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Difference between revisions of "cpp/thread/lock guard"

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< cpp‎ | thread
(filled out description, example)
(rm unused template args (I think?))
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===Member functions===
 
===Member functions===
 
{{dcl list begin}}
 
{{dcl list begin}}
−
{{dcl list template | cpp/thread/lock_guard/dcl list constructor | Locks the supplied mutex}}
+
{{dcl list template | cpp/thread/lock_guard/dcl list constructor}}
−
{{dcl list template | cpp/thread/lock_guard/dcl list destructor | Unlocks the supplied mutex}}
+
{{dcl list template | cpp/thread/lock_guard/dcl list destructor}}
 
{{dcl list end}}
 
{{dcl list end}}
  

Revision as of 15:39, 12 July 2012

 
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std::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 Template:concept concept.

Member types

Member type Definition
mutex_type Mutex

Member functions

Template:cpp/thread/lock guard/dcl list constructorTemplate:cpp/thread/lock guard/dcl list destructor

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();
}
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