How to use std::thread in C for multithreading programming? 1. Instantiate the std::thread object when creating a thread and pass it into a function or lambda expression, such as std::thread t(threadFunction); 2. Join() or detach() must be called to manage the thread life cycle to avoid unexpected program termination; 3. When passing parameters, directly attach parameters to the constructor. Reference passes must be used to ensure the original variables are modified; 4. To manage multiple threads, you can use std::vector container to store and loop join(); 5. To avoid accessing destroyed local variables and directly copying thread objects, you should use mobile semantics to process thread objects.
Using std::thread
in C for multithreading is pretty straightforward once you understand the basics. The key idea is that each std::thread
object represents a separate thread of execution, and you can launch functions to run concurrently by passing them into the thread constructor.

Here's how to get started and avoid common pitfalls.

Creating a Thread
To create a new thread, you simply instantiate a std::thread
object and pass it a function (or a lambda) to execute. That function will then run in parallel with the main thread (or whatever thread created it).
For example:

#include <iostream> #include <thread> void threadFunction() { std::cout << "Hello from thread!\n"; } int main() { std::thread t(threadFunction); t.join(); // Wait for the thread to finish return 0; }
A few important notes:
- You must either call
join()
ordetach()
on astd::thread
before it goes out of scope — otherwise your program will terminate unexpectedly. -
join()
blocks the calling thread until the thread finishes execution. -
detach()
lets the thread run independently (you lose control over when it ends).
Passing Arguments to Threads
You can pass arguments to the thread function just like regular function calls. Just provide them after the function name in the constructor.
void printNumber(int x) { std::cout << "Value from thread: " << x << "\n"; } std::thread t(printNumber, 42); t.join();
If you're passing objects by reference, use std::ref()
to make sure the thread gets a reference instead of a copy:
void increment(int& x) { x; } int value = 5; std::thread t(increment, std::ref(value)); t.join(); // Now 'value' is 6
Otherwise, changes inside the thread won't affect the original variable.
Managing Multiple Threads
In many cases, you'll want to launch multiple threads and wait for all of them to finish. To do this cleanly, store your threads in a container like a std::vector<std::thread>
.
#include <vector> void worker(int id) { std::cout << "Worker " << id << " running\n"; } int main() { std::vector<std::thread> threads; for (int i = 0; i < 5; i) { threads.emplace_back(worker, i); } for (auto& t : threads) { t.join(); } return 0; }
This pattern is very useful in practice, especially when you want to process data in parallel, such as splitting up a big loop across several threads.
Avoiding Common Mistakes
One easy mistake is letting a thread access local variables that have gone out of scope. For example:
void badFunc(const std::string& s) { std::cout << s << "\n"; } void createThread() { std::string msg = "Thread message"; std::thread t(badFunc, msg); t.detach(); // No join! // msg may be destroyed before the thread runs }
Since we detached the thread, there's no guaranteee msg
still exists when the thread uses it. This leads to undefined behavior.
Another thing to remember: threads are not copyable, only movable. So if you're working with containers or returning threads from functions, always use move semantics.
std::thread t1([]{ std::cout << "Hi\n"; }); std::thread t2 = std::move(t1); // OK // std::thread t2 = t1; // Error! Threads can't be copied
So basically, using std::thread
boils down to launching functions in separate threads, managing their lifecycle with join()
or detach()
, and being careful about data sharing and lifetimes. It's simple enough for basic concurrency but powerful enough to build more complex systems on top of.
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