Re: [boost] delayed_forward: good, bad, ugly?

10 Jan 2023

      Hans Dembinski wrote:
...
...
On 9. Jan 2023, at 19:15, Peter Dimov via Boost 
wrote:
It will be better if you show how the existing code (before the
delayed_forward
transformation) looks like.
I added FooOld, which corresponds to the unsafe design I want to replace.
https://godbolt.org/z/15q9EqnfP
Thanks. I note that as written, FooOld actually has the same problem even
if the argument is not taken by value.

template <class T>
struct FooOld2 {
    FooOld2(bool b, T const& targ) : t_(targ) {
        if (b)
            throw 1;
    }
    FooOld2(bool b, T&& targ = {}) : t_(std::move(targ)) {
        if (b)
            throw 1;
    }
private:
    T t_;
};

There might be a difference between passing by value or not, but for that,
the exception would have to be thrown from a base or previous member
initialization, and not the constructor body.