From 36d0ee6c87d3a32a3bd406806e330b13a6ce3133 Mon Sep 17 00:00:00 2001
From: Shoaib Meenai <smeenai@fb.com>
Date: Wed, 4 Oct 2017 23:44:38 +0000
Subject: [libc++] Allow users to explicitly specify ABI

libc++'s current heuristic for detecting Itanium vs. Microsoft ABI falls
short in some cases. For example, it will detect windows-itanium targets
as using the Microsoft ABI, since they set `_MSC_VER` (for compatibility
with Microsoft headers). Leave the current heuristic in place by default
but also allow users to explicitly specify the ABI if need be.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@314949 91177308-0d34-0410-b5e6-96231b3b80d8
---
 CMakeLists.txt           |  8 ++++++++
 include/__config         | 14 +++++++++-----
 include/__config_site.in |  2 ++
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6b111a871..ccf4b969b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -99,6 +99,8 @@ cmake_dependent_option(LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY
         "LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY;LIBCXX_INSTALL_LIBRARY" OFF)
 set(LIBCXX_ABI_VERSION 1 CACHE STRING "ABI version of libc++.")
 option(LIBCXX_ABI_UNSTABLE "Unstable ABI of libc++." OFF)
+option(LIBCXX_ABI_ITANIUM "Ignore auto-detection and force use of the Itanium ABI.")
+option(LIBCXX_ABI_MICROSOFT "Ignore auto-detection and force use of the Microsoft ABI.")
 option(LIBCXX_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
 
 if (NOT LIBCXX_ENABLE_SHARED AND NOT LIBCXX_ENABLE_STATIC)
@@ -337,6 +339,10 @@ if (LIBCXX_HAS_MUSL_LIBC AND NOT LIBCXX_INSTALL_SUPPORT_HEADERS)
                       "when building for Musl with LIBCXX_HAS_MUSL_LIBC.")
 endif()
 
+if (LIBCXX_ABI_ITANIUM AND LIBCXX_ABI_MICROSOFT)
+  message(FATAL_ERROR "Only one of LIBCXX_ABI_ITANIUM and LIBCXX_ABI_MICROSOFT can be specified.")
+endif ()
+
 #===============================================================================
 # Configure System
 #===============================================================================
@@ -594,6 +600,8 @@ if (NOT LIBCXX_ABI_VERSION EQUAL "1")
   config_define(${LIBCXX_ABI_VERSION} _LIBCPP_ABI_VERSION)
 endif()
 config_define_if(LIBCXX_ABI_UNSTABLE _LIBCPP_ABI_UNSTABLE)
+config_define_if(LIBCXX_ABI_ITANIUM _LIBCPP_ABI_ITANIUM)
+config_define_if(LIBCXX_ABI_MICROSOFT _LIBCPP_ABI_MICROSOFT)
 
 config_define_if_not(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE)
 config_define_if_not(LIBCXX_ENABLE_STDIN _LIBCPP_HAS_NO_STDIN)
diff --git a/include/__config b/include/__config
index 8d0eeb2c9..ad34fcfab 100644
--- a/include/__config
+++ b/include/__config
@@ -157,11 +157,15 @@
 
 // FIXME: ABI detection should be done via compiler builtin macros. This
 // is just a placeholder until Clang implements such macros. For now assume
-// that Windows compilers pretending to be MSVC++ target the microsoft ABI.
-#if defined(_WIN32) && defined(_MSC_VER)
-# define _LIBCPP_ABI_MICROSOFT
-#else
-# define _LIBCPP_ABI_ITANIUM
+// that Windows compilers pretending to be MSVC++ target the Microsoft ABI,
+// and allow the user to explicitly specify the ABI to handle cases where this
+// heuristic falls short.
+#if !defined(_LIBCPP_ABI_ITANIUM) && !defined(_LIBCPP_ABI_MICROSOFT)
+# if defined(_WIN32) && defined(_MSC_VER)
+#  define _LIBCPP_ABI_MICROSOFT
+# else
+#  define _LIBCPP_ABI_ITANIUM
+# endif
 #endif
 
 // Need to detect which libc we're using if we're on Linux.
diff --git a/include/__config_site.in b/include/__config_site.in
index b8de0baf2..80360aa42 100644
--- a/include/__config_site.in
+++ b/include/__config_site.in
@@ -12,6 +12,8 @@
 
 #cmakedefine _LIBCPP_ABI_VERSION @_LIBCPP_ABI_VERSION@
 #cmakedefine _LIBCPP_ABI_UNSTABLE
+#cmakedefine _LIBCPP_ABI_ITANIUM
+#cmakedefine _LIBCPP_ABI_MICROSOFT
 #cmakedefine _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 #cmakedefine _LIBCPP_HAS_NO_STDIN
 #cmakedefine _LIBCPP_HAS_NO_STDOUT
-- 
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