Move away from using 0 as a pointer constant

Cleans up most of corelib to use nullptr or default enums
where appropriate.

Change-Id: Ifcaac14ecdaaee730f87f10941db3ce407d71ef9
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
 
 

22 files changed, 102 insertions, 100 deletions

diff --git a/src/corelib/io/qabstractfileengine.cpp b/src/corelib/io/qabstractfileengine.cpp
index f2a895bbb8..8a1679c5af 100644
--- a/src/corelib/io/qabstractfileengine.cpp
+++ b/src/corelib/io/qabstractfileengine.cpp
@@ -159,7 +159,7 @@ QAbstractFileEngineHandler::~QAbstractFileEngineHandler()
 */
 QAbstractFileEngine *qt_custom_file_engine_handler_create(const QString &path)
 {
-    QAbstractFileEngine *engine = 0;
+    QAbstractFileEngine *engine = nullptr;
 
     if (qt_file_engine_handlers_in_use) {
         QReadLocker locker(fileEngineHandlerMutex());
@@ -658,7 +658,7 @@ QStringList QAbstractFileEngine::entryList(QDir::Filters filters, const QStringL
 QAbstractFileEngine::FileFlags QAbstractFileEngine::fileFlags(FileFlags type) const
 {
     Q_UNUSED(type);
-    return 0;
+    return nullptr;
 }
 
 /*!
@@ -838,7 +838,7 @@ uchar *QAbstractFileEngine::map(qint64 offset, qint64 size, QFile::MemoryMapFlag
     option.flags = flags;
     MapExtensionReturn r;
     if (!extension(MapExtension, &option, &r))
-        return 0;
+        return nullptr;
     return r.address;
 }
 
@@ -1118,7 +1118,7 @@ QAbstractFileEngine::Iterator *QAbstractFileEngine::beginEntryList(QDir::Filters
 {
     Q_UNUSED(filters);
     Q_UNUSED(filterNames);
-    return 0;
+    return nullptr;
 }
 
 /*!
@@ -1126,7 +1126,7 @@ QAbstractFileEngine::Iterator *QAbstractFileEngine::beginEntryList(QDir::Filters
 */
 QAbstractFileEngine::Iterator *QAbstractFileEngine::endEntryList()
 {
-    return 0;
+    return nullptr;
 }
 
 /*!
diff --git a/src/corelib/io/qbuffer.cpp b/src/corelib/io/qbuffer.cpp
index 7b3fa2ccad..8e980733de 100644
--- a/src/corelib/io/qbuffer.cpp
+++ b/src/corelib/io/qbuffer.cpp
@@ -50,7 +50,7 @@ class QBufferPrivate : public QIODevicePrivate
 
 public:
     QBufferPrivate()
-    : buf(0)
+        : buf(nullptr)
 #ifndef QT_NO_QOBJECT
         , writtenSinceLastEmit(0), signalConnectionCount(0), signalsEmitted(false)
 #endif
diff --git a/src/corelib/io/qdir.cpp b/src/corelib/io/qdir.cpp
index 671913e92f..62dae3577c 100644
--- a/src/corelib/io/qdir.cpp
+++ b/src/corelib/io/qdir.cpp
@@ -1431,7 +1431,7 @@ QStringList QDir::entryList(const QStringList &nameFilters, Filters filters,
         l.append(it.fileInfo());
     }
     QStringList ret;
-    d->sortFileList(sort, l, &ret, 0);
+    d->sortFileList(sort, l, &ret, nullptr);
     return ret;
 }
 
@@ -1473,7 +1473,7 @@ QFileInfoList QDir::entryInfoList(const QStringList &nameFilters, Filters filter
         l.append(it.fileInfo());
     }
     QFileInfoList ret;
-    d->sortFileList(sort, l, 0, &ret);
+    d->sortFileList(sort, l, nullptr, &ret);
     return ret;
 }
 
diff --git a/src/corelib/io/qfile.cpp b/src/corelib/io/qfile.cpp
index 8d871904bc..6959c7a40b 100644
--- a/src/corelib/io/qfile.cpp
+++ b/src/corelib/io/qfile.cpp
@@ -86,7 +86,7 @@ QFilePrivate::openExternalFile(int flags, int fd, QFile::FileHandleFlags handleF
     return false;
 #else
     delete fileEngine;
-    fileEngine = 0;
+    fileEngine = nullptr;
     QFSFileEngine *fe = new QFSFileEngine;
     fileEngine = fe;
     return fe->open(QIODevice::OpenMode(flags), fd, handleFlags);
@@ -102,7 +102,7 @@ QFilePrivate::openExternalFile(int flags, FILE *fh, QFile::FileHandleFlags handl
     return false;
 #else
     delete fileEngine;
-    fileEngine = 0;
+    fileEngine = nullptr;
     QFSFileEngine *fe = new QFSFileEngine;
     fileEngine = fe;
     return fe->open(QIODevice::OpenMode(flags), fh, handleFlags);
@@ -336,7 +336,7 @@ QFile::setFileName(const QString &name)
     }
     if(d->fileEngine) { //get a new file engine later
         delete d->fileEngine;
-        d->fileEngine = 0;
+        d->fileEngine = nullptr;
     }
     d->fileName = name;
 }
diff --git a/src/corelib/io/qfiledevice.cpp b/src/corelib/io/qfiledevice.cpp
index 0689118f3e..2f74547054 100644
--- a/src/corelib/io/qfiledevice.cpp
+++ b/src/corelib/io/qfiledevice.cpp
@@ -53,7 +53,7 @@ QT_BEGIN_NAMESPACE
 #endif
 
