Add POSIX IPC support to QSystemSemaphore and QSharedMemory

This patch is a forward-port from 4.8 branch
(d869e1ad4b0007757e97046609de2097cd9e9c5d).

Change-Id: I6ae36a5417d1176fbecf775668f6033b1cb22a94
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/kernel.pri

@@ -149,7 +149,11 @@ unix|integrity {
    contains(QT_CONFIG, clock-gettime):include($$QT_SOURCE_TREE/config.tests/unix/clock-gettime/clock-gettime.pri)
 
     !android {
-        SOURCES += kernel/qsharedmemory_unix.cpp \
+        SOURCES += kernel/qsharedmemory_posix.cpp \
+                   kernel/qsharedmemory_systemv.cpp \
+                   kernel/qsharedmemory_unix.cpp \
+                   kernel/qsystemsemaphore_posix.cpp \
+                   kernel/qsystemsemaphore_systemv.cpp \
                    kernel/qsystemsemaphore_unix.cpp
     } else {
         SOURCES += kernel/qsharedmemory_android.cpp \

src/corelib/kernel/qsharedmemory.cpp

@@ -69,6 +69,8 @@ QSharedMemoryPrivate::makePlatformSafeKey(const QString &key,
     result.append(QLatin1String(hex));
 #ifdef Q_OS_WIN
     return result;
+#elif defined(QT_POSIX_IPC)
+    return QLatin1Char('/') + result;
 #else
     return QDir::tempPath() + QLatin1Char('/') + result;
 #endif

src/corelib/kernel/qsharedmemory_p.h

@@ -122,6 +122,8 @@ public:
             const QString &prefix = QLatin1String("qipc_sharedmemory_"));
 #ifdef Q_OS_WIN
     Qt::HANDLE handle();
+#elif defined(QT_POSIX_IPC)
+    int handle();
 #else
     key_t handle();
 #endif
@@ -147,6 +149,8 @@ public:
 private:
 #ifdef Q_OS_WIN
     Qt::HANDLE hand;
+#elif defined(QT_POSIX_IPC)
+    int hand;
 #else
     key_t unix_key;
 #endif

src/corelib/kernel/qsharedmemory_posix.cpp

@@ -0,0 +1,210 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 Konstantin Ritt <ritt.ks@gmail.com>
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2015 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Tobias Koenig <tobias.koenig@kdab.com>
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qplatformdefs.h"
+
+#include "qsharedmemory.h"
+#include "qsharedmemory_p.h"
+#include "qsystemsemaphore.h"
+#include <qfile.h>
+
+#include <errno.h>
+
+#ifdef QT_POSIX_IPC
+
+#ifndef QT_NO_SHAREDMEMORY
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "private/qcore_unix_p.h"
+
+QT_BEGIN_NAMESPACE
+
+int QSharedMemoryPrivate::handle()
+{
+    // don't allow making handles on empty keys
+    const QString safeKey = makePlatformSafeKey(key);
+    if (safeKey.isEmpty()) {
+        errorString = QSharedMemory::tr("%1: key is empty").arg(QLatin1String("QSharedMemory::handle"));
+        error = QSharedMemory::KeyError;
+        return 0;
+    }
+
+    return 1;
+}
+
+bool QSharedMemoryPrivate::cleanHandle()
+{
+    qt_safe_close(hand);
+    hand = -1;
+
+    return true;
+}
+
+bool QSharedMemoryPrivate::create(int size)
+{
+    if (!handle())
+        return false;
+
+    const QByteArray shmName = QFile::encodeName(makePlatformSafeKey(key));
+
+    int fd;
+    EINTR_LOOP(fd, ::shm_open(shmName.constData(), O_RDWR | O_CREAT | O_EXCL, 0600));
+    if (fd == -1) {
+        const int errorNumber = errno;
+        const QString function = QLatin1String("QSharedMemory::create");
+        switch (errorNumber) {
+        case ENAMETOOLONG:
+        case EINVAL:
+            errorString = QSharedMemory::tr("%1: bad name").arg(function);
+            error = QSharedMemory::KeyError;
+            break;
+        default:
+            setErrorString(function);
+        }
+        return false;
+    }
+
+    // the size may only be set once
+    int ret;
+    EINTR_LOOP(ret, QT_FTRUNCATE(fd, size));
+    if (ret == -1) {
+        setErrorString(QLatin1String("QSharedMemory::create (ftruncate)"));
+        qt_safe_close(fd);
+        return false;
+    }
+
+    qt_safe_close(fd);
+
+    return true;
+}
+
+bool QSharedMemoryPrivate::attach(QSharedMemory::AccessMode mode)
+{
+    const QByteArray shmName = QFile::encodeName(makePlatformSafeKey(key));
+
+    const int oflag = (mode == QSharedMemory::ReadOnly ? O_RDONLY : O_RDWR);
+    const mode_t omode = (mode == QSharedMemory::ReadOnly ? 0400 : 0600);
+
+    EINTR_LOOP(hand, ::shm_open(shmName.constData(), oflag, omode));
+    if (hand == -1) {
+        const int errorNumber = errno;
+        const QString function = QLatin1String("QSharedMemory::attach (shm_open)");
+        switch (errorNumber) {
+        case ENAMETOOLONG:
+        case EINVAL:
+            errorString = QSharedMemory::tr("%1: bad name").arg(function);
+            error = QSharedMemory::KeyError;
+            break;
+        default:
+            setErrorString(function);
+        }
+        hand = -1;
+        return false;
+    }
+
+    // grab the size
+    QT_STATBUF st;
+    if (QT_FSTAT(hand, &st) == -1) {
+        setErrorString(QLatin1String("QSharedMemory::attach (fstat)"));
+        cleanHandle();
+        return false;
+    }
+    size = st.st_size;
+
+    // grab the memory
+    const int mprot = (mode == QSharedMemory::ReadOnly ? PROT_READ : PROT_READ | PROT_WRITE);
+    memory = QT_MMAP(0, size, mprot, MAP_SHARED, hand, 0);
+    if (memory == MAP_FAILED || !memory) {
+        setErrorString(QLatin1String("QSharedMemory::attach (mmap)"));
+        cleanHandle();
+        memory = 0;
+        size = 0;
+        return false;
+    }
+
+    return true;
+}
+
+bool QSharedMemoryPrivate::detach()
+{
+    // detach from the memory segment
+    if (::munmap(memory, size) == -1) {
+        setErrorString(QLatin1String("QSharedMemory::detach (munmap)"));
+        return false;
+    }
+    memory = 0;
+    size = 0;
+
+#ifdef Q_OS_QNX
+    // On QNX the st_nlink field of struct stat contains the number of
+    // active shm_open() connections to the shared memory file, so we
+    // can use it to automatically clean up the file once the last
+    // user has detached from it.
+
+    // get the number of current attachments
+    int shm_nattch = 0;
+    QT_STATBUF st;
+    if (QT_FSTAT(hand, &st) == 0) {
+        // subtract 2 from linkcount: one for our own open and one for the dir entry
+        shm_nattch = st.st_nlink - 2;
+    }
+
+    cleanHandle();
+
+    // if there are no attachments then unlink the shared memory
+    if (shm_nattch == 0) {
+        const QByteArray shmName = QFile::encodeName(makePlatformSafeKey(key));
+        if (::shm_unlink(shmName.constData()) == -1 && errno != ENOENT)
+            setErrorString(QLatin1String("QSharedMemory::detach (shm_unlink)"));
+    }
+#else
+    // On non-QNX systems (tested Linux and Haiku), the st_nlink field is always 1,
+    // so we'll simply leak the shared memory files.
+    cleanHandle();
+#endif
+
+    return true;
+}
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_SHAREDMEMORY
+
+#endif // QT_POSIX_IPC

