How do you run a function on exit in C++

Question

I have a function that I want to run whenever my program exits:

void foo() {
  std::cout<< \"Exiting\" << std::endl;
}

How do I reg

Answer 1

I am answering as a Linux user, but all of this should apply to windows.

I had this similar question, so hopefully I can sum up previous answers and add my two cents.

Signals and abort(): ^C and ^Z can be "intercepted" to call your function before exiting, presumably with exit(). Signals SIGQUIT AKA ^\ and SIGKILL which has no key stroke cannot be intercepted. Here's an example for using the csignal header and a C++ lambda.

#include 
#include 
#include 

using namespace std;

int main()
{
    //signal requires lam take an int parameter
    //this parameter is equal to the signals value
    auto lam = 
      [] (int i) { cout << "aborting" << endl; exit(0); };

    //^C
    signal(SIGINT, lam);
    //abort()
    signal(SIGABRT, lam);
    //sent by "kill" command
    signal(SIGTERM, lam);
    //^Z
    signal(SIGTSTP, lam);


    while(1)
    {
    }

    return 0;
}

Exit: Since I used exit() in my examples above, care must be taken here. If the function being run is a clean-up function that only needs to run once, perhaps a static variable has_run could be used. Or in the example above, raise() a signal that you can't intercept. But those tend to come with core dumps which just feels dirty. Your choice, here. An example follows

#include 
#include 

using namespace std;

int main()
{
    //called with no parameters
    auto lam = [] () { cout << "at exit"; };

    atexit(lam);

    return 0;
}

Take note that c++11 added a quick_exit which has an accompanying at_quick_exit which act the same as above. But with quick_exit no clean up tasks are performed. In contrast, with exit object destructors are called and C streams are closed, with only automatic storage variables not getting cleaned up.