 QFileDevicePrivate::QFileDevicePrivate()
-    : fileEngine(0),
+    : fileEngine(nullptr),
       cachedSize(0),
       error(QFile::NoError), lastWasWrite(false)
 {
@@ -63,7 +63,7 @@ QFileDevicePrivate::QFileDevicePrivate()
 QFileDevicePrivate::~QFileDevicePrivate()
 {
     delete fileEngine;
-    fileEngine = 0;
+    fileEngine = nullptr;
 }
 
 QAbstractFileEngine * QFileDevicePrivate::engine() const
diff --git a/src/corelib/io/qfileinfo.cpp b/src/corelib/io/qfileinfo.cpp
index 998382021d..f5b398feae 100644
--- a/src/corelib/io/qfileinfo.cpp
+++ b/src/corelib/io/qfileinfo.cpp
@@ -52,7 +52,7 @@ QString QFileInfoPrivate::getFileName(QAbstractFileEngine::FileName name) const
         return fileNames[(int)name];
 
     QString ret;
-    if (fileEngine == 0) { // local file; use the QFileSystemEngine directly
+    if (fileEngine == nullptr) { // local file; use the QFileSystemEngine directly
         switch (name) {
             case QAbstractFileEngine::CanonicalName:
             case QAbstractFileEngine::CanonicalPathName: {
@@ -103,7 +103,7 @@ QString QFileInfoPrivate::getFileOwner(QAbstractFileEngine::FileOwner own) const
     if (cache_enabled && !fileOwners[(int)own].isNull())
         return fileOwners[(int)own];
     QString ret;
-    if (fileEngine == 0) {
+    if (fileEngine == nullptr) {
         switch (own) {
         case QAbstractFileEngine::OwnerUser:
             ret = QFileSystemEngine::resolveUserName(fileEntry, metaData);
@@ -134,7 +134,7 @@ uint QFileInfoPrivate::getFileFlags(QAbstractFileEngine::FileFlags request) cons
     // extra syscall. Bundle detecton on Mac can be slow, expecially on network
     // paths, so we separate out that as well.
 
-    QAbstractFileEngine::FileFlags req = 0;
+    QAbstractFileEngine::FileFlags req = nullptr;
     uint cachedFlags = 0;
 
     if (request & (QAbstractFileEngine::FlagsMask | QAbstractFileEngine::TypesMask)) {
@@ -434,7 +434,7 @@ bool QFileInfo::operator==(const QFileInfo &fileinfo) const
         return true;
 
     Qt::CaseSensitivity sensitive;
-    if (d->fileEngine == 0 || fileinfo.d_ptr->fileEngine == 0) {
+    if (d->fileEngine == nullptr || fileinfo.d_ptr->fileEngine == nullptr) {
         if (d->fileEngine != fileinfo.d_ptr->fileEngine) // one is native, the other is a custom file-engine
             return false;
 
@@ -649,7 +649,7 @@ bool QFileInfo::isRelative() const
     Q_D(const QFileInfo);
     if (d->isDefaultConstructed)
         return true;
-    if (d->fileEngine == 0)
+    if (d->fileEngine == nullptr)
         return d->fileEntry.isRelative();
     return d->fileEngine->isRelativePath();
 }
@@ -682,7 +682,7 @@ bool QFileInfo::exists() const
     Q_D(const QFileInfo);
     if (d->isDefaultConstructed)
         return false;
-    if (d->fileEngine == 0) {
+    if (d->fileEngine == nullptr) {
         if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::ExistsAttribute))
             QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::ExistsAttribute);
         return d->metaData.exists();
@@ -982,7 +982,7 @@ bool QFileInfo::isNativePath() const
     Q_D(const QFileInfo);
     if (d->isDefaultConstructed)
         return false;
-    if (d->fileEngine == 0)
+    if (d->fileEngine == nullptr)
         return true;
     return d->getFileFlags(QAbstractFileEngine::LocalDiskFlag);
 }
@@ -1075,7 +1075,7 @@ bool QFileInfo::isRoot() const
     Q_D(const QFileInfo);
     if (d->isDefaultConstructed)
         return false;
-    if (d->fileEngine == 0) {
+    if (d->fileEngine == nullptr) {
         if (d->fileEntry.isRoot()) {
 #if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)
             //the path is a drive root, but the drive may not exist
diff --git a/src/corelib/io/qfilesystemengine.cpp b/src/corelib/io/qfilesystemengine.cpp
index 7abdf90bf5..21847c2a7c 100644
--- a/src/corelib/io/qfilesystemengine.cpp
+++ b/src/corelib/io/qfilesystemengine.cpp
@@ -124,7 +124,7 @@ static inline bool _q_checkEntry(QAbstractFileEngine *&engine, bool resolvingEnt
     if (resolvingEntry) {
         if (!(engine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::ExistsFlag)) {
             delete engine;
-            engine = 0;
+            engine = nullptr;
             return false;
         }
     }
@@ -191,7 +191,7 @@ static bool _q_resolveEntryAndCreateLegacyEngine_recursive(QFileSystemEntry &ent
 QAbstractFileEngine *QFileSystemEngine::resolveEntryAndCreateLegacyEngine(
         QFileSystemEntry &entry, QFileSystemMetaData &data) {
     QFileSystemEntry copy = entry;
-    QAbstractFileEngine *engine = 0;
+    QAbstractFileEngine *engine = nullptr;
 
