QLibrary: Use QTaggedPointer for the did_load flag

This makes the size nicely aligned and conveniently intializes
everything to the right values.

Change-Id: Ibad2defbbd323fd5cdd4bed8374f40558d80acc0
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/plugin/qlibrary.cpp

@@ -825,9 +825,10 @@ bool QLibrary::load()
 {
     if (!d)
         return false;
-    if (did_load)
+    if (d.tag() == Loaded)
         return d->pHnd.loadRelaxed();
-    did_load = true;
+    else
+        d.setTag(Loaded);
     return d->load();
 }
 
@@ -848,8 +849,8 @@ bool QLibrary::load()
 */
 bool QLibrary::unload()
 {
-    if (did_load) {
-        did_load = false;
+    if (d.tag() == Loaded) {
+        d.setTag(NotLoaded);
         return d->unload();
     }
     return false;
@@ -869,8 +870,7 @@ bool QLibrary::isLoaded() const
 /*!
     Constructs a library with the given \a parent.
  */
-QLibrary::QLibrary(QObject *parent)
-    :QObject(parent), d(nullptr), did_load(false)
+QLibrary::QLibrary(QObject *parent) : QObject(parent)
 {
 }
 
@@ -884,8 +884,7 @@ QLibrary::QLibrary(QObject *parent)
     suffix in accordance with the platform, e.g. ".so" on Unix,
     ".dylib" on \macos and iOS, and ".dll" on Windows. (See \l{fileName}.)
  */
-QLibrary::QLibrary(const QString& fileName, QObject *parent)
-    :QObject(parent), d(nullptr), did_load(false)
+QLibrary::QLibrary(const QString& fileName, QObject *parent) : QObject(parent)
 {
     setFileName(fileName);
 }
@@ -901,8 +900,7 @@ QLibrary::QLibrary(const QString& fileName, QObject *parent)
     suffix in accordance with the platform, e.g. ".so" on Unix,
     ".dylib" on \macos and iOS, and ".dll" on Windows. (See \l{fileName}.)
 */
-QLibrary::QLibrary(const QString& fileName, int verNum, QObject *parent)
-    :QObject(parent), d(nullptr), did_load(false)
+QLibrary::QLibrary(const QString& fileName, int verNum, QObject *parent) : QObject(parent)
 {
     setFileNameAndVersion(fileName, verNum);
 }
@@ -918,7 +916,7 @@ QLibrary::QLibrary(const QString& fileName, int verNum, QObject *parent)
     ".dylib" on \macos and iOS, and ".dll" on Windows. (See \l{fileName}.)
  */
 QLibrary::QLibrary(const QString& fileName, const QString &version, QObject *parent)
-    :QObject(parent), d(nullptr), did_load(false)
+    : QObject(parent)
 {
     setFileNameAndVersion(fileName, version);
 }
@@ -965,8 +963,7 @@ void QLibrary::setFileName(const QString &fileName)
     if (d) {
         lh = d->loadHints();
         d->release();
-        d = nullptr;
-        did_load = false;
+        d = {};
     }
     d = QLibraryPrivate::findOrCreate(fileName, QString(), lh);
 }
@@ -995,8 +992,7 @@ void QLibrary::setFileNameAndVersion(const QString &fileName, int verNum)
     if (d) {
         lh = d->loadHints();
         d->release();
-        d = nullptr;
-        did_load = false;
+        d = {};
     }
     d = QLibraryPrivate::findOrCreate(fileName, verNum >= 0 ? QString::number(verNum) : QString(), lh);
 }
@@ -1016,8 +1012,7 @@ void QLibrary::setFileNameAndVersion(const QString &fileName, const QString &ver
     if (d) {
         lh = d->loadHints();
         d->release();
-        d = nullptr;
-        did_load = false;
+        d = {};
     }
     d = QLibraryPrivate::findOrCreate(fileName, version, lh);
 }

src/corelib/plugin/qlibrary.h

@@ -41,6 +41,7 @@
 #define QLIBRARY_H
 
 #include <QtCore/qobject.h>
+#include <QtCore/qtaggedpointer.h>
 
 QT_REQUIRE_CONFIG(library);
 
@@ -92,8 +93,12 @@ public:
     void setLoadHints(LoadHints hints);
     LoadHints loadHints() const;
 private:
-    QLibraryPrivate *d;
-    bool did_load;
+    enum LoadStatusTag {
+        NotLoaded,
+        Loaded
+    };
+
+    QTaggedPointer<QLibraryPrivate, LoadStatusTag> d = nullptr;
     Q_DISABLE_COPY(QLibrary)
 };