src/corelib/kernel/qsharedmemory_systemv.cpp

@@ -0,0 +1,254 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qplatformdefs.h"
+
+#include "qsharedmemory.h"
+#include "qsharedmemory_p.h"
+#include "qsystemsemaphore.h"
+#include <qdir.h>
+#include <qdebug.h>
+
+#include <errno.h>
+
+#ifndef QT_POSIX_IPC
+
+#ifndef QT_NO_SHAREDMEMORY
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#endif //QT_NO_SHAREDMEMORY
+
+#include "private/qcore_unix_p.h"
+
+#ifndef QT_NO_SHAREDMEMORY
+QT_BEGIN_NAMESPACE
+
+/*!
+    \internal
+
+    If not already made create the handle used for accessing the shared memory.
+*/
+key_t QSharedMemoryPrivate::handle()
+{
+    // already made
+    if (unix_key)
+        return unix_key;
+
+    // don't allow making handles on empty keys
+    if (nativeKey.isEmpty()) {
+        errorString = QSharedMemory::tr("%1: key is empty").arg(QLatin1String("QSharedMemory::handle:"));
+        error = QSharedMemory::KeyError;
+        return 0;
+    }
+
+    // ftok requires that an actual file exists somewhere
+    if (!QFile::exists(nativeKey)) {
+        errorString = QSharedMemory::tr("%1: UNIX key file doesn't exist").arg(QLatin1String("QSharedMemory::handle:"));
+        error = QSharedMemory::NotFound;
+        return 0;
+    }
+
+    unix_key = ftok(QFile::encodeName(nativeKey).constData(), 'Q');
+    if (-1 == unix_key) {
+        errorString = QSharedMemory::tr("%1: ftok failed").arg(QLatin1String("QSharedMemory::handle:"));
+        error = QSharedMemory::KeyError;
+        unix_key = 0;
+    }
+    return unix_key;
+}
+
+#endif // QT_NO_SHAREDMEMORY
+
+#if !(defined(QT_NO_SHAREDMEMORY) && defined(QT_NO_SYSTEMSEMAPHORE))
+/*!
+    \internal
+    Creates the unix file if needed.
+    returns \c true if the unix file was created.
+
+    -1 error
+     0 already existed
+     1 created
+  */
+int QSharedMemoryPrivate::createUnixKeyFile(const QString &fileName)
+{
+    int fd = qt_safe_open(QFile::encodeName(fileName).constData(),
+            O_EXCL | O_CREAT | O_RDWR, 0640);
+    if (-1 == fd) {
+        if (errno == EEXIST)
+            return 0;
+        return -1;
+    } else {
+        close(fd);
+    }
+    return 1;
+}
+#endif // QT_NO_SHAREDMEMORY && QT_NO_SYSTEMSEMAPHORE
+
+#ifndef QT_NO_SHAREDMEMORY
+
+bool QSharedMemoryPrivate::cleanHandle()
+{
+    unix_key = 0;
+    return true;
+}
+
+bool QSharedMemoryPrivate::create(int size)
+{
+    // build file if needed
+    bool createdFile = false;
+    int built = createUnixKeyFile(nativeKey);
+    if (built == -1) {
+        errorString = QSharedMemory::tr("%1: unable to make key").arg(QLatin1String("QSharedMemory::handle:"));
+        error = QSharedMemory::KeyError;
+        return false;
+    }
+    if (built == 1) {
+        createdFile = true;
+    }
+
+    // get handle
+    if (!handle()) {
+        if (createdFile)
+            QFile::remove(nativeKey);
+        return false;
+    }
+
+    // create
+    if (-1 == shmget(unix_key, size, 0600 | IPC_CREAT | IPC_EXCL)) {
+        QString function = QLatin1String("QSharedMemory::create");
+        switch (errno) {
+        case EINVAL:
+            errorString = QSharedMemory::tr("%1: system-imposed size restrictions").arg(QLatin1String("QSharedMemory::handle"));
+            error = QSharedMemory::InvalidSize;
+            break;
