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Enable building and using atomic shared_ptr for GCC. 

Summary:
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.


Reviewers: mclow.lists, rmaprath, EricWF

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D21407

llvm-svn: 273076
This commit is contained in:
Eric Fiselier 2016-06-18 02:12:53 +00:00
parent ccc9826f56
commit df93bad1fe
2 changed files with 5 additions and 6 deletions
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7
libcxx/include/memory
View File

@ -5464,9 +5464,8 @@ inline _LIBCPP_INLINE_VISIBILITY
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 @@ atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v
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

4
libcxx/src/memory.cpp
View File

@ -124,7 +124,7 @@ __shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT
#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 @@ __get_sp_mut(const void* p)
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*)