Re-revert "Delay creation of the process manager"

This reverts commit daba2c507ad42c66dafa6a29cffa94e9641e0c58,
re-applying commit d9c06bf25210b3d0b31ee6126e57bcb82c292da1, because
the change was accidentally brought back in commit
eae8fb85997d82ecec0743ba3e470681129bff41.

There's a potential deadlock when a QProcess is created while a
QCoreApplication is instantiated but never executed, or if the main
thread waits() for the child thread.

Task-number: QTBUG-27260
Change-Id: I9e0fdc0341b3063de90979377bac35f2a827b260
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

3 files changed, 90 insertions, 0 deletions

diff --git a/tests/auto/corelib/io/io.pro b/tests/auto/corelib/io/io.pro
index f6542d9fd3..03b42a2cbb 100644
--- a/tests/auto/corelib/io/io.pro
+++ b/tests/auto/corelib/io/io.pro
@@ -16,6 +16,7 @@ SUBDIRS=\
     qipaddress \
     qnodebug \
     qprocess \
+    qprocess-noapplication \
     qprocessenvironment \
     qresourceengine \
     qsettings \
diff --git a/tests/auto/corelib/io/qprocess-noapplication/qprocess-noapplication.pro b/tests/auto/corelib/io/qprocess-noapplication/qprocess-noapplication.pro
new file mode 100644
index 0000000000..2f409ebdbc
--- /dev/null
+++ b/tests/auto/corelib/io/qprocess-noapplication/qprocess-noapplication.pro
@@ -0,0 +1,5 @@
+CONFIG += testcase
+CONFIG += parallel_test
+CONFIG -= app_bundle debug_and_release_target
+QT = core testlib
+SOURCES = tst_qprocessnoapplication.cpp
diff --git a/tests/auto/corelib/io/qprocess-noapplication/tst_qprocessnoapplication.cpp b/tests/auto/corelib/io/qprocess-noapplication/tst_qprocessnoapplication.cpp
new file mode 100644
index 0000000000..33146cafd1
--- /dev/null
+++ b/tests/auto/corelib/io/qprocess-noapplication/tst_qprocessnoapplication.cpp
@@ -0,0 +1,84 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 Intel Corporation.
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtCore/QCoreApplication>
+#include <QtCore/QProcess>
+#include <QtCore/QThread>
+#include <QtTest>
+
+class tst_QProcessNoApplication : public QObject
+{
+    Q_OBJECT
+
+private Q_SLOTS:
+    void initializationDeadlock();
+};
+
+void tst_QProcessNoApplication::initializationDeadlock()
+{
+    // see QTBUG-27260
+    // QProcess on Unix uses (or used to, at the time of the writing of this test)
+    // a global class called QProcessManager.
+    // This class is instantiated (or was) only in the main thread, which meant that
+    // blocking the main thread while waiting for QProcess could mean a deadlock.
+
+    struct MyThread : public QThread
+    {
+        void run()
+        {
+            // what we execute does not matter, as long as we try to
+            // and that the process exits
+            QProcess::execute("true");
+        }
+    };
+
+    static char argv0[] = "tst_QProcessNoApplication";
+    char *argv[] = { argv0, 0 };
+    int argc = 1;
+    QCoreApplication app(argc, argv);
+    MyThread thread;
+    thread.start();
+    QVERIFY(thread.wait(10000));
+}
+
+QTEST_APPLESS_MAIN(tst_QProcessNoApplication)
+
+#include "tst_qprocessnoapplication.moc"