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Merge 2017-11 LWG Motion 15
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‎source/future.tex

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\pnum\returns \tcode{use_count() == 1}.
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\end{itemdescr}
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\rSec1[depr.util.smartptr.shared.atomic]{Deprecated \tcode{shared_ptr} atomic access}
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\pnum
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The header \tcode{<memory>} has the following additions:
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\indexlibrary{\idxcode{shared_ptr}}%
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\begin{codeblock}
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namespace std {
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template<class T>
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bool atomic_is_lock_free(const shared_ptr<T>* p);
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template<class T>
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shared_ptr<T> atomic_load(const shared_ptr<T>* p);
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template<class T>
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shared_ptr<T> atomic_load_explicit(const shared_ptr<T>* p, memory_order mo);
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template<class T>
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void atomic_store(shared_ptr<T>* p, shared_ptr<T> r);
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template<class T>
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void atomic_store_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
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template<class T>
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shared_ptr<T> atomic_exchange(shared_ptr<T>* p, shared_ptr<T> r);
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template<class T>
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shared_ptr<T> atomic_exchange_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
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template<class T>
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bool atomic_compare_exchange_weak(shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
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template<class T>
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bool atomic_compare_exchange_strong(shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
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template<class T>
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bool atomic_compare_exchange_weak_explicit(
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shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w,
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memory_order success, memory_order failure);
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template<class T>
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bool atomic_compare_exchange_strong_explicit(
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shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w,
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memory_order success, memory_order failure);
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}
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\end{codeblock}
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\pnum
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Concurrent access to a \tcode{shared_ptr} object from multiple threads does not
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introduce a data race if the access is done exclusively via the functions in
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this subclause and the instance is passed as their first argument.
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\pnum
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The meaning of the arguments of type \tcode{memory_order} is explained in~\ref{atomics.order}.
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\indexlibrarymember{atomic_is_lock_free}{shared_ptr}%
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\begin{itemdecl}
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template<class T> bool atomic_is_lock_free(const shared_ptr<T>* p);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null.
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\pnum
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\returns \tcode{true} if atomic access to \tcode{*p} is lock-free, \tcode{false} otherwise.
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_load}{shared_ptr}%
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\begin{itemdecl}
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template<class T> shared_ptr<T> atomic_load(const shared_ptr<T>* p);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null.
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\pnum
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\returns \tcode{atomic_load_explicit(p, memory_order_seq_cst)}.
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_load_explicit}{shared_ptr}%
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\begin{itemdecl}
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template<class T> shared_ptr<T> atomic_load_explicit(const shared_ptr<T>* p, memory_order mo);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null.
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\pnum
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\requires \tcode{mo} shall not be \tcode{memory_order_release} or \tcode{memory_order_acq_rel}.
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\pnum
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\returns \tcode{*p}.
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_store}{shared_ptr}%
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\begin{itemdecl}
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template<class T> void atomic_store(shared_ptr<T>* p, shared_ptr<T> r);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null.
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\pnum
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\effects As if by \tcode{atomic_store_explicit(p, r, memory_order_seq_cst)}.
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_store_explicit}{shared_ptr}%
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\begin{itemdecl}
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template<class T> void atomic_store_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null.
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\pnum
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\requires \tcode{mo} shall not be \tcode{memory_order_acquire} or \tcode{memory_order_acq_rel}.
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\pnum
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\effects As if by \tcode{p->swap(r)}.
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_exchange}{shared_ptr}%
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\begin{itemdecl}
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template<class T> shared_ptr<T> atomic_exchange(shared_ptr<T>* p, shared_ptr<T> r);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null.
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\pnum
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\returns \tcode{atomic_exchange_explicit(p, r, memory_order_seq_cst)}.
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_exchange_explicit}{shared_ptr}%
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\begin{itemdecl}
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template<class T>
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shared_ptr<T> atomic_exchange_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null.
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\pnum
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\effects As if by \tcode{p->swap(r)}.
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\pnum
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\returns The previous value of \tcode{*p}.
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_compare_exchange_weak}{shared_ptr}%
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\begin{itemdecl}
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template<class T>
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bool atomic_compare_exchange_weak(shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null and \tcode{v} shall not be null.
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\pnum
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\returns
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\begin{codeblock}
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atomic_compare_exchange_weak_explicit(p, v, w, memory_order_seq_cst, memory_order_seq_cst)
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\end{codeblock}
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\pnum
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\throws Nothing.
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\end{itemdescr}
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\indexlibrarymember{atomic_compare_exchange_strong}{shared_ptr}%
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\begin{itemdecl}
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template<class T>
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bool atomic_compare_exchange_strong(shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\returns
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\begin{codeblock}
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atomic_compare_exchange_strong_explicit(p, v, w, memory_order_seq_cst, memory_order_seq_cst)
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\end{codeblock}
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\end{itemdescr}
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\indexlibrarymember{atomic_compare_exchange_weak_explicit}{shared_ptr}%
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\indexlibrarymember{atomic_compare_exchange_strong_explicit}{shared_ptr}%
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\begin{itemdecl}
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template<class T>
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bool atomic_compare_exchange_weak_explicit(
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shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w,
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memory_order success, memory_order failure);
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template<class T>
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bool atomic_compare_exchange_strong_explicit(
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shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w,
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memory_order success, memory_order failure);
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\end{itemdecl}
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\begin{itemdescr}
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\pnum
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\requires \tcode{p} shall not be null and \tcode{v} shall not be null.
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The \tcode{failure} argument shall not be \tcode{memory_order_release} nor
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\tcode{memory_order_acq_rel}.
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\pnum
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\effects If \tcode{*p} is equivalent to \tcode{*v}, assigns \tcode{w} to
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\tcode{*p} and has synchronization semantics corresponding to the value of
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\tcode{success}, otherwise assigns \tcode{*p} to \tcode{*v} and has
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synchronization semantics corresponding to the value of \tcode{failure}.
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\pnum
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\returns \tcode{true} if \tcode{*p} was equivalent to \tcode{*v}, \tcode{false} otherwise.
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\pnum
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\throws Nothing.
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\pnum
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\remarks Two \tcode{shared_ptr} objects are equivalent if they store the same
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pointer value and share ownership.
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The weak form may fail spuriously. See~\ref{atomics.types.operations}.
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\end{itemdescr}
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\rSec1[depr.locale.stdcvt]{Deprecated standard code conversion facets}
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\pnum

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