How to Pass C Standard Library Object References to Threads Without Compilation Errors?

Passing Object Reference Arguments to Thread Functions: Overcoming Compilation Errors

Passing references to C 11 standard library objects, such as std::ostream, to thread functions can encounter compilation issues. This is because threads, by default, copy their arguments.

To pass a reference explicitly, wrap it with std::ref or std::cref for constant references. Here's a modified version of the example provided:

void foo(std::ostream &os) {
    // Do something with os
    os << "This should be printed to os" << std::endl;
}

int main() {
    std::thread t(foo, std::ref(std::cout));
    t.join(); // Wait for the thread to complete
    return 0;
}

By using std::ref, you create a reference wrapper that behaves like a value-semantics object. Multiple copies of the wrapper will refer to the same underlying reference, allowing the thread to access the std::ostream object correctly.

Remember to ensure that the object referred to remains valid throughout the thread's lifetime.

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