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raddevus wrote:

* Cannot have its address taken.
* Cannot be called.

 #include <iostream>

int main(int argc, char **argv)
{
    if(argc <= 1) {
        auto main_ptr{main};
        std::cout << "pointer to main = " << main_ptr << std::endl;
        std::cout << "exiting ..." << std::endl;
        return 0;
    }
    std::cout << "argc = " << argc << std::endl;
    main(--argc, argv);
}

Richard MacCutchan wrote:

don't know why you would want to

Callback (computer programming) - Wikipedia[^]

a callback, also known as a "call-after"[1] function, is any executable code that is passed as an argument to other code that is expected to call back (execute) the argument at a given time.

#include <iostream>

using namespace std;

static int call_countdown = 3;
typedef int (*MyCallbackFun)();
int foo(MyCallbackFun cb, int count)
{
    static int foo_counter = 0;
    ++foo_counter;
    cout << "enter foo[" << foo_counter <<"]: " << count << endl;
    int result = cb();
    cout << "exit foo[" << foo_counter << "]: " << result << endl;
    return result;
}
int bar()
{
    static int bar_counter = 0;
    ++bar_counter;
    cout << "bar[" << bar_counter << "]" << endl;
    return -1;
}
int main()
{
    static int call_counter = 0;
    ++call_counter;
    cout << "enter main[" << call_counter << "]" << endl;

    int result = 0;
    if (call_counter < 5)
    {
        result = (call_counter>2)
            ? foo(bar, call_counter)
            : foo(main, call_counter);
    }
    cout << "exit main[" << call_counter << "]: " << result << endl;

    return call_counter;
}

enter main[1]
enter foo[1]: 1
enter main[2]
enter foo[2]: 2
enter main[3]
enter foo[3]: 3
bar[1]
exit foo[3]: -1
exit main[3]: -1
exit foo[3]: 3
exit main[3]: 3
exit foo[3]: 3
exit main[3]: 3