6 files changed, 52 insertions, 61 deletions
diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index 0702667042d..0f2de9e1ff7 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -782,7 +782,9 @@ void QProcessPrivate::Channel::clear()
 QProcessPrivate::QProcessPrivate()
 {
     readBufferChunkSize = QRINGBUFFER_CHUNKSIZE;
+#ifndef Q_OS_WIN
     writeBufferChunkSize = QRINGBUFFER_CHUNKSIZE;
+#endif
 }
 
 /*!
@@ -1585,11 +1587,11 @@ bool QProcess::isSequential() const
 */
 qint64 QProcess::bytesToWrite() const
 {
-    qint64 size = QIODevice::bytesToWrite();
 #ifdef Q_OS_WIN
-    size += d_func()->pipeWriterBytesToWrite();
+    return d_func()->pipeWriterBytesToWrite();
+#else
+    return QIODevice::bytesToWrite();
 #endif
-    return size;
 }
 
 /*!
diff --git a/src/corelib/io/qprocess.h b/src/corelib/io/qprocess.h
index f9c05a4f292..e1b8cc7f57f 100644
--- a/src/corelib/io/qprocess.h
+++ b/src/corelib/io/qprocess.h
@@ -281,7 +281,9 @@ private:
 
     Q_PRIVATE_SLOT(d_func(), bool _q_canReadStandardOutput())
     Q_PRIVATE_SLOT(d_func(), bool _q_canReadStandardError())
+#ifdef Q_OS_UNIX
     Q_PRIVATE_SLOT(d_func(), bool _q_canWrite())
+#endif
     Q_PRIVATE_SLOT(d_func(), bool _q_startupNotification())
     Q_PRIVATE_SLOT(d_func(), void _q_processDied())
 };
diff --git a/src/corelib/io/qprocess_p.h b/src/corelib/io/qprocess_p.h
index 078c617021c..74ab6ab4097 100644
--- a/src/corelib/io/qprocess_p.h
+++ b/src/corelib/io/qprocess_p.h
@@ -81,7 +81,6 @@ class QSocketNotifier;
 class QWindowsPipeReader;
 class QWindowsPipeWriter;
 class QWinEventNotifier;
-class QTimer;
 
 #ifdef Q_OS_WIN
 class QProcEnvKey : public QString
@@ -286,9 +285,12 @@ public:
     bool _q_canReadStandardOutput();
     bool _q_canReadStandardError();
 #ifdef Q_OS_WIN
+    qint64 pipeWriterBytesToWrite() const;
     void _q_bytesWritten(qint64 bytes);
-#endif
+#else
     bool _q_canWrite();
+    bool writeToStdin();
+#endif
     bool _q_startupNotification();
     void _q_processDied();
 
@@ -335,7 +337,6 @@ public:
     QSocketNotifier *stateNotifier = nullptr;
     int forkfd = -1;
 #else
-    QTimer *stdinWriteTrigger = nullptr;
     QWinEventNotifier *processFinishedNotifier = nullptr;
 #endif
 
@@ -357,7 +358,6 @@ public:
     STARTUPINFOW createStartupInfo();
     bool callCreateProcess(QProcess::CreateProcessArguments *cpargs);
     bool drainOutputPipes();
-    qint64 pipeWriterBytesToWrite() const;
 #endif
 
     bool startDetached(qint64 *pPid);
@@ -373,7 +373,6 @@ public:
 
     qint64 bytesAvailableInChannel(const Channel *channel) const;
     qint64 readFromChannel(const Channel *channel, char *data, qint64 maxlen);
-    bool writeToStdin();
 
     void destroyPipe(Q_PIPE pipe[2]);
     void cleanup();
diff --git a/src/corelib/io/qprocess_win.cpp b/src/corelib/io/qprocess_win.cpp
index e557d104534..24031b9163a 100644
--- a/src/corelib/io/qprocess_win.cpp
+++ b/src/corelib/io/qprocess_win.cpp
@@ -53,7 +53,6 @@
 #include <qrandom.h>
 #include <qwineventnotifier.h>
 #include <qscopedvaluerollback.h>
-#include <qtimer.h>
 #include <private/qsystemlibrary_p.h>
 #include <private/qthread_p.h>
 
@@ -376,8 +375,6 @@ void QProcessPrivate::cleanup()
     q_func()->setProcessState(QProcess::NotRunning);
 
     closeChannels();
-    delete stdinWriteTrigger;
-    stdinWriteTrigger = nullptr;
     delete processFinishedNotifier;
     processFinishedNotifier = nullptr;
     if (pid) {
@@ -618,6 +615,12 @@ void QProcessPrivate::startProcess()
         return;
     }
 
+    // The pipe writer may have already been created before we had
+    // the pipe handle, specifically if the user wrote data from the
+    // stateChanged() slot.
+    if (stdinChannel.writer)
+        stdinChannel.writer->setHandle(stdinChannel.pipe[1]);
+
     q->setProcessState(QProcess::Running);
     // User can call kill()/terminate() from the stateChanged() slot
     // so check before proceeding
@@ -713,9 +716,6 @@ bool QProcessPrivate::drainOutputPipes()
 bool QProcessPrivate::waitForReadyRead(const QDeadlineTimer &deadline)
 {
     forever {
-        if (!writeBuffer.isEmpty() && !_q_canWrite())
-            return false;
-
         QProcessPoller poller(*this);
         int ret = poller.poll(deadline);
         if (ret < 0)
@@ -748,10 +748,11 @@ bool QProcessPrivate::waitForReadyRead(const QDeadlineTimer &deadline)
 bool QProcessPrivate::waitForBytesWritten(const QDeadlineTimer &deadline)
 {
     forever {
-        // If no write is pending, try to start one. However, at entry into
-        // the loop the write buffer can be empty to start with, in which
-        // case _q_caWrite() fails immediately.
-        if (pipeWriterBytesToWrite() == 0 && !_q_canWrite())
+        // At entry into the loop the pipe writer's buffer can be empty to
+        // start with, in which case we fail immediately. Also, if the input
+        // pipe goes down somewhere in the code below, we avoid waiting for
+        // a full timeout.
+        if (pipeWriterBytesToWrite() == 0)
             return false;
 
