Index: src/OFEnumerator.h
==================================================================
--- src/OFEnumerator.h
+++ src/OFEnumerator.h
@@ -96,14 +96,10 @@
  */
 @interface OFEnumerator OF_GENERIC(ObjectType): OFObject <OFFastEnumeration>
 #if !defined(OF_HAVE_GENERICS) && !defined(DOXYGEN)
 # define ObjectType id
 #endif
-{
-	OF_RESERVE_IVARS(OFEnumerator, 4)
-}
-
 /**
  * @brief Returns the next object or `nil` if there is none left.
  *
  * @return The next object or `nil` if there is none left
  */

Index: src/OFMapTable.h
==================================================================
--- src/OFMapTable.h
+++ src/OFMapTable.h
@@ -229,10 +229,13 @@
  * @class OFMapTableEnumerator OFMapTable.h ObjFW/OFMapTable.h
  *
  * @brief A class which provides methods to enumerate through an OFMapTable's
  *	  keys or objects.
  */
+#ifndef OF_MAP_TABLE_M
+OF_SUBCLASSING_RESTRICTED
+#endif
 @interface OFMapTableEnumerator: OFObject
 {
 	OFMapTable *_mapTable;
 	struct OFMapTableBucket *_Nonnull *_Nullable _buckets;
 	uint32_t _capacity;

Index: src/OFMapTable.m
==================================================================
--- src/OFMapTable.m
+++ src/OFMapTable.m
@@ -10,10 +10,12 @@
  * Alternatively, it may be distributed under the terms of the GNU General
  * Public License, either version 2 or 3, which can be found in the file
  * LICENSE.GPLv2 or LICENSE.GPLv3 respectively included in the packaging of this
  * file.
  */
+
+#define OF_MAP_TABLE_M
 
 #include "config.h"
 
 #include <stdlib.h>
 #include <string.h>

Index: src/OFNotification.h
==================================================================
--- src/OFNotification.h
+++ src/OFNotification.h
@@ -31,16 +31,16 @@
  * @class OFNotification OFNotification.h ObjFW/OFNotification.h
  *
  * @brief A class to represent a notification for or from
  *	  @ref OFNotificationCenter.
  */
-OF_SUBCLASSING_RESTRICTED
 @interface OFNotification: OFObject <OFCopying>
 {
 	OFNotificationName _name;
 	id _Nullable _object;
 	OFDictionary *_Nullable _userInfo;
+	OF_RESERVE_IVARS(OFNotification, 4)
 }
 
 /**
  * @brief The name of the notification.
  */

Index: src/OFNotificationCenter.h
==================================================================
--- src/OFNotificationCenter.h
+++ src/OFNotificationCenter.h
@@ -37,17 +37,19 @@
  * @class OFNotificationCenter OFNotificationCenter.h \
  *	  ObjFW/OFNotificationCenter.h
  *
  * @brief A class to send and register for notifications.
  */
+#ifndef OF_NOTIFICATION_CENTER_M
+OF_SUBCLASSING_RESTRICTED
+#endif
 @interface OFNotificationCenter: OFObject
 {
 #ifdef OF_HAVE_THREADS
 	OFMutex *_mutex;
 #endif
 	OFMutableDictionary *_handles;
-	OF_RESERVE_IVARS(OFNotificationCenter, 4)
 }
 
 #ifdef OF_HAVE_CLASS_PROPERTIES
 @property (class, readonly, nonatomic) OFNotificationCenter *defaultCenter;
 #endif

Index: src/OFNotificationCenter.m
==================================================================
--- src/OFNotificationCenter.m
+++ src/OFNotificationCenter.m
@@ -10,10 +10,12 @@
  * Alternatively, it may be distributed under the terms of the GNU General
  * Public License, either version 2 or 3, which can be found in the file
  * LICENSE.GPLv2 or LICENSE.GPLv3 respectively included in the packaging of this
  * file.
  */
+
+#define OF_NOTIFICATION_CENTER_M
 
 #include "config.h"
 
 #import "OFNotificationCenter.h"
 #import "OFArray.h"

Index: src/OFRecursiveMutex.h
==================================================================
--- src/OFRecursiveMutex.h
+++ src/OFRecursiveMutex.h
@@ -29,10 +29,11 @@
 @interface OFRecursiveMutex: OFObject <OFLocking>
 {
 	OFPlainRecursiveMutex _rmutex;
 	bool _initialized;
 	OFString *_Nullable _name;
+	OF_RESERVE_IVARS(OFRecursiveMutex, 4)
 }
 
 /**
  * @brief Creates a new recursive mutex.
  *

Index: src/OFSPXStreamSocket.h
==================================================================
--- src/OFSPXStreamSocket.h
+++ src/OFSPXStreamSocket.h
@@ -67,12 +67,15 @@
  *	 use @ref OFSPXSocket instead.
  *
  * To connect to a server, create a socket and connect it.
  * To create a server, create a socket, bind it and listen on it.
  */
-OF_SUBCLASSING_RESTRICTED
 @interface OFSPXStreamSocket: OFStreamSocket
+{
+	OF_RESERVE_IVARS(OFSPXStreamSocket, 4)
+}
+
 /**
  * @brief The delegate for asynchronous operations on the socket.
  *
  * @note The delegate is retained for as long as asynchronous operations are
  *	 still ongoing.

