From 6a6d12ea4b90d24839f13b92237dbc8cce5eaf9d Mon Sep 17 00:00:00 2001
From: Alex Trotsenko <alex1973tr@gmail.com>
Date: Tue, 5 Jan 2021 18:59:40 +0200
Subject: Split QProcessPrivate::_q_processDied()

The completion of the child process can take place asynchronously or in
one of the waitFor...() functions. In both cases, we used the same
handler (_q_processDied()), which caused several problems:

  a. technically, waitForReadyRead() should have taken into account the
     result of the calls to _q_canRead...() slots inside the
     _q_processDied() function:

       - the user calls waitForReadyRead();
       - forkfd descriptor becomes signaled, while a grandchild
         process is still alive;
       - as readyRead() signal has not been emitted, _q_processDied()
         is called;
       - the grandchild process writes to stdout pipe;
       - now data arrives, and _q_processDied() will collect it, but
         won't report it.

  b. we had a bug with recursions on Unix:

       - death notification comes asynchronously;
       - waitForDeadChild() closes forkfd;
       - _q_canRead...() emits readyRead();
       - a slot connected to readyRead() calls waitForFinished();
       - waitForFinished() hangs (forkfd == -1).

   c. for blocking functions, drainOutputPipes() was called twice on
      Windows.

By introducing a new processFinished() function, we leave the read
operations in the _q_processDied() slot, while the process completion
code is guaranteed to run only once.

Change-Id: I5f9d09bc68a058169de4d9e490b48fc0b35e94cd
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
---
 src/corelib/io/qprocess_win.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 'src/corelib/io/qprocess_win.cpp')

diff --git a/src/corelib/io/qprocess_win.cpp b/src/corelib/io/qprocess_win.cpp
index 6ab854de16..2a5b8fd4fd 100644
--- a/src/corelib/io/qprocess_win.cpp
+++ b/src/corelib/io/qprocess_win.cpp
@@ -685,7 +685,7 @@ bool QProcessPrivate::waitForReadyRead(const QDeadlineTimer &deadline)
         if (WaitForSingleObjectEx(pid->hProcess, 0, false) == WAIT_OBJECT_0) {
             bool readyReadEmitted = drainOutputPipes();
             if (pid)
-                _q_processDied();
+                processFinished();
             return readyReadEmitted;
         }
 
@@ -743,7 +743,9 @@ bool QProcessPrivate::waitForBytesWritten(const QDeadlineTimer &deadline)
         // Wait for the process to signal any change in its state,
         // such as incoming data, or if the process died.
         if (WaitForSingleObjectEx(pid->hProcess, 0, false) == WAIT_OBJECT_0) {
-            _q_processDied();
+            drainOutputPipes();
+            if (pid)
+                processFinished();
             return false;
         }
 
@@ -782,7 +784,7 @@ bool QProcessPrivate::waitForFinished(const QDeadlineTimer &deadline)
         if (WaitForSingleObject(pid->hProcess, timer.nextSleepTime()) == WAIT_OBJECT_0) {
             drainOutputPipes();
             if (pid)
-                _q_processDied();
+                processFinished();
             return true;
         }
 
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