cpp
index 45d57856aa..0320d032b0 100644
--- a/src/gui/image/qimagereader.cpp
+++ b/src/gui/image/qimagereader.cpp
@@ -1151,7 +1151,7 @@ bool QImageReader::autoTransform() const
     case QImageReaderPrivate::UsePluginDefault:
         if (d->initHandler())
             return d->handler->supportsOption(QImageIOHandler::TransformedByDefault);
-        // no break
+        Q_FALLTHROUGH();
     default:
         break;
     }
diff --git a/src/gui/image/qpixmap_blitter.cpp b/src/gui/image/qpixmap_blitter.cpp
index 4032176efc..950695a9d7 100644
--- a/src/gui/image/qpixmap_blitter.cpp
+++ b/src/gui/image/qpixmap_blitter.cpp
@@ -113,10 +113,10 @@ int QBlittablePlatformPixmap::metric(QPaintDevice::PaintDeviceMetric metric) con
         return qRound(h * 25.4 / qt_defaultDpiY());
     case QPaintDevice::PdmDepth:
         return 32;
-    case QPaintDevice::PdmDpiX: // fall-through
+    case QPaintDevice::PdmDpiX:
     case QPaintDevice::PdmPhysicalDpiX:
         return qt_defaultDpiX();
-    case QPaintDevice::PdmDpiY: // fall-through
+    case QPaintDevice::PdmDpiY:
     case QPaintDevice::PdmPhysicalDpiY:
         return qt_defaultDpiY();
     case QPaintDevice::PdmDevicePixelRatio:
diff --git a/src/gui/kernel/qplatformgraphicsbufferhelper.cpp b/src/gui/kernel/qplatformgraphicsbufferhelper.cpp
index 82a88eca04..2afb5e6ba5 100644
--- a/src/gui/kernel/qplatformgraphicsbufferhelper.cpp
+++ b/src/gui/kernel/qplatformgraphicsbufferhelper.cpp
@@ -154,14 +154,14 @@ bool QPlatformGraphicsBufferHelper::bindSWToTexture(const QPlatformGraphicsBuffe
         switch (imageformat) {
         case QImage::Format_ARGB32_Premultiplied:
             premultiplied = true;
-            // no break
+            Q_FALLTHROUGH();
         case QImage::Format_RGB32:
         case QImage::Format_ARGB32:
             swizzle = true;
             break;
         case QImage::Format_RGBA8888_Premultiplied:
             premultiplied = true;
-            // no break
+            Q_FALLTHROUGH();
         case QImage::Format_RGBX8888:
         case QImage::Format_RGBA8888:
             break;
diff --git a/src/gui/painting/qcssutil.cpp b/src/gui/painting/qcssutil.cpp
index a826532b43..2d514e14e0 100644
--- a/src/gui/painting/qcssutil.cpp
+++ b/src/gui/painting/qcssutil.cpp
@@ -197,7 +197,7 @@ void qDrawEdge(QPainter *p, qreal x1, qreal y1, qreal x2, qreal y2, qreal dw1, q
         if ((style == BorderStyle_Outset && (edge == TopEdge || edge == LeftEdge))
             || (style == BorderStyle_Inset && (edge == BottomEdge || edge == RightEdge)))
             c = c.color().lighter();
-        // fall through!
+        Q_FALLTHROUGH();
     case BorderStyle_Solid: {
         p->setPen(Qt::NoPen);
         p->setBrush(c);
diff --git a/src/gui/painting/qpathclipper.cpp b/src/gui/painting/qpathclipper.cpp
index 4f2b59c775..f92a681eca 100644
--- a/src/gui/painting/qpathclipper.cpp
+++ b/src/gui/painting/qpathclipper.cpp
@@ -1760,7 +1760,7 @@ static bool bool_op(bool a, bool b, QPathClipper::Operation op)
     switch (op) {
     case QPathClipper::BoolAnd:
         return a && b;
-    case QPathClipper::BoolOr: // fall-through
+    case QPathClipper::BoolOr:
     case QPathClipper::Simplify:
         return a || b;
     case QPathClipper::BoolSub:
@@ -1956,7 +1956,7 @@ QPointF intersectLine(const QPointF &a, const QPointF &b, qreal t)
 {
     QLineF line(a, b);
     switch (edge) {
-    case Left: // fall-through
+    case Left:
     case Right:
         return line.pointAt((t - a.x()) / (b.x() - a.x()));
     default:
diff --git a/src/gui/painting/qpdf.cpp b/src/gui/painting/qpdf.cpp
index 34f1c51f6d..d246c96da6 100644
--- a/src/gui/painting/qpdf.cpp
+++ b/src/gui/painting/qpdf.cpp
@@ -2091,7 +2091,7 @@ int QPdfEnginePrivate::generateLinearGradientShader(const QLinearGradient *gradi
         break;
     case QGradient::ReflectSpread:
         reflect = true;
-        // fall through
+        Q_FALLTHROUGH();
     case QGradient::RepeatSpread: {
         // calculate required bounds
         QRectF pageRect = m_pageLayout.fullRectPixels(resolution);
@@ -2154,7 +2154,7 @@ int QPdfEnginePrivate::generateRadialGradientShader(const QRadialGradient *gradi
         break;
     case QGradient::ReflectSpread:
         reflect = true;
-        // fall through
+        Q_FALLTHROUGH();
     case QGradient::RepeatSpread: {
         Q_ASSERT(qFuzzyIsNull(r0)); // QPainter emulates if this is not 0
 