Index: src/exceptions/OFAcceptFailedException.h
==================================================================
--- src/exceptions/OFAcceptFailedException.h
+++ src/exceptions/OFAcceptFailedException.h
@@ -29,10 +29,11 @@
  */
 @interface OFAcceptFailedException: OFException
 {
 	id _socket;
 	int _errNo;
+	OF_RESERVE_IVARS(OFAcceptFailedException, 4)
 }
 
 /**
  * @brief The socket which could not accept a connection.
  */

Index: src/exceptions/OFAllocFailedException.h
==================================================================
--- src/exceptions/OFAllocFailedException.h
+++ src/exceptions/OFAllocFailedException.h
@@ -32,10 +32,11 @@
  * This is the only exception which is not an OFException as it's special. It
  * does not know for which class allocation failed and it should not be handled
  * like other exceptions, as the exception handling code is not allowed to
  * allocate *any* memory.
  */
+OF_SUBCLASSING_RESTRICTED
 @interface OFAllocFailedException: OFObject
 + (instancetype)exception OF_UNAVAILABLE;
 - (instancetype)init OF_UNAVAILABLE;
 
 /**

Index: src/exceptions/OFAlreadyConnectedException.h
==================================================================
--- src/exceptions/OFAlreadyConnectedException.h
+++ src/exceptions/OFAlreadyConnectedException.h
@@ -29,10 +29,11 @@
  *        connected or bound socket.
  */
 @interface OFAlreadyConnectedException: OFException
 {
 	id _socket;
+	OF_RESERVE_IVARS(OFAlreadyConnectedException, 4)
 }
 
 /**
  * @brief The socket which is already connected.
  */

Index: src/exceptions/OFBindFailedException.h
==================================================================
--- src/exceptions/OFBindFailedException.h
+++ src/exceptions/OFBindFailedException.h
@@ -38,10 +38,11 @@
 	uint8_t _packetType;
 	/* UNIX socket */
 	OFString *_Nullable _path;
 	id _socket;
 	int _errNo;
+	OF_RESERVE_IVARS(OFBindFailedException, 4)
 }
 
 /**
  * @brief The host on which binding failed.
  */

Index: src/exceptions/OFChangeCurrentDirectoryPathFailedException.h
==================================================================
--- src/exceptions/OFChangeCurrentDirectoryPathFailedException.h
+++ src/exceptions/OFChangeCurrentDirectoryPathFailedException.h
@@ -27,10 +27,11 @@
  */
 @interface OFChangeCurrentDirectoryPathFailedException: OFException
 {
 	OFString *_path;
 	int _errNo;
+	OF_RESERVE_IVARS(OFChangeCurrentDirectoryPathFailedException, 4)
 }
 
 /**
  * @brief The path of the directory to which the current path could not be
  *	  changed.

Index: src/exceptions/OFChecksumMismatchException.h
==================================================================
--- src/exceptions/OFChecksumMismatchException.h
+++ src/exceptions/OFChecksumMismatchException.h
@@ -24,10 +24,11 @@
  * @brief An exception indicating that a checksum did not match.
  */
 @interface OFChecksumMismatchException: OFException
 {
 	OFString *_actualChecksum, *_expectedChecksum;
+	OF_RESERVE_IVARS(OFChecksumMismatchException, 4)
 }
 
 /**
  * @brief The actual checksum calculated.
  */

Index: src/exceptions/OFConditionBroadcastFailedException.h
==================================================================
--- src/exceptions/OFConditionBroadcastFailedException.h
+++ src/exceptions/OFConditionBroadcastFailedException.h
@@ -32,10 +32,11 @@
  */
 @interface OFConditionBroadcastFailedException: OFException
 {
 	OFCondition *_condition;
 	int _errNo;
+	OF_RESERVE_IVARS(OFConditionBroadcastFailedException, 4)
 }
 
 /**
  * @brief The condition which could not be broadcasted.
  */

Index: src/exceptions/OFConditionSignalFailedException.h
==================================================================
--- src/exceptions/OFConditionSignalFailedException.h
+++ src/exceptions/OFConditionSignalFailedException.h
@@ -32,10 +32,11 @@
  */
 @interface OFConditionSignalFailedException: OFException
 {
 	OFCondition *_condition;
 	int _errNo;
+	OF_RESERVE_IVARS(OFConditionSignalFailedException, 4)
 }
 
 /**
  * @brief The condition which could not be signaled.
  */

Index: src/exceptions/OFConditionStillWaitingException.h
==================================================================
--- src/exceptions/OFConditionStillWaitingException.h
+++ src/exceptions/OFConditionStillWaitingException.h
@@ -32,10 +32,11 @@
  *	  condition.
  */
 @interface OFConditionStillWaitingException: OFException
 {
 	OFCondition *_condition;
+	OF_RESERVE_IVARS(OFConditionStillWaitingException, 4)
 }
 
 /**
  * @brief The condition for which is still being waited.
  */

Index: src/exceptions/OFConditionWaitFailedException.h
==================================================================
--- src/exceptions/OFConditionWaitFailedException.h
+++ src/exceptions/OFConditionWaitFailedException.h
@@ -32,10 +32,11 @@
  */
 @interface OFConditionWaitFailedException: OFException
 {
 	OFCondition *_condition;
 	int _errNo;
+	OF_RESERVE_IVARS(OFConditionWaitFailedException, 4)
 }
 
