Question

I’m quite confident that globally declared variables get allocated (and initialized, if applicable) at program start time.

int globalgarbage; unsigned int anumber = 42; 

But what about static ones defined within a function?

void doSomething() {   static bool globalish = true;   // ... } 

When is the space for globalish allocated? I’m guessing when the program starts. But does it get initialized then too? Or is it initialized when doSomething() is first called?

Answer 1

I was curious about this so I wrote the following test program and compiled it with g++ version 4.1.2.

include <iostream> #include <string>  using namespace std;  class test { public:         test(const char *name)                 : _name(name)         {                 cout << _name << ' created' << endl;         }          ~test()         {                 cout << _name << ' destroyed' << endl;         }          string _name; };  test t('global variable');  void f() {         static test t('static variable');          test t2('Local variable');          cout << 'Function executed' << endl; }   int main() {         test t('local to main');          cout << 'Program start' << endl;          f();          cout << 'Program end' << endl;         return 0; } 

The results were not what I expected. The constructor for the static object was not called until the first time the function was called. Here is the output:

global variable created local to main created Program start static variable created Local variable created Function executed Local variable destroyed Program end local to main destroyed static variable destroyed global variable destroyed