[libc++] Use a function to set warning flags per target

This is part of a larger shift to move to per-target settings and
eradicate global variables from the CMake build. I'm starting small
with warnings only because those are easy to transition over and I
want to see how it pans out, but we can handle all flags like exceptions
and RTTI in the future.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@373511 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -568,19 +568,19 @@ if (LIBCXX_HAS_COMMENT_LIB_PRAGMA)
 endif()
 
 # Warning flags ===============================================================
-add_definitions(-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-add_compile_flags_if_supported(
-    -Wall -Wextra -W -Wwrite-strings
-    -Wno-unused-parameter -Wno-long-long
-    -Werror=return-type -Wextra-semi)
-if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
-    add_compile_flags_if_supported(
-        -Wno-user-defined-literals
-        -Wno-covered-switch-default
-        -Wno-ignored-attributes # FIXME: Caused by _LIBCPP_NODEBUG_TYPE not being supported on older clangs
-        )
+function(cxx_add_warning_flags target)
+  target_compile_definitions(${target} PUBLIC -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+  target_add_compile_flags_if_supported(${target} PRIVATE -Wall -Wextra -W -Wwrite-strings
+                                                          -Wno-unused-parameter -Wno-long-long
+                                                          -Werror=return-type -Wextra-semi)
+  if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+    target_add_compile_flags_if_supported(${target} PRIVATE
+      -Wno-user-defined-literals
+      -Wno-covered-switch-default
+      -Wno-ignored-attributes # FIXME: Caused by _LIBCPP_NODEBUG_TYPE not being supported on older clangs
+    )
     if (LIBCXX_TARGETING_CLANG_CL)
-      add_compile_flags_if_supported(
+      target_add_compile_flags_if_supported(${target} PRIVATE
         -Wno-c++98-compat
         -Wno-c++98-compat-pedantic
         -Wno-c++11-compat
@@ -597,26 +597,27 @@ if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
         -Wno-double-promotion # FIXME: remove me
       )
     endif()
-elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
-    add_compile_flags_if_supported(
-        -Wno-literal-suffix
-        -Wno-c++14-compat
-        -Wno-noexcept-type)
-endif()
-if (LIBCXX_ENABLE_WERROR)
-  add_compile_flags_if_supported(-Werror)
-  add_compile_flags_if_supported(-WX)
-else()
-  # TODO(EricWF) Remove this. We shouldn't be suppressing errors when -Werror is
-  # added elsewhere.
-  add_compile_flags_if_supported(-Wno-error)
-endif()
-if (LIBCXX_ENABLE_PEDANTIC)
-  add_compile_flags_if_supported(-pedantic)
-endif()
-if (LIBCXX_DISABLE_MACRO_CONFLICT_WARNINGS)
-  add_definitions(-D_LIBCPP_DISABLE_MACRO_CONFLICT_WARNINGS)
-endif()
+  elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
+    target_add_compile_flags_if_supported(${target} PRIVATE
+      -Wno-literal-suffix
+      -Wno-c++14-compat
+      -Wno-noexcept-type)
+  endif()
+  if (LIBCXX_ENABLE_WERROR)
+    target_add_compile_flags_if_supported(${target} PRIVATE -Werror)
+    target_add_compile_flags_if_supported(${target} PRIVATE -WX)
+  else()
+    # TODO(EricWF) Remove this. We shouldn't be suppressing errors when -Werror is
+    # added elsewhere.
+    target_add_compile_flags_if_supported(${target} PRIVATE -Wno-error)
+  endif()
+  if (LIBCXX_ENABLE_PEDANTIC)
+    target_add_compile_flags_if_supported(${target} PRIVATE -pedantic)
+  endif()
+  if (LIBCXX_DISABLE_MACRO_CONFLICT_WARNINGS)
+    target_compile_definitions(${target} PRIVATE -D_LIBCPP_DISABLE_MACRO_CONFLICT_WARNINGS)
+  endif()
+endfunction()
 
 # Exception flags =============================================================
 if (LIBCXX_ENABLE_EXCEPTIONS)

src/CMakeLists.txt

@@ -260,6 +260,7 @@ if (LIBCXX_ENABLE_SHARED)
       DEFINE_SYMBOL ""
   )
   cxx_set_common_defines(cxx_shared)
+  cxx_add_warning_flags(cxx_shared)
 
   # Link against LLVM libunwind
   if (LIBCXXABI_USE_LLVM_UNWINDER)
@@ -360,6 +361,7 @@ if (LIBCXX_ENABLE_STATIC)
       OUTPUT_NAME   "c++"
   )
   cxx_set_common_defines(cxx_static)
+  cxx_add_warning_flags(cxx_static)
 
   if (LIBCXX_HERMETIC_STATIC_LIBRARY)
     # If the hermetic library doesn't define the operator new/delete functions