 /**
  * @brief The condition for which could not be waited.
  */

Index: src/exceptions/OFConnectionFailedException.h
==================================================================
--- src/exceptions/OFConnectionFailedException.h
+++ src/exceptions/OFConnectionFailedException.h
@@ -36,10 +36,11 @@
 	OFString *_Nullable _path;
 	uint32_t _network;
 	unsigned char _node[IPX_NODE_LEN];
 	id _socket;
 	int _errNo;
+	OF_RESERVE_IVARS(OFConnectionFailedException, 4)
 }
 
 /**
  * @brief The host to which the connection failed.
  */

Index: src/exceptions/OFCopyItemFailedException.h
==================================================================
--- src/exceptions/OFCopyItemFailedException.h
+++ src/exceptions/OFCopyItemFailedException.h
@@ -27,10 +27,11 @@
  */
 @interface OFCopyItemFailedException: OFException
 {
 	OFURL *_sourceURL, *_destinationURL;
 	int _errNo;
+	OF_RESERVE_IVARS(OFCopyItemFailedException, 4)
 }
 
 /**
  * @brief The URL of the source item.
  */

Index: src/exceptions/OFCreateDirectoryFailedException.h
==================================================================
--- src/exceptions/OFCreateDirectoryFailedException.h
+++ src/exceptions/OFCreateDirectoryFailedException.h
@@ -28,10 +28,11 @@
  */
 @interface OFCreateDirectoryFailedException: OFException
 {
 	OFURL *_URL;
 	int _errNo;
+	OF_RESERVE_IVARS(OFCreateDirectoryFailedException, 4)
 }
 
 /**
  * @brief The URL of the directory which couldn't be created.
  */

Index: src/exceptions/OFCreateSymbolicLinkFailedException.h
==================================================================
--- src/exceptions/OFCreateSymbolicLinkFailedException.h
+++ src/exceptions/OFCreateSymbolicLinkFailedException.h
@@ -29,10 +29,11 @@
 @interface OFCreateSymbolicLinkFailedException: OFException
 {
 	OFURL *_URL;
 	OFString *_target;
 	int _errNo;
+	OF_RESERVE_IVARS(OFCreateSymbolicLinkFailedException, 4)
 }
 
 /**
  * @brief The URL at which the symlink should have been created.
  */

Index: src/exceptions/OFCreateWindowsRegistryKeyFailedException.h
==================================================================
--- src/exceptions/OFCreateWindowsRegistryKeyFailedException.h
+++ src/exceptions/OFCreateWindowsRegistryKeyFailedException.h
@@ -33,10 +33,11 @@
 	OFString *_path;
 	DWORD _options;
 	REGSAM _accessRights;
 	LPSECURITY_ATTRIBUTES _Nullable _securityAttributes;
 	LSTATUS _status;
+	OF_RESERVE_IVARS(OFCreateWindowsRegistryKeyFailedException, 4)
 }
 
 /**
  * @brief The registry key on which creating the subkey failed.
  */

Index: src/exceptions/OFDNSQueryFailedException.h
==================================================================
--- src/exceptions/OFDNSQueryFailedException.h
+++ src/exceptions/OFDNSQueryFailedException.h
@@ -28,10 +28,11 @@
  */
 @interface OFDNSQueryFailedException: OFException
 {
 	OFDNSQuery *_query;
 	OFDNSResolverErrorCode _errorCode;
+	OF_RESERVE_IVARS(OFDNSQueryFailedException, 4)
 }
 
 /**
  * @brief The query which could not be performed.
  */

Index: src/exceptions/OFDeleteWindowsRegistryKeyFailedException.h
==================================================================
--- src/exceptions/OFDeleteWindowsRegistryKeyFailedException.h
+++ src/exceptions/OFDeleteWindowsRegistryKeyFailedException.h
@@ -30,10 +30,11 @@
 @interface OFDeleteWindowsRegistryKeyFailedException: OFException
 {
 	OFWindowsRegistryKey *_registryKey;
 	OFString *_subkeyPath;
 	LSTATUS _status;
+	OF_RESERVE_IVARS(OFDeleteWindowsRegistryKeyFailedException, 4)
 }
 
 /**
  * @brief The registry key on which deleting the subkey failed.
  */

Index: src/exceptions/OFDeleteWindowsRegistryValueFailedException.h
==================================================================
--- src/exceptions/OFDeleteWindowsRegistryValueFailedException.h
+++ src/exceptions/OFDeleteWindowsRegistryValueFailedException.h
@@ -30,10 +30,11 @@
 @interface OFDeleteWindowsRegistryValueFailedException: OFException
 {
 	OFWindowsRegistryKey *_registryKey;
 	OFString *_Nullable _valueName;
 	LSTATUS _status;
+	OF_RESERVE_IVARS(OFDeleteWindowsRegistryValueFailedException, 4)
 }
 
 /**
  * @brief The registry key on which deleting the value failed.
  */

Index: src/exceptions/OFEnumerationMutationException.h
==================================================================
--- src/exceptions/OFEnumerationMutationException.h
+++ src/exceptions/OFEnumerationMutationException.h
@@ -26,10 +26,11 @@
  *        enumeration.
  */
 @interface OFEnumerationMutationException: OFException
 {
 	id _object;
+	OF_RESERVE_IVARS(OFEnumerationMutationException, 4)
 }
 
