[libcxx] Introduce an externally-threaded libc++ variant.
This patch further decouples libc++ from pthread, allowing libc++ to be built
against other threading systems. There are two main use cases:
- Building libc++ against a thread library other than pthreads.
- Building libc++ with an "external" thread API, allowing a separate library to
provide the implementation of that API.
The two use cases are quite similar, the second one being sligtly more
de-coupled than the first. The cmake option LIBCXX_HAS_EXTERNAL_THREAD_API
enables both kinds of builds. One needs to place an <__external_threading>
header file containing an implementation of the "libc++ thread API" declared
in the <__threading_support> header.
For the second use case, the implementation of the libc++ thread API can
delegate to a custom "external" thread API where the implementation of this
external API is provided in a seperate library. This mechanism allows toolchain
vendors to distribute a build of libc++ with a custom thread-porting-layer API
(which is the "external" API above), platform vendors (recipients of the
toolchain/libc++) are then required to provide their implementation of this API
to be linked with (end-user) C++ programs.
Note that the second use case still requires establishing the basic types that
get passed between the external thread library and the libc++ library
(e.g. __libcpp_mutex_t). These cannot be opaque pointer types (libc++ sources
won't compile otherwise). It should also be noted that the second use case can
have a slight performance penalty; as all the thread constructs need to cross a
library boundary through an additional function call.
When the header <__external_threading> is omitted, libc++ is built with the
"libc++ thread API" (declared in <__threading_support>) as the "external" thread
API (basic types are pthread based). An implementation (pthread based) of this
API is provided in test/support/external_threads.cpp, which is built into a
separate DSO and linked in when running the libc++ test suite. A test run
therefore demonstrates the second use case (less the intermediate custom API).
Differential revision: https://reviews.llvm.org/D21968
Reviewers: bcraig, compnerd, EricWF, mclow.lists
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@281179 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index da68c59..c139174 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -140,6 +140,9 @@
This option may only be set to OFF when LIBCXX_ENABLE_THREADS=OFF." ON)
option(LIBCXX_HAS_MUSL_LIBC "Build libc++ with support for the Musl C library" OFF)
option(LIBCXX_HAS_PTHREAD_API "Ignore auto-detection and force use of pthread API" OFF)
+option(LIBCXX_HAS_EXTERNAL_THREAD_API
+ "Build libc++ with an externalized threading API.
+ This option may only be set to ON when LIBCXX_ENABLE_THREADS=ON." OFF)
# Misc options ----------------------------------------------------------------
# FIXME: Turn -pedantic back ON. It is currently off because it warns
@@ -197,6 +200,11 @@
" when LIBCXX_ENABLE_THREADS is also set to ON.")
endif()
+if(LIBCXX_HAS_EXTERNAL_THREAD_API AND NOT LIBCXX_ENABLE_THREADS)
+ message(FATAL_ERROR "LIBCXX_HAS_EXTERNAL_THREAD_API can only be set to ON"
+ " when LIBCXX_ENABLE_THREADS is also set to ON.")
+endif()
+
# Ensure LLVM_USE_SANITIZER is not specified when LIBCXX_GENERATE_COVERAGE
# is ON.
if (LLVM_USE_SANITIZER AND LIBCXX_GENERATE_COVERAGE)
@@ -371,6 +379,17 @@
add_compile_flags_if_supported(-fno-rtti)
endif()
+# Threading flags =============================================================
+if (LIBCXX_HAS_EXTERNAL_THREAD_API AND LIBCXX_ENABLE_SHARED)
+ # Need to allow unresolved symbols if this is to work with shared library builds
+ if (APPLE)
+ add_link_flags("-undefined dynamic_lookup")
+ else()
+ # Relax this restriction from HandleLLVMOptions
+ string(REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
+ endif()
+endif()
+
# Assertion flags =============================================================
define_if(LIBCXX_ENABLE_ASSERTIONS -UNDEBUG)
define_if_not(LIBCXX_ENABLE_ASSERTIONS -DNDEBUG)
@@ -432,6 +451,7 @@
config_define_if_not(LIBCXX_ENABLE_THREAD_UNSAFE_C_FUNCTIONS _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS)
config_define_if(LIBCXX_HAS_PTHREAD_API _LIBCPP_HAS_THREAD_API_PTHREAD)
+config_define_if(LIBCXX_HAS_EXTERNAL_THREAD_API _LIBCPP_HAS_THREAD_API_EXTERNAL)
config_define_if(LIBCXX_HAS_MUSL_LIBC _LIBCPP_HAS_MUSL_LIBC)
if (LIBCXX_NEEDS_SITE_CONFIG)
diff --git a/include/__config b/include/__config
index b462191..c4e1101 100644
--- a/include/__config
+++ b/include/__config
@@ -831,7 +831,9 @@
#endif
// Thread API
-#if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+#if !defined(_LIBCPP_HAS_NO_THREADS) && \
+ !defined(_LIBCPP_HAS_THREAD_API_PTHREAD) && \
+ !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
# if defined(__FreeBSD__) || \
defined(__NetBSD__) || \
defined(__linux__) || \
@@ -849,6 +851,11 @@
_LIBCPP_HAS_NO_THREADS is not defined.
