Modbus server: fix data conversion error handling

In line
 ok = modbusDevice->setData(..., value.toUShort(&ok, 16));
the value of 'ok' variable after the toUShort() conversion is
immediately overwritten by the return value of setData() method.
As a result, the code could never detect that toUShort() conversion
failed.

This commit splits the line into several independent statements, adding
an if (ok) check in between.

Task-number: QTBUG-110890
Pick-to: 6.5
Change-Id: I98a9275262f5a05fee77905ce7c7d861f2dce6fe
Reviewed-by: André Hartmann <aha_1980@gmx.de>

1 files changed, 9 insertions, 4 deletions

diff --git a/examples/serialbus/modbus/server/mainwindow.cpp b/examples/serialbus/modbus/server/mainwindow.cpp
index 3bdcefa..1dc9f35 100644
--- a/examples/serialbus/modbus/server/mainwindow.cpp
+++ b/examples/serialbus/modbus/server/mainwindow.cpp
@@ -212,10 +212,15 @@ void MainWindow::setRegister(const QString &value)
     if (registers.contains(objectName)) {
         bool ok = true;
         const quint16 id = quint16(QObject::sender()->property("ID").toUInt());
-        if (objectName.startsWith(QStringLiteral("inReg")))
-            ok = modbusDevice->setData(QModbusDataUnit::InputRegisters, id, value.toUShort(&ok, 16));
-        else if (objectName.startsWith(QStringLiteral("holdReg")))
-            ok = modbusDevice->setData(QModbusDataUnit::HoldingRegisters, id, value.toUShort(&ok, 16));
+        if (objectName.startsWith(QStringLiteral("inReg"))) {
+            const auto uval = value.toUShort(&ok, 16);
+            if (ok)
+                ok = modbusDevice->setData(QModbusDataUnit::InputRegisters, id, uval);
+        } else if (objectName.startsWith(QStringLiteral("holdReg"))) {
+            const auto uval = value.toUShort(&ok, 16);
+            if (ok)
+                ok = modbusDevice->setData(QModbusDataUnit::HoldingRegisters, id, uval);
+        }
 
         if (!ok)
             statusBar()->showMessage(tr("Could not set register: ") + modbusDevice->errorString(),