I think the parent's point is that we started with raw pointers to implement PIMPL, then we had std::unique_ptr, and now we have std::indirect. So there are now three different ways how PIMPL can be implemented, each has its gotcha's and subtle differences that one needs to keep in mind. In large codebases you will now have to deal with all three solutions being used, depending on how old the code is.

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feelamee 4 days ago | parent | next [-]

I think point was another. And even if u are right - this is a silly point. In any general language you have enormous amount of ways to write something. I'm at least implemented pimpl in two different ways (despite lot of little quircks): classic pimpl with heap allocated implementation and fastpimpl which accepts size as compile time argument and create implementation directly in local stack buffer.

> In large codebases you will now have to deal with all three solutions being used, depending on how old the code is.

this is really a problem of "large codebases" and not C++ complexity. If people writing badly organized code.. than.. nothing will help them. Even such string language as Rust.

---

But, I go aside. I can be wrong here, but this is how I see this: - author author worked with C++ early in his career - now his work with something like python or javascript or "promptscript" or don't programming at all - he managed to taste C++ drawbacks - now he reading such article just to see "what's new" in technology he was interested in the past. - he see something what he don't understand from first sight - this looks like a complex and quirky thing => he decide that problem in the language, not in his incompetence in this area

I see such comments very often and usually people don't provide any technical expertise. But just their feeling that "oh, this thing was so complex, now it even more complex".

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daemin 3 days ago | parent | prev | next [-]

The article's point of view is that using unique_ptr to implement a PIMPL idiom is inadequate since it doesn't allow copying of the outer type without implementing your own dedicated operators. Hence the new type which does act more like a value, leaving the decision to have the outer class move-only or copyable up to that class, without needing to write any special code.

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gblargg 4 days ago | parent | prev [-]

The point of each improvement is fewer easily-made errors. Having implicit deep copying handled avoids lots of errors with manually implementing it the oldest way.

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jstimpfle 4 days ago | parent [-]

Well that's a lie. I've long been back to raw pointers and it's by far the easiest way to do it. All of Pimpl, unique_ptr, and whatever other clever mechanism (I'm not even looking at std::indirect anymore) just aren't really ergonomic.

Nobody needs "deep copying", ever. It's not even well defined what it should mean (i.e. how deep etc.). It's purely a theoretical problem with no good practical (one-fits-all) solution. The only practical way is to copy what you need copied, when you need it. Done.

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gblargg 4 days ago | parent | next [-]

The whole point of pimpl is to store additional per-object state in a separate object (to reduce header dependencies). So it should act just like normal member variables for standard constructors and assignment.

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bluGill 4 days ago | parent | prev [-]

Easiest way to make a silly mistake and have your program break from memory safety errors.

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jstimpfle 4 days ago | parent [-]

Well, the best way to prevent mistakes is to make everything super complicated and damn hard to do. The best way to prevent mistakes is to approach it to do the essential stuff and avoid the fluffy stuff.

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bluGill 4 days ago | parent [-]

Huh? The best way to prevent mistakes is to make doing it right easy. Manually doing everything just means a lot of room to mess up. Using the newer constructs my means you can't make a mistake as the hard work is done correctly for you. Zero cost abstraction means that it has no downside to manually doing it.

C++ is trivial compared to the code I work on. If you are writing hello world complexity then C++ might be complex but some of us work on hard problems.

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jstimpfle 4 days ago | parent [-]

I understand C++ as well, or better, than most (or all) of my peers, and certainly betters than people on here thinking they need to explain to me how RAII works. Do you want to argue that C++ RAII / objects stuff isn't complex and doesn't put considerably restrictions on how you design your app, then maybe you should reconsider.

I would argue that if cleaning up resources properly is among the hard problems, or among the most error-prone problems in your code, then maybe you're problems aren't that hard or complex after all.

I'm currently working on a distributed caching system and on real time voxel geometry boolean operations simulation (on GPU), both on the scale of >= 10^9. Is that "complex" enough? Both are done in C++. C++ helps exactly 0 in achieving any of these things (as opposed to using plain C), well the one help is I don't have to type 'struct' all the time.

In fact, in one of these projects I was pushed to use STL initially. I'm now working on getting rid of the last of them because we have had concurrency bugs and performance problems from using them. The code was not obvious and using STL containers (std::deque is very bad specifically) meant the actual runtime characteristics depend on which STL implementation is being compiled in. It would have been easier to just do straightforward obvious manual code.

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feelamee 4 days ago | parent [-]

I'm interesting which C++ features also helps you to design such systems. I think basic RAII/function overloading/templates should give a lot of capabilities comparing with plain C?

> (as opposed to using plain C)

Also, curious - how plain C helps with this?

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jstimpfle 3 days ago | parent [-]

I've found that RAII and the stuff you have to buy into in order to use RAII come with more downsides than upsides once you scale beyond high level programs that try to get done a lot with very few lines.

> how plain C helps with this?

By staying out of the way and providing everything of what you actually need in the end. That is assuming a detail oriented approach where you deeply think about, and want to be flexible about, the organization of what your program should do. As programs grow into large architectures, and as programs get more performance conscious, they also get more detail oriented like that, and they tend to opt out of unflexible high level language features.

	▲	feelamee 3 days ago \| parent [-]
		thx, I don't understand fully, but see something truthy in this. It would be interesting to read more detailed blog post about this.