         QProcessPoller poller(*this);
@@ -797,9 +798,6 @@ bool QProcessPrivate::waitForFinished(const QDeadlineTimer &deadline)
 #endif
 
     forever {
-        if (!writeBuffer.isEmpty() && !_q_canWrite())
-            return false;
-
         QProcessPoller poller(*this);
         int ret = poller.poll(deadline);
         if (ret < 0)
@@ -854,16 +852,16 @@ qint64 QProcess::writeData(const char *data, qint64 len)
         return 0;
     }
 
-    if (!d->stdinWriteTrigger) {
-        d->stdinWriteTrigger = new QTimer;
-        d->stdinWriteTrigger->setSingleShot(true);
-        QObjectPrivate::connect(d->stdinWriteTrigger, &QTimer::timeout,
-                                d, &QProcessPrivate::_q_canWrite);
+    if (!d->stdinChannel.writer) {
+        d->stdinChannel.writer = new QWindowsPipeWriter(d->stdinChannel.pipe[1], this);
+        QObjectPrivate::connect(d->stdinChannel.writer, &QWindowsPipeWriter::bytesWritten,
+                                d, &QProcessPrivate::_q_bytesWritten);
     }
 
-    d->write(data, len);
-    if (!d->stdinWriteTrigger->isActive())
-        d->stdinWriteTrigger->start();
+    if (d->isWriteChunkCached(data, len))
+        d->stdinChannel.writer->write(*(d->currentWriteChunk));
+    else
+        d->stdinChannel.writer->write(data, len);
 
 #if defined QPROCESS_DEBUG
     qDebug("QProcess::writeData(%p \"%s\", %lld) == %lld (written to buffer)",
@@ -885,38 +883,8 @@ void QProcessPrivate::_q_bytesWritten(qint64 bytes)
         QScopedValueRollback<bool> guard(emittedBytesWritten, true);
         emit q->bytesWritten(bytes);
     }
-    _q_canWrite();
-}
-
-bool QProcessPrivate::_q_canWrite()
-{
-    if (writeBuffer.isEmpty()) {
-        if (stdinChannel.closed && pipeWriterBytesToWrite() == 0)
-            closeWriteChannel();
-#if defined QPROCESS_DEBUG
-        qDebug("QProcessPrivate::canWrite(), not writing anything (empty write buffer).");
-#endif
-        return false;
-    }
-
-    return writeToStdin();
-}
-
-bool QProcessPrivate::writeToStdin()
-{
-    Q_Q(QProcess);
-
-    if (!stdinChannel.writer) {
-        stdinChannel.writer = new QWindowsPipeWriter(stdinChannel.pipe[1], q);
-        QObjectPrivate::connect(stdinChannel.writer, &QWindowsPipeWriter::bytesWritten,
-                                this, &QProcessPrivate::_q_bytesWritten);
-    } else {
-        if (stdinChannel.writer->isWriteOperationActive())
-            return true;
-    }
-
-    stdinChannel.writer->write(writeBuffer.read());
-    return true;
+    if (stdinChannel.closed && pipeWriterBytesToWrite() == 0)
+        closeWriteChannel();
 }
 
 // Use ShellExecuteEx() to trigger an UAC prompt when CreateProcess()fails
diff --git a/src/corelib/io/qwindowspipewriter.cpp b/src/corelib/io/qwindowspipewriter.cpp
index 83282032e21..6a5e43db0df 100644
--- a/src/corelib/io/qwindowspipewriter.cpp
+++ b/src/corelib/io/qwindowspipewriter.cpp
@@ -73,6 +73,19 @@ QWindowsPipeWriter::~QWindowsPipeWriter()
 }
 
 /*!
+    Assigns the handle to this writer. The handle must be valid.
+    Call this function if data was buffered before getting the handle.
+ */
+void QWindowsPipeWriter::setHandle(HANDLE hPipeWriteEnd)
+{
+    Q_ASSERT(!stopped);
+
+    handle = hPipeWriteEnd;
+    QMutexLocker locker(&mutex);
+    startAsyncWriteLocked(&locker);
+}
+
+/*!
     Stops the asynchronous write sequence.
     If the write sequence is running then the I/O operation is canceled.
  */
@@ -150,6 +163,12 @@ inline bool QWindowsPipeWriter::writeImpl(Args... args)
         return true;
 
     stopped = false;
+
+    // If we don't have an assigned handle yet, defer writing until
+    // setHandle() is called.
+    if (handle == INVALID_HANDLE_VALUE)
+        return true;
+
     startAsyncWriteLocked(&locker);
     return true;
 }
diff --git a/src/corelib/io/qwindowspipewriter_p.h b/src/corelib/io/qwindowspipewriter_p.h
index 11d1abba59f..e20f1ec90a5 100644
--- a/src/corelib/io/qwindowspipewriter_p.h
+++ b/src/corelib/io/qwindowspipewriter_p.h
@@ -68,6 +68,7 @@ public:
     explicit QWindowsPipeWriter(HANDLE pipeWriteEnd, QObject *parent = nullptr);
     ~QWindowsPipeWriter();
 
+    void setHandle(HANDLE hPipeWriteEnd);
     bool write(const QByteArray &ba);
     bool write(const char *data, qint64 size);
     void stop();