 /**
  * @brief The object which was mutated during enumeration.
  */

Index: src/exceptions/OFException.h
==================================================================
--- src/exceptions/OFException.h
+++ src/exceptions/OFException.h
@@ -148,10 +148,11 @@
  * the OFAllocFailedException.
  */
 @interface OFException: OFObject
 {
 	void *_backtrace[OFBacktraceSize];
+	OF_RESERVE_IVARS(OFException, 4)
 }
 
 /**
  * @brief Creates a new, autoreleased exception.
  *

Index: src/exceptions/OFGetCurrentDirectoryPathFailedException.h
==================================================================
--- src/exceptions/OFGetCurrentDirectoryPathFailedException.h
+++ src/exceptions/OFGetCurrentDirectoryPathFailedException.h
@@ -26,10 +26,11 @@
  *	  failed.
  */
 @interface OFGetCurrentDirectoryPathFailedException: OFException
 {
 	int _errNo;
+	OF_RESERVE_IVARS(OFGetCurrentDirectoryPathFailedException, 4)
 }
 
 /**
  * @brief The errno of the error that occurred.
  */

Index: src/exceptions/OFGetOptionFailedException.h
==================================================================
--- src/exceptions/OFGetOptionFailedException.h
+++ src/exceptions/OFGetOptionFailedException.h
@@ -25,10 +25,11 @@
  */
 @interface OFGetOptionFailedException: OFException
 {
 	id _object;
 	int _errNo;
+	OF_RESERVE_IVARS(OFGetOptionFailedException, 4)
 }
 
 /**
  * @brief The object for which the option could not be retrieved.
  */

Index: src/exceptions/OFGetWindowsRegistryValueFailedException.h
==================================================================
--- src/exceptions/OFGetWindowsRegistryValueFailedException.h
+++ src/exceptions/OFGetWindowsRegistryValueFailedException.h
@@ -30,10 +30,11 @@
 @interface OFGetWindowsRegistryValueFailedException: OFException
 {
 	OFWindowsRegistryKey *_registryKey;
 	OFString *_Nullable _valueName;
 	LSTATUS _status;
+	OF_RESERVE_IVARS(OFGetWindowsRegistryValueFailedException, 4)
 }
 
 /**
  * @brief The registry key on which getting the value at the key path failed.
  */

Index: src/exceptions/OFHTTPRequestFailedException.h
==================================================================
--- src/exceptions/OFHTTPRequestFailedException.h
+++ src/exceptions/OFHTTPRequestFailedException.h
@@ -33,10 +33,11 @@
  */
 @interface OFHTTPRequestFailedException: OFException
 {
 	OFHTTPRequest *_request;
 	OFHTTPResponse *_response;
+	OF_RESERVE_IVARS(OFHTTPRequestFailedException, 4)
 }
 
 /**
  * @brief The HTTP request which failed.
  */

Index: src/exceptions/OFHashAlreadyCalculatedException.h
==================================================================
--- src/exceptions/OFHashAlreadyCalculatedException.h
+++ src/exceptions/OFHashAlreadyCalculatedException.h
@@ -25,10 +25,11 @@
  * @brief An exception indicating that the hash has already been calculated.
  */
 @interface OFHashAlreadyCalculatedException: OFException
 {
 	id _object;
+	OF_RESERVE_IVARS(OFHashAlreadyCalculatedException, 4)
 }
 
 /**
  * @brief The hash which has already been calculated.
  */

Index: src/exceptions/OFHashNotCalculatedException.h
==================================================================
--- src/exceptions/OFHashNotCalculatedException.h
+++ src/exceptions/OFHashNotCalculatedException.h
@@ -24,10 +24,11 @@
  * @brief An exception indicating that the hash has not been calculated yet.
  */
 @interface OFHashNotCalculatedException: OFException
 {
 	id _object;
+	OF_RESERVE_IVARS(OFHashNotCalculatedException, 4)
 }
 
 /**
  * @brief The hash which has not been calculated yet.
  */

Index: src/exceptions/OFInitializationFailedException.h
==================================================================
--- src/exceptions/OFInitializationFailedException.h
+++ src/exceptions/OFInitializationFailedException.h
@@ -25,10 +25,11 @@
  * @brief An exception indicating that initializing something failed.
  */
 @interface OFInitializationFailedException: OFException
 {
 	Class _inClass;
+	OF_RESERVE_IVARS(OFInitializationFailedException, 4)
 }
 
