199. Lambdas and Callback Management

Question.4

A developer captures a local variable by reference in a timer callback:

void setup_timer() {
   int interval = 100;
   timer.onExpire([&interval]() {
       set_period(interval);  // Use captured reference
   });
} // interval goes out of scope here!

When the timer fires later, what happens?

Need Help? Refer to the Quick Guide below

set_period(100) is called correctly
Undefined behavior -- interval was destroyed when setup_timer returned; the reference now points to reclaimed stack memory (dangling reference)
set_period(0) is called -- default value
Compilation error -- references cannot be captured

Restart quiz!