IPC: use QNativeIpcKey for QtIpcCommon::legacyPlatformSafeKey()

The implementation only has #if now for Apple compatibility; otherwise,
we're relying on the QNativeIpcKey::Type parameter, because I intend to
allow Unix systems to support both POSIX realtime and System V / XSI
shared memory and semaphores.

Most of the uses of QtIpcCommon::isIpcSupported() will be constant
expressions because they don't depend on the ipcType.

Change-Id: I12a088d1ae424825abd3fffd171d38dfb6b5de74
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/ipc/qtipccommon.cpp

@@ -96,28 +96,30 @@ static QNativeIpcKey::Type stringToType(QStringView typeString)
 
     On Unix this will be a file name
 */
-QString QtIpcCommon::legacyPlatformSafeKey(const QString &key, QtIpcCommon::IpcType ipcType)
+QString QtIpcCommon::legacyPlatformSafeKey(const QString &key, QtIpcCommon::IpcType ipcType,
+                                           QNativeIpcKey::Type type)
 {
     if (key.isEmpty())
         return QString();
 
     QByteArray hex = QCryptographicHash::hash(key.toUtf8(), QCryptographicHash::Sha1).toHex();
 
-#if defined(Q_OS_DARWIN) && defined(QT_POSIX_IPC)
-    if (qt_apple_isSandboxed()) {
-        // Sandboxed applications on Apple platforms require the shared memory name
-        // to be in the form <application group identifier>/<custom identifier>.
-        // Since we don't know which application group identifier the user wants
-        // to apply, we instead document that requirement, and use the key directly.
-        return key;
-    } else {
+    if (type == QNativeIpcKey::Type::PosixRealtime) {
+#if defined(Q_OS_DARWIN)
+        if (qt_apple_isSandboxed()) {
+            // Sandboxed applications on Apple platforms require the shared memory name
+            // to be in the form <application group identifier>/<custom identifier>.
+            // Since we don't know which application group identifier the user wants
+            // to apply, we instead document that requirement, and use the key directly.
+            return key;
+        }
         // The shared memory name limit on Apple platforms is very low (30 characters),
         // so we can't use the logic below of combining the prefix, key, and a hash,
         // to ensure a unique and valid name. Instead we use the first part of the
         // hash, which should still long enough to avoid collisions in practice.
         return u'/' + hex.left(SHM_NAME_MAX - 1);
-    }
 #endif
+    }
 
     QString result;
     result.reserve(1 + 18 + key.size() + 40);
@@ -137,13 +139,21 @@ QString QtIpcCommon::legacyPlatformSafeKey(const QString &key, QtIpcCommon::IpcT
     }
     result.append(QLatin1StringView(hex));
 
-#ifdef Q_OS_WIN
-    return result;
-#elif defined(QT_POSIX_IPC)
-    return u'/' + result;
-#else
+    switch (type) {
+    case QNativeIpcKey::Type::Windows:
+        if (!isIpcSupported(ipcType, QNativeIpcKey::Type::Windows))
+            return QString();
+        return result;
+    case QNativeIpcKey::Type::PosixRealtime:
+        if (!isIpcSupported(ipcType, QNativeIpcKey::Type::PosixRealtime))
+            return QString();
+        return result.prepend(u'/');
+    case QNativeIpcKey::Type::SystemV:
+        break;
+    }
+    if (!isIpcSupported(ipcType, QNativeIpcKey::Type::SystemV))
+        return QString();
     return QDir::tempPath() + u'/' + result;
-#endif
 }
 
 /*!

src/corelib/ipc/qtipccommon_p.h

@@ -15,7 +15,9 @@
 // We mean it.
 //
 
+#include "qtipccommon.h"
 #include <private/qglobal_p.h>
+#include <private/qtcore-config_p.h>
 
 #if QT_CONFIG(sharedmemory) || QT_CONFIG(systemsemaphore)
 
@@ -32,7 +34,33 @@ enum class IpcType {
     SystemSemaphore
 };
 
-Q_AUTOTEST_EXPORT QString legacyPlatformSafeKey(const QString &key, IpcType ipcType);
+static constexpr bool isIpcSupported(IpcType ipcType, QNativeIpcKey::Type type)
+{
+    switch (type) {
+    case QNativeIpcKey::Type::SystemV:
+        break;
+
+    case QNativeIpcKey::Type::PosixRealtime:
+        if (ipcType == IpcType::SharedMemory)
+            return QT_CONFIG(posix_shm);
+        return QT_CONFIG(posix_sem);
+
+    case QNativeIpcKey::Type::Windows:
+#ifdef Q_OS_WIN
+        return true;
+#else
+        return false;
+#endif
+    }
+
+    if (ipcType == IpcType::SharedMemory)
+        return QT_CONFIG(sysv_shm);
+    return QT_CONFIG(sysv_sem);
+}
+
+Q_AUTOTEST_EXPORT QString
+legacyPlatformSafeKey(const QString &key, IpcType ipcType,
+                      QNativeIpcKey::Type type = QNativeIpcKey::legacyDefaultTypeForOs());
 
 #ifdef Q_OS_UNIX
 // Convenience function to create the file if needed