#endif
+#if defined(_LIBCPP_HAS_NO_THREADS) && defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+# error _LIBCPP_HAS_EXTERNAL_THREAD_API may not be defined when \
+ _LIBCPP_HAS_NO_THREADS is defined.
+#endif
+
#if defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK) && !defined(_LIBCPP_HAS_NO_THREADS)
# error _LIBCPP_HAS_NO_MONOTONIC_CLOCK may only be defined when \
_LIBCPP_HAS_NO_THREADS is defined.
diff --git a/include/__config_site.in b/include/__config_site.in
index 6c2b7bb..dce30bc 100644
--- a/include/__config_site.in
+++ b/include/__config_site.in
@@ -20,5 +20,6 @@
#cmakedefine _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
#cmakedefine _LIBCPP_HAS_MUSL_LIBC
#cmakedefine _LIBCPP_HAS_THREAD_API_PTHREAD
+#cmakedefine _LIBCPP_HAS_THREAD_API_EXTERNAL
#endif // _LIBCPP_CONFIG_SITE
diff --git a/include/__threading_support b/include/__threading_support
index c9a4ea9..b36a52e 100644
--- a/include/__threading_support
+++ b/include/__threading_support
@@ -19,20 +19,83 @@
#ifndef _LIBCPP_HAS_NO_THREADS
-#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL) && (!defined(__has_include) || __has_include(<__external_threading>))
+#include <__external_threading>
+#else
#include <pthread.h>
#include <sched.h>
#endif
+#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+#define _LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_FUNC_VIS
+#else
+#define _LIBCPP_THREAD_ABI_VISIBILITY inline _LIBCPP_INLINE_VISIBILITY
+#endif
+
_LIBCPP_BEGIN_NAMESPACE_STD
-#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
-
// Mutex
-#define _LIBCPP_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
typedef pthread_mutex_t __libcpp_mutex_t;
+#define _LIBCPP_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
-inline _LIBCPP_ALWAYS_INLINE
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_recursive_mutex_init(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_lock(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_trylock(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_unlock(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_destroy(__libcpp_mutex_t* __m);
+
+// Condition variable
+typedef pthread_cond_t __libcpp_condvar_t;
+#define _LIBCPP_CONDVAR_INITIALIZER PTHREAD_COND_INITIALIZER
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_signal(__libcpp_condvar_t* __cv);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_broadcast(__libcpp_condvar_t* __cv);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_wait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_timedwait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m, timespec* __ts);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_destroy(__libcpp_condvar_t* __cv);
+
+// Thread id
+typedef pthread_t __libcpp_thread_id;
+_LIBCPP_THREAD_ABI_VISIBILITY
+bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2);
+_LIBCPP_THREAD_ABI_VISIBILITY
+bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2);
+
+// Thread
+typedef pthread_t __libcpp_thread_t;
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_create(__libcpp_thread_t* __t, void* (*__func)(void*), void* __arg);
+_LIBCPP_THREAD_ABI_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_current_id();
+_LIBCPP_THREAD_ABI_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t* __t);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_join(__libcpp_thread_t* __t);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_detach(__libcpp_thread_t* __t);
+_LIBCPP_THREAD_ABI_VISIBILITY
+void __libcpp_thread_yield();
+
+// Thread local storage
+typedef pthread_key_t __libcpp_tls_key;
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_tls_create(__libcpp_tls_key* __key, void (*__at_exit)(void*));
+_LIBCPP_THREAD_ABI_VISIBILITY
+void* __libcpp_tls_get(__libcpp_tls_key __key);
+_LIBCPP_THREAD_ABI_VISIBILITY
+void __libcpp_tls_set(__libcpp_tls_key __key, void* __p);
+