+        default:
+            setErrorString(function);
+        }
+        if (createdFile && error != QSharedMemory::AlreadyExists)
+            QFile::remove(nativeKey);
+        return false;
+    }
+
+    return true;
+}
+
+bool QSharedMemoryPrivate::attach(QSharedMemory::AccessMode mode)
+{
+    // grab the shared memory segment id
+    int id = shmget(unix_key, 0, (mode == QSharedMemory::ReadOnly ? 0400 : 0600));
+    if (-1 == id) {
+        setErrorString(QLatin1String("QSharedMemory::attach (shmget)"));
+        return false;
+    }
+
+    // grab the memory
+    memory = shmat(id, 0, (mode == QSharedMemory::ReadOnly ? SHM_RDONLY : 0));
+    if ((void*) - 1 == memory) {
+        memory = 0;
+        setErrorString(QLatin1String("QSharedMemory::attach (shmat)"));
+        return false;
+    }
+
+    // grab the size
+    shmid_ds shmid_ds;
+    if (!shmctl(id, IPC_STAT, &shmid_ds)) {
+        size = (int)shmid_ds.shm_segsz;
+    } else {
+        setErrorString(QLatin1String("QSharedMemory::attach (shmctl)"));
+        return false;
+    }
+
+    return true;
+}
+
+bool QSharedMemoryPrivate::detach()
+{
+    // detach from the memory segment
+    if (-1 == shmdt(memory)) {
+        QString function = QLatin1String("QSharedMemory::detach");
+        switch (errno) {
+        case EINVAL:
+            errorString = QSharedMemory::tr("%1: not attached").arg(function);
+            error = QSharedMemory::NotFound;
+            break;
+        default:
+            setErrorString(function);
+        }
+        return false;
+    }
+    memory = 0;
+    size = 0;
+
+    // Get the number of current attachments
+    int id = shmget(unix_key, 0, 0400);
+    cleanHandle();
+
+    struct shmid_ds shmid_ds;
+    if (0 != shmctl(id, IPC_STAT, &shmid_ds)) {
+        switch (errno) {
+        case EINVAL:
+            return true;
+        default:
+            return false;
+        }
+    }
+    // If there are no attachments then remove it.
+    if (shmid_ds.shm_nattch == 0) {
+        // mark for removal
+        if (-1 == shmctl(id, IPC_RMID, &shmid_ds)) {
+            setErrorString(QLatin1String("QSharedMemory::remove"));
+            switch (errno) {
+            case EINVAL:
+                return true;
+            default:
+                return false;
+            }
+        }
+
+        // remove file
+        if (!QFile::remove(nativeKey))
+            return false;
+    }
+    return true;
+}
+
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_SHAREDMEMORY
+
+#endif // QT_POSIX_IPC

src/corelib/kernel/qsharedmemory_unix.cpp

@@ -36,7 +36,6 @@
 #include "qsharedmemory.h"
 #include "qsharedmemory_p.h"
 #include "qsystemsemaphore.h"
-#include <qdir.h>
 #include <qdebug.h>
 
 #include <errno.h>
@@ -44,7 +43,11 @@
 #ifndef QT_NO_SHAREDMEMORY
 #include <sys/types.h>
 #include <sys/ipc.h>
+#ifndef QT_POSIX_IPC
 #include <sys/shm.h>
+#else
+#include <sys/mman.h>
+#endif
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
@@ -60,7 +63,11 @@ QSharedMemoryPrivate::QSharedMemoryPrivate()
 #ifndef QT_NO_SYSTEMSEMAPHORE
       systemSemaphore(QString()), lockedByMe(false),
 #endif
+#ifndef QT_POSIX_IPC
       unix_key(0)
+#else
+      hand(-1)
+#endif
 {
 }
 
@@ -95,196 +102,6 @@ void QSharedMemoryPrivate::setErrorString(const QString &function)
     }
 }
 
