consistently handle empty program string in QProcess::start overloads

All overloads of QProcess::start will now check whether the program
string is empty and in that case
  - set error to FailedToStart,
  - set errorString to "No program defined",
  - emit error.

Until now only one of the three overloads behaved like this.

As a side effect, start(QString(), QStringList()) will not crash on
Windows anymore.

Task-number: QTBUG-47404
Change-Id: I2f93657204fe3643b1d74a74817843c05fc4a96b
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/tests/auto/corelib/io/qprocess/tst_qprocess.cpp b/tests/auto/corelib/io/qprocess/tst_qprocess.cpp
index 0c65ceb0eb..99cb9ad6cb 100644
--- a/tests/auto/corelib/io/qprocess/tst_qprocess.cpp
+++ b/tests/auto/corelib/io/qprocess/tst_qprocess.cpp
@@ -156,6 +156,8 @@ private slots:
     void failToStart();
     void failToStartWithWait();
     void failToStartWithEventLoop();
+    void failToStartEmptyArgs_data();
+    void failToStartEmptyArgs();
 
 protected slots:
     void readFromProcess();
@@ -1672,6 +1674,42 @@ void tst_QProcess::failToStartWithEventLoop()
     }
 }
 
+void tst_QProcess::failToStartEmptyArgs_data()
+{
+    QTest::addColumn<int>("startOverload");
+    QTest::newRow("start(QString, QStringList, OpenMode)") << 0;
+    QTest::newRow("start(QString, OpenMode)") << 1;
+    QTest::newRow("start(OpenMode)") << 2;
+}
+
+void tst_QProcess::failToStartEmptyArgs()
+{
+    QFETCH(int, startOverload);
+    qRegisterMetaType<QProcess::ProcessError>("QProcess::ProcessError");
+
+    QProcess process;
+    QSignalSpy errorSpy(&process, static_cast<void (QProcess::*)(QProcess::ProcessError)>(&QProcess::error));
+    QVERIFY(errorSpy.isValid());
+
+    switch (startOverload) {
+    case 0:
+        process.start(QString(), QStringList(), QIODevice::ReadWrite);
+        break;
+    case 1:
+        process.start(QString(), QIODevice::ReadWrite);
+        break;
+    case 2:
+        process.start(QIODevice::ReadWrite);
+        break;
+    default:
+        QFAIL("Unhandled QProcess::start overload.");
+    };
+
+    QVERIFY(!process.waitForStarted());
+    QCOMPARE(errorSpy.count(), 1);
+    QCOMPARE(process.error(), QProcess::FailedToStart);
+}
+
 //-----------------------------------------------------------------------------
 #ifndef Q_OS_WINCE
 // Reading and writing to a process is not supported on Qt/CE