     if (_q_resolveEntryAndCreateLegacyEngine_recursive(copy, data, engine))
         // Reset entry to resolved copy.
diff --git a/src/corelib/io/qfilesystemengine_unix.cpp b/src/corelib/io/qfilesystemengine_unix.cpp
index b78e037865..066a7c3f01 100644
--- a/src/corelib/io/qfilesystemengine_unix.cpp
+++ b/src/corelib/io/qfilesystemengine_unix.cpp
@@ -813,7 +813,7 @@ QString QFileSystemEngine::resolveUserName(uint userId)
 #endif
 
 #if !defined(Q_OS_INTEGRITY) && !defined(Q_OS_WASM)
-    struct passwd *pw = 0;
+    struct passwd *pw = nullptr;
 #if QT_CONFIG(thread) && defined(_POSIX_THREAD_SAFE_FUNCTIONS) && !defined(Q_OS_OPENBSD) && !defined(Q_OS_VXWORKS)
     struct passwd entry;
     getpwuid_r(userId, &entry, buf.data(), buf.size(), &pw);
@@ -837,7 +837,7 @@ QString QFileSystemEngine::resolveGroupName(uint groupId)
 #endif
 
 #if !defined(Q_OS_INTEGRITY) && !defined(Q_OS_WASM)
-    struct group *gr = 0;
+    struct group *gr = nullptr;
 #if QT_CONFIG(thread) && defined(_POSIX_THREAD_SAFE_FUNCTIONS) && !defined(Q_OS_OPENBSD) && !defined(Q_OS_VXWORKS) && (!defined(Q_OS_ANDROID) || defined(Q_OS_ANDROID) && (__ANDROID_API__ >= 24))
     size_max = sysconf(_SC_GETGR_R_SIZE_MAX);
     if (size_max == -1)
diff --git a/src/corelib/io/qfilesystemiterator_unix.cpp b/src/corelib/io/qfilesystemiterator_unix.cpp
index a9acf542d4..5ac7e13a2e 100644
--- a/src/corelib/io/qfilesystemiterator_unix.cpp
+++ b/src/corelib/io/qfilesystemiterator_unix.cpp
@@ -50,15 +50,15 @@ QT_BEGIN_NAMESPACE
 QFileSystemIterator::QFileSystemIterator(const QFileSystemEntry &entry, QDir::Filters filters,
                                          const QStringList &nameFilters, QDirIterator::IteratorFlags flags)
     : nativePath(entry.nativeFilePath())
-    , dir(0)
-    , dirEntry(0)
+    , dir(nullptr)
+    , dirEntry(nullptr)
     , lastError(0)
 {
     Q_UNUSED(filters)
     Q_UNUSED(nameFilters)
     Q_UNUSED(flags)
 
-    if ((dir = QT_OPENDIR(nativePath.constData())) == 0) {
+    if ((dir = QT_OPENDIR(nativePath.constData())) == nullptr) {
         lastError = errno;
     } else {
         if (!nativePath.endsWith('/'))
diff --git a/src/corelib/io/qfsfileengine.cpp b/src/corelib/io/qfsfileengine.cpp
index 387990ed79..0db27f3e25 100644
--- a/src/corelib/io/qfsfileengine.cpp
+++ b/src/corelib/io/qfsfileengine.cpp
@@ -127,7 +127,7 @@ void QFSFileEnginePrivate::init()
     is_link = 0;
     openMode = QIODevice::NotOpen;
     fd = -1;
-    fh = 0;
+    fh = nullptr;
     lastIOCommand = IOFlushCommand;
     lastFlushFailed = false;
     closeFileHandle = false;
@@ -240,7 +240,7 @@ bool QFSFileEngine::open(QIODevice::OpenMode openMode)
     d->openMode = openMode;
     d->lastFlushFailed = false;
     d->tried_stat = 0;
-    d->fh = 0;
+    d->fh = nullptr;
     d->fd = -1;
 
     return d->nativeOpen(openMode);
@@ -299,7 +299,7 @@ bool QFSFileEnginePrivate::openFh(QIODevice::OpenMode openMode, FILE *fh)
                         QSystemError::stdString());
 
             this->openMode = QIODevice::NotOpen;
-            this->fh = 0;
+            this->fh = nullptr;
 
             return false;
         }
@@ -328,7 +328,7 @@ bool QFSFileEngine::open(QIODevice::OpenMode openMode, int fd, QFile::FileHandle
     d->lastFlushFailed = false;
     d->closeFileHandle = (handleFlags & QFile::AutoCloseHandle);
     d->fileEntry.clear();
-    d->fh = 0;
+    d->fh = nullptr;
     d->fd = -1;
     d->tried_stat = 0;
 
@@ -344,7 +344,7 @@ bool QFSFileEnginePrivate::openFd(QIODevice::OpenMode openMode, int fd)
 {
     Q_Q(QFSFileEngine);
     this->fd = fd;
-    fh = 0;
+    fh = nullptr;
 
     // Seek to the end when in Append mode.
     if (openMode & QFile::Append) {
@@ -405,7 +405,7 @@ bool QFSFileEnginePrivate::closeFdFh()
 
