From a382216407036b10a5429441e101823a776f8caa Mon Sep 17 00:00:00 2001
From: Volodymyr Sapsai <vsapsai@apple.com>
Date: Tue, 8 May 2018 22:50:35 +0000
Subject: [PATCH] Revert "Emit an error when mixing <stdatomic.h> and <atomic>"

It reverts commit r331379 because turned out `__ALLOW_STDC_ATOMICS_IN_CXX__`
doesn't work well in practice.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@331818 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/atomic                               |  3 ---
 test/libcxx/atomics/c_compatibility.fail.cpp | 28 --------------------
 2 files changed, 31 deletions(-)
 delete mode 100644 test/libcxx/atomics/c_compatibility.fail.cpp

diff --git a/include/atomic b/include/atomic
index adffc354a..34a2a58b2 100644
--- a/include/atomic
+++ b/include/atomic
@@ -555,9 +555,6 @@ void atomic_signal_fence(memory_order m) noexcept;
 #if !defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_GCC_ATOMIC_IMP)
 #error <atomic> is not implemented
 #endif
-#ifdef __ALLOW_STDC_ATOMICS_IN_CXX__
-#error <stdatomic.h> is incompatible with the C++ standard library
-#endif
 
 #if _LIBCPP_STD_VER > 14
 # define __cpp_lib_atomic_is_always_lock_free 201603L
diff --git a/test/libcxx/atomics/c_compatibility.fail.cpp b/test/libcxx/atomics/c_compatibility.fail.cpp
deleted file mode 100644
index 092687d5b..000000000
--- a/test/libcxx/atomics/c_compatibility.fail.cpp
+++ /dev/null
@@ -1,28 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// UNSUPPORTED: libcpp-has-no-threads
-//
-// <atomic>
-
-// Test that including <atomic> fails to compile when we want to use C atomics
-// in C++ and have corresponding macro defined.
-
-// MODULES_DEFINES: __ALLOW_STDC_ATOMICS_IN_CXX__
-#ifndef __ALLOW_STDC_ATOMICS_IN_CXX__
-#define __ALLOW_STDC_ATOMICS_IN_CXX__
-#endif
-
-#include <atomic>
-// expected-error@atomic:* {{<stdatomic.h> is incompatible with the C++ standard library}}
-
-int main()
-{
-}
-