-/*!
-    \internal
-
-    If not already made create the handle used for accessing the shared memory.
-*/
-key_t QSharedMemoryPrivate::handle()
-{
-    // already made
-    if (unix_key)
-        return unix_key;
-
-    // don't allow making handles on empty keys
-    if (nativeKey.isEmpty()) {
-        errorString = QSharedMemory::tr("%1: key is empty").arg(QLatin1String("QSharedMemory::handle:"));
-        error = QSharedMemory::KeyError;
-        return 0;
-    }
-
-    // ftok requires that an actual file exists somewhere
-    if (!QFile::exists(nativeKey)) {
-        errorString = QSharedMemory::tr("%1: UNIX key file doesn't exist").arg(QLatin1String("QSharedMemory::handle:"));
-        error = QSharedMemory::NotFound;
-        return 0;
-    }
-
-    unix_key = ftok(QFile::encodeName(nativeKey).constData(), 'Q');
-    if (-1 == unix_key) {
-        errorString = QSharedMemory::tr("%1: ftok failed").arg(QLatin1String("QSharedMemory::handle:"));
-        error = QSharedMemory::KeyError;
-        unix_key = 0;
-    }
-    return unix_key;
-}
-
-#endif // QT_NO_SHAREDMEMORY
-
-#if !(defined(QT_NO_SHAREDMEMORY) && defined(QT_NO_SYSTEMSEMAPHORE))
-/*!
-    \internal
-    Creates the unix file if needed.
-    returns \c true if the unix file was created.
-
-    -1 error
-     0 already existed
-     1 created
-  */
-int QSharedMemoryPrivate::createUnixKeyFile(const QString &fileName)
-{
-    int fd = qt_safe_open(QFile::encodeName(fileName).constData(),
-            O_EXCL | O_CREAT | O_RDWR, 0640);
-    if (-1 == fd) {
-        if (errno == EEXIST)
-            return 0;
-        return -1;
-    } else {
-        close(fd);
-    }
-    return 1;
-}
-#endif // QT_NO_SHAREDMEMORY && QT_NO_SYSTEMSEMAPHORE
-
-#ifndef QT_NO_SHAREDMEMORY
-
-bool QSharedMemoryPrivate::cleanHandle()
-{
-    unix_key = 0;
-    return true;
-}
-
-bool QSharedMemoryPrivate::create(int size)
-{
-    // build file if needed
-    bool createdFile = false;
-    int built = createUnixKeyFile(nativeKey);
-    if (built == -1) {
-        errorString = QSharedMemory::tr("%1: unable to make key").arg(QLatin1String("QSharedMemory::handle:"));
-        error = QSharedMemory::KeyError;
-        return false;
-    }
-    if (built == 1) {
-        createdFile = true;
-    }
-
-    // get handle
-    if (!handle()) {
-        if (createdFile)
-            QFile::remove(nativeKey);
-        return false;
-    }
-
-    // create
-    if (-1 == shmget(unix_key, size, 0600 | IPC_CREAT | IPC_EXCL)) {
-        QString function = QLatin1String("QSharedMemory::create");
-        switch (errno) {
-        case EINVAL:
-            errorString = QSharedMemory::tr("%1: system-imposed size restrictions").arg(QLatin1String("QSharedMemory::handle"));
-            error = QSharedMemory::InvalidSize;
-            break;
-        default:
-            setErrorString(function);
-        }
-        if (createdFile && error != QSharedMemory::AlreadyExists)
-            QFile::remove(nativeKey);
-        return false;
-    }
-
-    return true;
-}
-
-bool QSharedMemoryPrivate::attach(QSharedMemory::AccessMode mode)
-{
-    // grab the shared memory segment id
-    int id = shmget(unix_key, 0, (mode == QSharedMemory::ReadOnly ? 0400 : 0600));
-    if (-1 == id) {
-        setErrorString(QLatin1String("QSharedMemory::attach (shmget)"));
-        return false;
-    }
-
-    // grab the memory
-    memory = shmat(id, 0, (mode == QSharedMemory::ReadOnly ? SHM_RDONLY : 0));
-    if ((void*) - 1 == memory) {
-        memory = 0;
-        setErrorString(QLatin1String("QSharedMemory::attach (shmat)"));
-        return false;
-    }
-
-    // grab the size
-    shmid_ds shmid_ds;
-    if (!shmctl(id, IPC_STAT, &shmid_ds)) {
-        size = (int)shmid_ds.shm_segsz;
-    } else {
-        setErrorString(QLatin1String("QSharedMemory::attach (shmctl)"));
-        return false;
-    }
-
-    return true;
-}
-
-bool QSharedMemoryPrivate::detach()
-{
-    // detach from the memory segment
-    if (-1 == shmdt(memory)) {
-        QString function = QLatin1String("QSharedMemory::detach");
-        switch (errno) {
-        case EINVAL:
-            errorString = QSharedMemory::tr("%1: not attached").arg(function);
-            error = QSharedMemory::NotFound;
-            break;
-        default:
-            setErrorString(function);
-        }
-        return false;
-    }
-    memory = 0;
-    size = 0;
-
-    // Get the number of current attachments
-    int id = shmget(unix_key, 0, 0400);
-    cleanHandle();
-
-    struct shmid_ds shmid_ds;
-    if (0 != shmctl(id, IPC_STAT, &shmid_ds)) {
-        switch (errno) {
-        case EINVAL:
-            return true;
-        default:
-            return false;
-        }
-    }
-    // If there are no attachments then remove it.
-    if (shmid_ds.shm_nattch == 0) {
-        // mark for removal
-        if (-1 == shmctl(id, IPC_RMID, &shmid_ds)) {
-            setErrorString(QLatin1String("QSharedMemory::remove"));
-            switch (errno) {
-            case EINVAL:
-                return true;
-            default:
-                return false;
-            }
-        }
-
-        // remove file
-        if (!QFile::remove(nativeKey))
-            return false;
-    }
-    return true;
-}
-
-
 QT_END_NAMESPACE
 
