A sample C++11 idiom for RAII scoped action.

sample-raii-scoped-action.cc

#include <iostream>
#include <functional>


using namespace std;


class ScopedAction
{
public:
    ScopedAction(function<void()> f) : func_(f) {}
    ~ScopedAction() { func_(); }
private:
    function<void()> func_;
};


static void print_function_entry(const string &name)
{
    cout << "Function entry: " << name << endl;
}


static void print_function_exit(const string &name)
{
    cout << "Function exit: " << name << endl;
}


// plain ol' function with no exception
void f() throw()
{
    const string fname("f()");
    print_function_entry(fname);

    ScopedAction sa([=]()->void {
                print_function_exit(fname);
            });
    {
        // ...
    }

    cout << "Before exit: " << fname << endl;
}

// premature return
void f_exit() throw()
{
    const string fname("f_exit()");
    print_function_entry(fname);

    ScopedAction sa([=]()->void {
                print_function_exit(fname);
            });
    {
        // ...
        // something happened, must return fast
        return;
    }

    // will not get reached
    cout << "Before exit: " << fname << endl;
}

// throw before return
void f_throw()
{
    const string fname("f_throw()");
    print_function_entry(fname);

    ScopedAction sa([=]()->void {
                print_function_exit(fname);
            });
    {
        // ...
        throw string("An exception occurred.");
    }

    // will not get reached
    cout << "Before exit: " << fname << endl;
}


int main()
{
    f();
    f_exit();
    try
    {
        f_throw();
    }
    catch (string &exc_str)
    {
        cout << "Caught an exception: " << exc_str << endl;
    }
    return 0;
}