Workaround for superfluous shared memory segments

When the simulator application crashes shared memory segments are left
unused. This patch checks on simulator startup for unused segments and
deletes them.

Reviewed-by: ckamm
Task-number: QTSIM-73

1 files changed, 47 insertions, 0 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 540fce7..3ce9aa0 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -37,6 +37,14 @@
 #include "qsimulatordata_p.h"
 #include "messaging.h"
 
+#ifdef Q_OS_UNIX
+    extern "C" {
+        #include <sys/types.h>
+        #include <sys/ipc.h>
+        #include <sys/shm.h>
+    }
+#endif
+
 #include <QtCore/QDebug>
 #include <QtCore/QDir>
 #include <QtCore/QSettings>
@@ -99,8 +107,47 @@ static void registerSimulator(const QString &location)
         settings->setValue(dataKey, appDataLocation);
 }
 
+void cleanupUnusedSharedMemory()
+{
+#ifdef Q_OS_UNIX
+    // This code depends on the implementation of QSharedMemory
+    QDir tmp(QDir::tempPath());
+    QStringList possibleFiles = tmp.entryList(QStringList("qipc_sharedmemory_QTSIMULATORSHAREDMEMORY*"), QDir::Files);
+
+    foreach (QString fileName, possibleFiles) {
+        int unix_key = ::ftok(QFile::encodeName(tmp.absoluteFilePath(fileName)).constData(), 'Q');
+
+        // Get the number of current attachments
+        int id = ::shmget(unix_key, 0, 0444);
+
+        struct shmid_ds shmid_ds;
+        if (0 != ::shmctl(id, IPC_STAT, &shmid_ds)) {
+            qWarning("getting the number of current attachments failed");
+            continue;
+        }
+
+        // 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)) {
+                qWarning("mark shared memory segment for removal failed");
+                continue;
+            }
+
+            // remove file
+            if (!tmp.remove(fileName)) {
+                qWarning("could not remove shared memory segment 'file'");
+                continue;
+            }
+            qDebug() << "superfluous shared memory segment removed";
+        }
+    }
+#endif
+}
 int main(int argc, char **argv)
 {
+    cleanupUnusedSharedMemory();
+
     QCoreApplication::setOrganizationName(SIMULATOR_APP_VENDOR);
     QCoreApplication::setApplicationName(SIMULATOR_APP_NAME);