[libcxx] [cmake] Add a config option LIBCXX_HAS_WIN32_THREADS for enforcing win32 threads

[mstorsjo]

Summary

This allows keeping libcxx using win32 threads even if a version of pthread.h is installed. This matches the existing cmake option LIBCXX_HAS_PTHREAD_API.

[smeenai]

I think LIBCXX_HAS_WIN32_THREAD_API would be more consistent with the existing configuration define names?

CMakeLists.txt

277 ↗

(On Diff #128734)

The inconsistent usage of if( vs if ( in this file is annoying me haha. Not this diff's fault of course, but still.

[mstorsjo]

In D41764#968318, @smeenai wrote:

I think LIBCXX_HAS_WIN32_THREAD_API would be more consistent with the existing configuration define names?

That sounds good to me too. I can update the patch later, or before committing if it's otherwise ok.

CMakeLists.txt

277 ↗

(On Diff #128734)

Oh, yes... The new lines here were copypasted from the pthread ones a bit further above, explaining the inconsistency.

[smeenai]

Can you add documentation for _LIBCPP_HAS_THREAD_API_WIN32 to docs/DesignDocs/ThreadingSupportAPI.rst? It should have been documented before, but this seems like a good opportunity to correct that.

LGTM with that and the rename.

libcxx/trunk/CMakeLists.txt

 option(LIBCXX_ENABLE_STDOUT "Build libc++ with support for stdout/std::cout." ON)
 option(LIBCXX_ENABLE_THREADS "Build libc++ with support for threads." ON)
 option(LIBCXX_ENABLE_THREAD_UNSAFE_C_FUNCTIONS "Build libc++ with support for thread-unsafe C functions" ON)
 option(LIBCXX_ENABLE_MONOTONIC_CLOCK
   "Build libc++ with support for a monotonic clock.
    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_WIN32_THREAD_API "Ignore auto-detection and force use of win32 thread 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)
 option(LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY
     "Build libc++ with an externalized threading library.
      This option may only be set to ON when LIBCXX_ENABLE_THREADS=ON" OFF)
 
 # Misc options ----------------------------------------------------------------
if(NOT LIBCXX_ENABLE_THREADS)
   if(LIBCXX_HAS_EXTERNAL_THREAD_API)
     message(FATAL_ERROR "LIBCXX_HAS_EXTERNAL_THREAD_API can only be set to ON"
                         " when LIBCXX_ENABLE_THREADS is also set to ON.")
   endif()
   if (LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY)
     message(FATAL_ERROR "LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY can only be set "
                         "to ON when LIBCXX_ENABLE_THREADS is also set to ON.")
   endif()
+  if (LIBCXX_HAS_WIN32_THREAD_API)
+    message(FATAL_ERROR "LIBCXX_HAS_WIN32_THREAD_API can only be set to ON"
+                        " when LIBCXX_ENABLE_THREADS is also set to ON.")
+  endif()
 
 endif()
 
 if (LIBCXX_HAS_EXTERNAL_THREAD_API)
   if (LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY)
     message(FATAL_ERROR "The options LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY and "
                         "LIBCXX_HAS_EXTERNAL_THREAD_API cannot both be ON at "
                         "the same time")
   endif()
   if (LIBCXX_HAS_PTHREAD_API)
     message(FATAL_ERROR "The options LIBCXX_HAS_EXTERNAL_THREAD_API"
                         "and LIBCXX_HAS_PTHREAD_API cannot be both"
                         "set to ON at the same time.")
   endif()
+  if (LIBCXX_HAS_WIN32_THREAD_API)
+    message(FATAL_ERROR "The options LIBCXX_HAS_EXTERNAL_THREAD_API"
+                        "and LIBCXX_HAS_WIN32_THREAD_API cannot be both"
+                        "set to ON at the same time.")
+  endif()
+endif()
+
+if (LIBCXX_HAS_PTHREAD_API)
+  if (LIBCXX_HAS_WIN32_THREAD_API)
+    message(FATAL_ERROR "The options LIBCXX_HAS_PTHREAD_API"
+                        "and LIBCXX_HAS_WIN32_THREAD_API cannot be both"
+                        "set to ON at the same time.")
+  endif()
 endif()
 
 # Ensure LLVM_USE_SANITIZER is not specified when LIBCXX_GENERATE_COVERAGE
 # is ON.
 if (LLVM_USE_SANITIZER AND LIBCXX_GENERATE_COVERAGE)
   message(FATAL_ERROR "LLVM_USE_SANITIZER cannot be used with LIBCXX_GENERATE_COVERAGE")
 endif()
 

 config_define_if_not(LIBCXX_ENABLE_STDIN _LIBCPP_HAS_NO_STDIN)
 config_define_if_not(LIBCXX_ENABLE_STDOUT _LIBCPP_HAS_NO_STDOUT)
 config_define_if_not(LIBCXX_ENABLE_THREADS _LIBCPP_HAS_NO_THREADS)
 config_define_if_not(LIBCXX_ENABLE_MONOTONIC_CLOCK _LIBCPP_HAS_NO_MONOTONIC_CLOCK)
 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_WIN32_THREAD_API _LIBCPP_HAS_THREAD_API_WIN32)
 config_define_if(LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL)
 config_define_if(LIBCXX_HAS_MUSL_LIBC _LIBCPP_HAS_MUSL_LIBC)
 config_define_if(LIBCXX_NO_VCRUNTIME _LIBCPP_NO_VCRUNTIME)
 
 if (LIBCXX_ABI_DEFINES)
   set(abi_defines)
   foreach (abi_define ${LIBCXX_ABI_DEFINES})
     if (NOT abi_define MATCHES "^_LIBCPP_ABI_")

libcxx/trunk/docs/DesignDocs/ThreadingSupportAPI.rst

**_LIBCPP_HAS_THREAD_API_EXTERNAL**
   This macro is defined when libc++ should use the ``<__external_threading>``
   header to provide the internal threading API. This macro overrides
   ``_LIBCPP_HAS_THREAD_API_PTHREAD``.
 
 **_LIBCPP_HAS_THREAD_API_PTHREAD**
   This macro is defined when libc++ should use POSIX threads to implement the
   internal threading API.
 
+**_LIBCPP_HAS_THREAD_API_WIN32**
+  This macro is defined when libc++ should use Win32 threads to implement the
+  internal threading API.
+
 **_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL**
   This macro is defined when libc++ expects the definitions of the internal
   threading API to be provided by an external library. When defined
   ``<__threading_support>`` will only provide the forward declarations and
   typedefs for the internal threading API.
 
 **_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL**
   This macro is used to build an external threading library using the
   ``<__threading_support>``. Specifically it exposes the threading API
   definitions in ``<__threading_support>`` as non-inline definitions meant to
   be compiled into a library.

libcxx/trunk/include/__config_site.in

 #cmakedefine _LIBCPP_HAS_NO_STDIN
 #cmakedefine _LIBCPP_HAS_NO_STDOUT
 #cmakedefine _LIBCPP_HAS_NO_THREADS
 #cmakedefine _LIBCPP_HAS_NO_MONOTONIC_CLOCK
 #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
+#cmakedefine _LIBCPP_HAS_THREAD_API_WIN32
 #cmakedefine _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL
 #cmakedefine _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
 #cmakedefine _LIBCPP_NO_VCRUNTIME
 
 @_LIBCPP_ABI_DEFINES@
 
 #endif // _LIBCPP_CONFIG_SITE