c++ - How to know if the main() is running? -

context : in application, have functions using global variables. due undefined order of allocation of global variables, want forbid call these functions before main function running. moment, document \attention in doxygen, add assertion.

my question : is there elegant way know main function not running yet ?

example (uniqid.cpp):

#include <boost/thread.hpp> #include <cassert> unsigned long int uid = 0; boost::mutex uniqid_mutex; unsigned long int uniquid() {   assert(main_is_running() && "forbidden call before main running");   boost::mutex::scoped_lock lock(uniqid_mutex);   return ++uid; } 

my first (ugly) idea : first idea checking global variable specific value. probability have value in variable before initialisation small :

// file main_is_running.h void launch_main(); bool main_is_running();  // file main_is_running.cpp unsigned long int main_is_running_check_value = 0; void launch_main() {   main_is_running_check_value = 135798642; } bool main_is_running() {   return (main_is_running_check_value == 135798642); }  // file main.cpp #include "main_is_running.h" int main() {   launch_main();   // ...   return 0; } 

is there better way ?

note can't use c++11 because have compatible gcc 4.1.2.

if static std::atomic<bool> s; defined, along little toggling struct:

struct toggle {     toggle(std::atomic<bool>& b) : m_b(b)     {         m_b = true;     }        ~toggle()     {         m_b = false;     }     std::atomic<bool>& m_b; }; 

then, in main, write toggle t(s); first statement. 1 of instances having reference member variable idea.

s can tell if you're in main or not. using std::atomic overkill given behaviour of main calling undefined in c++. if don't have c++11, volatile bool adequate: effectively not in main until statement has completed.