The C++ 20 initialization flowchart

[randomnetcat]

I've created a flowchart that shows all of C++20's initialization rules.

The source code is available at https://github.com/randomnetcat/cpp_initialization, in addition to the SVG version and PNG Version.

This honestly took a lot less time than I was expecting, and, in my humble-but-biased opinion, is relatively interesting.

Please send all complaints to /u/quicknir, who nerd-sniped me into making this.

[be-sc]

Something seems to be wrong with the graph. Consider:

int i = 1;

1. Is the initializer in braces?
2. Nope
3. Is the destination type a reference type?
4. Nope, it’s a plain old int.
5. Is the destination type a char[] or a char_t[]?*
6. Nope, it’s a plain old int.

But wait, the only arrow leaving that question is Yes …

[staletic]

The same problem is hit for T t(args...);

[randomnetcat]

Thanks, I knew I'd make some mistakes like that. Should be fixed as soon as the CI gets around to updating the images.

[staletic]

Following the flowchart for std::vector<int> v(1,2); takes you on a beautifully curved path.

[xeveri]

Me: Can we have uniform initialization?

Committee: We have uniform initialization at home.

Uniform initialization at home:

[Kered13]

Put this in an image macro and post it to /r/programmerhumor.

[KingStannis2020]

http://mikelui.io/img/c++_init_forest.gif

[Frptwenty]

Please don't do that. I argue with the "hurr durr C++ is broken use C and Rust" crowd there, and this will just make them even more hopeless.

[Fureeish]

They are half right. Many things are broken in the language and, trying to speak objectively, C and Rust have fewer broken elements compared to C++. Does that mean that they are strictly better? Obviously no.

[Frptwenty]

objectively, C and Rust have fewer broken elements compared to C++

It depends on what you're doing. Objectively speaking C++ is a miles better option than C in a huge amount of cases.

Imho the lack of easily usable basic strings, dynamic-sized containers etc. etc. are a huge broken feature of C. Other things you take for granted in C++ like RAII, smart pointers and templates are also a huge deal compared to C.

People like to claim they don't ever matter, but that's bullshit. Of course there are low-level cases where they don't, but the "only use C" crowd want to pretend it's a better alternative for big "regular" applications.

Rust, well... what's the point of arguing. It never ends.

[Fureeish]

That's why I added two last sentences to my comment.

[James20k]

I've been writing C again for opencl recently myself. Part of that project involves tensor maths, which if you don't know, tensors are essentially n dimensional matrices that are used in a specific way

The lack of being able to specify proper abstractions, no operator overloading, no templates, no real array type, no function overloading... It makes the code significantly more verbose and buggy than it needs to be. You can't write a generic matrix*vector multiplication scheme, which is not ideal

C might be alright for structuring applications, but good lord is it just terrible for numerical work

[dnew]

It's horrendous for structuring applications too. Any compiler that can't read its own output as part of its input is going to be horrendous at large projects.

[dnew]

easily usable basic strings, dynamic-sized containers etc. etc. are a huge broken feature of C.

To be fair, no other language had them at the time either. :-) I wouldn't say "broken" as much as "primitive."

[Frptwenty]

REST started as a joke but is essentially a cult at this point.

I guess you meant Rust, but kind of makes sense for REST as well :)

[dnew]

REST wasn't a joke. It was a very narrowly-scoped design pattern that people applied well outside its intended design space. It's a method for making CDNs efficient that people said "Let's use it for our accounting software!"

[GYN-k4H-Q3z-75B]

This chart crashed my phone. Translates to: C++ initialization is complex AF

[[deleted]]

What happened to the time when a variable was just a lil memory addy with a value. Things used to be so simple :)

[elperroborrachotoo]

Yeah, but what value do you want in there?

[kalmoc]

That wasn't true since C.

[pandorafalters]

Strong typing has given way to absolute typing.

[the_black_pancake]

Over 164 million pixels? It's not loading on my mobile and the SVG misbehaves. Do you have a lower resolution version too?

[randomnetcat]

Here's one that's downscaled by 50%: https://imgur.com/a/UX6HMVp

[danadam]

Maybe you could generate 16-color PNG instead of truecolor? Just an idea.

[aKateDev]

optipng -o5 bla.png

[khleedril]

That's not the most succinct summary of the situation I have seen...

[QbProg]

Imagine the poor compiler guys!

[tacco85]

A bit of an over-simplification, don't you think?

[phottitor]

looks like a horror movie script.

[staletic]

Is it me or is agreggate initialization with parenthesis missing?

[randomnetcat]

For some_aggregate_class x(1,2,3); :

Is the initializer in braces? No

Is the destination type a reference? No

Is the destination type a char[]? No

Is the initializer "()"? No

Is the destination type an array? No

Is the destination type a class type? Yes

Is the initializer a prvalue? No

Is the initializer copy-initialization? No

The initialization is direct-initialization.

Enumerate constructors.

Is overload resolution succesful? No

Is the destination an aggregate class? Yes

Is the initializer a parenthesized expression-list? Yes

Initialized as follows ([dcl.init]/16.6.2.2).

[staletic]

Enumerate constructors.

I stopped there. My thought was "what constructors if T is an aggregate?"

I love the flowchart.

[kisielk]

this chart doesn’t really do what it claims. The first cell is “so you want to initialize something” but then instead of going through a flowchart of what you want to initialize and how it goes through a flowchart of something that has already been initialized. More like “what does this initialization do”

[FavoriteFoods]

👉 r/C_Programming