Fix libcxx build with MinGW winpthreads

[SquallATF]

Summary

1. winpthreads build broken after D42214, should not build thread_win32.cpp when enable pthread witht MinGW.
2. _LIBCPP_SAFE_STATIC incompatible with winpthreads, because winpthread PTHREAD_*_INITIALIZER use reinterpret_cast are not const.

[mclow.lists]

include/__config

1228 ↗

(On Diff #170802)

I think you want to look at line #1155, and see if _LIBCPP_HAS_THREAD_API_WIN32 is the condition you want here.

[EricWF]

_LIBCPP_SAFE_STATIC incompatible with winpthreads, because winpthread PTHREAD_*_INITIALIZER use reinterpret_cast are not const.

winpthread PTHREAD_*_INITIALIZER is incompatible with the POSIX specification for PTHREAD_*_INITIALIZER. If we need to work around that, then fine, but it causes mutex to become really dangerous.

this is a bug in winpthreads and they should fix it.

include/__config

1228 ↗

(On Diff #170802)

This change is *not* OK.

You want to disable the application of this macro only in the specific case that's giving you problems, not generally.

[SquallATF]

• I created a patch to MinGW winpthreads, remove _LIBCPP_SAFE_STATIC winpthread block

[EricWF]

LGTM. Thanks for the patch.

[mati865]

Can somebody land it before LLVM 8 is branched? Patch author does not have commit access.

Thanks in advance.

[mgorny]

I'm sorry that nobody has replied to your request earlier. AFAICS the libcxx code has changed. Does it work now, or do we need to make thread_win32.cpp conditional to LIBCXX_HAS_WIN32_THREAD_API still?

lib/CMakeLists.txt

 set(LIBCXX_LIB_CMAKEFILES_DIR "${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}"  PARENT_SCOPE)
 
 # Get sources
 # FIXME: Don't use glob here
 file(GLOB LIBCXX_SOURCES ../src/*.cpp)
 if(WIN32)
-  file(GLOB LIBCXX_WIN32_SOURCES ../src/support/win32/*.cpp)
+  set(LIBCXX_WIN32_SOURCES
+    ../src/support/win32/locale_win32.cpp
+    ../src/support/win32/support.cpp
+  )
+  if(LIBCXX_HAS_WIN32_THREAD_API)
+    list(APPEND LIBCXX_WIN32_SOURCES ../src/support/win32/thread_win32.cpp)
+  endif()
   list(APPEND LIBCXX_SOURCES ${LIBCXX_WIN32_SOURCES})
 elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "SunOS")
   file(GLOB LIBCXX_SOLARIS_SOURCES ../src/support/solaris/*.cpp)
   list(APPEND LIBCXX_SOURCES ${LIBCXX_SOLARIS_SOURCES})
 endif()
 
 # Add all the headers to the project for IDEs.
 if (LIBCXX_CONFIGURE_IDE)