Index: src/OFUDPSocket.h
==================================================================
--- src/OFUDPSocket.h
+++ src/OFUDPSocket.h
@@ -321,13 +321,6 @@
  *	  datagrams.
  */
 - (void)close;
 @end
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-#ifdef __cplusplus
-}
-#endif
-
 OF_ASSUME_NONNULL_END

Index: src/condition.h
==================================================================
--- src/condition.h
+++ src/condition.h
@@ -38,12 +38,18 @@
 	HANDLE event;
 	int count;
 } of_condition_t;
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 extern bool of_condition_new(of_condition_t *condition);
 extern bool of_condition_signal(of_condition_t *condition);
 extern bool of_condition_broadcast(of_condition_t *condition);
 extern bool of_condition_wait(of_condition_t *condition, of_mutex_t *mutex);
 extern bool of_condition_timed_wait(of_condition_t *condition,
     of_mutex_t *mutex, of_time_interval_t timeout);
 extern bool of_condition_free(of_condition_t *condition);
+#ifdef __cplusplus
+}
+#endif

Index: src/mutex.h
==================================================================
--- src/mutex.h
+++ src/mutex.h
@@ -55,10 +55,13 @@
 	of_mutex_t mutex;
 	of_tlskey_t count;
 } of_rmutex_t;
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 extern bool of_mutex_new(of_mutex_t *mutex);
 extern bool of_mutex_lock(of_mutex_t *mutex);
 extern bool of_mutex_trylock(of_mutex_t *mutex);
 extern bool of_mutex_unlock(of_mutex_t *mutex);
 extern bool of_mutex_free(of_mutex_t *mutex);
@@ -65,10 +68,13 @@
 extern bool of_rmutex_new(of_rmutex_t *rmutex);
 extern bool of_rmutex_lock(of_rmutex_t *rmutex);
 extern bool of_rmutex_trylock(of_rmutex_t *rmutex);
 extern bool of_rmutex_unlock(of_rmutex_t *rmutex);
 extern bool of_rmutex_free(of_rmutex_t *rmutex);
+#ifdef __cplusplus
+}
+#endif
 
 /* Spinlocks are inlined for performance. */
 
 static OF_INLINE void
 of_thread_yield(void)

Index: src/once.h
==================================================================
--- src/once.h
+++ src/once.h
@@ -29,6 +29,12 @@
 #elif !defined(OF_HAVE_THREADS)
 typedef int of_once_t;
 # define OF_ONCE_INIT 0
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 extern void of_once(of_once_t *control, void (*func)(void));
+#ifdef __cplusplus
+}
+#endif

Index: src/thread.h
==================================================================
--- src/thread.h
+++ src/thread.h
@@ -45,11 +45,17 @@
 #elif defined(OF_WINDOWS)
 # define of_thread_is_current(t) (t == GetCurrentThread())
 # define of_thread_current GetCurrentThread
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 extern bool of_thread_attr_init(of_thread_attr_t *attr);
 extern bool of_thread_new(of_thread_t *thread, void (*function)(id), id object,
     const of_thread_attr_t *attr);
 extern void of_thread_set_name(const char *name);
 extern bool of_thread_join(of_thread_t thread);
 extern bool of_thread_detach(of_thread_t thread);
+#ifdef __cplusplus
+}
+#endif

Index: src/tlskey.h
==================================================================
--- src/tlskey.h
+++ src/tlskey.h
@@ -31,12 +31,19 @@
 typedef pthread_key_t of_tlskey_t;
 #elif defined(OF_WINDOWS)
 # include <windows.h>
 typedef DWORD of_tlskey_t;
 #endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
 extern bool of_tlskey_new(of_tlskey_t *key);
 extern bool of_tlskey_free(of_tlskey_t key);
+#ifdef __cplusplus
+}
+#endif
 
 /* TLS keys are inlined for performance. */
 
 #if defined(OF_HAVE_PTHREADS)
 static OF_INLINE void *