+#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD) || defined(_LIBCPP_BUILDING_EXTERNAL_THREADS)
+
int __libcpp_recursive_mutex_init(__libcpp_mutex_t* __m)
{
pthread_mutexattr_t attr;
@@ -59,144 +122,112 @@
return 0;
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_lock(__libcpp_mutex_t* __m)
{
return pthread_mutex_lock(__m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_trylock(__libcpp_mutex_t* __m)
{
return pthread_mutex_trylock(__m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_unlock(__libcpp_mutex_t* __m)
{
return pthread_mutex_unlock(__m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_destroy(__libcpp_mutex_t* __m)
{
return pthread_mutex_destroy(__m);
}
// Condition variable
-#define _LIBCPP_CONDVAR_INITIALIZER PTHREAD_COND_INITIALIZER
-typedef pthread_cond_t __libcpp_condvar_t;
-
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_signal(__libcpp_condvar_t* __cv)
{
return pthread_cond_signal(__cv);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_broadcast(__libcpp_condvar_t* __cv)
{
return pthread_cond_broadcast(__cv);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_wait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m)
{
return pthread_cond_wait(__cv, __m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_timedwait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m, timespec* __ts)
{
return pthread_cond_timedwait(__cv, __m, __ts);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_destroy(__libcpp_condvar_t* __cv)
{
return pthread_cond_destroy(__cv);
}
-// Thread id
-typedef pthread_t __libcpp_thread_id;
-
// Returns non-zero if the thread ids are equal, otherwise 0
-inline _LIBCPP_ALWAYS_INLINE
bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2)
{
return pthread_equal(t1, t2) != 0;
}
// Returns non-zero if t1 < t2, otherwise 0
-inline _LIBCPP_ALWAYS_INLINE
bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2)
{
return t1 < t2;
}
// Thread
-typedef pthread_t __libcpp_thread_t;
-
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_thread_create(__libcpp_thread_t* __t, void* (*__func)(void*), void* __arg)
{
return pthread_create(__t, 0, __func, __arg);
}
-inline _LIBCPP_ALWAYS_INLINE
__libcpp_thread_id __libcpp_thread_get_current_id()
{
return pthread_self();
}
-inline _LIBCPP_ALWAYS_INLINE
__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t* __t)
{
return *__t;
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_thread_join(__libcpp_thread_t* __t)
{
return pthread_join(*__t, 0);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_thread_detach(__libcpp_thread_t* __t)
{
return pthread_detach(*__t);
}
-inline _LIBCPP_ALWAYS_INLINE
void __libcpp_thread_yield()
{
sched_yield();
}
// Thread local storage
-typedef pthread_key_t __libcpp_tl_key;
-
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_tl_create(__libcpp_tl_key* __key, void (*__at_exit)(void*))
+int __libcpp_tls_create(__libcpp_tls_key* __key, void (*__at_exit)(void*))
{
return pthread_key_create(__key, __at_exit);
}
-inline _LIBCPP_ALWAYS_INLINE
-void* __libcpp_tl_get(__libcpp_tl_key __key)
+void* __libcpp_tls_get(__libcpp_tls_key __key)
{
return pthread_getspecific(__key);
}
-inline _LIBCPP_ALWAYS_INLINE
-void __libcpp_tl_set(__libcpp_tl_key __key, void* __p)
+void __libcpp_tls_set(__libcpp_tls_key __key, void* __p)
{
pthread_setspecific(__key, __p);
}
-#else // !_LIBCPP_HAS_THREAD_API_PTHREAD
- #error "No thread API selected."
-#endif
+#endif // _LIBCPP_HAS_THREAD_API_PTHREAD || _LIBCPP_BUILDING_EXTERNAL_THREADS
_LIBCPP_END_NAMESPACE_STD
diff --git a/include/thread b/include/thread
index 21cc761..7fe4c77 100644
--- a/include/thread
+++ b/include/thread
@@ -137,7 +137,7 @@
template <class _Tp>
class __thread_specific_ptr
{
- __libcpp_tl_key __key_;
+ __libcpp_tls_key __key_;
// Only __thread_local_data() may construct a __thread_specific_ptr
// and only with _Tp == __thread_struct.
