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most of that criticism only works on C++. rust does enforce RAII but uses stack allocation for locals by default instead of touching the heap so it skips the slow part.

on the other hand there are no constructors (just normal functions) so you cant initialize values in place, only stack allocate and return. i think rust needs to add in place init and change the rules from "always init at declaration site" to "must be initialized at first use" like kotlin.

the big missing piece is custom allocators that let you use something like a bump arena with the same convenience as system malloc. they already exist on nightly but nobody knows when they will land on stable.

honestly thats the biggest problem with rust, they come up with a lot of useful changes but then take ages to stabilize because the core team is overworked. they also have a kind of perfectionist culture as a reaction to all the half baked features shipping in C++.

there should be a stage between nightly and full release where feature is in stable toolchains behind a cfg flag and you get a warning if upstream crates use it. show commitment to shipping it in time but still make it clear that it can change (in minor incompatible ways) before release.

by scott0120 minutes ago|

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Thanks for this, I’m actually learning Rust (albeit slowly) atm, and still can’t wrap my head around how arena allocs would fit the borrow checker

by CyberDildonics2 hours ago|

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The ease of use of smart pointers makes it tempting to allocate/free of temporary structures even within one single function. Given enough number of such occurrences, it kills performance by a thousand cuts.

This isn't true and doesn't make any sense. Smart pointers don't need to enter into it. If you need a lot of something you make a vector and allocate once.

Also I remember they mentioned it’s not necessary to free memory if you’re about to close your program, because the OS will take the memory back.

It is an extremely niche scenario to need a program to shut down so much faster that you can't even deallocate memory. If you don't make lots of small allocations in the first place the deallocations won't take any time.

Obviously you need to gracefully deinitialise some things, like audio or other devices, but that’s beyond the discussion.

It's actually a pretty big advantage to destructors to deal with stuff like this as well as memory and locks.

IMO, their RAII critique is a but nuanced, but because of their personality the discourse often gets polarising.

I think it gets polarizing because they are both undeniably sharp programmers but don't have any real evidence of this stuff, they are just grasping at rationalizations.