From 84be76133282f8bd66820ca93402a741c0ee632e Mon Sep 17 00:00:00 2001
From: Eric Fiselier <eric@efcs.ca>
Date: Thu, 7 Jun 2018 19:57:43 +0000
Subject: [PATCH] [CMake] Fix Libc++ Modules build.

When building the dylib, the C++ headers are fundamentally non-module.
They require special versions of the headers in order to provide C++03 and
legacy ABI definitions. This causes ODR issues when modules are enabled
during both the build and the usage of the libc++ headers.

This patch fixes the build error by disabling modules when building the
libc++ sources.

llvm-svn: 334220
---
 compiler-rt/cmake/Modules/AddCompilerRT.cmake | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/compiler-rt/cmake/Modules/AddCompilerRT.cmake b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
index 8338eb3406a4..380a4a372d0c 100644
--- a/compiler-rt/cmake/Modules/AddCompilerRT.cmake
+++ b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
@@ -537,6 +537,14 @@ macro(add_custom_libcxx name prefix)
   string(REPLACE "-Wl,-z,defs" "" LIBCXX_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS}")
   string(REPLACE "-Wl,-z,defs" "" LIBCXX_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
 
+  # The libc++ sources are fundamentally non-modular. They need special
+  # versions of the headers in order to provide C++03 and legacy ABI definitions.
+  # NOTE: The public headers can be used with modules in all other contexts
+  if (LLVM_ENABLE_MODULES)
+    set(LIBCXX_CXX_FLAGS "${LIBCXX_CXX_FLAGS} -Wno-unused-command-line-argument")
+    set(LIBCXX_CXX_FLAGS "${LIBCXX_CXX_FLAGS} -fno-modules")
+  endif()
+
   ExternalProject_Add(${name}
     DEPENDS ${name}-clobber ${LIBCXX_DEPS}
     PREFIX ${prefix}