diff --git a/src/gui/painting/qplatformbackingstore.cpp b/src/gui/painting/qplatformbackingstore.cpp
index e2c5a82ffc..0c5de36981 100644
--- a/src/gui/painting/qplatformbackingstore.cpp
+++ b/src/gui/painting/qplatformbackingstore.cpp
@@ -471,14 +471,14 @@ GLuint QPlatformBackingStore::toTexture(const QRegion &dirtyRegion, QSize *textu
     switch (image.format()) {
     case QImage::Format_ARGB32_Premultiplied:
         *flags |= TexturePremultiplied;
-        // no break
+        Q_FALLTHROUGH();
     case QImage::Format_RGB32:
     case QImage::Format_ARGB32:
         *flags |= TextureSwizzle;
         break;
     case QImage::Format_RGBA8888_Premultiplied:
         *flags |= TexturePremultiplied;
-        // no break
+        Q_FALLTHROUGH();
     case QImage::Format_RGBX8888:
     case QImage::Format_RGBA8888:
         break;
diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index 6058811176..2d841b2953 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -446,7 +446,7 @@ QTransform &QTransform::translate(qreal dx, qreal dy)
         break;
     case TxProject:
         m_33 += dx*m_13 + dy*m_23;
-        // Fall through
+        Q_FALLTHROUGH();
     case TxShear:
     case TxRotate:
         affine._dx += dx*affine._m11 + dy*affine._m21;
@@ -508,12 +508,12 @@ QTransform & QTransform::scale(qreal sx, qreal sy)
     case TxProject:
         m_13 *= sx;
         m_23 *= sy;
-        // fall through
+        Q_FALLTHROUGH();
     case TxRotate:
     case TxShear:
         affine._m12 *= sx;
         affine._m21 *= sy;
-        // fall through
+        Q_FALLTHROUGH();
     case TxScale:
         affine._m11 *= sx;
         affine._m22 *= sy;
@@ -581,7 +581,7 @@ QTransform & QTransform::shear(qreal sh, qreal sv)
         m_13 += tm13;
         m_23 += tm23;
     }
-        // fall through
+        Q_FALLTHROUGH();
     case TxRotate:
     case TxShear: {
         qreal tm11 = sv*affine._m21;
@@ -663,7 +663,7 @@ QTransform & QTransform::rotate(qreal a, Qt::Axis axis)
             qreal tm23 = -sina*m_13 + cosa*m_23;
             m_13 = tm13;
             m_23 = tm23;
-            // fall through
+            Q_FALLTHROUGH();
         }
         case TxRotate:
         case TxShear: {
@@ -742,7 +742,7 @@ QTransform & QTransform::rotateRadians(qreal a, Qt::Axis axis)
             qreal tm23 = -sina*m_13 + cosa*m_23;
             m_13 = tm13;
             m_23 = tm23;
-            // fall through
+            Q_FALLTHROUGH();
         }
         case TxRotate:
         case TxShear: {
diff --git a/src/gui/painting/qtriangulator.cpp b/src/gui/painting/qtriangulator.cpp
index 7906011cd2..6604d407f0 100644
--- a/src/gui/painting/qtriangulator.cpp
+++ b/src/gui/painting/qtriangulator.cpp
@@ -874,7 +874,7 @@ void QTriangulator<T>::initialize(const QVectorPath &path, const QTransform &mat
             case QPainterPath::MoveToElement:
                 if (!m_indices.isEmpty())
                     m_indices.push_back(T(-1)); // Q_TRIANGULATE_END_OF_POLYGON
-                // Fall through.
+                Q_FALLTHROUGH();
             case QPainterPath::LineToElement:
                 m_indices.push_back(T(m_vertices.size()));
                 m_vertices.resize(m_vertices.size() + 1);
@@ -2100,7 +2100,7 @@ void QTriangulator<T>::SimpleToMonotone::monotoneDecomposition()
             } else {
                 qWarning("Inconsistent polygon. (#3)");
             }
-            // Fall through.
+            Q_FALLTHROUGH();
         case StartVertex:
             if (m_clockwiseOrder) {
                 leftEdgeNode = searchEdgeLeftOfEdge(j);
@@ -2129,7 +2129,7 @@ void QTriangulator<T>::SimpleToMonotone::monotoneDecomposition()
             } else {
                 qWarning("Inconsistent polygon. (#4)");
             }
-            // Fall through.
+            Q_FALLTHROUGH();
         case EndVertex:
             if (m_clockwiseOrder) {
                 if (m_edges.at(m_edges.at(i).helper).type == MergeVertex)
diff --git a/src/gui/text/qfontsubset.cpp b/src/gui/text/qfontsubset.cpp
index c8f0393084..49638832e0 100644
--- a/src/gui/text/qfontsubset.cpp
+++ b/src/gui/text/qfontsubset.cpp
@@ -740,7 +740,7 @@ static void convertPath(const QPainterPath &path, QVector<TTF_POINT> *points, QV
                     points->takeLast();
                 endPoints->append(points->size() - 1);
             }
-            // fall through
+            Q_FALLTHROUGH();
         case QPainterPath::LineToElement:
             p.flags = OnCurve;
             break;
diff --git a/src/gui/text/qtextcursor.cpp b/src/gui/text/qtextcursor.cpp
index f824d1b369..f32c31d18e 100644
--- a/src/gui/text/qtextcursor.cpp
+++ b/src/gui/text/qtextcursor.cpp
@@ -438,7 +438,7 @@ bool QTextCursorPrivate::movePosition(QTextCursor::MoveOperation op, QTextCursor
         if (relativePos < blockIt.length()-1)
             ++position;
 
