diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -274,7 +274,8 @@
 
 namespace __thread_detail {
 
-inline __libcpp_timespec_t __convert_to_timespec(const chrono::nanoseconds& __ns)
+_LIBCPP_HIDE_FROM_ABI inline
+__libcpp_timespec_t __convert_to_timespec(const chrono::nanoseconds& __ns)
 {
   using namespace chrono;
   seconds __s = duration_cast<seconds>(__ns);
@@ -300,6 +301,7 @@
 
 #if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m)
 {
   pthread_mutexattr_t attr;
@@ -324,74 +326,88 @@
   return 0;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_lock(__libcpp_recursive_mutex_t *__m)
 {
   return pthread_mutex_lock(__m);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_recursive_mutex_trylock(__libcpp_recursive_mutex_t *__m)
 {
   return pthread_mutex_trylock(__m) == 0;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_unlock(__libcpp_recursive_mutex_t *__m)
 {
   return pthread_mutex_unlock(__m);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_destroy(__libcpp_recursive_mutex_t *__m)
 {
   return pthread_mutex_destroy(__m);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_mutex_lock(__libcpp_mutex_t *__m)
 {
   return pthread_mutex_lock(__m);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_mutex_trylock(__libcpp_mutex_t *__m)
 {
   return pthread_mutex_trylock(__m) == 0;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_mutex_unlock(__libcpp_mutex_t *__m)
 {
   return pthread_mutex_unlock(__m);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_mutex_destroy(__libcpp_mutex_t *__m)
 {
   return pthread_mutex_destroy(__m);
 }
 
 // Condition Variable
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_signal(__libcpp_condvar_t *__cv)
 {
   return pthread_cond_signal(__cv);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_broadcast(__libcpp_condvar_t *__cv)
 {
   return pthread_cond_broadcast(__cv);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_wait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m)
 {
   return pthread_cond_wait(__cv, __m);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
                                __libcpp_timespec_t *__ts)
 {
   return pthread_cond_timedwait(__cv, __m, __ts);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_destroy(__libcpp_condvar_t *__cv)
 {
   return pthread_cond_destroy(__cv);
 }
 
 // Execute once
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_execute_once(__libcpp_exec_once_flag *flag,
                           void (*init_routine)()) {
   return pthread_once(flag, init_routine);
@@ -399,34 +415,40 @@
 
 // Thread id
 // Returns non-zero if the thread ids are equal, otherwise 0
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2)
 {
   return t1 == t2;
 }
 
 // Returns non-zero if t1 < t2, otherwise 0
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2)
 {
   return t1 < t2;
 }
 
 // Thread
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_thread_isnull(const __libcpp_thread_t *__t) {
   return __libcpp_thread_get_id(__t) == 0;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
                            void *__arg)
 {
   return pthread_create(__t, nullptr, __func, __arg);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 __libcpp_thread_id __libcpp_thread_get_current_id()
 {
   const __libcpp_thread_t thread = pthread_self();
   return __libcpp_thread_get_id(&thread);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 __libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t)
 {
 #if defined(__MVS__)
@@ -436,21 +458,25 @@
 #endif
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_thread_join(__libcpp_thread_t *__t)
 {
   return pthread_join(*__t, nullptr);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_thread_detach(__libcpp_thread_t *__t)
 {
   return pthread_detach(*__t);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 void __libcpp_thread_yield()
 {
   sched_yield();
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns)
 {
    __libcpp_timespec_t __ts = __thread_detail::__convert_to_timespec(__ns);
@@ -458,16 +484,19 @@
 }
 
 // Thread local storage
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_tls_create(__libcpp_tls_key *__key, void (*__at_exit)(void *))
 {
   return pthread_key_create(__key, __at_exit);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 void *__libcpp_tls_get(__libcpp_tls_key __key)
 {
   return pthread_getspecific(__key);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
 {
     return pthread_setspecific(__key, __p);
@@ -475,47 +504,56 @@
 
 #elif defined(_LIBCPP_HAS_THREAD_API_C11)
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m)
 {
   return mtx_init(__m, mtx_plain | mtx_recursive) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_lock(__libcpp_recursive_mutex_t *__m)
 {
   return mtx_lock(__m) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_recursive_mutex_trylock(__libcpp_recursive_mutex_t *__m)
 {
   return mtx_trylock(__m) == thrd_success;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_unlock(__libcpp_recursive_mutex_t *__m)
 {
   return mtx_unlock(__m) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_recursive_mutex_destroy(__libcpp_recursive_mutex_t *__m)
 {
   mtx_destroy(__m);
   return 0;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_mutex_lock(__libcpp_mutex_t *__m)
 {
   return mtx_lock(__m) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_mutex_trylock(__libcpp_mutex_t *__m)
 {
   return mtx_trylock(__m) == thrd_success;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_mutex_unlock(__libcpp_mutex_t *__m)
 {
   return mtx_unlock(__m) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_mutex_destroy(__libcpp_mutex_t *__m)
 {
   mtx_destroy(__m);
@@ -523,21 +561,25 @@
 }
 
 // Condition Variable
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_signal(__libcpp_condvar_t *__cv)
 {
   return cnd_signal(__cv) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_broadcast(__libcpp_condvar_t *__cv)
 {
   return cnd_broadcast(__cv) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_wait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m)
 {
   return cnd_wait(__cv, __m) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
                                timespec *__ts)
 {
@@ -545,6 +587,7 @@
   return __ec == thrd_timedout ? ETIMEDOUT : __ec;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_condvar_destroy(__libcpp_condvar_t *__cv)
 {
   cnd_destroy(__cv);
@@ -552,6 +595,7 @@
 }
 
 // Execute once
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_execute_once(__libcpp_exec_once_flag *flag,
                           void (*init_routine)(void)) {
   ::call_once(flag, init_routine);
@@ -560,22 +604,26 @@
 
 // Thread id
 // Returns non-zero if the thread ids are equal, otherwise 0
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2)
 {
   return thrd_equal(t1, t2) != 0;
 }
 
 // Returns non-zero if t1 < t2, otherwise 0
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2)
 {
   return t1 < t2;
 }
 
 // Thread
+_LIBCPP_HIDE_FROM_ABI inline
 bool __libcpp_thread_isnull(const __libcpp_thread_t *__t) {
   return __libcpp_thread_get_id(__t) == 0;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
                            void *__arg)
 {
@@ -583,31 +631,37 @@
   return __ec == thrd_nomem ? ENOMEM : __ec;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 __libcpp_thread_id __libcpp_thread_get_current_id()
 {
   return thrd_current();
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 __libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t)
 {
   return *__t;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_thread_join(__libcpp_thread_t *__t)
 {
   return thrd_join(*__t, nullptr) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_thread_detach(__libcpp_thread_t *__t)
 {
   return thrd_detach(*__t) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 void __libcpp_thread_yield()
 {
   thrd_yield();
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns)
 {
    __libcpp_timespec_t __ts = __thread_detail::__convert_to_timespec(__ns);
@@ -615,16 +669,19 @@
 }
 
 // Thread local storage
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_tls_create(__libcpp_tls_key *__key, void (*__at_exit)(void *))
 {
   return tss_create(__key, __at_exit) == thrd_success ? 0 : EINVAL;
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 void *__libcpp_tls_get(__libcpp_tls_key __key)
 {
   return tss_get(__key);
 }
 
+_LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
 {
   return tss_set(__key, __p) == thrd_success ? 0 : EINVAL;