QIODevicePrivate: rearrange class members

As this class is a subject of the library hook data, there must be a
solid understanding of the member's alignment and padding across
different architectures. By reordering the layout, this patch provides
a clearer way of adding new members to the class.

Bump the TypeInformationVersion field in qtHookData, to notify the
Qt Creator developers that the offset of QFilePrivate::fileName was
changed and dumpers should be adapted.

Change-Id: Ied8b69bdeb9da50ff05aba2107bc75509674b18e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qhooks.cpp

@@ -67,7 +67,7 @@ quintptr Q_CORE_EXPORT qtHookData[] = {
     // The required sizes and offsets are tested in tests/auto/other/toolsupport.
     // When this fails and the change was intentional, adjust the test and
     // adjust this value here.
-    19
+    20
 };
 
 static_assert(QHooks::LastHookIndex == sizeof(qtHookData) / sizeof(qtHookData[0]));

src/corelib/io/qiodevice.cpp

@@ -156,22 +156,6 @@ static void checkWarnMessage(const QIODevice *device, const char *function, cons
     \internal
  */
 QIODevicePrivate::QIODevicePrivate()
-    : openMode(QIODevice::NotOpen),
-      pos(0), devicePos(0),
-      transactionPos(0),
-      readChannelCount(0),
-      writeChannelCount(0),
-      currentReadChannel(0),
-      currentWriteChannel(0),
-      readBufferChunkSize(QIODEVICE_BUFFERSIZE),
-      writeBufferChunkSize(0),
-      currentWriteChunk(nullptr),
-      transactionStarted(false)
-       , baseReadLineDataCalled(false)
-       , accessMode(Unset)
-#ifdef QT_NO_QOBJECT
-       , q_ptr(nullptr)
-#endif
 {
 }
 

src/corelib/io/qiodevice_p.h

@@ -80,11 +80,14 @@ public:
     QIODevicePrivate();
     virtual ~QIODevicePrivate();
 
-    QIODevice::OpenMode openMode;
+    // The size of this class is a subject of the library hook data.
-    QString errorString;
+    // When adding a new member, do not make gaps and be aware
-
+    // about the padding. Accordingly, adjust offsets in
-    QList<QRingBuffer> readBuffers;
+    // tests/auto/other/toolsupport and bump the TypeInformationVersion
-    QList<QRingBuffer> writeBuffers;
+    // field in src/corelib/global/qhooks.cpp, to notify the developers.
+    qint64 pos = 0;
+    qint64 devicePos = 0;
+    qint64 transactionPos = 0;
 
     class QRingBufferRef {
         QRingBuffer *m_buf;
@@ -122,27 +125,30 @@ public:
 
     QRingBufferRef buffer;
     QRingBufferRef writeBuffer;
-    qint64 pos;
+    const QByteArray *currentWriteChunk = nullptr;
-    qint64 devicePos;
+    int readChannelCount = 0;
-    qint64 transactionPos;
+    int writeChannelCount = 0;
-    int readChannelCount;
+    int currentReadChannel = 0;
-    int writeChannelCount;
+    int currentWriteChannel = 0;
-    int currentReadChannel;
+    int readBufferChunkSize = QIODEVICE_BUFFERSIZE;
-    int currentWriteChannel;
+    int writeBufferChunkSize = 0;
-    int readBufferChunkSize;
+
-    int writeBufferChunkSize;
+    QList<QRingBuffer> readBuffers;
-    const QByteArray *currentWriteChunk;
+    QList<QRingBuffer> writeBuffers;
-    bool transactionStarted;
+    QString errorString;
-    bool baseReadLineDataCalled;
+    QIODevice::OpenMode openMode = QIODevice::NotOpen;
+
+    bool transactionStarted = false;
+    bool baseReadLineDataCalled = false;
 
     virtual bool putCharHelper(char c);
 
-    enum AccessMode {
+    enum AccessMode : quint8 {
         Unset,
         Sequential,
         RandomAccess
     };
-    mutable AccessMode accessMode;
+    mutable AccessMode accessMode = Unset;
     inline bool isSequential() const
     {
         if (accessMode == Unset)
@@ -179,7 +185,7 @@ public:
     void write(const char *data, qint64 size);
 
 #ifdef QT_NO_QOBJECT
-    QIODevice *q_ptr;
+    QIODevice *q_ptr = nullptr;
 #endif
 };
 

tests/auto/other/toolsupport/tst_toolsupport.cpp

@@ -126,9 +126,9 @@ void tst_toolsupport::offsets_data()
 #ifdef Q_PROCESSOR_X86
         // x86 32-bit has weird alignment rules. Refer to QtPrivate::AlignOf in
         // qglobal.h for more details.
-        data << 188 << 296;
+        data << 180 << 288;
 #else
-        data << 192 << 296;
+        data << 184 << 288;
 #endif
     }
 #endif