-        // FALL THROUGH!
+        Q_FALLTHROUGH();
     }
     case QTextCursor::PreviousWord:
     case QTextCursor::WordLeft:
@@ -590,9 +590,9 @@ bool QTextCursorPrivate::movePosition(QTextCursor::MoveOperation op, QTextCursor
         adjustX = false;
         break;
     }
-    case QTextCursor::NextCell: // fall through
-    case QTextCursor::PreviousCell: // fall through
-    case QTextCursor::NextRow: // fall through
+    case QTextCursor::NextCell:
+    case QTextCursor::PreviousCell:
+    case QTextCursor::NextRow:
     case QTextCursor::PreviousRow: {
         QTextTable *table = qobject_cast<QTextTable *>(priv->frameAt(position));
         if (!table)
diff --git a/src/gui/text/qtextdocumentfragment.cpp b/src/gui/text/qtextdocumentfragment.cpp
index 5727b34e86..079b2e01f7 100644
--- a/src/gui/text/qtextdocumentfragment.cpp
+++ b/src/gui/text/qtextdocumentfragment.cpp
@@ -827,7 +827,7 @@ bool QTextHtmlImporter::closeTag()
             case Html_div:
                 if (closedNode->children.isEmpty())
                     break;
-                // fall through
+                Q_FALLTHROUGH();
             default:
                 if (closedNode->isBlock())
                     blockTagClosed = true;
diff --git a/src/gui/text/qtextengine.cpp b/src/gui/text/qtextengine.cpp
index d9b648b170..1aaacdd00d 100644
--- a/src/gui/text/qtextengine.cpp
+++ b/src/gui/text/qtextengine.cpp
@@ -508,7 +508,7 @@ static bool bidiItemize(QTextEngine *engine, QScriptAnalysis *analysis, QBidiCon
                 case QChar::DirAN:
                     if (eor >= 0)
                         appendItems(analysis, sor, eor, control, dir);
-                    // fall through
+                    Q_FALLTHROUGH();
                 case QChar::DirR:
                 case QChar::DirAL:
                     dir = QChar::DirR; eor = current; status.eor = QChar::DirR; break;
@@ -564,7 +564,7 @@ static bool bidiItemize(QTextEngine *engine, QScriptAnalysis *analysis, QBidiCon
                             status.eor = QChar::DirON;
                             dir = QChar::DirAN;
                         }
-                        // fall through
+                        Q_FALLTHROUGH();
                     case QChar::DirEN:
                     case QChar::DirL:
                         eor = current;
@@ -744,7 +744,7 @@ static bool bidiItemize(QTextEngine *engine, QScriptAnalysis *analysis, QBidiCon
                 status.last = QChar::DirL;
                 break;
             }
-            // fall through
+            Q_FALLTHROUGH();
         default:
             status.last = dirCurrent;
         }
@@ -1663,7 +1663,7 @@ void QTextEngine::itemize() const
                 analysis->bidiLevel = control.baseLevel();
                 break;
             }
-        // fall through
+            Q_FALLTHROUGH();
         default:
             analysis->flags = QScriptAnalysis::None;
             break;
@@ -2250,7 +2250,6 @@ void QTextEngine::justify(const QScriptLine &line)
             case Justification_Prohibited:
                 break;
             case Justification_Space:
-                // fall through
             case Justification_Arabic_Space:
                 if (kashida_pos >= 0) {
 //                     qDebug("kashida position at %d in word", kashida_pos);
@@ -2263,7 +2262,7 @@ void QTextEngine::justify(const QScriptLine &line)
                 }
                 kashida_pos = -1;
                 kashida_type = Justification_Arabic_Normal;
-                // fall through
+                Q_FALLTHROUGH();
             case Justification_Character:
                 set(&justificationPoints[nPoints++], justification, g.mid(i), fontEngine(si));
                 maxJustify = qMax(maxJustify, justification);
@@ -2966,9 +2965,8 @@ QFixed QTextEngine::calculateTabWidth(int item, QFixed x) const
                     switch (tabSpec.type) {
                     case QTextOption::CenterTab:
                         length /= 2;
-                        // fall through
+                        Q_FALLTHROUGH();
                     case QTextOption::DelimiterTab:
-                        // fall through
                     case QTextOption::RightTab:
                         tab = QFixed::fromReal(tabSpec.position) * dpiScale - length;
                         if (tab < x) // default to tab taking no space
diff --git a/src/gui/text/qtexthtmlparser.cpp b/src/gui/text/qtexthtmlparser.cpp
index 7bca50325c..7fac3331f1 100644
--- a/src/gui/text/qtexthtmlparser.cpp
+++ b/src/gui/text/qtexthtmlparser.cpp
@@ -1871,7 +1871,7 @@ QVector<QCss::Declaration> standardDeclarationForNode(const QTextHtmlParserNode
         decls << decl;
         if (node.id == Html_b || node.id == Html_strong)
             break;
-        // Delibrate fall through
+        Q_FALLTHROUGH();
     case Html_big:
     case Html_small:
         if (node.id != Html_th) {
@@ -1892,7 +1892,7 @@ QVector<QCss::Declaration> standardDeclarationForNode(const QTextHtmlParserNode
             decls << decl;
             break;
         }
-        // Delibrate fall through
+        Q_FALLTHROUGH();
     case Html_center:
     case Html_td:
         decl = QCss::Declaration();
@@ -1969,7 +1969,7 @@ QVector<QCss::Declaration> standardDeclarationForNode(const QTextHtmlParserNode
         }
         if (node.id != Html_pre)
             break;
-        // Delibrate fall through
+        Q_FALLTHROUGH();
     case Html_br:
     case Html_nobr:
         decl = QCss::Declaration();
diff --git a/src/network/access/qftp.cpp b/src/network/access/qftp.cpp
index 7b6f830333..52b9dd9169 100644
--- a/src/network/access/qftp.cpp
+++ b/src/network/access/qftp.cpp
@@ -1121,7 +1121,7 @@ bool QFtpPI::processReply()
         case Success:
             // success handling
             state = Idle;
-            // no break!
+            Q_FALLTHROUGH();
         case Idle:
             if (dtp.hasError()) {
                 emit error(QFtp::UnknownError, dtp.errorMessage());
diff --git a/src/network/access/qhttpnetworkconnectionchannel.cpp b/src/network/access/qhttpnetworkconnectionchannel.cpp
index 3a780f636b..87f88aad5f 100644
--- a/src/network/access/qhttpnetworkconnectionchannel.cpp
+++ b/src/network/access/qhttpnetworkconnectionchannel.cpp
@@ -1036,7 +1036,7 @@ void QHttpNetworkConnectionChannel::_q_encrypted()
 
     if (!protocolHandler) {
         switch (sslSocket->sslConfiguration().nextProtocolNegotiationStatus()) {
-        case QSslConfiguration::NextProtocolNegotiationNegotiated: /* fall through */
+        case QSslConfiguration::NextProtocolNegotiationNegotiated:
         case QSslConfiguration::NextProtocolNegotiationUnsupported: {
             QByteArray nextProtocol = sslSocket->sslConfiguration().nextNegotiatedProtocol();
             if (nextProtocol == QSslConfiguration::NextProtocolHttp1_1) {
@@ -1056,6 +1056,7 @@ void QHttpNetworkConnectionChannel::_q_encrypted()
                                       "detected unknown Next Protocol Negotiation protocol");
                 break;
             }
+            Q_FALLTHROUGH();
         }
         case QSslConfiguration::NextProtocolNegotiationNone:
             protocolHandler.reset(new QHttpProtocolHandler(this));
diff --git a/src/network/access/qhttpprotocolhandler.cpp b/src/network/access/qhttpprotocolhandler.cpp
index b486b75449..37e8b9bed8 100644
--- a/src/network/access/qhttpprotocolhandler.cpp
+++ b/src/network/access/qhttpprotocolhandler.cpp
@@ -99,7 +99,7 @@ void QHttpProtocolHandler::_q_receiveReply()
         switch (state) {
         case QHttpNetworkReplyPrivate::NothingDoneState: {
             m_reply->d_func()->state = QHttpNetworkReplyPrivate::ReadingStatusState;
-            // fallthrough
+            Q_FALLTHROUGH();
         }
         case QHttpNetworkReplyPrivate::ReadingStatusState: {
             qint64 statusBytes = m_reply->d_func()->readStatus(m_socket);
@@ -213,7 +213,8 @@ void QHttpProtocolHandler::_q_receiveReply()
             if (replyPrivate->state == QHttpNetworkReplyPrivate::ReadingDataState)
                 break;
 
