From 6bd61513290ef23783220b0e7507c4f03d5114e7 Mon Sep 17 00:00:00 2001
From: Alex Trotsenko <alex1973tr@gmail.com>
Date: Sun, 7 Mar 2021 14:44:23 +0200
Subject: [PATCH] QProcess/Win: implement async closing of write channel

Instead of blocking in QProcessPrivate::closeWriteChannel(), we can
handle a pending close in _q_canWrite() slot when there is no more
data to write.

Change-Id: I2a30789b6099a2ec075292348ebe33a11341bca3
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
---
 src/corelib/io/qprocess.cpp     | 14 ++++++++------
 src/corelib/io/qprocess_p.h     |  1 -
 src/corelib/io/qprocess_win.cpp |  6 ------
 3 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index f03fc067cf..745c88e726 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -1097,8 +1097,13 @@ bool QProcessPrivate::_q_canReadStandardError()
 bool QProcessPrivate::_q_canWrite()
 {
     if (writeBuffer.isEmpty()) {
+#ifdef Q_OS_WIN
+        if (stdinChannel.closed && pipeWriterBytesToWrite() == 0)
+            closeWriteChannel();
+#else
         if (stdinChannel.notifier)
             stdinChannel.notifier->setEnabled(false);
+#endif
 #if defined QPROCESS_DEBUG
         qDebug("QProcessPrivate::canWrite(), not writing anything (empty write buffer).");
 #endif
@@ -1107,10 +1112,12 @@ bool QProcessPrivate::_q_canWrite()
 
     const bool writeSucceeded = writeToStdin();
 
+#ifdef Q_OS_UNIX
     if (writeBuffer.isEmpty() && stdinChannel.closed)
         closeWriteChannel();
     else if (stdinChannel.notifier)
         stdinChannel.notifier->setEnabled(!writeBuffer.isEmpty());
+#endif
     return writeSucceeded;
 }
 
@@ -1211,11 +1218,6 @@ void QProcessPrivate::closeWriteChannel()
     qDebug("QProcessPrivate::closeWriteChannel()");
 #endif
 
-#ifdef Q_OS_WIN
-    // ### Find a better fix, feeding the process little by little
-    // instead.
-    flushPipeWriter();
-#endif
     closeChannel(&stdinChannel);
 }
 
@@ -1373,7 +1375,7 @@ void QProcess::closeWriteChannel()
 {
     Q_D(QProcess);
     d->stdinChannel.closed = true; // closing
-    if (d->writeBuffer.isEmpty())
+    if (bytesToWrite() == 0)
         d->closeWriteChannel();
 }
 
diff --git a/src/corelib/io/qprocess_p.h b/src/corelib/io/qprocess_p.h
index 7b58b32369..73db9423e6 100644
--- a/src/corelib/io/qprocess_p.h
+++ b/src/corelib/io/qprocess_p.h
@@ -365,7 +365,6 @@ public:
     STARTUPINFOW createStartupInfo();
     bool callCreateProcess(QProcess::CreateProcessArguments *cpargs);
     bool drainOutputPipes();
-    void flushPipeWriter();
     qint64 pipeWriterBytesToWrite() const;
 #endif
 
diff --git a/src/corelib/io/qprocess_win.cpp b/src/corelib/io/qprocess_win.cpp
index 0088284d2d..3bdf070be4 100644
--- a/src/corelib/io/qprocess_win.cpp
+++ b/src/corelib/io/qprocess_win.cpp
@@ -796,12 +796,6 @@ void QProcessPrivate::findExitCode()
     }
 }
 
-void QProcessPrivate::flushPipeWriter()
-{
-    if (stdinChannel.writer && stdinChannel.writer->bytesToWrite() > 0)
-        stdinChannel.writer->waitForWrite(ULONG_MAX);
-}
-
 qint64 QProcessPrivate::pipeWriterBytesToWrite() const
 {
     return stdinChannel.writer ? stdinChannel.writer->bytesToWrite() : qint64(0);