Report the error as being AlreadyExists if this is why it fails

On Windows it would never report this error, and on Unix it would
report a different error ulimately instead as it tried to obtain the
semaphore a second time which could cause a different error to what
should be reported.

Task-number: QTBUG-9610
Reviewed-by: Frans Englich

2 files changed, 7 insertions, 3 deletions

diff --git a/src/corelib/kernel/qsystemsemaphore_unix.cpp b/src/corelib/kernel/qsystemsemaphore_unix.cpp
index 07e3618..d6c6c37 100644
--- a/src/corelib/kernel/qsystemsemaphore_unix.cpp
+++ b/src/corelib/kernel/qsystemsemaphore_unix.cpp
@@ -145,10 +145,10 @@ key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
     // Get semaphore
     semaphore = semget(unix_key, 1, 0666 | IPC_CREAT | IPC_EXCL);
     if (-1 == semaphore) {
+        setErrorString(QLatin1String("QSystemSemaphore::handle"));
         if (errno == EEXIST)
             semaphore = semget(unix_key, 1, 0666 | IPC_CREAT);
         if (-1 == semaphore) {
-            setErrorString(QLatin1String("QSystemSemaphore::handle"));
             cleanHandle();
             return -1;
         }
diff --git a/src/corelib/kernel/qsystemsemaphore_win.cpp b/src/corelib/kernel/qsystemsemaphore_win.cpp
index 96a47f5..74f253a 100644
--- a/src/corelib/kernel/qsystemsemaphore_win.cpp
+++ b/src/corelib/kernel/qsystemsemaphore_win.cpp
@@ -69,6 +69,10 @@ void QSystemSemaphorePrivate::setErrorString(const QString &function)
         error = QSystemSemaphore::PermissionDenied;
         errorString = QCoreApplication::translate("QSystemSemaphore", "%1: permission denied").arg(function);
         break;
+    case ERROR_ALREADY_EXISTS:
+        error = QSystemSemaphore::AlreadyExists;
+        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: already exists").arg(function);
+        break;
     default:
         errorString = QCoreApplication::translate("QSystemSemaphore", "%1: unknown error %2").arg(function).arg(windowsError);
         error = QSystemSemaphore::UnknownError;
@@ -88,8 +92,8 @@ HANDLE QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode)
     if (semaphore == 0) {
         QString safeName = makeKeyFileName();
         semaphore = CreateSemaphore(0, initialValue, MAXLONG, (wchar_t*)safeName.utf16());
-        if (semaphore == NULL)
-            setErrorString(QLatin1String("QSystemSemaphore::handle"));
+        // If the semaphore exists then the handle is still valid but there is still an error
+        setErrorString(QLatin1String("QSystemSemaphore::handle"));
     }
 
     return semaphore;