What is the lifetime of a static variable in a C++ function?

Question

If a variable is declared as `static` in a function's scope it is only initialized once and retains its value between function calls. What exactly is its lifetime? When do its constructor and destructor get called? void foo() { static string plonk = "When will I die?"; }

Answer 1

What exactly is its lifetime?

The space for the static variable is allocated only one time and this is used for the entirety of the program.

Once this variable is declared, it exists till the program executes. So, the lifetime of a static variable is the lifetime of the program.

When do its constructor and destructor get called?

Let's demonstrate it with the help of a static object in C++

#include <iostream>

class Test {

public:

Test() {

std::cout << "Constructor is executed\n";

}

~Test() {

std::cout << "Destructor is executed\n";

}

};

void foo() {

static Test test;

} // Object 'test' is still not destroyed because it is static

int main() {

std::cout << "main() starts\n";

foo(); // Destructor for object 'test' will not be called here

std::cout << "main() terminates\n";

return 0;

}

Output:

main() starts

Constructor is executed

main() terminates

Destructor is executed

If we remove the static keyword from the function foo(), we get the output as below:

main() starts

Constructor is called

Destructor is called

main() terminates