-            // everything done, fall through
+            // everything done
+            Q_FALLTHROUGH();
             }
       case QHttpNetworkReplyPrivate::AllDoneState:
             m_channel->allDone();
@@ -428,7 +429,7 @@ bool QHttpProtocolHandler::sendRequest()
     }
     case QHttpNetworkConnectionChannel::ReadingState:
         // ignore _q_bytesWritten in these states
-        // fall through
+        Q_FALLTHROUGH();
     default:
         break;
     }
diff --git a/src/network/access/qnetworkcookie.cpp b/src/network/access/qnetworkcookie.cpp
index 7a538cbf08..b7cf989477 100644
--- a/src/network/access/qnetworkcookie.cpp
+++ b/src/network/access/qnetworkcookie.cpp
@@ -644,7 +644,7 @@ static QDateTime parseDateString(const QByteArray &dateString)
             switch (end - 1) {
             case 4:
                 minutes = atoi(dateString.mid(at + 3, 2).constData());
-                // fall through
+                Q_FALLTHROUGH();
             case 2:
                 hours = atoi(dateString.mid(at + 1, 2).constData());
                 break;
diff --git a/src/network/kernel/qhostaddress.cpp b/src/network/kernel/qhostaddress.cpp
index 95f90af49e..7e3d2c5d6e 100644
--- a/src/network/kernel/qhostaddress.cpp
+++ b/src/network/kernel/qhostaddress.cpp
@@ -536,7 +536,7 @@ QHostAddress::QHostAddress(SpecialAddress address)
 
     case LocalHostIPv6:
         ip6[15] = 1;
-        // fall through
+        Q_FALLTHROUGH();
     case AnyIPv6:
         d->setAddress(ip6);
         return;
diff --git a/src/network/socket/qnativesocketengine_win.cpp b/src/network/socket/qnativesocketengine_win.cpp
index 9ae2d8ba8f..5a9641a9fe 100644
--- a/src/network/socket/qnativesocketengine_win.cpp
+++ b/src/network/socket/qnativesocketengine_win.cpp
@@ -712,7 +712,7 @@ bool QNativeSocketEnginePrivate::nativeConnect(const QHostAddress &address, quin
 
                 if (errorDetected)
                     break;
-                // fall through
+                Q_FALLTHROUGH();
             }
             case WSAEINPROGRESS:
                 setError(QAbstractSocket::UnfinishedSocketOperationError, InvalidSocketErrorString);
diff --git a/src/network/socket/qsocks5socketengine.cpp b/src/network/socket/qsocks5socketengine.cpp
index 518ec21f90..a1a8e4649d 100644
--- a/src/network/socket/qsocks5socketengine.cpp
+++ b/src/network/socket/qsocks5socketengine.cpp
@@ -618,7 +618,7 @@ void QSocks5SocketEnginePrivate::setErrorState(Socks5State state, const QString
                                  QSocks5SocketEngine::tr("Connection to proxy timed out"));
                     break;
                 }
-                /* fall through */
+                Q_FALLTHROUGH();
             default:
                 q->setError(controlSocketError, data->controlSocket->errorString());
                 break;
@@ -1205,7 +1205,7 @@ void QSocks5SocketEnginePrivate::_q_controlSocketReadNotification()
                 break;
             }
 
-            // fall through
+            Q_FALLTHROUGH();
         default:
             qWarning("QSocks5SocketEnginePrivate::_q_controlSocketReadNotification: "
                      "Unexpectedly received data while in state=%d and mode=%d",
diff --git a/src/platformsupport/fbconvenience/qfbvthandler.cpp b/src/platformsupport/fbconvenience/qfbvthandler.cpp
index 4c4a01a82e..2429cb7c5c 100644
--- a/src/platformsupport/fbconvenience/qfbvthandler.cpp
+++ b/src/platformsupport/fbconvenience/qfbvthandler.cpp
@@ -171,7 +171,7 @@ void QFbVtHandler::handleSignal()
     char sigNo;
     if (QT_READ(m_sigFd[1], &sigNo, sizeof(sigNo)) == sizeof(sigNo)) {
         switch (sigNo) {
-        case SIGINT: // fallthrough
+        case SIGINT:
         case SIGTERM:
             handleInt();
             break;
diff --git a/src/plugins/bearer/qnetworksession_impl.cpp b/src/plugins/bearer/qnetworksession_impl.cpp
index 426cca139d..85942b56f1 100644
--- a/src/plugins/bearer/qnetworksession_impl.cpp
+++ b/src/plugins/bearer/qnetworksession_impl.cpp
@@ -111,10 +111,10 @@ void QNetworkSessionPrivateImpl::syncStateWithInterface()
     case QNetworkConfiguration::ServiceNetwork:
         serviceConfig = publicConfig;
         // Defer setting engine and signals until open().
-        // fall through
+        Q_FALLTHROUGH();
     case QNetworkConfiguration::UserChoice:
         // Defer setting serviceConfig and activeConfig until open().
-        // fall through
+        Q_FALLTHROUGH();
     default:
         engine = 0;
     }
diff --git a/src/plugins/platforms/android/qandroidplatformtheme.cpp b/src/plugins/platforms/android/qandroidplatformtheme.cpp
index 3949113240..b9009fe704 100644
--- a/src/plugins/platforms/android/qandroidplatformtheme.cpp
+++ b/src/plugins/platforms/android/qandroidplatformtheme.cpp
@@ -489,7 +489,7 @@ QVariant QAndroidPlatformTheme::themeHint(ThemeHint hint) const
             if (ret > 0)
                 return ret;
 
-            // fall through
+            Q_FALLTHROUGH();
     }
     default:
         return QPlatformTheme::themeHint(hint);
diff --git a/src/plugins/platforms/cocoa/qprintengine_mac.mm b/src/plugins/platforms/cocoa/qprintengine_mac.mm
index 3d0c91c36c..0b5b06c44f 100644
--- a/src/plugins/platforms/cocoa/qprintengine_mac.mm
+++ b/src/plugins/platforms/cocoa/qprintengine_mac.mm
@@ -200,7 +200,7 @@ int QMacPrintEngine::metric(QPaintDevice::PaintDeviceMetric m) const
             val = (int)resolution.vRes;
             break;
         }
-        //otherwise fall through
+        Q_FALLTHROUGH();
     }
     case QPaintDevice::PdmDpiY:
         val = (int)d->resolution.vRes;
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp
index 730d5de450..0ea2fcfa74 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp
@@ -563,7 +563,7 @@ public:
             if (newPen.widthF() <= 1.0)
                 props.startCap = props.endCap = props.dashCap = D2D1_CAP_STYLE_FLAT;
 
