Break out the list of available converters to a static method

Mostly to pave the way for moving the class code to a file of its own,
but this incidentally saves the need to std::as_const() every use.
Moving the underlying object to a local static of a private method
also saves the need for heap allocation (which was leaked).

Task-number: QTBUG-111228
Change-Id: I30f4bf3c46d39e04d0ac4e3e9ba431945ebb9193
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
(cherry picked from commit d57a78657e09e38dc4137e3c6c80c1a42817cc8c)
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
(cherry picked from commit d46d1db4c64800c5990957007c9fd0ff2e5a120f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

examples/corelib/serialization/convert/converter.h

@@ -5,16 +5,19 @@
 #define CONVERTER_H
 
 #include <QIODevice>
+#include <QList>
 #include <QStringList>
 #include <QVariant>
 
 class Converter
 {
+    static QList<const Converter *> &converters();
 protected:
     Converter();
     static bool isNull(const Converter *converter); // in nullconverter.cpp
 
 public:
+    static const QList<const Converter *> &allConverters();
 
     enum class Direction { In = 1, Out = 2, InOut = In | Out };
     Q_DECLARE_FLAGS(Directions, Direction)

examples/corelib/serialization/convert/main.cpp

@@ -14,18 +14,25 @@
 
 using namespace Qt::StringLiterals;
 
-static QList<const Converter *> *availableConverters;
-
 Converter::Converter()
 {
-    if (!availableConverters)
+    converters().append(this);
-        availableConverters = new QList<const Converter *>;
-    availableConverters->append(this);
 }
 
 Converter::~Converter()
 {
-    availableConverters->removeAll(this);
+    converters().removeAll(this);
+}
+
+QList<const Converter *> &Converter::converters()
+{
+    Q_CONSTINIT static QList<const Converter *> store;
+    return store;
+}
+
+const QList<const Converter *> &Converter::allConverters()
+{
+    return converters();
 }
 
 static const Converter *prepareConverter(QString format, Converter::Direction direction,
@@ -46,7 +53,7 @@ static const Converter *prepareConverter(QString format, Converter::Direction di
         qFatal("Could not open \"%s\" for %s: %s",
                qPrintable(stream->fileName()), dirn, qPrintable(stream->errorString()));
     } else if (format == "auto"_L1) {
-        for (const Converter *conv : std::as_const(*availableConverters)) {
+        for (const Converter *conv : Converter::allConverters()) {
             if (conv->directions().testFlag(direction) && conv->probeFile(stream))
                 return conv;
         }
@@ -56,7 +63,7 @@ static const Converter *prepareConverter(QString format, Converter::Direction di
         // Input format, however, we must know before we can call that:
         qFatal("Could not determine input format. Specify it with the -I option.");
     } else {
-        for (const Converter *conv : std::as_const(*availableConverters)) {
+        for (const Converter *conv : Converter::allConverters()) {
             if (conv->name() == format) {
                 if (!conv->directions().testFlag(direction)) {
                     qWarning("File format \"%s\" cannot be used for %s",
@@ -77,7 +84,7 @@ int main(int argc, char *argv[])
 
     QStringList inputFormats;
     QStringList outputFormats;
-    for (const Converter *conv : std::as_const(*availableConverters)) {
+    for (const Converter *conv : Converter::allConverters()) {
         auto direction = conv->directions();
         QString name = conv->name();
         if (direction.testFlag(Converter::Direction::In))
@@ -130,7 +137,7 @@ int main(int argc, char *argv[])
 
     if (parser.isSet(formatOptionsOption)) {
         QString format = parser.value(formatOptionsOption);
-        for (const Converter *conv : std::as_const(*availableConverters)) {
+        for (const Converter *conv : Converter::allConverters()) {
             if (conv->name() == format) {
                 const char *help = conv->optionsHelp();
                 if (help) {