 /**
  * @brief The class for which initialization failed.
  */

Index: src/exceptions/OFInvalidArgumentException.h
==================================================================
--- src/exceptions/OFInvalidArgumentException.h
+++ src/exceptions/OFInvalidArgumentException.h
@@ -22,8 +22,11 @@
  *	  OFInvalidArgumentException.h ObjFW/OFInvalidArgumentException.h
  *
  * @brief An exception indicating that the argument is invalid for this method.
  */
 @interface OFInvalidArgumentException: OFException
+{
+	OF_RESERVE_IVARS(OFInvalidArgumentException, 4)
+}
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/exceptions/OFInvalidEncodingException.h
==================================================================
--- src/exceptions/OFInvalidEncodingException.h
+++ src/exceptions/OFInvalidEncodingException.h
@@ -22,8 +22,11 @@
  *	  OFInvalidEncodingException.h ObjFW/OFInvalidEncodingException.h
  *
  * @brief An exception indicating that the encoding is invalid for this object.
  */
 @interface OFInvalidEncodingException: OFException
+{
+	OF_RESERVE_IVARS(OFInvalidEncodingException, 4)
+}
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/exceptions/OFInvalidFormatException.h
==================================================================
--- src/exceptions/OFInvalidFormatException.h
+++ src/exceptions/OFInvalidFormatException.h
@@ -22,8 +22,11 @@
  *	  OFInvalidFormatException.h ObjFW/OFInvalidFormatException.h
  *
  * @brief An exception indicating that the format is invalid.
  */
 @interface OFInvalidFormatException: OFException
+{
+	OF_RESERVE_IVARS(OFInvalidFormatException, 4)
+}
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/exceptions/OFInvalidJSONException.h
==================================================================
--- src/exceptions/OFInvalidJSONException.h
+++ src/exceptions/OFInvalidJSONException.h
@@ -25,10 +25,11 @@
  */
 @interface OFInvalidJSONException: OFException
 {
 	OFString *_string;
 	size_t _line;
+	OF_RESERVE_IVARS(OFInvalidJSONException, 4)
 }
 
 /**
  * @brief The string containing the invalid JSON representation.
  */

Index: src/exceptions/OFInvalidServerReplyException.h
==================================================================
--- src/exceptions/OFInvalidServerReplyException.h
+++ src/exceptions/OFInvalidServerReplyException.h
@@ -22,8 +22,11 @@
  *	  OFInvalidServerReplyException.h ObjFW/OFInvalidServerReplyException.h
  *
  * @brief An exception indicating that the server sent an invalid reply.
  */
 @interface OFInvalidServerReplyException: OFException
+{
+	OF_RESERVE_IVARS(OFInvalidServerReplyException, 4)
+}
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/exceptions/OFLinkFailedException.h
==================================================================
--- src/exceptions/OFLinkFailedException.h
+++ src/exceptions/OFLinkFailedException.h
@@ -27,10 +27,11 @@
  */
 @interface OFLinkFailedException: OFException
 {
 	OFURL *_sourceURL, *_destinationURL;
 	int _errNo;
+	OF_RESERVE_IVARS(OFLinkFailedException, 4)
 }
 
 /**
  * @brief A URL with the source for the link.
  */

Index: src/exceptions/OFListenFailedException.h
==================================================================
--- src/exceptions/OFListenFailedException.h
+++ src/exceptions/OFListenFailedException.h
@@ -29,10 +29,11 @@
  */
 @interface OFListenFailedException: OFException
 {
 	id _socket;
 	int _backlog, _errNo;
+	OF_RESERVE_IVARS(OFListenFailedException, 4)
 }
 
 /**
  * @brief The socket which failed to listen.
  */

Index: src/exceptions/OFLoadPluginFailedException.h
==================================================================
--- src/exceptions/OFLoadPluginFailedException.h
+++ src/exceptions/OFLoadPluginFailedException.h
@@ -24,10 +24,11 @@
  * @brief An exception indicating a plugin could not be loaded.
  */
 @interface OFLoadPluginFailedException: OFException
 {
 	OFString *_path, *_Nullable _error;
+	OF_RESERVE_IVARS(OFLoadPluginFailedException, 4)
 }
 
 /**
  * @brief The path of the plugin which could not be loaded
  */

Index: src/exceptions/OFLockFailedException.h
==================================================================
--- src/exceptions/OFLockFailedException.h
+++ src/exceptions/OFLockFailedException.h
@@ -26,10 +26,11 @@
  */
 @interface OFLockFailedException: OFException
 {
 	id <OFLocking> _Nullable _lock;
 	int _errNo;
+	OF_RESERVE_IVARS(OFLockFailedException, 4)
 }
 
 /**
  * @brief The lock which could not be locked.
  */

Index: src/exceptions/OFMalformedXMLException.h
==================================================================
--- src/exceptions/OFMalformedXMLException.h
+++ src/exceptions/OFMalformedXMLException.h
@@ -26,10 +26,11 @@
  * @brief An exception indicating that a parser encountered malformed XML.
  */
 @interface OFMalformedXMLException: OFException
 {
 	OFXMLParser *_parser;
+	OF_RESERVE_IVARS(OFMalformedXMLException, 4)
 }
 
 /**
  * @brief The parser which encountered malformed XML.
  */

Index: src/exceptions/OFMoveItemFailedException.h
==================================================================
--- src/exceptions/OFMoveItemFailedException.h
+++ src/exceptions/OFMoveItemFailedException.h
@@ -27,10 +27,11 @@
  */
 @interface OFMoveItemFailedException: OFException
 {
 	OFURL *_sourceURL, *_destinationURL;
 	int _errNo;
+	OF_RESERVE_IVARS(OFMoveItemFailedException, 4)
 }
 
 /**
  * @brief The original URL.
  */

Index: src/exceptions/OFNotImplementedException.h
==================================================================
--- src/exceptions/OFNotImplementedException.h
+++ src/exceptions/OFNotImplementedException.h
@@ -26,10 +26,11 @@
  */
 @interface OFNotImplementedException: OFException
 {
 	SEL _selector;
 	id _Nullable _object;
+	OF_RESERVE_IVARS(OFNotImplementedException, 4)
 }
 