         // We must reset these guys regardless; calling close again after a
         // failed close causes crashes on some systems.
-        fh = 0;
+        fh = nullptr;
         fd = -1;
         closed = (ret == 0);
     }
@@ -822,7 +822,7 @@ QAbstractFileEngine::Iterator *QFSFileEngine::beginEntryList(QDir::Filters filte
 */
 QAbstractFileEngine::Iterator *QFSFileEngine::endEntryList()
 {
-    return 0;
+    return nullptr;
 }
 #endif // QT_NO_FILESYSTEMITERATOR
 
@@ -870,7 +870,7 @@ bool QFSFileEngine::extension(Extension extension, const ExtensionOption *option
         const MapExtensionOption *options = (const MapExtensionOption*)(option);
         MapExtensionReturn *returnValue = static_cast<MapExtensionReturn*>(output);
         returnValue->address = d->map(options->offset, options->size, options->flags);
-        return (returnValue->address != 0);
+        return (returnValue->address != nullptr);
     }
     if (extension == UnMapExtension) {
         const UnMapExtensionOption *options = (const UnMapExtensionOption*)option;
diff --git a/src/corelib/io/qfsfileengine_unix.cpp b/src/corelib/io/qfsfileengine_unix.cpp
index 90ad0126d6..d4983c72af 100644
--- a/src/corelib/io/qfsfileengine_unix.cpp
+++ b/src/corelib/io/qfsfileengine_unix.cpp
@@ -153,7 +153,7 @@ bool QFSFileEnginePrivate::nativeOpen(QIODevice::OpenMode openMode)
             }
         }
 
-        fh = 0;
+        fh = nullptr;
     }
 
     closeFileHandle = true;
@@ -451,14 +451,14 @@ QAbstractFileEngine::FileFlags QFSFileEngine::fileFlags(FileFlags type) const
     if (type & Refresh)
         d->metaData.clear();
 
-    QAbstractFileEngine::FileFlags ret = 0;
+    QAbstractFileEngine::FileFlags ret = { };
 
     if (type & FlagsMask)
         ret |= LocalDiskFlag;
 
     bool exists;
     {
-        QFileSystemMetaData::MetaDataFlags queryFlags = 0;
+        QFileSystemMetaData::MetaDataFlags queryFlags = { };
 
         queryFlags |= QFileSystemMetaData::MetaDataFlags(uint(type))
                 & QFileSystemMetaData::Permissions;
@@ -590,9 +590,9 @@ bool QFSFileEngine::setPermissions(uint perms)
     QSystemError error;
     bool ok;
     if (d->fd != -1)
-        ok = QFileSystemEngine::setPermissions(d->fd, QFile::Permissions(perms), error, 0);
+        ok = QFileSystemEngine::setPermissions(d->fd, QFile::Permissions(perms), error);
     else
-        ok = QFileSystemEngine::setPermissions(d->fileEntry, QFile::Permissions(perms), error, 0);
+        ok = QFileSystemEngine::setPermissions(d->fileEntry, QFile::Permissions(perms), error);
     if (!ok) {
         setError(QFile::PermissionsError, error.toString());
         return false;
@@ -651,13 +651,13 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size, QFile::MemoryMapFla
     Q_Q(QFSFileEngine);
     if (openMode == QIODevice::NotOpen) {
         q->setError(QFile::PermissionsError, qt_error_string(int(EACCES)));
-        return 0;
+        return nullptr;
     }
 
     if (offset < 0 || offset > maxFileOffset
             || size < 0 || quint64(size) > quint64(size_t(-1))) {
         q->setError(QFile::UnspecifiedError, qt_error_string(int(EINVAL)));
-        return 0;
+        return nullptr;
     }
 
     // If we know the mapping will extend beyond EOF, fail early to avoid
@@ -685,14 +685,14 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size, QFile::MemoryMapFla
 
     if (quint64(size + extra) > quint64((size_t)-1)) {
         q->setError(QFile::UnspecifiedError, qt_error_string(int(EINVAL)));
-        return 0;
+        return nullptr;
     }
 
     size_t realSize = (size_t)size + extra;
     QT_OFF_T realOffset = QT_OFF_T(offset);
     realOffset &= ~(QT_OFF_T(pageSize - 1));
 
-    void *mapAddress = QT_MMAP((void*)0, realSize,
+    void *mapAddress = QT_MMAP((void*)nullptr, realSize,
                    access, sharemode, nativeHandle(), realOffset);
     if (MAP_FAILED != mapAddress) {
         uchar *address = extra + static_cast<uchar*>(mapAddress);
@@ -714,7 +714,7 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size, QFile::MemoryMapFla
         q->setError(QFile::UnspecifiedError, qt_error_string(int(errno)));
         break;
     }
-    return 0;
+    return nullptr;
 }
 
 bool QFSFileEnginePrivate::unmap(uchar *ptr)
diff --git a/src/corelib/io/qiodevice.cpp b/src/corelib/io/qiodevice.cpp
index 74df0f71ef..e26508e631 100644
--- a/src/corelib/io/qiodevice.cpp
+++ b/src/corelib/io/qiodevice.cpp
@@ -169,7 +169,7 @@ QIODevicePrivate::QIODevicePrivate()
        , baseReadLineDataCalled(false)
        , accessMode(Unset)
 #ifdef QT_NO_QOBJECT
-       , q_ptr(0)
+       , q_ptr(nullptr)
 #endif
 {
 }
diff --git a/src/corelib/io/qipaddress.cpp b/src/corelib/io/qipaddress.cpp
index d9f7916dd4..131795330b 100644
--- a/src/corelib/io/qipaddress.cpp
+++ b/src/corelib/io/qipaddress.cpp
@@ -67,7 +67,7 @@ static const QChar *checkedToAscii(Buffer &buffer, const QChar *begin, const QCh
         *dst++ = *src++;
     }
     *dst = '\0';
-    return 0;
+    return nullptr;
 }
 
