Use nullptr in some more places.

This patch was generated using clang-tidy:

  clang-tidy -checks="-*,modernize-use-nullptr" -fix

main.cpp

@@ -84,12 +84,12 @@ int main(int argc, char *argv[])
 	// Parse arguments
 	while (1) {
 		static const struct option long_options[] = {
-			{"help", no_argument, 0, 'h'},
-			{"version", no_argument, 0, 'V'},
-			{"loglevel", required_argument, 0, 'l'},
-			{"input-file", required_argument, 0, 'i'},
-			{"input-format", required_argument, 0, 'I'},
-			{0, 0, 0, 0}
+			{"help", no_argument, nullptr, 'h'},
+			{"version", no_argument, nullptr, 'V'},
+			{"loglevel", required_argument, nullptr, 'l'},
+			{"input-file", required_argument, nullptr, 'i'},
+			{"input-format", required_argument, nullptr, 'I'},
+			{nullptr, 0, nullptr, 0}
 		};
 
 		const int c = getopt_long(argc, argv,

pv/view/signal.cpp

@@ -116,7 +116,7 @@ void Signal::populate_popup_form(QWidget *parent, QFormLayout *form)
 {
 	name_widget_ = new QComboBox(parent);
 	name_widget_->setEditable(true);
-	name_widget_->setCompleter(0);
+	name_widget_->setCompleter(nullptr);
 
 	for (unsigned int i = 0; i < countof(ChannelNames); i++)
 		name_widget_->insertItem(i, ChannelNames[i]);

pv/widgets/wellarray.cpp

@@ -104,7 +104,7 @@ WellArray::WellArray(int rows, int cols, QWidget *parent)
     : QWidget(parent)
         ,nrows(rows), ncols(cols)
 {
-    d = 0;
+    d = nullptr;
     setFocusPolicy(Qt::StrongFocus);
     cellw = 28;
     cellh = 24;

signalhandler.cpp

@@ -42,8 +42,8 @@ bool SignalHandler::prepare_signals()
 	sigemptyset(&sig_action.sa_mask);
 	sig_action.sa_flags = SA_RESTART;
 
-	if (sigaction(SIGINT, &sig_action, 0) != 0 ||
-		sigaction(SIGTERM, &sig_action, 0) != 0) {
+	if (sigaction(SIGINT, &sig_action, nullptr) != 0 ||
+		sigaction(SIGTERM, &sig_action, nullptr) != 0) {
 		close(sockets_[0]);
 		close(sockets_[1]);
 		return false;
@@ -53,7 +53,7 @@ bool SignalHandler::prepare_signals()
 }
 
 SignalHandler::SignalHandler(QObject* parent) : QObject(parent),
-	socket_notifier_(0)
+	socket_notifier_(nullptr)
 {
 	socket_notifier_ = new QSocketNotifier(sockets_[1],
 		QSocketNotifier::Read, this);