CODEWITHSUNDEEP
c++multithreadingstlstdthread
Jazzy
Jazzy

Reputation: 344

Why are member functions passed differently than local functions to a std::thread?

I'm trying to understand how std::thread is used.

The header looks as follows:

template< class Function, class... Args >
explicit thread( Function&& f, Args&&... args );

"If T is getting deduced and variable / parameter type is unqualified T&& , then only it’s a Universal Reference."

what does unqualified T&& refer to? auto or template?

void Class::foo(vector<int>v)
{
   std::cout<<v[0]; // prints nothing
}

int main(void)
{
    std::vector<int>v = {12,3};

    Class obj;

    std::thread t1(&Class::foo, &obj, v);

    t1.join();

}

Upvotes: 1

Views: 98

Answers (1)

eerorika
eerorika

Reputation: 238401

what does unqualified T&& refer to?

It refers to the function parameter of the function template. f and args... are the parameters. They satifsy the described requirment of being forwarding references (as long as the template type argument isn't passed explicitly inn which case the type would not be deduced from the function argument).

Why does the way a function is passed differ from in the case of member functions?

Because non static member functions have an implicit instance parameter, and because they don't implicitly decay to pointer to member function.

How does one pass a local variable/vector to a thread?

Depends on context. Copying is usually simplest.

Upvotes: 1

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