-            // fall through
+            Q_FALLTHROUGH();
         default:
             props.dashStyle = D2D1_DASH_STYLE_CUSTOM;
             break;
diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index 3a683bd7a0..d4cdf3ef3c 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -945,7 +945,8 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
     switch (et) {
     case QtWindows::KeyboardLayoutChangeEvent:
         if (QWindowsInputContext *wic = windowsInputContext())
-            wic->handleInputLanguageChanged(wParam, lParam); // fallthrough intended.
+            wic->handleInputLanguageChanged(wParam, lParam);
+        Q_FALLTHROUGH();
     case QtWindows::KeyDownEvent:
     case QtWindows::KeyEvent:
     case QtWindows::InputMethodKeyEvent:
diff --git a/src/plugins/platforms/windows/qwindowstheme.cpp b/src/plugins/platforms/windows/qwindowstheme.cpp
index 79befc56c2..841464391d 100644
--- a/src/plugins/platforms/windows/qwindowstheme.cpp
+++ b/src/plugins/platforms/windows/qwindowstheme.cpp
@@ -551,14 +551,14 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &pixmapSiz
         break;
     case FileLinkIcon:
         stockFlags = SHGSI_LINKOVERLAY;
-        // Fall through
+        Q_FALLTHROUGH();
     case FileIcon:
         stockId = SIID_DOCNOASSOC;
         resourceId = 1;
         break;
     case DirLinkIcon:
         stockFlags = SHGSI_LINKOVERLAY;
-        // Fall through
+        Q_FALLTHROUGH();
     case DirClosedIcon:
     case DirIcon:
         stockId = SIID_FOLDER;
@@ -572,7 +572,7 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &pixmapSiz
         break;
     case DirLinkOpenIcon:
         stockFlags = SHGSI_LINKOVERLAY;
-        // Fall through
+        Q_FALLTHROUGH();
     case DirOpenIcon:
         stockId = SIID_FOLDEROPEN;
         resourceId = 5;
diff --git a/src/printsupport/kernel/qprintengine_pdf.cpp b/src/printsupport/kernel/qprintengine_pdf.cpp
index ed0422468d..278bb044e1 100644
--- a/src/printsupport/kernel/qprintengine_pdf.cpp
+++ b/src/printsupport/kernel/qprintengine_pdf.cpp
@@ -150,7 +150,7 @@ void QPdfPrintEngine::setProperty(PrintEnginePropertyKey key, const QVariant &va
         else
             d->m_pageLayout.setMode(QPageLayout::StandardMode);
         break;
-    case PPK_CopyCount: // fallthrough
+    case PPK_CopyCount:
     case PPK_NumberOfCopies:
         d->copies = value.toInt();
         break;
diff --git a/src/printsupport/kernel/qprintengine_win.cpp b/src/printsupport/kernel/qprintengine_win.cpp
index b3dc33895b..b0f85dc825 100644
--- a/src/printsupport/kernel/qprintengine_win.cpp
+++ b/src/printsupport/kernel/qprintengine_win.cpp
@@ -1141,7 +1141,7 @@ void QWin32PrintEngine::setProperty(PrintEnginePropertyKey key, const QVariant &
 #endif // QT_DEBUG_METRICS
         break;
 
-    case PPK_CopyCount: // fallthrough
+    case PPK_CopyCount:
     case PPK_NumberOfCopies:
         if (!d->devMode)
             break;
diff --git a/src/testlib/qtestmouse.h b/src/testlib/qtestmouse.h
index 632b801221..1143361323 100644
--- a/src/testlib/qtestmouse.h
+++ b/src/testlib/qtestmouse.h
@@ -115,14 +115,14 @@ namespace QTest
         case MouseDClick:
             qt_handleMouseEvent(w, pos, global, button, stateKey, ++lastMouseTimestamp);
             qt_handleMouseEvent(w, pos, global, Qt::NoButton, stateKey, ++lastMouseTimestamp);
-            // fall through
+            Q_FALLTHROUGH();
         case MousePress:
         case MouseClick:
             qt_handleMouseEvent(w, pos, global, button, stateKey, ++lastMouseTimestamp);
             lastMouseButton = button;
             if (action == MousePress)
                 break;
-            // fall through
+            Q_FALLTHROUGH();
         case MouseRelease:
             qt_handleMouseEvent(w, pos, global, Qt::NoButton, stateKey, ++lastMouseTimestamp);
             lastMouseTimestamp += 500; // avoid double clicks being generated
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index 87fb1318f9..afe64bb889 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -163,7 +163,7 @@ Type Moc::parseType()
             case SIGNED:
             case UNSIGNED:
                 hasSignedOrUnsigned = true;
-                // fall through
+                Q_FALLTHROUGH();
             case CONST:
             case VOLATILE:
                 type.name += lexem();
diff --git a/src/tools/moc/preprocessor.cpp b/src/tools/moc/preprocessor.cpp
index 415003e6b1..5ce28d931b 100644
--- a/src/tools/moc/preprocessor.cpp
+++ b/src/tools/moc/preprocessor.cpp
@@ -251,7 +251,7 @@ Symbols Preprocessor::tokenize(const QByteArray& input, int lineNum, Preprocesso
                     }
                     token = FLOATING_LITERAL;
                     ++data;
-                    // fall through
+                    Q_FALLTHROUGH();
                 case FLOATING_LITERAL:
                     while (is_digit_char(*data))
                         ++data;
@@ -321,7 +321,7 @@ Symbols Preprocessor::tokenize(const QByteArray& input, int lineNum, Preprocesso
                         ++data;
                     }
                     token = WHITESPACE; // one comment, one whitespace
-                    // fall through;
+                    Q_FALLTHROUGH();
                 case WHITESPACE:
                     if (column == 1)
                         column = 0;
@@ -428,7 +428,7 @@ Symbols Preprocessor::tokenize(const QByteArray& input, int lineNum, Preprocesso
                 }
                 token = PP_FLOATING_LITERAL;
                 ++data;
-                // fall through
+                Q_FALLTHROUGH();
             case PP_FLOATING_LITERAL:
                 while (is_digit_char(*data))
                     ++data;
@@ -482,7 +482,7 @@ Symbols Preprocessor::tokenize(const QByteArray& input, int lineNum, Preprocesso
                     ++data;
                 }
                 token = PP_WHITESPACE; // one comment, one whitespace
-                // fall through;
+                Q_FALLTHROUGH();
             case PP_WHITESPACE:
                 while (*data && (*data == ' ' || *data == '\t'))
                     ++data;
@@ -1177,7 +1177,7 @@ void Preprocessor::preprocess(const QByteArray &filename, Symbols &preprocessed)
         case PP_ELIF:
         case PP_ELSE:
             skipUntilEndif();
-            // fall through
+            Q_FALLTHROUGH();
         case PP_ENDIF:
             until(PP_NEWLINE);
             continue;
diff --git a/src/tools/qdbuscpp2xml/qdbuscpp2xml.cpp b/src/tools/qdbuscpp2xml/qdbuscpp2xml.cpp
index 083187555d..26e7b086d9 100644
--- a/src/tools/qdbuscpp2xml/qdbuscpp2xml.cpp
+++ b/src/tools/qdbuscpp2xml/qdbuscpp2xml.cpp
@@ -335,28 +335,28 @@ static void parseCmdLine(QStringList &arguments)
         switch (c) {
         case 'P':
             flags |= QDBusConnection::ExportNonScriptableProperties;
-            // fall through
+            Q_FALLTHROUGH();
         case 'p':
             flags |= QDBusConnection::ExportScriptableProperties;
             break;
 