 #endif // QT_NO_SHAREDMEMORY

src/corelib/kernel/qsystemsemaphore.cpp

@@ -222,7 +222,7 @@ void QSystemSemaphore::setKey(const QString &key, int initialValue, AccessMode m
     if (key == d->key && mode == Open)
         return;
     d->clearError();
-#if !defined(Q_OS_WIN)
+#if !defined(Q_OS_WIN) && !defined(QT_POSIX_IPC)
     // optimization to not destroy/create the file & semaphore
     if (key == d->key && mode == Create && d->createdSemaphore && d->createdFile) {
         d->initialValue = initialValue;

src/corelib/kernel/qsystemsemaphore_p.h

@@ -53,6 +53,9 @@
 #ifndef Q_OS_WINCE
 #   include <sys/types.h>
 #endif
+#ifdef QT_POSIX_IPC
+#   include <semaphore.h>
+#endif
 
 QT_BEGIN_NAMESPACE
 
@@ -75,6 +78,9 @@ public:
 #ifdef Q_OS_WIN
     Qt::HANDLE handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
     void setErrorString(const QString &function);
+#elif defined(QT_POSIX_IPC)
+    bool handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
+    void setErrorString(const QString &function);
 #else
     key_t handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
     void setErrorString(const QString &function);
@@ -88,11 +94,14 @@ public:
 #ifdef Q_OS_WIN
     Qt::HANDLE semaphore;
     Qt::HANDLE semaphoreLock;
+#elif defined(QT_POSIX_IPC)
+    sem_t *semaphore;
+    bool createdSemaphore;
 #else
+    key_t unix_key;
     int semaphore;
     bool createdFile;
     bool createdSemaphore;
-    key_t unix_key;
 #endif
     QString errorString;
     QSystemSemaphore::SystemSemaphoreError error;

src/corelib/kernel/qsystemsemaphore_posix.cpp

@@ -0,0 +1,182 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 Konstantin Ritt <ritt.ks@gmail.com>
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2015 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Tobias Koenig <tobias.koenig@kdab.com>
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qsystemsemaphore.h"
+#include "qsystemsemaphore_p.h"
+
+#include <qdebug.h>
+#include <qfile.h>
+#include <qcoreapplication.h>
+
+#ifdef QT_POSIX_IPC
+
+#ifndef QT_NO_SYSTEMSEMAPHORE
+
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "private/qcore_unix_p.h"
+
+// OpenBSD 4.2 doesn't define EIDRM, see BUGS section:
+// http://www.openbsd.org/cgi-bin/man.cgi?query=semop&manpath=OpenBSD+4.2
+#if defined(Q_OS_OPENBSD) && !defined(EIDRM)
+#define EIDRM EINVAL
+#endif
+
+QT_BEGIN_NAMESPACE
+
+bool QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
+{
+    if (semaphore != SEM_FAILED)
+        return true;  // we already have a semaphore
+
+    if (fileName.isEmpty()) {
+        errorString = QCoreApplication::tr("%1: key is empty", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle"));
+        error = QSystemSemaphore::KeyError;
+        return false;
+    }
+
+    const QByteArray semName = QFile::encodeName(fileName);
+
+    // Always try with O_EXCL so we know whether we created the semaphore.
+    int oflag = O_CREAT | O_EXCL;
+    for (int tryNum = 0, maxTries = 1; tryNum < maxTries; ++tryNum) {
+        do {
+            semaphore = ::sem_open(semName.constData(), oflag, 0600, initialValue);
+        } while (semaphore == SEM_FAILED && errno == EINTR);
+        if (semaphore == SEM_FAILED && errno == EEXIST) {
+            if (mode == QSystemSemaphore::Create) {
+                if (::sem_unlink(semName.constData()) == -1 && errno != ENOENT) {
+                    setErrorString(QLatin1String("QSystemSemaphore::handle (sem_unlink)"));
+                    return false;
+                }
+                // Race condition: the semaphore might be recreated before
+                // we call sem_open again, so we'll retry several times.
+                maxTries = 3;
+            } else {
+                // Race condition: if it no longer exists at the next sem_open
+                // call, we won't realize we created it, so we'll leak it later.
+                oflag &= ~O_EXCL;
+                maxTries = 2;
+            }
+        } else {
+            break;
+        }
+    }
+
+    if (semaphore == SEM_FAILED) {
+        setErrorString(QLatin1String("QSystemSemaphore::handle"));
+        return false;
+    }
+
+    createdSemaphore = (oflag & O_EXCL) != 0;
+
+    return true;
+}
+
+void QSystemSemaphorePrivate::cleanHandle()
+{
+    if (semaphore != SEM_FAILED) {
+        if (::sem_close(semaphore) == -1) {
+            setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_close)"));
+#if defined QSYSTEMSEMAPHORE_DEBUG
+            qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_close failed.");
+#endif
+        }
+        semaphore = SEM_FAILED;
+    }
+
+    if (createdSemaphore) {
+        if (::sem_unlink(QFile::encodeName(fileName).constData()) == -1 && errno != ENOENT) {
+            setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_unlink)"));
+#if defined QSYSTEMSEMAPHORE_DEBUG
+            qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_unlink failed.");
+#endif
+        }
+        createdSemaphore = false;
+    }
+}
+
+bool QSystemSemaphorePrivate::modifySemaphore(int count)
+{
+    if (!handle())
+        return false;
+
+    if (count > 0) {
+        int cnt = count;
+        do {
+            if (::sem_post(semaphore) == -1) {
+                setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_post)"));
+#if defined QSYSTEMSEMAPHORE_DEBUG
+                qDebug() << QLatin1String("QSystemSemaphore::modify sem_post failed") << count << errno;
+#endif
+                // rollback changes to preserve the SysV semaphore behavior
+                for ( ; cnt < count; ++cnt) {
+                    int res;
+                    EINTR_LOOP(res, ::sem_wait(semaphore));
+                }
+                return false;
+            }
+            --cnt;
+        } while (cnt > 0);
+    } else {
+        int res;
+        EINTR_LOOP(res, ::sem_wait(semaphore));
+        if (res == -1) {
+            // If the semaphore was removed be nice and create it and then modifySemaphore again
+            if (errno == EINVAL || errno == EIDRM) {
+                semaphore = SEM_FAILED;
+                return modifySemaphore(count);
+            }
+            setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_wait)"));
+#if defined QSYSTEMSEMAPHORE_DEBUG
+            qDebug() << QLatin1String("QSystemSemaphore::modify sem_wait failed") << count << errno;
+#endif
+            return false;
+        }
+    }
+
+    clearError();
+    return true;
+}
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_SYSTEMSEMAPHORE
+
+#endif // QT_POSIX_IPC

