Can't catch a C++ exception - c++

Question

I'd like to catch an exception while trying to use copy constructor of some class, which would throw.
#include <iostream>
class dont_copy_me {
public:
dont_copy_me() {}
dont_copy_me(const dont_copy_me& rhs) {throw;}
dont_copy_me(dont_copy_me&& rhs) {throw;}
~dont_copy_me() {}
};
int main() {
try {
dont_copy_me obj;
dont_copy_me obj_1(obj);
} catch(...) {
std::cout << "exception caught" << std::endl;
}
return 0;
}
But I keep getting
terminate called without an active exception
Aborted (core dumped)
What is wrong? How do I catch the exception thrown by copy constructor? (because that's what I need)

Answer 1

Actually throw an exception like this:
#include <iostream>
#include <stdexcept>
class dont_copy_me {
public:
dont_copy_me() {}
dont_copy_me(const dont_copy_me& rhs) {throw std::runtime_error("Fail!");}
dont_copy_me(dont_copy_me&& rhs) {throw std::runtime_error("Fail!");}
~dont_copy_me() {}
};
int main() {
try {
dont_copy_me obj;
dont_copy_me obj_1(obj);
} catch(...) {
std::cout << "exception caught" << std::endl;
}
return 0;
}
This does what you need. Here you can find a list of standard exceptions (under "Exception categories").
The empty throw expression only works when you are already handling an active exception:
Rethrows the currently handled exception. Abandons the execution of the current catch block and passes control to the next matching exception handler (but not to another catch clause after the same try block: its compound-statement is considered to have been 'exited'), reusing the existing exception object: no new objects are made. This form is only allowed when an exception is presently being handled (it calls std::terminate if used otherwise). The catch clause associated with a function-try-block must exit via rethrowing if used on a constructor.
From here, emphasis mine.

Answer 2

Your catch (...) block is fine, the problem is your program does not throw an exception.
There are two forms of throw expression:
throw <some-exception> create and throw an exception
throw re-throw the current exception
In your code, you are calling the second form from your copy constructors. Use the first form instead.
The second form is used when you want to some partial handling of an exception. Here's a contrived example program that uses both forms:
#include <cstdexcept>
#include <cstdlib>
#include <iostream>
int main()
{
int ret = EXIT_FAILURE ;
try
{
try
{
throw std::logic_error("Fail!"); // form 1
ret = EXIT_SUCCESS;
}
catch (...)
{
std::clog << "re-throwing" << std::endl;
throw; // form 2
}
}
catch (...)
{
std::cerr << "unhandled exception" << std::endl;
}
return ret;
}
See: http://en.cppreference.com/w/cpp/language/throw