Rust mandates that every field in a user-defined type is initialized at once. How do you propose to retrofit that into C without "constructors"?

C has had designated initializers since C99, if you want you can initialise every struct field at once.

I encourage you to read (at least) this section of this blog before making simplistic suggestions: https://thephd.dev/just-put-raii-in-c-bro-please-bro-just-on...

How do you mandate initialization, handle copies, move objects, prevent double frees? What's RAII without any of that?

You mandate it like you mandate anything else in C. You don't.

You pick C because you want a language that doesn't require a variable to be initialised before mutably referencing it, and you write your defer statements or "destructors" defensively, expecting that a variable could be in any state when it comes time to dispose of it.

Or if you find that unacceptable, you accept that C isn't the language you want. There's many other choices available.

There's no way to write a "destructor" defensively, if the contents of memory it is trying to "destroy" are undefined.

Whereas it's perfectly possible to only defer a statement when you know the "object" has been properly initialized.

That's why defer makes sense in a language like C (even Go), but RAII does not.

I agree with everything you've said, except the conclusion: C can't add proper safe RAII, but being "proper and safe" is not a threshold C even tries to uphold.

But would a destructor that runs automagically when a value goes out of scope, even if it's not properly initialized (and with zero regards for copies or moves) be in any way better than a defer that's explicitly called after it is initialized?

Cause, like, that's the entire thread.

Nope, it wouldn't be. I'm just pointing out that it being unsafe or hard to use is no barrier at all to it being in the language.

Hell, since RAII is an opt-in type-level infectious (in the sense that if you have an RAII member in a struct the struct is RAII) mechanism you can require that RAII structs be initialised.

Given the compiler would already need to know that a local is of an RAII type in order to insert the drop, move, and copy glues it’s not exactly a big requirement.