         case 'S':
             flags |= QDBusConnection::ExportNonScriptableSignals;
-            // fall through
+            Q_FALLTHROUGH();
         case 's':
             flags |= QDBusConnection::ExportScriptableSignals;
             break;
 
         case 'M':
             flags |= QDBusConnection::ExportNonScriptableSlots;
-            // fall through
+            Q_FALLTHROUGH();
         case 'm':
             flags |= QDBusConnection::ExportScriptableSlots;
             break;
 
         case 'A':
             flags |= QDBusConnection::ExportNonScriptableContents;
-            // fall through
+            Q_FALLTHROUGH();
         case 'a':
             flags |= QDBusConnection::ExportScriptableContents;
             break;
diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index 689704884f..96046b7ff4 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/src/widgets/dialogs/qmessagebox.cpp
@@ -1379,7 +1379,7 @@ void QMessageBox::changeEvent(QEvent *ev)
         d->buttonBox->setCenterButtons(style()->styleHint(QStyle::SH_MessageBox_CenterButtons, 0, this));
         if (d->informativeLabel)
             d->informativeLabel->setTextInteractionFlags(flags);
-        // intentional fall through
+        Q_FALLTHROUGH();
     }
     case QEvent::FontChange:
     case QEvent::ApplicationFontChange:
@@ -1390,6 +1390,7 @@ void QMessageBox::changeEvent(QEvent *ev)
         d->label->setFont(f);
     }
 #endif
+        Q_FALLTHROUGH();
     default:
         break;
     }
diff --git a/src/widgets/graphicsview/qgraphicsitem.cpp b/src/widgets/graphicsview/qgraphicsitem.cpp
index 4b5e380f4b..5492862287 100644
--- a/src/widgets/graphicsview/qgraphicsitem.cpp
+++ b/src/widgets/graphicsview/qgraphicsitem.cpp
@@ -9570,7 +9570,7 @@ public:
                 shape = qt_regionToPath(QRegion(mask).translated(offset.toPoint()));
                 break;
             }
-            // FALL THROUGH
+            Q_FALLTHROUGH();
         }
         case QGraphicsPixmapItem::BoundingRectShape:
             shape.addRect(QRectF(offset.x(), offset.y(), pixmap.width(), pixmap.height()));
diff --git a/src/widgets/itemviews/qheaderview.cpp b/src/widgets/itemviews/qheaderview.cpp
index 7b393463a6..6f1e301d4f 100644
--- a/src/widgets/itemviews/qheaderview.cpp
+++ b/src/widgets/itemviews/qheaderview.cpp
@@ -2563,7 +2563,7 @@ void QHeaderView::mouseReleaseEvent(QMouseEvent *e)
             int section = logicalIndexAt(pos);
             updateSection(section);
         }
-        // fall through
+        Q_FALLTHROUGH();
     case QHeaderViewPrivate::NoState:
         if (d->clickableSections) {
             int section = logicalIndexAt(pos);
@@ -2669,7 +2669,7 @@ bool QHeaderView::viewportEvent(QEvent *e)
     case QEvent::FontChange:
     case QEvent::StyleChange:
         d->invalidateCachedSizeHint();
-        // Fall through
+        Q_FALLTHROUGH();
     case QEvent::Hide:
     case QEvent::Show: {
         QAbstractScrollArea *parent = qobject_cast<QAbstractScrollArea *>(parentWidget());
diff --git a/src/widgets/itemviews/qtreewidget.cpp b/src/widgets/itemviews/qtreewidget.cpp
index 74ca7d2827..5e0f13277c 100644
--- a/src/widgets/itemviews/qtreewidget.cpp
+++ b/src/widgets/itemviews/qtreewidget.cpp
@@ -1737,7 +1737,7 @@ void QTreeWidgetItem::setData(int column, int role, const QVariant &value)
                 }
             }
         }
-        // Don't break, but fall through
+        Q_FALLTHROUGH();
     default:
         if (column < values.count()) {
             bool found = false;
@@ -1787,7 +1787,7 @@ QVariant QTreeWidgetItem::data(int column, int role) const
         // special case for check state in tristate
         if (children.count() && (itemFlags & Qt::ItemIsAutoTristate))
             return childrenCheckState(column);
-        // fallthrough intended
+        Q_FALLTHROUGH();
    default:
         if (column >= 0 && column < values.size()) {
             const QVector<QWidgetItemData> &column_values = values.at(column);
diff --git a/src/widgets/kernel/qwhatsthis.cpp b/src/widgets/kernel/qwhatsthis.cpp
index 66b622911a..32fe5f5e64 100644
--- a/src/widgets/kernel/qwhatsthis.cpp
+++ b/src/widgets/kernel/qwhatsthis.cpp
@@ -450,8 +450,8 @@ bool QWhatsThisPrivate::eventFilter(QObject *o, QEvent *e)
         QApplication::changeOverrideCursor((!sentEvent || !e.isAccepted())?
                                            Qt::ForbiddenCursor:Qt::WhatsThisCursor);
 #endif
+        Q_FALLTHROUGH();
     }
-    // fall through
     case QEvent::MouseButtonRelease:
     case QEvent::MouseButtonDblClick:
         if (leaveOnMouseRelease && e->type() == QEvent::MouseButtonRelease)
diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 25874e9bcc..e0b8024f9a 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -8835,7 +8835,7 @@ bool QWidget::event(QEvent *event)
 
     case QEvent::KeyRelease:
         keyReleaseEvent((QKeyEvent*)event);
-        // fall through
+        Q_FALLTHROUGH();
     case QEvent::ShortcutOverride:
         break;
 
