C++ Weekly - Ep 231 - Multiple Destructors in C++20?! How and Why

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[goodecheeseburgers]

Holy shit Jason the learning curve only gets curvier.

[gnulinux]

One word wow.... C++ going so fast and so vast, it just feels like we always catching up

[-taz-]

"Choose! Choose the form of the destructor." -Ghostbusters

[guest]

I've been out of the loop in C++ development for a few years already and I'm just learning that concepts finally made it into C++20. That, and there's GCC 11. Shit's bananas.

[TNothingFree]

Was expecting some shenanigens, wasn't dissappointed,
Very intereseting thanks!

[LesleyLai]

This is insanely good. Though it makes me sad that STL implementations may not use it for backward compatibility.

[johnjohnson]

This is not "multiple destructors".
An Optional<int> only has one destructor (a trivial destructor) and an Optional<string> only has one destructor (a non trivial destructor)!

However there are multiple destructors in C++. Try to look at the generated assembler for a classes destructor for a class with non-trivial destructible members.

[ujosnah]

In any case you end up with user-declared destructor. In such case compiler does not generate implicit move constructor for you. Therefore, you have to define move constructor explicitly, otherwise your optional<int> is not movable. So, is there a way to not define `~Struct() = default` at all?

[YourCRTube]

Great episode. Finally some more advanced material in Weekly.

[jasoncole]

Really this should be called "Conditional Inheritance" ;)

[SalingToMars]

Regarding the audio clicking sound. Have you tried increasing the buffer size in whatever software you use to record? If the buffer is too small, then every once in a while the computer won't be able to process a buffer completely in time and this results in random clicks in the recording. I've definitely been there. Super annoying, super random

[Wimpielef]

Because of the anonymous union the data destructor is not called I guess?
Or does the union serve another purpose?

[olafurw]

Black screen around 6:22, and again at around 10:03

[kwkfortythree]

Can this be applied to any function member or only to destructors?

[STOJATEK]

That's actually pretty awesome, thanks for sharing!

[matt_]

Great video. Btw seems like some portions you were holding arrow keys to move characters. Ctrl+arrow (I think alt+arrow on mac) jumps by word.

[larswadefalk]

Now I must have chosen the wrong Jason turner weekly. This one flew right over my head. I can't still wrap my head around its necessity. But, well, thanks anyway.

[rajatgirotra]

Thanks Jason for this insight..!!
Really nice and to the point video.

[tzlom]

Apparently, code on 9:40 can't be compiled with Optional<std::string> being instantiated. Because of the union for non-trivial destructible type and because of line 8 where unknown name Contained being used. But that is not my question, my question is - in the presented shape code does compile, that mean that gcc does not fully figured out how exactly you can destruct the object, but already knew that is is not trivially destructible. That level of laizyness I was not expecting, do you have any other examples or explainations how it works under the hood?

[Elite]

There are so many cases where you have to carefully analyse the generated assembly to understand which overload actually gets chosen.