Portably handle exceptional errors in C++

struct my_exception_type : public logic_error {
    my_exception_type(char const* msg) : logic_error(msg) { }
};

try {
    throw my_exception_type("An error occurred");
} catch (my_exception_type& ex) {
    cerr << ex.what << endl;
}

try {
    // …
}
catch (...) {
}

int foo(int x) try {
  // body of foo
} catch (...) {
   // be careful what's done here!
}

try
{
   /* code that may throw exceptions */
}
catch (Error1 e1)
{
   /* code if Error1 is thrown */
}
catch (Error2 e2)
{
   /* code if Error2 is thrown */
}
catch (...)
{
   /* any exception that was not expected will be caught here */
}