@@ -8954,7 +8954,7 @@ bool QWidget::event(QEvent *event)
                             0, this);
                 break;
             }
-            // fall through
+            Q_FALLTHROUGH();
 #endif
         default:
             event->ignore();
@@ -9193,7 +9193,7 @@ bool QWidget::event(QEvent *event)
         }
         if (windowHandle() && !qstrncmp(propName, "_q_platform_", 12))
             windowHandle()->setProperty(propName, property(propName));
-        // fall through
+        Q_FALLTHROUGH();
     }
 #endif
     default:
@@ -11194,13 +11194,13 @@ void QWidget::setAttribute(Qt::WidgetAttribute attribute, bool on)
             d->enforceNativeChildren();
         }
 #endif
-        // fall through
+        Q_FALLTHROUGH();
     case Qt::WA_OpaquePaintEvent:
         d->updateIsOpaque();
         break;
     case Qt::WA_NoSystemBackground:
         d->updateIsOpaque();
-        // fall through...
+        Q_FALLTHROUGH();
     case Qt::WA_UpdatesDisabled:
         d->updateSystemBackground();
         break;
diff --git a/src/widgets/styles/qcommonstyle.cpp b/src/widgets/styles/qcommonstyle.cpp
index 6cdfc061e1..140f0ad2f3 100644
--- a/src/widgets/styles/qcommonstyle.cpp
+++ b/src/widgets/styles/qcommonstyle.cpp
@@ -4232,7 +4232,6 @@ QRect QCommonStyle::subControlRect(ComplexControl cc, const QStyleOptionComplex
         if (const QStyleOptionGroupBox *groupBox = qstyleoption_cast<const QStyleOptionGroupBox *>(opt)) {
             switch (sc) {
             case SC_GroupBoxFrame:
-                // FALL THROUGH
             case SC_GroupBoxContents: {
                 int topMargin = 0;
                 int topHeight = 0;
@@ -4261,7 +4260,6 @@ QRect QCommonStyle::subControlRect(ComplexControl cc, const QStyleOptionComplex
                 break;
             }
             case SC_GroupBoxCheckBox:
-                // FALL THROUGH
             case SC_GroupBoxLabel: {
                 QFontMetrics fontMetrics = groupBox->fontMetrics;
                 int h = fontMetrics.height();
@@ -4327,7 +4325,7 @@ QRect QCommonStyle::subControlRect(ComplexControl cc, const QStyleOptionComplex
             if (numSubControls == 1)
                 break;
             offset += buttonWidth + 2;
-            //FALL THROUGH
+            Q_FALLTHROUGH();
         case SC_MdiNormalButton:
             // No offset needed if
             // 1) There's only one sub control
@@ -4895,7 +4893,7 @@ QSize QCommonStyle::sizeFromContents(ContentsType ct, const QStyleOption *opt,
     case CT_ProgressBar:
     case CT_TabBarTab:
         // just return the contentsSize for now
-        // fall through intended
+        Q_FALLTHROUGH();
     default:
         break;
     }
diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 44555c3058..c5904a5a96 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -1100,7 +1100,7 @@ void QRenderRule::fixupBorder(int nativeWidth)
             case BorderStyle_Native:
                 if (bd->borders[i] == 0)
                     bd->borders[i] = nativeWidth;
-                // intentional fall through
+                Q_FALLTHROUGH();
             default:
                 if (bd->colors[i].style() == Qt::NoBrush) // auto-acquire 'color'
                     bd->colors[i] = color;
diff --git a/src/widgets/styles/qwindowsstyle.cpp b/src/widgets/styles/qwindowsstyle.cpp
index c3a50968e2..e3bf28608c 100644
--- a/src/widgets/styles/qwindowsstyle.cpp
+++ b/src/widgets/styles/qwindowsstyle.cpp
@@ -808,7 +808,8 @@ void QWindowsStyle::drawPrimitive(PrimitiveElement pe, const QStyleOption *opt,
             p->setPen(opt->palette.dark().color());
         else
             p->setPen(opt->palette.text().color());
-        } // Fall through!
+        }
+        Q_FALLTHROUGH();
     case PE_IndicatorViewItemCheck:
         if (!doRestore) {
             p->save();
@@ -2383,7 +2384,7 @@ QSize QWindowsStyle::sizeFromContents(ContentsType ct, const QStyleOption *opt,
     case CT_ToolButton:
         if (qstyleoption_cast<const QStyleOptionToolButton *>(opt))
             return sz += QSize(7, 6);
-        // Otherwise, fall through
+        Q_FALLTHROUGH();
 
     default:
         sz = QCommonStyle::sizeFromContents(ct, opt, csz, widget);
diff --git a/src/widgets/styles/qwindowsxpstyle.cpp b/src/widgets/styles/qwindowsxpstyle.cpp
index ffedc37edb..f3a8544d96 100644
--- a/src/widgets/styles/qwindowsxpstyle.cpp
+++ b/src/widgets/styles/qwindowsxpstyle.cpp
@@ -3465,13 +3465,13 @@ QRect QWindowsXPStyle::subControlRect(ComplexControl cc, const QStyleOptionCompl
             case SC_TitleBarContextHelpButton:
                 if (tb->titleBarFlags & Qt::WindowContextHelpButtonHint)
                     offset += delta;
-                //fall through
+                Q_FALLTHROUGH();
             case SC_TitleBarMinButton:
                 if (!isMinimized && (tb->titleBarFlags & Qt::WindowMinimizeButtonHint))
                     offset += delta;
                 else if (subControl == SC_TitleBarMinButton)
                     break;
-                //fall through
+                Q_FALLTHROUGH();
             case SC_TitleBarNormalButton:
                 if (isMinimized && (tb->titleBarFlags & Qt::WindowMinimizeButtonHint))
                     offset += delta;
@@ -3479,25 +3479,25 @@ QRect QWindowsXPStyle::subControlRect(ComplexControl cc, const QStyleOptionCompl
                     offset += delta;
                 else if (subControl == SC_TitleBarNormalButton)
                     break;
-                //fall through
+                Q_FALLTHROUGH();
             case SC_TitleBarMaxButton:
                 if (!isMaximized && (tb->titleBarFlags & Qt::WindowMaximizeButtonHint))
                     offset += delta;
                 else if (subControl == SC_TitleBarMaxButton)
                     break;
-                //fall through
+                Q_FALLTHROUGH();
             case SC_TitleBarShadeButton:
                 if (!isMinimized && (tb->titleBarFlags & Qt::WindowShadeButtonHint))
                     offset += delta;
                 else if (subControl == SC_TitleBarShadeButton)
                     break;
-                //fall through
+                Q_FALLTHROUGH();
             case SC_TitleBarUnshadeButton:
                 if (isMinimized && (tb->titleBarFlags & Qt::WindowShadeButtonHint))
                     offset += delta;
                 else if (subControl == SC_TitleBarUnshadeButton)
                     break;
-                //fall through
+                Q_FALLTHROUGH();
             case SC_TitleBarCloseButton:
                 if (tb->titleBarFlags & Qt::WindowSystemMenuHint)
                     offset += delta;
@@ -3576,7 +3576,7 @@ QRect QWindowsXPStyle::subControlRect(ComplexControl cc, const QStyleOptionCompl
             if (numSubControls == 1)
                 break;
             offset += buttonWidth;
-            //FALL THROUGH
+            Q_FALLTHROUGH();
         case SC_MdiNormalButton:
             // No offset needed if
             // 1) There's only one sub control
diff --git a/src/widgets/util/qflickgesture.cpp b/src/widgets/util/qflickgesture.cpp
index 4f08664784..57db9ff7fc 100644
--- a/src/widgets/util/qflickgesture.cpp
+++ b/src/widgets/util/qflickgesture.cpp
@@ -551,11 +551,11 @@ QGestureRecognizer::Result QFlickGestureRecognizer::recognize(QGesture *state,
 
