How to execute a piece of code only once?
Compact version using lambda function:
void foo()
{
static bool once = [](){
cout << "once" << endl;
return true;
} ();
cout << "foo" << endl;
}
Code within lambda function is executed only once, when the static variable is initialized to the return value of lambda function. It should be thread-safe as long as your compiler support thread-safe static initialization.
Using C++11 -- use the std::call_once
#include <mutex>
std::once_flag onceFlag;
{
....
std::call_once ( onceFlag, [ ]{ /* my code body here runs only once */ } );
....
}