From eaca1e4e54905815b444e1234096c70adc9812f6 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne@apple.com>
Date: Tue, 14 Jul 2020 16:28:41 -0400
Subject: [PATCH] [libc++] Automatically detect whether RTTI is enabled

Instead of detecting it automatically but also allowing for the setting
to be specified explicitly, always detect whether exceptions are enabled
based on whether -fno-rtti (or equivalent) is used. It's less confusing
to have a single way of tweaking that knob.

This change follows the lead of 71d88cebfb42.
---
 libcxx/CMakeLists.txt                       |  1 -
 libcxx/include/__config                     | 17 ++++++-----------
 libcxx/utils/libcxx/test/config.py          |  2 +-
 llvm/utils/gn/secondary/libcxx/src/BUILD.gn |  1 -
 4 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 88dc4553069e..aabe31fa6ec1 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -639,7 +639,6 @@ endfunction()
 # RTTI flags ==================================================================
 function(cxx_add_rtti_flags target)
   if (NOT LIBCXX_ENABLE_RTTI)
-    target_compile_definitions(${target} PUBLIC -D_LIBCPP_NO_RTTI)
     target_add_compile_flags_if_supported(${target} PUBLIC -GR-)
     target_add_compile_flags_if_supported(${target} PUBLIC -fno-rtti)
   endif()
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 7e4c37431ea4..575147cead42 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -423,10 +423,6 @@ typedef __char32_t char32_t;
 #  define _LIBCPP_NO_EXCEPTIONS
 #endif
 
-#if !(__has_feature(cxx_rtti)) && !defined(_LIBCPP_NO_RTTI)
-#define _LIBCPP_NO_RTTI
-#endif
-
 #if !(__has_feature(cxx_strong_enums))
 #define _LIBCPP_HAS_NO_STRONG_ENUMS
 #endif
@@ -1109,13 +1105,12 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #endif
 
 // Try to find out if RTTI is disabled.
-// g++ and cl.exe have RTTI on by default and define a macro when it is.
-#if !defined(_LIBCPP_NO_RTTI)
-#  if defined(__GNUC__) && !defined(__GXX_RTTI)
-#    define _LIBCPP_NO_RTTI
-#  elif defined(_LIBCPP_COMPILER_MSVC) && !defined(_CPPRTTI)
-#    define _LIBCPP_NO_RTTI
-#  endif
+#if defined(_LIBCPP_COMPILER_CLANG) && !__has_feature(cxx_rtti)
+#  define _LIBCPP_NO_RTTI
+#elif defined(__GNUC__) && !defined(__GXX_RTTI)
+#  define _LIBCPP_NO_RTTI
+#elif defined(_LIBCPP_COMPILER_MSVC) && !defined(_CPPRTTI)
+#  define _LIBCPP_NO_RTTI
 #endif
 
 #ifndef _LIBCPP_WEAK
diff --git a/libcxx/utils/libcxx/test/config.py b/libcxx/utils/libcxx/test/config.py
index 99a966dbfdfd..b88b085d408f 100644
--- a/libcxx/utils/libcxx/test/config.py
+++ b/libcxx/utils/libcxx/test/config.py
@@ -410,7 +410,7 @@ class Configuration(object):
         enable_rtti = self.get_lit_bool('enable_rtti', True)
         if not enable_rtti:
             self.config.available_features.add('-fno-rtti')
-            self.cxx.compile_flags += ['-fno-rtti', '-D_LIBCPP_NO_RTTI']
+            self.cxx.compile_flags += ['-fno-rtti']
 
     def configure_link_flags(self):
         # Configure library path
diff --git a/llvm/utils/gn/secondary/libcxx/src/BUILD.gn b/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
index 1c52d341ec82..09d850036ad1 100644
--- a/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
@@ -102,7 +102,6 @@ config("cxx_config") {
     } else {
       cflags_cc += [ "-fno-rtti" ]
     }
-    defines += [ "_LIBCPP_NO_RTTI" ]
   }
 }
 
-- 
2.34.1