fix assertion in QProcess/Win

Do not call bytesAvailableInChannel if the source pipe end is
invalid. This is the case when redirecting channels on Windows.
The assertions in bytesAvailableInChannel were triggered whenever
an output process or output file was set and waitForBytesWritten
was called.

Task-number: QTBUG-45548
Change-Id: I225dfea2c5e27e122f75008a3a06d425554e00fe
Reviewed-by: Alex Trotsenko <alex1973tr@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

src/corelib/io/qprocess_win.cpp

@@ -704,13 +704,15 @@ bool QProcessPrivate::waitForBytesWritten(int msecs)
             return true;
 
         // If we wouldn't write anything, check if we can read stdout.
-        if (bytesAvailableInChannel(&stdoutChannel) != 0) {
+        if (stdoutChannel.pipe[0] != INVALID_Q_PIPE
+                && bytesAvailableInChannel(&stdoutChannel) != 0) {
             tryReadFromChannel(&stdoutChannel);
             timer.resetIncrements();
         }
 
         // Check if we can read stderr.
-        if (bytesAvailableInChannel(&stderrChannel) != 0) {
+        if (stderrChannel.pipe[0] != INVALID_Q_PIPE
+                && bytesAvailableInChannel(&stderrChannel) != 0) {
             tryReadFromChannel(&stderrChannel);
             timer.resetIncrements();
         }

tests/auto/corelib/io/qprocess/tst_qprocess.cpp

@@ -118,6 +118,7 @@ private slots:
     void setStandardOutputFile_data();
     void setStandardOutputFile();
     void setStandardOutputFile2();
+    void setStandardOutputFileAndWaitForBytesWritten();
     void setStandardOutputProcess_data();
     void setStandardOutputProcess();
     void removeFileWhileProcessIsRunning();
@@ -2068,6 +2069,26 @@ void tst_QProcess::setStandardOutputFile()
 
     QCOMPARE(all.size(), expectedsize);
 }
+
+void tst_QProcess::setStandardOutputFileAndWaitForBytesWritten()
+{
+    static const char testdata[] = "Test data.";
+
+    QFile file("data");
+    QProcess process;
+    process.setStandardOutputFile(file.fileName());
+    process.start("testProcessEcho2/testProcessEcho2");
+    process.write(testdata, sizeof testdata);
+    process.waitForBytesWritten();
+    QPROCESS_VERIFY(process, waitForFinished());
+
+    // open the file again and verify the data
+    QVERIFY(file.open(QIODevice::ReadOnly));
+    QByteArray all = file.readAll();
+    file.close();
+
+    QCOMPARE(all, QByteArray::fromRawData(testdata, sizeof testdata - 1));
+}
 #endif
 
 //-----------------------------------------------------------------------------
@@ -2076,17 +2097,19 @@ void tst_QProcess::setStandardOutputFile()
 void tst_QProcess::setStandardOutputProcess_data()
 {
     QTest::addColumn<bool>("merged");
-    QTest::newRow("separate") << false;
+    QTest::addColumn<bool>("waitForBytesWritten");
-    QTest::newRow("merged") << true;
+    QTest::newRow("separate") << false << false;
+    QTest::newRow("separate with waitForBytesWritten") << false << true;
+    QTest::newRow("merged") << true << false;
 }
 
 void tst_QProcess::setStandardOutputProcess()
 {
-
     QProcess source;
     QProcess sink;
 
     QFETCH(bool, merged);
+    QFETCH(bool, waitForBytesWritten);
     source.setReadChannelMode(merged ? QProcess::MergedChannels : QProcess::SeparateChannels);
     source.setStandardOutputProcess(&sink);
 
@@ -2095,6 +2118,8 @@ void tst_QProcess::setStandardOutputProcess()
 
     QByteArray data("Hello, World");
     source.write(data);
+    if (waitForBytesWritten)
+        source.waitForBytesWritten();
     source.closeWriteChannel();
     QPROCESS_VERIFY(source, waitForFinished());
     QPROCESS_VERIFY(sink, waitForFinished());