 static bool parseIp4Internal(IPv4Address &address, const char *ptr, bool acceptLeadingZero);
@@ -175,7 +175,7 @@ const QChar *parseIp6(IPv6Address &address, const QChar *begin, const QChar *end
 
     memset(address, 0, sizeof address);
     if (colonCount == 2 && end - begin == 2) // "::"
-        return 0;
+        return nullptr;
 
     // if there's a double colon ("::"), this is how many zeroes it means
     int zeroWordsToFill;
@@ -236,7 +236,7 @@ const QChar *parseIp6(IPv6Address &address, const QChar *begin, const QChar *end
             address[13] = ip4 >> 16;
             address[14] = ip4 >> 8;
             address[15] = ip4;
-            return 0;
+            return nullptr;
         }
 
         address[pos++] = x >> 8;
@@ -248,7 +248,7 @@ const QChar *parseIp6(IPv6Address &address, const QChar *begin, const QChar *end
             return begin + (endptr - buffer.data());
         ptr = endptr + 1;
     }
-    return pos == 16 ? 0 : end;
+    return pos == 16 ? nullptr : end;
 }
 
 static inline QChar toHex(uchar c)
diff --git a/src/corelib/io/qloggingcategory.cpp b/src/corelib/io/qloggingcategory.cpp
index 33253429a2..91b3396217 100644
--- a/src/corelib/io/qloggingcategory.cpp
+++ b/src/corelib/io/qloggingcategory.cpp
@@ -214,8 +214,8 @@ static void setBoolLane(QBasicAtomicInt *atomic, bool enable, int shift)
     Note that \a category must be kept valid during the lifetime of this object.
 */
 QLoggingCategory::QLoggingCategory(const char *category)
-    : d(0),
-      name(0)
+    : d(nullptr),
+      name(nullptr)
 {
     init(category, QtDebugMsg);
 }
@@ -231,8 +231,8 @@ QLoggingCategory::QLoggingCategory(const char *category)
     \since 5.4
 */
 QLoggingCategory::QLoggingCategory(const char *category, QtMsgType enableForLevel)
-    : d(0),
-      name(0)
+    : d(nullptr),
+      name(nullptr)
 {
     init(category, enableForLevel);
 }
diff --git a/src/corelib/io/qloggingregistry.cpp b/src/corelib/io/qloggingregistry.cpp
index 9792d956cc..7849dfd14c 100644
--- a/src/corelib/io/qloggingregistry.cpp
+++ b/src/corelib/io/qloggingregistry.cpp
@@ -165,7 +165,7 @@ void QLoggingRule::parse(const QStringRef &pattern)
             p = QStringRef(p.string(), p.position() + 1, p.length() - 1);
         }
         if (p.contains(QLatin1Char('*'))) // '*' only supported at start/end
-            flags = 0;
+            flags = PatternFlags();
     }
 
     category = p.toString();
@@ -415,7 +415,7 @@ QLoggingRegistry::installFilter(QLoggingCategory::CategoryFilter filter)
 {
     QMutexLocker locker(&registryMutex);
 
-    if (filter == 0)
+    if (!filter)
         filter = defaultCategoryFilter;
 
     QLoggingCategory::CategoryFilter old = categoryFilter;
diff --git a/src/corelib/io/qresource.cpp b/src/corelib/io/qresource.cpp
index e7d739b4dc..d143f7fda3 100644
--- a/src/corelib/io/qresource.cpp
+++ b/src/corelib/io/qresource.cpp
@@ -147,7 +147,7 @@ private:
 public:
     mutable QAtomicInt ref;
 
-    inline QResourceRoot(): tree(0), names(0), payloads(0), version(0) {}
+    inline QResourceRoot(): tree(nullptr), names(nullptr), payloads(nullptr), version(0) {}
     inline QResourceRoot(int version, const uchar *t, const uchar *n, const uchar *d) { setSource(version, t, n, d); }
     virtual ~QResourceRoot() { }
     int findNode(const QString &path, const QLocale &locale=QLocale()) const;
@@ -165,7 +165,7 @@ public:
     quint64 lastModified(int node) const;
     QStringList children(int node) const;
     virtual QString mappingRoot() const { return QString(); }
-    bool mappingRootSubdir(const QString &path, QString *match=0) const;
+    bool mappingRootSubdir(const QString &path, QString *match = nullptr) const;
     inline bool operator==(const QResourceRoot &other) const
     { return tree == other.tree && names == other.names && payloads == other.payloads && version == other.version; }
     inline bool operator!=(const QResourceRoot &other) const
@@ -320,7 +320,7 @@ QResourcePrivate::clear()
 {
     absoluteFilePath.clear();
     compressionAlgo = QResource::NoCompression;
-    data = 0;
+    data = nullptr;
     size = 0;
     children.clear();
     lastModified = 0;
@@ -864,7 +864,7 @@ const uchar *QResourceRoot::data(int node, qint64 *size) const
 {
     if(node == -1) {
         *size = 0;
-        return 0;
+        return nullptr;
     }
     int offset = findOffset(node) + 4; //jump past name
 