 /**
  * @brief The selector which is not or not fully implemented.
  */

Index: src/exceptions/OFNotOpenException.h
==================================================================
--- src/exceptions/OFNotOpenException.h
+++ src/exceptions/OFNotOpenException.h
@@ -23,10 +23,11 @@
  * @brief An exception indicating an object is not open, connected or bound.
  */
 @interface OFNotOpenException: OFException
 {
 	id _object;
+	OF_RESERVE_IVARS(OFNotOpenException, 4)
 }
 
 /**
  * @brief The object which is not open, connected or bound.
  */

Index: src/exceptions/OFObserveFailedException.h
==================================================================
--- src/exceptions/OFObserveFailedException.h
+++ src/exceptions/OFObserveFailedException.h
@@ -27,10 +27,11 @@
  */
 @interface OFObserveFailedException: OFException
 {
 	OFKernelEventObserver *_observer;
 	int _errNo;
+	OF_RESERVE_IVARS(OFObserveFailedException, 4)
 }
 
 /**
  * @brief The observer which failed to observe.
  */

Index: src/exceptions/OFOpenItemFailedException.h
==================================================================
--- src/exceptions/OFOpenItemFailedException.h
+++ src/exceptions/OFOpenItemFailedException.h
@@ -29,10 +29,11 @@
 {
 	OFURL *_Nullable _URL;
 	OFString *_Nullable _path;
 	OFString *_mode;
 	int _errNo;
+	OF_RESERVE_IVARS(OFOpenItemFailedException, 4)
 }
 
 /**
  * @brief The URL of the item which could not be opened.
  */

Index: src/exceptions/OFOpenWindowsRegistryKeyFailedException.h
==================================================================
--- src/exceptions/OFOpenWindowsRegistryKeyFailedException.h
+++ src/exceptions/OFOpenWindowsRegistryKeyFailedException.h
@@ -33,10 +33,11 @@
 	OFString *_path;
 	REGSAM _accessRights;
 	LPSECURITY_ATTRIBUTES _Nullable _securityAttributes;
 	DWORD _options;
 	LSTATUS _status;
+	OF_RESERVE_IVARS(OFOpenWindowsRegistryKeyFailedException, 4)
 }
 
 /**
  * @brief The registry key on which opening the subkey failed.
  */

Index: src/exceptions/OFOutOfMemoryException.h
==================================================================
--- src/exceptions/OFOutOfMemoryException.h
+++ src/exceptions/OFOutOfMemoryException.h
@@ -24,10 +24,11 @@
  * @brief An exception indicating there is not enough memory available.
  */
 @interface OFOutOfMemoryException: OFException
 {
 	size_t _requestedSize;
+	OF_RESERVE_IVARS(OFOutOfMemoryException, 4)
 }
 
 /**
  * @brief The size of the memory that could not be allocated.
  */

Index: src/exceptions/OFOutOfRangeException.h
==================================================================
--- src/exceptions/OFOutOfRangeException.h
+++ src/exceptions/OFOutOfRangeException.h
@@ -22,8 +22,11 @@
  *	  OFOutOfRangeException.h ObjFW/OFOutOfRangeException.h
  *
  * @brief An exception indicating the given value is out of range.
  */
 @interface OFOutOfRangeException: OFException
+{
+	OF_RESERVE_IVARS(OFOutOfRangeException, 4)
+}
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/exceptions/OFReadFailedException.h
==================================================================
--- src/exceptions/OFReadFailedException.h
+++ src/exceptions/OFReadFailedException.h
@@ -22,8 +22,11 @@
  *	  OFReadFailedException.h ObjFW/OFReadFailedException.h
  *
  * @brief An exception indicating that reading from an object failed.
  */
 @interface OFReadFailedException: OFReadOrWriteFailedException
+{
+	OF_RESERVE_IVARS(OFReadFailedException, 4)
+}
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/exceptions/OFReadOrWriteFailedException.h
==================================================================
--- src/exceptions/OFReadOrWriteFailedException.h
+++ src/exceptions/OFReadOrWriteFailedException.h
@@ -27,10 +27,11 @@
 @interface OFReadOrWriteFailedException: OFException
 {
 	id _object;
 	size_t _requestedLength;
 	int _errNo;
+	OF_RESERVE_IVARS(OFReadOrWriteFailedException, 4)
 }
 
 /**
  * @brief The stream which caused the read or write failed exception.
  */

Index: src/exceptions/OFRemoveItemFailedException.h
==================================================================
--- src/exceptions/OFRemoveItemFailedException.h
+++ src/exceptions/OFRemoveItemFailedException.h
@@ -27,10 +27,11 @@
  */
 @interface OFRemoveItemFailedException: OFException
 {
 	OFURL *_URL;
 	int _errNo;
+	OF_RESERVE_IVARS(OFRemoveItemFailedException, 4)
 }
 
