std::lock_guard

 

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std::lock_guard

Member functions

lock_guard::lock_guard

lock_guard::~lock_guard

 

Defined in header <mutex>
template< class Mutex > class lock_guard;		(since C++11)

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. The supplied Mutex type shall implement the BasicLockable concept.

Member types

Member type	Definition
mutex_type	Mutex

Member functions

(constructor)	constructs a lock_guard, optionally locking the given mutex (public member function)
(destructor)	destructs the lock_guard object, unlocks the underlying mutex (public member function)

Example

run this code

#include <thread>
#include <mutex>
 
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;
 
    // g_i_mutex is automatically released when lock
    // goes out of scope
}
 
int main()
{
    std::thread t1(safe_increment);
    std::thread t2(safe_increment);
 
    t1.join();
    t2.join();
}