C++ c-tor handle default member value construction exception?

Question

I want to handle exception in a default-value constructed class member. Something like this:

int func()
{
    throw 9.0;

    return 9;
}

struct T
{
    T() try {
    }
    catch(...)
    {
        cout << __func__ << endl;
    }
    int a{func()};
} ;

Is it possible? And what does the latest ISO C++ standard says about it?

EDIT: I actually verified myself it works on most compilers but is it well-defined and should I normally use this construct?

Answer 1

Is it possible?

Yes, that exception would be handled by the function-level handler just like any other thrown by a member's initialiser. Note that, in the function-try-block of a constructor, the exception is rethrown after handling it. This is what you want if the initialisation of a sub-object failed, since the complete object is not valid.

And what does the latest ISO C++ standard says about it?

I don't have C++14 yet, but C++11 said:

15/4: An exception thrown during the execution of the compound-statement or, for constructors and destructors, during the initialization or destruction, respectively, of the class’s subobjects, transfers control to a handler in a function-try-block in the same way as an exception thrown during the execution of a try-block transfers control to other handlers.

and 15.3/15 specifies that it's rethrown in this case.

should I normally use this construct?

Probably not - there's little you can do to handle the failure of a sub-object's initialisation, so usually no point in catching and rethrowing the exception. You might want to report the error as the exception passes through.