 /**
  * @brief The URL of the item which could not be removed.
  */

Index: src/exceptions/OFResolveHostFailedException.h
==================================================================
--- src/exceptions/OFResolveHostFailedException.h
+++ src/exceptions/OFResolveHostFailedException.h
@@ -27,10 +27,11 @@
 @interface OFResolveHostFailedException: OFException
 {
 	OFString *_host;
 	OFSocketAddressFamily _addressFamily;
 	OFDNSResolverErrorCode _errorCode;
+	OF_RESERVE_IVARS(OFResolveHostFailedException, 4)
 }
 
 /**
  * @brief The host which could not be resolved.
  */

Index: src/exceptions/OFRetrieveItemAttributesFailedException.h
==================================================================
--- src/exceptions/OFRetrieveItemAttributesFailedException.h
+++ src/exceptions/OFRetrieveItemAttributesFailedException.h
@@ -28,10 +28,11 @@
  */
 @interface OFRetrieveItemAttributesFailedException: OFException
 {
 	OFURL *_URL;
 	int _errNo;
+	OF_RESERVE_IVARS(OFRetrieveItemAttributesFailedException, 4)
 }
 
 /**
  * @brief The URL of the item whose attributes could not be retrieved.
  */

Index: src/exceptions/OFSeekFailedException.h
==================================================================
--- src/exceptions/OFSeekFailedException.h
+++ src/exceptions/OFSeekFailedException.h
@@ -28,10 +28,11 @@
 {
 	OFSeekableStream *_stream;
 	OFStreamOffset _offset;
 	OFSeekWhence _whence;
 	int _errNo;
+	OF_RESERVE_IVARS(OFSeekFailedException, 4)
 }
 
 /**
  * @brief The stream for which seeking failed.
  */

Index: src/exceptions/OFSetItemAttributesFailedException.h
==================================================================
--- src/exceptions/OFSetItemAttributesFailedException.h
+++ src/exceptions/OFSetItemAttributesFailedException.h
@@ -31,10 +31,11 @@
 {
 	OFURL *_URL;
 	OFFileAttributes _attributes;
 	OFFileAttributeKey _failedAttribute;
 	int _errNo;
+	OF_RESERVE_IVARS(OFSetItemAttributesFailedException, 4)
 }
 
 /**
  * @brief The URL of the item whose attributes could not be set.
  */

Index: src/exceptions/OFSetOptionFailedException.h
==================================================================
--- src/exceptions/OFSetOptionFailedException.h
+++ src/exceptions/OFSetOptionFailedException.h
@@ -25,10 +25,11 @@
  */
 @interface OFSetOptionFailedException: OFException
 {
 	id _object;
 	int _errNo;
+	OF_RESERVE_IVARS(OFSetOptionFailedException, 4)
 }
 
 /**
  * @brief The object for which the option could not be set.
  */

Index: src/exceptions/OFSetWindowsRegistryValueFailedException.h
==================================================================
--- src/exceptions/OFSetWindowsRegistryValueFailedException.h
+++ src/exceptions/OFSetWindowsRegistryValueFailedException.h
@@ -32,10 +32,11 @@
 	OFWindowsRegistryKey *_registryKey;
 	OFString *_Nullable _valueName;
 	OFData *_Nullable _data;
 	DWORD _type;
 	LSTATUS _status;
+	OF_RESERVE_IVARS(OFSetWindowsRegistryValueFailedException, 4)
 }
 
 /**
  * @brief The registry key on which setting the value failed.
  */

Index: src/exceptions/OFStillLockedException.h
==================================================================
--- src/exceptions/OFStillLockedException.h
+++ src/exceptions/OFStillLockedException.h
@@ -25,10 +25,11 @@
  * @brief An exception indicating that a lock is still locked.
  */
 @interface OFStillLockedException: OFException
 {
 	id <OFLocking> _Nullable _lock;
+	OF_RESERVE_IVARS(OFStillLockedException, 4)
 }
 
 /**
  * @brief The lock which is still locked.
  */

Index: src/exceptions/OFTLSHandshakeFailedException.h
==================================================================
--- src/exceptions/OFTLSHandshakeFailedException.h
+++ src/exceptions/OFTLSHandshakeFailedException.h
@@ -40,10 +40,11 @@
 @interface OFTLSHandshakeFailedException: OFException
 {
 	OFTLSStream *_stream;
 	OFString *_Nullable _host;
 	OFTLSStreamErrorCode _errorCode;
+	OF_RESERVE_IVARS(OFTLSHandshakeFailedException, 4)
 }
 
 /**
  * @brief The TLS stream which failed the handshake.
  */

Index: src/exceptions/OFThreadJoinFailedException.h
==================================================================
--- src/exceptions/OFThreadJoinFailedException.h
+++ src/exceptions/OFThreadJoinFailedException.h
@@ -31,10 +31,11 @@
  */
 @interface OFThreadJoinFailedException: OFException
 {
 	OFThread *_Nullable _thread;
 	int _errNo;
+	OF_RESERVE_IVARS(OFThreadJoinFailedException, 4)
 }
 
 /**
  * @brief The thread which could not be joined.
  */

Index: src/exceptions/OFThreadStartFailedException.h
==================================================================
--- src/exceptions/OFThreadStartFailedException.h
+++ src/exceptions/OFThreadStartFailedException.h
@@ -31,10 +31,11 @@
  */
 @interface OFThreadStartFailedException: OFException
 {
 	OFThread *_Nullable _thread;
 	int _errNo;
+	OF_RESERVE_IVARS(OFThreadStartFailedException, 4)
 }
 