@@ -881,7 +881,7 @@ const uchar *QResourceRoot::data(int node, qint64 *size) const
         return ret;
     }
     *size = 0;
-    return 0;
+    return nullptr;
 }
 
 quint64 QResourceRoot::lastModified(int node) const
@@ -991,7 +991,7 @@ class QDynamicBufferResourceRoot: public QResourceRoot
     const uchar *buffer;
 
 public:
-    inline QDynamicBufferResourceRoot(const QString &_root) : root(_root), buffer(0) { }
+    inline QDynamicBufferResourceRoot(const QString &_root) : root(_root), buffer(nullptr) { }
     inline ~QDynamicBufferResourceRoot() { }
     inline const uchar *mappingBuffer() const { return buffer; }
     QString mappingRoot() const override { return root; }
@@ -1063,12 +1063,14 @@ class QDynamicFileResourceRoot: public QDynamicBufferResourceRoot
     qsizetype unmapLength;
 
 public:
-    inline QDynamicFileResourceRoot(const QString &_root) : QDynamicBufferResourceRoot(_root), unmapPointer(0), unmapLength(0) { }
+    QDynamicFileResourceRoot(const QString &_root)
+        : QDynamicBufferResourceRoot(_root), unmapPointer(nullptr), unmapLength(0)
+    { }
     ~QDynamicFileResourceRoot() {
 #if defined(QT_USE_MMAP)
         if (unmapPointer) {
             munmap((char*)unmapPointer, unmapLength);
-            unmapPointer = 0;
+            unmapPointer = nullptr;
             unmapLength = 0;
         } else
 #endif
diff --git a/src/corelib/io/qsavefile.cpp b/src/corelib/io/qsavefile.cpp
index bde5133cb3..915d0a0a00 100644
--- a/src/corelib/io/qsavefile.cpp
+++ b/src/corelib/io/qsavefile.cpp
@@ -151,7 +151,7 @@ QSaveFile::~QSaveFile()
     if (d->fileEngine) {
         d->fileEngine->remove();
         delete d->fileEngine;
-        d->fileEngine = 0;
+        d->fileEngine = nullptr;
     }
 }
 
@@ -252,7 +252,7 @@ bool QSaveFile::open(OpenMode mode)
                 return true;
             d->setError(d->fileEngine->error(), d->fileEngine->errorString());
             delete d->fileEngine;
-            d->fileEngine = 0;
+            d->fileEngine = nullptr;
         } else {
             QString msg =
                     QSaveFile::tr("QSaveFile cannot open '%1' without direct write fallback "
@@ -285,7 +285,7 @@ bool QSaveFile::open(OpenMode mode)
             err = QFileDevice::OpenError;
         d->setError(err, d->fileEngine->errorString());
         delete d->fileEngine;
-        d->fileEngine = 0;
+        d->fileEngine = nullptr;
         return false;
     }
 
@@ -339,7 +339,7 @@ bool QSaveFile::commit()
             d->fileEngine->remove();
             d->writeError = QFileDevice::NoError;
             delete d->fileEngine;
-            d->fileEngine = 0;
+            d->fileEngine = nullptr;
             return false;
         }
         // atomically replace old file with new file
@@ -349,12 +349,12 @@ bool QSaveFile::commit()
             d->setError(d->fileEngine->error(), d->fileEngine->errorString());
             d->fileEngine->remove();
             delete d->fileEngine;
-            d->fileEngine = 0;
+            d->fileEngine = nullptr;
             return false;
         }
     }
     delete d->fileEngine;
-    d->fileEngine = 0;
+    d->fileEngine = nullptr;
     return true;
 }
 
diff --git a/src/corelib/io/qtemporaryfile.cpp b/src/corelib/io/qtemporaryfile.cpp
index ced08a9a87..c89ad06a1f 100644
--- a/src/corelib/io/qtemporaryfile.cpp
+++ b/src/corelib/io/qtemporaryfile.cpp
@@ -327,7 +327,7 @@ bool QTemporaryFileEngine::isReallyOpen() const
 {
     Q_D(const QFSFileEngine);
 
-    if (!((0 == d->fh) && (-1 == d->fd)
+    if (!((nullptr == d->fh) && (-1 == d->fd)
 #if defined Q_OS_WIN
                 && (INVALID_HANDLE_VALUE == d->fileHandle)
 #endif
@@ -902,7 +902,7 @@ QTemporaryFile *QTemporaryFile::createNativeFile(QFile &file)
 {
     if (QAbstractFileEngine *engine = file.d_func()->engine()) {
         if(engine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::LocalDiskFlag)
-            return 0; //native already
+            return nullptr; // native already
         //cache
         bool wasOpen = file.isOpen();
         qint64 old_off = 0;
@@ -934,7 +934,7 @@ QTemporaryFile *QTemporaryFile::createNativeFile(QFile &file)
         //done
         return ret;
     }
-    return 0;
+    return nullptr;
 }
 