src/corelib/kernel/qsystemsemaphore_systemv.cpp

@@ -0,0 +1,198 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qsystemsemaphore.h"
+#include "qsystemsemaphore_p.h"
+
+#include <qdebug.h>
+#include <qfile.h>
+#include <qcoreapplication.h>
+
+#ifndef QT_POSIX_IPC
+
+#ifndef QT_NO_SYSTEMSEMAPHORE
+
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "private/qcore_unix_p.h"
+
+// OpenBSD 4.2 doesn't define EIDRM, see BUGS section:
+// http://www.openbsd.org/cgi-bin/man.cgi?query=semop&manpath=OpenBSD+4.2
+#if defined(Q_OS_OPENBSD) && !defined(EIDRM)
+#define EIDRM EINVAL
+#endif
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \internal
+
+    Setup unix_key
+ */
+key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
+{
+    if (key.isEmpty()){
+        errorString = QCoreApplication::tr("%1: key is empty", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle:"));
+        error = QSystemSemaphore::KeyError;
+        return -1;
+    }
+
+    // ftok requires that an actual file exists somewhere
+    if (-1 != unix_key)
+        return unix_key;
+
+    // Create the file needed for ftok
+    int built = QSharedMemoryPrivate::createUnixKeyFile(fileName);
+    if (-1 == built) {
+        errorString = QCoreApplication::tr("%1: unable to make key", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle:"));
+        error = QSystemSemaphore::KeyError;
+        return -1;
+    }
+    createdFile = (1 == built);
+
+    // Get the unix key for the created file
+    unix_key = ftok(QFile::encodeName(fileName).constData(), 'Q');
+    if (-1 == unix_key) {
+        errorString = QCoreApplication::tr("%1: ftok failed", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle:"));
+        error = QSystemSemaphore::KeyError;
+        return -1;
+    }
+
+    // Get semaphore
+    semaphore = semget(unix_key, 1, 0600 | IPC_CREAT | IPC_EXCL);
+    if (-1 == semaphore) {
+        if (errno == EEXIST)
+            semaphore = semget(unix_key, 1, 0600 | IPC_CREAT);
+        if (-1 == semaphore) {
+            setErrorString(QLatin1String("QSystemSemaphore::handle"));
+            cleanHandle();
+            return -1;
+        }
+    } else {
+        createdSemaphore = true;
+        // Force cleanup of file, it is possible that it can be left over from a crash
+        createdFile = true;
+    }
+
+    if (mode == QSystemSemaphore::Create) {
+        createdSemaphore = true;
+        createdFile = true;
+    }
+
+    // Created semaphore so initialize its value.
+    if (createdSemaphore && initialValue >= 0) {
+        qt_semun init_op;
+        init_op.val = initialValue;
+        if (-1 == semctl(semaphore, 0, SETVAL, init_op)) {
+            setErrorString(QLatin1String("QSystemSemaphore::handle"));
+            cleanHandle();
+            return -1;
+        }
+    }
+
+    return unix_key;
+}
+
+/*!
+    \internal
+
+    Cleanup the unix_key
+ */
+void QSystemSemaphorePrivate::cleanHandle()
+{
+    unix_key = -1;
+
+    // remove the file if we made it
+    if (createdFile) {
+        QFile::remove(fileName);
+        createdFile = false;
+    }
+
+    if (createdSemaphore) {
+        if (-1 != semaphore) {
+            if (-1 == semctl(semaphore, 0, IPC_RMID, 0)) {
+                setErrorString(QLatin1String("QSystemSemaphore::cleanHandle"));
+#if defined QSYSTEMSEMAPHORE_DEBUG
+                qDebug() << QLatin1String("QSystemSemaphore::cleanHandle semctl failed.");
+#endif
+            }
+            semaphore = -1;
+        }
+        createdSemaphore = false;
+    }
+}
+
+/*!
+    \internal
+ */
+bool QSystemSemaphorePrivate::modifySemaphore(int count)
+{
+    if (-1 == handle())
+        return false;
+
+    struct sembuf operation;
+    operation.sem_num = 0;
+    operation.sem_op = count;
+    operation.sem_flg = SEM_UNDO;
+
+    int res;
+    EINTR_LOOP(res, semop(semaphore, &operation, 1));
+    if (-1 == res) {
+        // If the semaphore was removed be nice and create it and then modifySemaphore again
+        if (errno == EINVAL || errno == EIDRM) {
+            semaphore = -1;
+            cleanHandle();
+            handle();
+            return modifySemaphore(count);
+        }
+        setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore"));
+#if defined QSYSTEMSEMAPHORE_DEBUG
+        qDebug() << QLatin1String("QSystemSemaphore::modify failed") << count << semctl(semaphore, 0, GETVAL) << errno << EIDRM << EINVAL;
+#endif
+        return false;
+    }
+
+    clearError();
+    return true;
+}
+
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_SYSTEMSEMAPHORE
+
+#endif // QT_POSIX_IPC

