[#std-shared_lock-0b-2constructor-0c]
= xref:std.adoc[std]::xref:std/shared_lock-0b.adoc[shared_lock<folly::SharedMutexImpl<ReaderPriority, Tag_, Atom, Policy>>]::shared_lock
:relfileprefix: ../../
:mrdocs:

Constructors

== Synopses

Declared in `<folly/SharedMutex.h>`

Constructs a lock that owns no mutex.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:std/shared_lock-0b/2constructor-04.adoc[shared_lock]() noexcept = default;
----

[.small]#xref:std/shared_lock-0b/2constructor-04.adoc[_» more..._]#

Deleted copy constructor; the lock is not copyable.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:std/shared_lock-0b/2constructor-07d.adoc[shared_lock](xref:std/shared_lock-0b.adoc[shared_lock] const& other) = delete;
----

[.small]#xref:std/shared_lock-0b/2constructor-07d.adoc[_» more..._]#

Move‐constructs a lock, transferring ownership from another lock.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:std/shared_lock-0b/2constructor-00b.adoc[shared_lock](xref:std/shared_lock-0b.adoc[shared_lock]&& other) noexcept;
----

[.small]#xref:std/shared_lock-0b/2constructor-00b.adoc[_» more..._]#

Constructs a lock and acquires the mutex in shared mode.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[nodiscard]]
explicit
xref:std/shared_lock-0b/2constructor-0d.adoc[shared_lock](xref:std/shared_lock-0b/mutex_type.adoc[mutex_type]& mutex);
----

[.small]#xref:std/shared_lock-0b/2constructor-0d.adoc[_» more..._]#

Constructs a lock that adopts an already‐held shared lock.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[nodiscard]]
xref:std/shared_lock-0b/2constructor-05.adoc[shared_lock](
    xref:std/shared_lock-0b/mutex_type.adoc[mutex_type]& mutex,
    std::adopt_lock_t unused);
----

[.small]#xref:std/shared_lock-0b/2constructor-05.adoc[_» more..._]#

Constructs a lock that manages a mutex without acquiring it.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:std/shared_lock-0b/2constructor-0a.adoc[shared_lock](
    xref:std/shared_lock-0b/mutex_type.adoc[mutex_type]& mutex,
    std::defer_lock_t unused) noexcept;
----

[.small]#xref:std/shared_lock-0b/2constructor-0a.adoc[_» more..._]#

Constructs a lock and tries to acquire the mutex without blocking.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[nodiscard]]
xref:std/shared_lock-0b/2constructor-08.adoc[shared_lock](
    xref:std/shared_lock-0b/mutex_type.adoc[mutex_type]& mutex,
    std::try_to_lock_t unused);
----

[.small]#xref:std/shared_lock-0b/2constructor-08.adoc[_» more..._]#

Constructs a lock and tries to acquire the mutex within a duration.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename Rep,
    typename Period>
[[nodiscard]]
xref:std/shared_lock-0b/2constructor-00e.adoc[shared_lock](
    xref:std/shared_lock-0b/mutex_type.adoc[mutex_type]& mutex,
    std::chrono::duration<Rep, Period> const& timeout);
----

[.small]#xref:std/shared_lock-0b/2constructor-00e.adoc[_» more..._]#

Constructs a lock and tries to acquire the mutex by a deadline.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename Clock,
    typename Duration>
[[nodiscard]]
xref:std/shared_lock-0b/2constructor-078.adoc[shared_lock](
    xref:std/shared_lock-0b/mutex_type.adoc[mutex_type]& mutex,
    std::chrono::time_point<Clock, Duration> const& deadline);
----

[.small]#xref:std/shared_lock-0b/2constructor-078.adoc[_» more..._]#

== Parameters

[cols="1,4"]
|===
| Name| Description
| *other*
| The lock that would be copied from.
| *mutex*
| Mutex to lock.
| *unused*
| Tag selecting lock adoption.
| *timeout*
| Maximum time to wait for the lock.
| *deadline*
| Absolute time by which the lock must be acquired.
|===


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