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diff --git a/src/include/refstring.h b/src/include/refstring.h
index 0675b39..c32630c 100644
--- a/src/include/refstring.h
+++ b/src/include/refstring.h
@@ -13,7 +13,13 @@
#include <stdexcept>
#include <cstddef>
#include <cstring>
+
+#if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_CXX03_LANG) && !defined(_LIBCPP_USE_ATOMIC)
+#define _LIBCPP_USE_ATOMIC
+#include <atomic>
+#else
#include "atomic_support.h"
+#endif
// MacOS and iOS used to ship with libstdc++, and still support old applications
// linking against libstdc++. The libc++ and libstdc++ exceptions are supposed
@@ -40,7 +46,11 @@ typedef int count_t;
struct _Rep_base {
std::size_t len;
std::size_t cap;
+#ifdef _LIBCPP_USE_ATOMIC
+ std::atomic<count_t> count;
+#else
count_t count;
+#endif
};
inline _Rep_base* rep_from_data(const char *data_) noexcept {
@@ -96,7 +106,11 @@ __libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) noexcept
: __imp_(s.__imp_)
{
if (__uses_refcount())
+#ifdef _LIBCPP_USE_ATOMIC
+ rep_from_data(__imp_)->count.fetch_add(1);
+#else
__libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
+#endif
}
inline
@@ -105,10 +119,19 @@ __libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) n
struct _Rep_base *old_rep = rep_from_data(__imp_);
__imp_ = s.__imp_;
if (__uses_refcount())
+#ifdef _LIBCPP_USE_ATOMIC
+ rep_from_data(__imp_)->count.fetch_add(1);
+#else
__libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
+#endif
+
if (adjust_old_count)
{
+#ifdef _LIBCPP_USE_ATOMIC
+ if (old_rep->count.fetch_sub(1) == 0)
+#else
if (__libcpp_atomic_add(&old_rep->count, count_t(-1)) < 0)
+#endif
{
::operator delete(old_rep);
}
@@ -120,7 +143,11 @@ inline
__libcpp_refstring::~__libcpp_refstring() {
if (__uses_refcount()) {
_Rep_base* rep = rep_from_data(__imp_);
+#ifdef _LIBCPP_USE_ATOMIC
+ if (rep->count.fetch_sub(1) == 0) {
+#else
if (__libcpp_atomic_add(&rep->count, count_t(-1)) < 0) {
+#endif
::operator delete(rep);
}
}
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