src/corelib/kernel/qsystemsemaphore_unix.cpp

@@ -35,30 +35,29 @@
 #include "qsystemsemaphore_p.h"
 
 #include <qdebug.h>
-#include <qfile.h>
 #include <qcoreapplication.h>
 
 #ifndef QT_NO_SYSTEMSEMAPHORE
 
 #include <sys/types.h>
 #include <sys/ipc.h>
+#ifndef QT_POSIX_IPC
 #include <sys/sem.h>
+#endif
 #include <fcntl.h>
 #include <errno.h>
 
 #include "private/qcore_unix_p.h"
 
-// OpenBSD 4.2 doesn't define EIDRM, see BUGS section:
-// http://www.openbsd.org/cgi-bin/man.cgi?query=semop&manpath=OpenBSD+4.2
-#if defined(Q_OS_OPENBSD) && !defined(EIDRM)
-#define EIDRM EINVAL
-#endif
-
 QT_BEGIN_NAMESPACE
 
 QSystemSemaphorePrivate::QSystemSemaphorePrivate() :
-        semaphore(-1), createdFile(false),
+#ifndef QT_POSIX_IPC
-        createdSemaphore(false), unix_key(-1), error(QSystemSemaphore::NoError)
+    unix_key(-1), semaphore(-1), createdFile(false),
+#else
+    semaphore(SEM_FAILED),
+#endif // QT_POSIX_IPC
+    createdSemaphore(false), error(QSystemSemaphore::NoError)
 {
 }
 
@@ -93,139 +92,6 @@ void QSystemSemaphorePrivate::setErrorString(const QString &function)
     }
 }
 
