[PATCH] D21407: Enable building and using atomic shared_ptr for GCC.

[Eric Fiselier via cfe-commits]

EricWF created this revision.
EricWF added reviewers: mclow.lists, rmaprath.
EricWF added a subscriber: cfe-commits.

Currently the  implementation of [util.smartptr.shared.atomic] is provided only when using Clang, and not with GCC. This is a relic of not having a GCC implementation of <atomic>, even though <atomic> isn't actually used in the implementation. This patch enables support for atomic shared_ptr functions when using GCC.

Note that this is not a header only change. Previously only Clang builds of libc++.so would provide the required symbols. There is no reason  for this restriction.
After this change both Clang and GCC builds should be binary compatible with each other WRT these symbols.


http://reviews.llvm.org/D21407

Files:
  include/memory
  src/memory.cpp

Index: src/memory.cpp
===================================================================
--- src/memory.cpp
+++ src/memory.cpp
@@ -124,7 +124,7 @@
 
 #endif  // _LIBCPP_NO_RTTI
 
-#if defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_NO_THREADS)
+#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
 static const std::size_t __sp_mut_count = 16;
 static __libcpp_mutex_t mut_back_imp[__sp_mut_count] =
@@ -177,7 +177,7 @@
     return muts[hash<const void*>()(p) & (__sp_mut_count-1)];
 }
 
-#endif // defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_NO_THREADS)
+#endif // !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
 void
 declare_reachable(void*)
Index: include/memory
===================================================================
--- include/memory
+++ include/memory
@@ -5464,9 +5464,8 @@
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os, shared_ptr<_Yp> const& __p);
 
-// TODO(EricWF): Enable this for both Clang and GCC. Currently it is only
-// enabled with clang.
-#if defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_NO_THREADS)
+
+#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
 class _LIBCPP_TYPE_VIS __sp_mut
 {
@@ -5595,7 +5594,7 @@
     return atomic_compare_exchange_weak(__p, __v, __w);
 }
 
-#endif  // defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_NO_THREADS)
+#endif  // !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
 //enum class
 struct _LIBCPP_TYPE_VIS pointer_safety


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