std::lock_guard
From cppreference.com
| Defined in header <mutex>
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| template< class Mutex > class lock_guard; |
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The class lock_guard is a mutex wrapper that provides a convenient RAII-style mechanism for owning a mutex for the duration of a scoped block.
When a lock_guard object is created, it attempts to take ownership of the mutex it is given. When control leaves the scope in which the lock_guard object was created, the lock_guard is destructed and the mutex is released.
The lock_guard class is non-copyable.
Template parameters
| Mutex | - | the type of the mutex to lock. The type must meet the BasicLockable requirements
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Member types
| Member type | Definition |
mutex_type
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Mutex |
Member functions
| constructs a lock_guard, optionally locking the given mutex (public member function) | |
| destructs the lock_guard object, unlocks the underlying mutex (public member function) | |
| operator= [deleted] |
not copy-assignable (public member function) |
Example
Run this code
#include <thread> #include <mutex> #include <iostream> int g_i = 0; std::mutex g_i_mutex; // protects g_i void safe_increment() { std::lock_guard<std::mutex> lock(g_i_mutex); ++g_i; std::cout << std::this_thread::get_id() << ": " << g_i << '\n'; // g_i_mutex is automatically released when lock // goes out of scope } int main() { std::cout << __func__ << ": " << g_i << '\n'; std::thread t1(safe_increment); std::thread t2(safe_increment); t1.join(); t2.join(); std::cout << __func__ << ": " << g_i << '\n'; }
Possible output:
main: 0 140641306900224: 1 140641298507520: 2 main: 2
See also
| (C++11) |
implements movable mutex ownership wrapper (class template) |
| (C++17) |
deadlock-avoiding RAII wrapper for multiple mutexes (class template) |