 /*!
diff --git a/src/corelib/io/qurl.cpp b/src/corelib/io/qurl.cpp
index 681a0c7ef2..4d0306abde 100644
--- a/src/corelib/io/qurl.cpp
+++ b/src/corelib/io/qurl.cpp
@@ -523,7 +523,7 @@ public:
     Error *cloneError() const;
     void clearError();
     void setError(ErrorCode errorCode, const QString &source, int supplement = -1);
-    ErrorCode validityError(QString *source = 0, int *position = 0) const;
+    ErrorCode validityError(QString *source = nullptr, int *position = nullptr) const;
     bool validateComponent(Section section, const QString &input, int begin, int end);
     bool validateComponent(Section section, const QString &input)
     { return validateComponent(section, input, 0, uint(input.length())); }
@@ -591,7 +591,7 @@ public:
 
 inline QUrlPrivate::QUrlPrivate()
     : ref(1), port(-1),
-      error(0),
+      error(nullptr),
       sectionIsPresent(0),
       flags(0)
 {
@@ -619,13 +619,13 @@ inline QUrlPrivate::~QUrlPrivate()
 
 inline QUrlPrivate::Error *QUrlPrivate::cloneError() const
 {
-    return error ? new Error(*error) : 0;
+    return error ? new Error(*error) : nullptr;
 }
 
 inline void QUrlPrivate::clearError()
 {
     delete error;
-    error = 0;
+    error = nullptr;
 }
 
 inline void QUrlPrivate::setError(ErrorCode errorCode, const QString &source, int supplement)
@@ -826,7 +826,7 @@ recodeFromUser(const QString &input, const ushort *actions, int from, int to)
     QString output;
     const QChar *begin = input.constData() + from;
     const QChar *end = input.constData() + to;
-    if (qt_urlRecode(output, begin, end, 0, actions))
+    if (qt_urlRecode(output, begin, end, nullptr, actions))
         return output;
 
     return input.mid(from, to - from);
@@ -954,7 +954,7 @@ inline void QUrlPrivate::appendFragment(QString &appendTo, QUrl::FormattingOptio
 {
     appendToUser(appendTo, fragment, options,
                  options & QUrl::EncodeDelimiters ? fragmentInUrl :
-                 appendingTo == FullUrl ? 0 : fragmentInIsolation);
+                 appendingTo == FullUrl ? nullptr : fragmentInIsolation);
 }
 
 inline void QUrlPrivate::appendQuery(QString &appendTo, QUrl::FormattingOptions options, Section appendingTo) const
@@ -1179,7 +1179,7 @@ inline void QUrlPrivate::appendHost(QString &appendTo, QUrl::FormattingOptions o
     if (host.at(0).unicode() == '[') {
         // IPv6 addresses might contain a zone-id which needs to be recoded
         if (options != 0)
-            if (qt_urlRecode(appendTo, host.constBegin(), host.constEnd(), options, 0))
+            if (qt_urlRecode(appendTo, host.constBegin(), host.constEnd(), options, nullptr))
                 return;
         appendTo += host;
     } else {
@@ -1221,7 +1221,7 @@ static const QChar *parseIpFuture(QString &host, const QChar *begin, const QChar
         --end;
 
         QString decoded;
-        if (mode == QUrl::TolerantMode && qt_urlRecode(decoded, begin, end, QUrl::FullyDecoded, 0)) {
+        if (mode == QUrl::TolerantMode && qt_urlRecode(decoded, begin, end, QUrl::FullyDecoded, nullptr)) {
             begin = decoded.constBegin();
             end = decoded.constEnd();
         }
@@ -1233,13 +1233,13 @@ static const QChar *parseIpFuture(QString &host, const QChar *begin, const QChar
                 host += *begin;
             else if (begin->unicode() >= '0' && begin->unicode() <= '9')
                 host += *begin;
-            else if (begin->unicode() < 0x80 && strchr(acceptable, begin->unicode()) != 0)
+            else if (begin->unicode() < 0x80 && strchr(acceptable, begin->unicode()) != nullptr)
                 host += *begin;
             else
                 return decoded.isEmpty() ? begin : &origBegin[2];
         }
         host += QLatin1Char(']');
-        return 0;
+        return nullptr;
     }
     return &origBegin[2];
 }
@@ -1286,7 +1286,7 @@ static const QChar *parseIp6(QString &host, const QChar *begin, const QChar *end
         host += zoneId;
     }
     host += QLatin1Char(']');
-    return 0;
+    return nullptr;
 }
 
 inline bool QUrlPrivate::setHost(const QString &value, int from, int iend, QUrl::ParsingMode mode)
@@ -1352,7 +1352,7 @@ inline bool QUrlPrivate::setHost(const QString &value, int from, int iend, QUrl:
 
     // check for percent-encoding first
     QString s;
-    if (mode == QUrl::TolerantMode && qt_urlRecode(s, begin, end, 0, 0)) {
+    if (mode == QUrl::TolerantMode && qt_urlRecode(s, begin, end, { }, nullptr)) {
         // something was decoded
         // anything encoded left?
         int pos = s.indexOf(QChar(0x25)); // '%'
@@ -1837,7 +1837,7 @@ inline void QUrlPrivate::validate() const
 
     \sa setUrl(), fromEncoded(), TolerantMode
 */
-QUrl::QUrl(const QString &url, ParsingMode parsingMode) : d(0)
+QUrl::QUrl(const QString &url, ParsingMode parsingMode) : d(nullptr)
 {
     setUrl(url, parsingMode);
 }
@@ -1845,7 +1845,7 @@ QUrl::QUrl(const QString &url, ParsingMode parsingMode) : d(0)
 /*!
     Constructs an empty QUrl object.
 */
-QUrl::QUrl() : d(0)
+QUrl::QUrl() : d(nullptr)
 {
 }
 
