complete, so it will be tried again the next time control passes through the

If control passes through the declaration concurrently while the variable is

being initialized, the concurrent execution waits for completion

\begin{example}

\begin{codeblock}

void f() {

static int x = 2; // OK

static std::string s = "hello"; // OK; if an exception is thrown during the

// initialization of \tcode{s}, \tcode{s} remains uninitialized, and

// an attempt to initialize \tcode{s} (but not \tcode{x}) will be

// made the next time \tcode{f} is called.

thread_local const char* w = "world"; // OK, initializes \tcode{w} to \tcode{"world"} on the main thread.

std::jthread([] {

thread_local int k = 4;

std::cout << k + x; // OK, prints \tcode{"6"}.

std::cout << s << ' '; // OK, prints \tcode{"hello "}.

std::cout << w; // Undefined behavior if \tcode{w} hasn't been constant initialized\iref{basic.start.static}.

// On this thread, control hasn't yet passed through

}); // the declaration of \tcode{w}.

}

\end{codeblock}

\end{example}