Make QWindowsPipeWriter thread-free.

Re-work QWindowsPipeWriter to not use a thread anymore but the
WriteFileEx API, similar to QWindowsPipeReader. This saves us a lot of
thread synchronization code and enables us to directly write data
without yet another buffering layer.
  Also, this fixes the dreaded deadlocks in the QWindowsPipeWriter
destructor that could occur when the reading end was closed before
the write was finished.

Task-number: QTBUG-23378
Task-number: QTBUG-38185
Change-Id: If0ae96dcd756f716ddf6fa38016080095bf3bd4e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

1 files changed, 1 insertions, 5 deletions

diff --git a/src/corelib/io/qprocess_win.cpp b/src/corelib/io/qprocess_win.cpp
index 98ada82446..e7cd9d9a17 100644
--- a/src/corelib/io/qprocess_win.cpp
+++ b/src/corelib/io/qprocess_win.cpp
@@ -666,10 +666,7 @@ bool QProcessPrivate::waitForBytesWritten(int msecs)
     QIncrementalSleepTimer timer(msecs);
 
     forever {
-        // Check if we have any data pending: the pipe writer has
-        // bytes waiting to written, or it has written data since the
-        // last time we called stdinChannel.writer->waitForWrite().
-        bool pendingDataInPipe = stdinChannel.writer && (stdinChannel.writer->bytesToWrite() || stdinChannel.writer->hadWritten());
+        bool pendingDataInPipe = stdinChannel.writer && stdinChannel.writer->bytesToWrite();
 
         // If we don't have pending data, and our write buffer is
         // empty, we fail.
@@ -797,7 +794,6 @@ qint64 QProcessPrivate::writeToStdin(const char *data, qint64 maxlen)
         stdinChannel.writer = new QWindowsPipeWriter(stdinChannel.pipe[1], q);
         QObjectPrivate::connect(stdinChannel.writer, &QWindowsPipeWriter::canWrite,
                                 this, &QProcessPrivate::_q_canWrite);
-        stdinChannel.writer->start();
     }
 
     return stdinChannel.writer->write(data, maxlen);