@@ -155,7 +155,7 @@
~__thread_specific_ptr();
_LIBCPP_INLINE_VISIBILITY
- pointer get() const {return static_cast<_Tp*>(__libcpp_tl_get(__key_));}
+ pointer get() const {return static_cast<_Tp*>(__libcpp_tls_get(__key_));}
_LIBCPP_INLINE_VISIBILITY
pointer operator*() const {return *get();}
_LIBCPP_INLINE_VISIBILITY
@@ -173,7 +173,7 @@
template <class _Tp>
__thread_specific_ptr<_Tp>::__thread_specific_ptr()
{
- int __ec = __libcpp_tl_create(
+ int __ec = __libcpp_tls_create(
&__key_,
&__thread_specific_ptr::__at_thread_exit);
if (__ec)
@@ -196,7 +196,7 @@
{
_LIBCPP_ASSERT(get() == nullptr,
"Attempting to overwrite thread local data");
- __libcpp_tl_set(__key_, __p);
+ __libcpp_tls_set(__key_, __p);
}
class _LIBCPP_TYPE_VIS thread;
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index dd0f663..8ebda51 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -201,6 +201,23 @@
)
endif()
+if (LIBCXX_HAS_EXTERNAL_THREAD_API)
+ file(GLOB LIBCXX_EXTERNAL_THREADING_SUPPORT_SOURCES ../test/support/external_threads.cpp)
+
+ if (LIBCXX_ENABLE_SHARED)
+ add_library(cxx_external_threads SHARED ${LIBCXX_EXTERNAL_THREADING_SUPPORT_SOURCES})
+ else()
+ add_library(cxx_external_threads STATIC ${LIBCXX_EXTERNAL_THREADING_SUPPORT_SOURCES})
+ endif()
+
+ set_target_properties(cxx_external_threads
+ PROPERTIES
+ LINK_FLAGS "${LIBCXX_LINK_FLAGS}"
+ COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
+ OUTPUT_NAME "c++external_threads"
+ )
+endif()
+
# Generate a linker script inplace of a libc++.so symlink. Rerun this command
# after cxx builds.
if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index ed6f20d..d9be0df 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -22,6 +22,7 @@
pythonize_bool(LIBCXXABI_USE_LLVM_UNWINDER)
pythonize_bool(LIBCXX_HAS_ATOMIC_LIB)
pythonize_bool(LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB)
+pythonize_bool(LIBCXX_HAS_EXTERNAL_THREAD_API)
# The tests shouldn't link to any ABI library when it has been linked into
# libc++ statically or via a linker script.
@@ -52,10 +53,14 @@
set(experimental_dep cxx_experimental)
endif()
+if (LIBCXX_HAS_EXTERNAL_THREAD_API)
+ set(external_threads_dep cxx_external_threads)
+endif()
+
add_lit_testsuite(check-cxx
"Running libcxx tests"
${CMAKE_CURRENT_BINARY_DIR}
- DEPENDS cxx ${experimental_dep})
+ DEPENDS cxx ${experimental_dep} ${external_threads_dep})
add_custom_target(check-libcxx DEPENDS check-cxx)
diff --git a/test/libcxx/test/config.py b/test/libcxx/test/config.py
index 579089a..70f2094 100644
--- a/test/libcxx/test/config.py
+++ b/test/libcxx/test/config.py
@@ -510,6 +510,10 @@
self.cxx.link_flags += [abs_path]
else:
self.cxx.link_flags += ['-lc++']
+ # This needs to come after -lc++ as we want its unresolved thread-api symbols
+ # to be picked up from this one.
+ if self.get_lit_bool('libcxx_external_thread_api', default=False):
+ self.cxx.link_flags += ['-lc++external_threads']
def configure_link_flags_abi_library(self):
cxx_abi = self.get_lit_conf('cxx_abi', 'libcxxabi')
diff --git a/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp b/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp
index bf28e01..6ebba14 100644
--- a/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp
+++ b/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <condition_variable>
diff --git a/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp b/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp
index 12c80f0..c6ed66c 100644
--- a/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp
+++ b/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <mutex>
diff --git a/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp b/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp
index 10626bc..2031e4d 100644
--- a/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp
+++ b/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <mutex>
diff --git a/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp b/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp
index c8807a9..1b1cbf8 100644
--- a/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp
+++ b/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <thread>
diff --git a/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp b/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp
index a5bf770..e864af7 100644
--- a/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp
+++ b/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <thread>
diff --git a/test/lit.site.cfg.in b/test/lit.site.cfg.in
index a1ae90c..943c840 100644
--- a/test/lit.site.cfg.in
+++ b/test/lit.site.cfg.in
@@ -26,6 +26,7 @@
config.use_libatomic = "@LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB@"
config.libcxxabi_shared = "@LIBCXXABI_ENABLE_SHARED@"
+config.libcxx_external_thread_api = "@LIBCXX_HAS_EXTERNAL_THREAD_API@"
# Let the main config do the real work.
lit_config.load_config(config, "@LIBCXX_SOURCE_DIR@/test/lit.cfg")
diff --git a/test/support/external_threads.cpp b/test/support/external_threads.cpp
new file mode 100644
index 0000000..381ec65
--- /dev/null
+++ b/test/support/external_threads.cpp
@@ -0,0 +1,10 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#define _LIBCPP_BUILDING_EXTERNAL_THREADS
+#include <__threading_support>