@@ -1879,7 +1879,7 @@ QUrl::~QUrl()
 bool QUrl::isValid() const
 {
     if (isEmpty()) {
-        // also catches d == 0
+        // also catches d == nullptr
         return false;
     }
     return d->validityError() == QUrlPrivate::NoError;
@@ -1907,7 +1907,7 @@ void QUrl::clear()
 {
     if (d && !d->ref.deref())
         delete d;
-    d = 0;
+    d = nullptr;
 }
 
 /*!
@@ -4187,7 +4187,7 @@ static QUrl adjustFtpPath(QUrl url)
 static bool isIp6(const QString &text)
 {
     QIPAddressUtils::IPv6Address address;
-    return !text.isEmpty() && QIPAddressUtils::parseIp6(address, text.begin(), text.end()) == 0;
+    return !text.isEmpty() && QIPAddressUtils::parseIp6(address, text.begin(), text.end()) == nullptr;
 }
 
 /*!
diff --git a/src/corelib/io/qurlidna.cpp b/src/corelib/io/qurlidna.cpp
index 2305e66407..2f89d22660 100644
--- a/src/corelib/io/qurlidna.cpp
+++ b/src/corelib/io/qurlidna.cpp
@@ -1444,7 +1444,7 @@ static void mapToLowerCase(QString *str, int from)
 {
     int N = sizeof(NameprepCaseFolding) / sizeof(NameprepCaseFolding[0]);
 
-    ushort *d = 0;
+    ushort *d = nullptr;
     for (int i = from; i < str->size(); ++i) {
         uint uc = str->at(i).unicode();
         if (uc < 0x80) {
@@ -1474,7 +1474,7 @@ static void mapToLowerCase(QString *str, int from)
                     else
                         str->replace(--i, 2, reinterpret_cast<const QChar *>(&entry->mapping[0]), l);
                     i += l - 1;
-                    d = 0;
+                    d = nullptr;
                 } else {
                     if (!d)
                         d = reinterpret_cast<ushort *>(str->data());
@@ -2404,7 +2404,7 @@ static const char * const idn_whitelist[] = {
 };
 static const size_t idn_whitelist_size = sizeof idn_whitelist / sizeof *idn_whitelist;
 
-static QStringList *user_idn_whitelist = 0;
+static QStringList *user_idn_whitelist = nullptr;
 
 static bool lessThan(const QChar *a, int l, const char *c)
 {
diff --git a/src/corelib/io/qurlquery.cpp b/src/corelib/io/qurlquery.cpp
index d76107abfd..a8f40a3a12 100644
--- a/src/corelib/io/qurlquery.cpp
+++ b/src/corelib/io/qurlquery.cpp
@@ -262,7 +262,7 @@ inline QString QUrlQueryPrivate::recodeToUser(const QString &input, QUrl::Compon
     if (!(encoding & QUrl::EncodeDelimiters)) {
         QString output;
         if (qt_urlRecode(output, input.constData(), input.constData() + input.length(),
-                         encoding, 0))
+                         encoding, nullptr))
             return output;
         return input;
     }
@@ -290,7 +290,7 @@ void QUrlQueryPrivate::setQuery(const QString &query)
     const QChar *const end = pos + query.size();
     while (pos != end) {
         const QChar *begin = pos;
-        const QChar *delimiter = 0;
+        const QChar *delimiter = nullptr;
         while (pos != end) {
             // scan for the component parts of this pair
             if (!delimiter && pos->unicode() == valueDelimiter)
@@ -345,7 +345,7 @@ QSharedDataPointer<QUrlQueryPrivate>::clone()
     \sa setQuery(), addQueryItem()
 */
 QUrlQuery::QUrlQuery()
-    : d(0)
+    : d(nullptr)
 {
 }
 
@@ -356,7 +356,7 @@ QUrlQuery::QUrlQuery()
     set the query with setQuery().
 */
 QUrlQuery::QUrlQuery(const QString &queryString)
-    : d(queryString.isEmpty() ? 0 : new QUrlQueryPrivate(queryString))
+    : d(queryString.isEmpty() ? nullptr : new QUrlQueryPrivate(queryString))
 {
 }
 
@@ -369,7 +369,7 @@ QUrlQuery::QUrlQuery(const QString &queryString)
     \sa QUrl::query()
 */
 QUrlQuery::QUrlQuery(const QUrl &url)
-    : d(0)
+    : d(nullptr)
 {
     // use internals to avoid unnecessary recoding
     // ### FIXME: actually do it
diff --git a/src/corelib/io/qurlrecode.cpp b/src/corelib/io/qurlrecode.cpp
index f23480c755..35ede8d078 100644
--- a/src/corelib/io/qurlrecode.cpp
+++ b/src/corelib/io/qurlrecode.cpp
@@ -377,7 +377,7 @@ static int recode(QString &result, const ushort *begin, const ushort *end, QUrl:
 {
     const int origSize = result.size();
     const ushort *input = begin;
-    ushort *output = 0;
+    ushort *output = nullptr;
 
     EncodingAction action = EncodeCharacter;
     for ( ; input != end; ++input) {