std::thread (C++11)

In a Nutshell

The C++ Standard Library's native thread wrapper: constructing an object starts the underlying OS thread right away, giving you true multi-task concurrency.

Header

#include <thread>

Core API Cheat Sheet

Operation	Signature	Description
Constructor	thread() noexcept;	Default construction; not associated with any thread
Constructor	template< class Function, class... Args > explicit thread( Function&& f, Args&&... args );	Constructs and immediately starts a thread
Destructor	~thread();	Must already be joined or detached before destruction, otherwise std::terminate is called
Assignment	thread& operator=( thread&& other ) noexcept;	Move assignment
Joinable	bool joinable() const noexcept;	Checks whether the thread can be joined (i.e., whether it is associated with an active thread)
Join	void join();	Blocks the current thread and waits for the target thread to finish
Detach	void detach();	Separates the thread from the thread object so it runs independently in the background
Get ID	id get_id() const noexcept;	Returns the thread identifier
Hardware Concurrency	static unsigned int hardware_concurrency() noexcept;	Returns the number of concurrent threads supported by the implementation

Minimal Example

#include <iostream>
#include <thread>

void task(int n) {
    for (int i = 0; i < n; ++i)
        std::cout << "worker: " << i << "\n";
}

int main() {
    std::thread t(task, 3);
    t.join(); // Block until thread t finishes executing
    std::cout << "done\n";
}
// Standard: C++11

Embedded Applicability: High

• Zero abstraction overhead: std::thread maps directly onto the underlying OS thread (an RTOS task or a POSIX pthread, for example)
• hardware_concurrency() can probe the available core count at runtime to size a thread pool dynamically
• Combined with std::mutex and std::atomic, it can safely guard shared peripheral registers or global buffers
• Watch out for OS thread stack overhead (typically a few KB to a few tens of KB); on very small-memory MCUs we need to tightly control thread count and stack size

Compiler Support

GCC	Clang	MSVC
4.6	3.1	19.0

See Also

• cppreference: std::thread

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