std::mutex (C++11)

In a Nutshell

The most basic kind of mutex: only one thread may hold it at any moment, making it the tool of choice for protecting data shared across threads.

Header File

#include <mutex>

Core API Cheat Sheet

Operation	Signature	Description
Construct	mutex()	Constructs the mutex
Destruct	~mutex()	Destroys the mutex
Lock	void lock()	Locks the mutex; blocks if it is unavailable
Try lock	bool try_lock()	Attempts to lock; returns false immediately if unavailable
Unlock	void unlock()	Unlocks the mutex
Native handle	native_handle_type native_handle()	Returns the underlying, implementation-defined native handle

Minimal Example

#include <iostream>
#include <mutex>
#include <thread>

int counter = 0;
std::mutex m;

void increment() {
    std::lock_guard<std::mutex> lock(m);
    ++counter;
}

int main() {
    std::thread t1(increment);
    std::thread t2(increment);
    t1.join();
    t2.join();
    std::cout << counter << '\n'; // Output: 2
}

Embedded Applicability: High

• Typically a zero-overhead abstraction: when uncontended, the only cost is that of an atomic operation
• Neither copyable nor movable, with an explicit and controllable memory layout
• Best paired with lock_guard to keep exception paths from causing a deadlock
• Note: in RTOS environments, make sure the underlying pthread or OS primitives are available

Compiler Support

GCC	Clang	MSVC
4.4	3.3	2010

See Also

• Tutorial: mutex and RAII Locks
• cppreference: std::mutex

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