 /**
  * @brief The thread which could not be started.
  */

Index: src/exceptions/OFThreadStillRunningException.h
==================================================================
--- src/exceptions/OFThreadStillRunningException.h
+++ src/exceptions/OFThreadStillRunningException.h
@@ -30,10 +30,11 @@
  * @brief An exception indicating that a thread is still running.
  */
 @interface OFThreadStillRunningException: OFException
 {
 	OFThread *_Nullable _thread;
+	OF_RESERVE_IVARS(OFThreadStillRunningException, 4)
 }
 
 /**
  * @brief The thread which is still running.
  */

Index: src/exceptions/OFTruncatedDataException.h
==================================================================
--- src/exceptions/OFTruncatedDataException.h
+++ src/exceptions/OFTruncatedDataException.h
@@ -23,8 +23,11 @@
  *
  * @brief An exception indicating that data was truncated while it should not
  *	  have been truncated.
  */
 @interface OFTruncatedDataException: OFException
+{
+	OF_RESERVE_IVARS(OFTruncatedDataException, 4)
+}
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/exceptions/OFUnboundNamespaceException.h
==================================================================
--- src/exceptions/OFUnboundNamespaceException.h
+++ src/exceptions/OFUnboundNamespaceException.h
@@ -27,10 +27,11 @@
  */
 @interface OFUnboundNamespaceException: OFException
 {
 	OFString *_namespace;
 	OFXMLElement *_element;
+	OF_RESERVE_IVARS(OFUnboundNamespaceException, 4)
 }
 
 /**
  * @brief The unbound namespace.
  */

Index: src/exceptions/OFUnboundPrefixException.h
==================================================================
--- src/exceptions/OFUnboundPrefixException.h
+++ src/exceptions/OFUnboundPrefixException.h
@@ -27,10 +27,11 @@
  */
 @interface OFUnboundPrefixException: OFException
 {
 	OFString *_prefix;
 	OFXMLParser *_parser;
+	OF_RESERVE_IVARS(OFUnboundPrefixException, 4)
 }
 
 /**
  * @brief The unbound prefix.
  */

Index: src/exceptions/OFUndefinedKeyException.h
==================================================================
--- src/exceptions/OFUndefinedKeyException.h
+++ src/exceptions/OFUndefinedKeyException.h
@@ -27,10 +27,11 @@
 @interface OFUndefinedKeyException: OFException
 {
 	id _object;
 	OFString *_Nullable _key;
 	id _Nullable _value;
+	OF_RESERVE_IVARS(OFUndefinedKeyException, 4)
 }
 
 /**
  * @brief The object on which the key is undefined.
  */

Index: src/exceptions/OFUnknownXMLEntityException.h
==================================================================
--- src/exceptions/OFUnknownXMLEntityException.h
+++ src/exceptions/OFUnknownXMLEntityException.h
@@ -25,10 +25,11 @@
  *	  entity.
  */
 @interface OFUnknownXMLEntityException: OFException
 {
 	OFString *_entityName;
+	OF_RESERVE_IVARS(OFUnknownXMLEntityException, 4)
 }
 
 /**
  * @brief The name of the unknown XML entity.
  */

Index: src/exceptions/OFUnlockFailedException.h
==================================================================
--- src/exceptions/OFUnlockFailedException.h
+++ src/exceptions/OFUnlockFailedException.h
@@ -26,10 +26,11 @@
  */
 @interface OFUnlockFailedException: OFException
 {
 	id <OFLocking> _Nullable _lock;
 	int _errNo;
+	OF_RESERVE_IVARS(OFUnlockFailedException, 4)
 }
 
 /**
  * @brief The lock which could not be unlocked.
  */

Index: src/exceptions/OFUnsupportedProtocolException.h
==================================================================
--- src/exceptions/OFUnsupportedProtocolException.h
+++ src/exceptions/OFUnsupportedProtocolException.h
@@ -28,10 +28,11 @@
  *	  supported.
  */
 @interface OFUnsupportedProtocolException: OFException
 {
 	OFURL *_Nullable _URL;
+	OF_RESERVE_IVARS(OFUnsupportedProtocolException, 4)
 }
 
 /**
  * @brief The URL whose protocol is unsupported.
  */

Index: src/exceptions/OFUnsupportedVersionException.h
==================================================================
--- src/exceptions/OFUnsupportedVersionException.h
+++ src/exceptions/OFUnsupportedVersionException.h
@@ -25,10 +25,11 @@
  *	  protocol is not supported.
  */
 @interface OFUnsupportedVersionException: OFException
 {
 	OFString *_version;
+	OF_RESERVE_IVARS(OFUnsupportedVersionException, 4)
 }
 
 /**
  * @brief The version which is unsupported.
  */

Index: src/exceptions/OFWriteFailedException.h
==================================================================
--- src/exceptions/OFWriteFailedException.h
+++ src/exceptions/OFWriteFailedException.h
@@ -24,10 +24,11 @@
  * @brief An exception indicating that writing to an object failed.
  */
 @interface OFWriteFailedException: OFReadOrWriteFailedException
 {
 	size_t _bytesWritten;
+	OF_RESERVE_IVARS(OFWriteFailedException, 4)
 }
 
 /**
  * @brief The number of bytes already written before the write failed.
  *