[PATCH] D21827: [CMake] Make -fmodules-local-submodule-visibility optional.

[Adrian Prantl via llvm-commits]

aprantl created this revision.
aprantl added reviewers: bruno, rsmith, beanz.
aprantl added a subscriber: llvm-commits.

On Darwin it is currently impossible to build LLVM with modules because the Darwin system module map is not compatible with -fmodules-local-submodule-visibility at this point in time.
This patch makes the flag optional and off by default on Darwin so it becomes possible to build LLVM with modules again.

http://reviews.llvm.org/D21827

Files:
  CMakeLists.txt
  cmake/modules/HandleLLVMOptions.cmake

Index: cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- cmake/modules/HandleLLVMOptions.cmake
+++ cmake/modules/HandleLLVMOptions.cmake
@@ -463,9 +463,18 @@
       message(FATAL_ERROR "LLVM requires C++11 support but the '-std=c++11' flag isn't supported.")
     endif()
   endif()
+
   if (LLVM_ENABLE_MODULES)
     set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
-    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fmodules -Xclang -fmodules-local-submodule-visibility -fmodules-cache-path=module.cache")
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fmodules -Xclang -fmodules-cache-path=module.cache")
+    if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+      # On Darwin -fmodules does not imply -fcxx-modules.
+      set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fcxx-modules")
+    endif()
+    if (LLVM_ENABLE_LOCAL_SUBMODULE_VISIBILITY)
+      set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fmodules-local-submodule-visibility")
+    endif()
+
     # Check that we can build code with modules enabled, and that repeatedly
     # including <cassert> still manages to respect NDEBUG properly.
     CHECK_CXX_SOURCE_COMPILES("#undef NDEBUG
@@ -476,7 +485,13 @@
                                CXX_SUPPORTS_MODULES)
     set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
     if (CXX_SUPPORTS_MODULES)
-      append_if(CXX_SUPPORTS_MODULES "-fmodules -Xclang -fmodules-local-submodule-visibility -fmodules-cache-path=module.cache" CMAKE_CXX_FLAGS)
+      append("-fmodules -Xclang -fmodules-cache-path=module.cache" CMAKE_CXX_FLAGS)
+      if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+        append("-fcxx-modules" CMAKE_CXX_FLAGS)
+      endif()
+      if (LLVM_ENABLE_LOCAL_SUBMODULE_VISIBILITY)
+        append("-fmodules-local-submodule-visibility" CMAKE_CXX_FLAGS)
+      endif()
     else()
       message(FATAL_ERROR "LLVM_ENABLE_MODULES is not supported by this compiler")
     endif()
Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -283,6 +283,11 @@
 option(LLVM_ENABLE_PIC "Build Position-Independent Code" ON)
 option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." ON)
 option(LLVM_ENABLE_MODULES "Compile with C++ modules enabled." OFF)
+if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+  option(LLVM_ENABLE_LOCAL_SUBMODULE_VISIBILITY "Compile with -fmodules-local-submodule-visibility." OFF)
+else()
+  option(LLVM_ENABLE_LOCAL_SUBMODULE_VISIBILITY "Compile with -fmodules-local-submodule-visibility." ON)
+endif()
 option(LLVM_ENABLE_CXX1Y "Compile with C++1y enabled." OFF)
 option(LLVM_ENABLE_LIBCXX "Use libc++ if available." OFF)
 option(LLVM_ENABLE_LIBCXXABI "Use libc++abi when using libc++." OFF)


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