-/*!
-    \internal
-
-    Setup unix_key
- */
-key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
-{
-    if (key.isEmpty()){
-        errorString = QCoreApplication::tr("%1: key is empty", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle:"));
-        error = QSystemSemaphore::KeyError;
-        return -1;
-    }
-
-    // ftok requires that an actual file exists somewhere
-    if (-1 != unix_key)
-        return unix_key;
-
-    // Create the file needed for ftok
-    int built = QSharedMemoryPrivate::createUnixKeyFile(fileName);
-    if (-1 == built) {
-        errorString = QCoreApplication::tr("%1: unable to make key", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle:"));
-        error = QSystemSemaphore::KeyError;
-        return -1;
-    }
-    createdFile = (1 == built);
-
-    // Get the unix key for the created file
-    unix_key = ftok(QFile::encodeName(fileName).constData(), 'Q');
-    if (-1 == unix_key) {
-        errorString = QCoreApplication::tr("%1: ftok failed", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle:"));
-        error = QSystemSemaphore::KeyError;
-        return -1;
-    }
-
-    // Get semaphore
-    semaphore = semget(unix_key, 1, 0600 | IPC_CREAT | IPC_EXCL);
-    if (-1 == semaphore) {
-        if (errno == EEXIST)
-            semaphore = semget(unix_key, 1, 0600 | IPC_CREAT);
-        if (-1 == semaphore) {
-            setErrorString(QLatin1String("QSystemSemaphore::handle"));
-            cleanHandle();
-            return -1;
-        }
-    } else {
-        createdSemaphore = true;
-        // Force cleanup of file, it is possible that it can be left over from a crash
-        createdFile = true;
-    }
-
-    if (mode == QSystemSemaphore::Create) {
-        createdSemaphore = true;
-        createdFile = true;
-    }
-
-    // Created semaphore so initialize its value.
-    if (createdSemaphore && initialValue >= 0) {
-        qt_semun init_op;
-        init_op.val = initialValue;
-        if (-1 == semctl(semaphore, 0, SETVAL, init_op)) {
-            setErrorString(QLatin1String("QSystemSemaphore::handle"));
-            cleanHandle();
-            return -1;
-        }
-    }
-
-    return unix_key;
-}
-
-/*!
-    \internal
-
-    Cleanup the unix_key
- */
-void QSystemSemaphorePrivate::cleanHandle()
-{
-    unix_key = -1;
-
-    // remove the file if we made it
-    if (createdFile) {
-        QFile::remove(fileName);
-        createdFile = false;
-    }
-
-    if (createdSemaphore) {
-        if (-1 != semaphore) {
-            if (-1 == semctl(semaphore, 0, IPC_RMID, 0)) {
-                setErrorString(QLatin1String("QSystemSemaphore::cleanHandle"));
-#if defined QSYSTEMSEMAPHORE_DEBUG
-                qDebug() << QLatin1String("QSystemSemaphore::cleanHandle semctl failed.");
-#endif
-            }
-            semaphore = -1;
-        }
-        createdSemaphore = false;
-    }
-}
-
-/*!
-    \internal
- */
-bool QSystemSemaphorePrivate::modifySemaphore(int count)
-{
-    if (-1 == handle())
-        return false;
-
-    struct sembuf operation;
-    operation.sem_num = 0;
-    operation.sem_op = count;
-    operation.sem_flg = SEM_UNDO;
-
-    int res;
-    EINTR_LOOP(res, semop(semaphore, &operation, 1));
-    if (-1 == res) {
-        // If the semaphore was removed be nice and create it and then modifySemaphore again
-        if (errno == EINVAL || errno == EIDRM) {
-            semaphore = -1;
-            cleanHandle();
-            handle();
-            return modifySemaphore(count);
-        }
-        setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore"));
-#if defined QSYSTEMSEMAPHORE_DEBUG
-        qDebug() << QLatin1String("QSystemSemaphore::modify failed") << count << semctl(semaphore, 0, GETVAL) << errno << EIDRM << EINVAL;
-#endif
-        return false;
-    }
-
-    clearError();
-    return true;
-}
-
-
 QT_END_NAMESPACE
 
 #endif // QT_NO_SYSTEMSEMAPHORE

tests/auto/corelib/kernel/qsharedmemory/test/test.pro

@@ -3,6 +3,7 @@ CONFIG += testcase
 QT = core-private testlib
 
 mac:CONFIG -= app_bundle
+linux:LIBS += -lrt
 
 SOURCES += tst_qsharedmemory.cpp
 TARGET = tst_qsharedmemory

tests/auto/corelib/kernel/qsharedmemory/test/tst_qsharedmemory.cpp

@@ -174,7 +174,11 @@ void tst_QSharedMemory::cleanup()
 #include <private/qsharedmemory_p.h>
 #include <sys/types.h>
 #include <sys/ipc.h>
+#ifndef QT_POSIX_IPC
 #include <sys/shm.h>
+#else
+#include <sys/mman.h>
+#endif // QT_POSIX_IPC
 #include <errno.h>
 #endif
 
@@ -189,7 +193,10 @@ QString tst_QSharedMemory::helperBinary()
 
 int tst_QSharedMemory::remove(const QString &key)
 {
-#ifndef Q_OS_WIN
+#ifdef Q_OS_WIN
+    Q_UNUSED(key);
+    return 0;
+#else
     // On unix the shared memory might exists from a previously failed test
     // or segfault, remove it it does
     if (key.isEmpty())
@@ -202,6 +209,7 @@ int tst_QSharedMemory::remove(const QString &key)
         return -2;
     }
 
+#ifndef QT_POSIX_IPC
     int unix_key = ftok(fileName.toLatin1().constData(), 'Q');
     if (-1 == unix_key) {
         qDebug() << "ftok failed";
@@ -219,11 +227,15 @@ int tst_QSharedMemory::remove(const QString &key)
         qDebug() << "shmctl failed";
         return -5;
     }
-    return QFile::remove(fileName);
 #else
-    Q_UNUSED(key);
+    if (shm_unlink(QFile::encodeName(fileName).constData()) == -1) {
-    return 0;
+        qDebug() << "shm_unlink failed";
-#endif
+        return -5;
+    }
+#endif // QT_POSIX_IPC
+
+    return QFile::remove(fileName);
+#endif // Q_OS_WIN
 }
 
 /*!

tests/auto/corelib/kernel/qsystemsemaphore/test/tst_qsystemsemaphore.cpp

@@ -65,7 +65,7 @@ private slots:
     void processes_data();
     void processes();
 
-#ifndef Q_OS_WIN
+#if !defined(Q_OS_WIN) && !defined(QT_POSIX_IPC)
     void undo();
 #endif
     void initialValue();
@@ -233,8 +233,8 @@ void tst_QSystemSemaphore::processes()
     }
 }
 
-// This test only checks a unix behavior.
+// This test only checks a system v unix behavior.
-#ifndef Q_OS_WIN
+#if !defined(Q_OS_WIN) && !defined(QT_POSIX_IPC)
 void tst_QSystemSemaphore::undo()
 {
     QSystemSemaphore sem("store", 1, QSystemSemaphore::Create);