     case QEvent::TouchBegin:
         inputType = QScroller::InputPress;
-        // fall through
+        Q_FALLTHROUGH();
     case QEvent::TouchEnd:
         if (!inputType)
             inputType = QScroller::InputRelease;
-        // fallthrough
+        Q_FALLTHROUGH();
     case QEvent::TouchUpdate:
         if (!inputType)
             inputType = QScroller::InputMove;
@@ -669,7 +669,7 @@ QGestureRecognizer::Result QFlickGestureRecognizer::recognize(QGesture *state,
                     event->accept();
                 }
             }
-            // fall through
+            Q_FALLTHROUGH();
         case QEvent::TouchBegin:
             q->setHotSpot(globalPos);
             result |= scrollerIsActive ? TriggerGesture : MayBeGesture;
@@ -681,7 +681,7 @@ QGestureRecognizer::Result QFlickGestureRecognizer::recognize(QGesture *state,
 #endif
             if (PressDelayHandler::instance()->isDelaying())
                 result |= ConsumeEventHint;
-            // fall through
+            Q_FALLTHROUGH();
         case QEvent::TouchUpdate:
             result |= scrollerIsActive ? TriggerGesture : Ignore;
             break;
@@ -692,7 +692,7 @@ QGestureRecognizer::Result QFlickGestureRecognizer::recognize(QGesture *state,
         case QEvent::MouseButtonRelease:
             if (PressDelayHandler::instance()->released(event, scrollerWasDragging || scrollerWasScrolling, scrollerIsActive))
                 result |= ConsumeEventHint;
-            // fall through
+            Q_FALLTHROUGH();
         case QEvent::TouchEnd:
             result |= scrollerIsActive ? FinishGesture : CancelGesture;
             break;
diff --git a/src/widgets/widgets/qabstractbutton.cpp b/src/widgets/widgets/qabstractbutton.cpp
index 1a5b8db33c..d04ee24861 100644
--- a/src/widgets/widgets/qabstractbutton.cpp
+++ b/src/widgets/widgets/qabstractbutton.cpp
@@ -1058,7 +1058,7 @@ void QAbstractButton::keyPressEvent(QKeyEvent *e)
         break;
     case Qt::Key_Up:
         next = false;
-        // fall through
+        Q_FALLTHROUGH();
     case Qt::Key_Left:
     case Qt::Key_Right:
     case Qt::Key_Down: {
diff --git a/src/widgets/widgets/qabstractslider.cpp b/src/widgets/widgets/qabstractslider.cpp
index 4221ff40ef..e85d82edb8 100644
--- a/src/widgets/widgets/qabstractslider.cpp
+++ b/src/widgets/widgets/qabstractslider.cpp
@@ -933,7 +933,7 @@ void QAbstractSlider::changeEvent(QEvent *ev)
             d->repeatActionTimer.stop();
             setSliderDown(false);
         }
-        // fall through...
+        Q_FALLTHROUGH();
     default:
         QWidget::changeEvent(ev);
     }
diff --git a/src/widgets/widgets/qcombobox.cpp b/src/widgets/widgets/qcombobox.cpp
index af178ce8f5..693d5f9e93 100644
--- a/src/widgets/widgets/qcombobox.cpp
+++ b/src/widgets/widgets/qcombobox.cpp
@@ -676,7 +676,7 @@ bool QComboBoxPrivateContainer::eventFilter(QObject *o, QEvent *e)
         case Qt::Key_Down:
             if (!(keyEvent->modifiers() & Qt::AltModifier))
                 break;
-            // fall through
+            Q_FALLTHROUGH();
         case Qt::Key_F4:
             combo->hidePopup();
             return true;
@@ -3140,7 +3140,7 @@ void QComboBox::keyPressEvent(QKeyEvent *e)
             return;
         } else if (e->modifiers() & Qt::ControlModifier)
             break; // pass to line edit for auto completion
-        // fall through
+        Q_FALLTHROUGH();
     case Qt::Key_PageDown:
 #ifdef QT_KEYPAD_NAVIGATION
         if (QApplication::keypadNavigationEnabled())
diff --git a/src/widgets/widgets/qmenu.cpp b/src/widgets/widgets/qmenu.cpp
index cb99b58d97..2131025c8d 100644
--- a/src/widgets/widgets/qmenu.cpp
+++ b/src/widgets/widgets/qmenu.cpp
@@ -2979,7 +2979,7 @@ void QMenu::keyPressEvent(QKeyEvent *e)
             key_consumed = true;
             break;
         }
-        //FALL THROUGH
+        Q_FALLTHROUGH();
     case Qt::Key_Left: {
         if (d->currentAction && !d->scroll) {
             QAction *nextAction = 0;
@@ -3026,6 +3026,7 @@ void QMenu::keyPressEvent(QKeyEvent *e)
         if (!style()->styleHint(QStyle::SH_Menu_SpaceActivatesItem, 0, this))
             break;
         // for motif, fall through
+        Q_FALLTHROUGH();
 #ifdef QT_KEYPAD_NAVIGATION
     case Qt::Key_Select:
 #endif