The trouble here is the same problem that affects tons of static analyses: what do you do about higher order functions. I'm pretty skeptical that heap allocating every call to a function pointer/closure/virtual method is going to be fast enough.
What do you mean by saying heap allocation? Do you mean syscall or libc? Zig has a extremely explicit requirement for any allocation. You can have a preallocated region of memory in the allocator for recursion and only move the needle for each “heap allocation”.
Ah, I see, it's a split stack. Well, we experimented with those in Rust for Rust->C calls and they were not fast enough (also, they cause problems with debuggers and tooling). Perhaps if virtual calls are uncommon, though.
At that point I have to wonder what the advantage is over just using explicit checks for overflow on the machine stack though.
Re:Some Thoughts on Zig
by Schroedingersat on Saturday July 23, 2022 @03:47AM
(#32201288)
You're still forcing a mindset onto the language that isn't present.
It's not 'a split stack' or any other particular solution. You pass in an allocator and it does it whichever way your chose allocator picks.
The goal is to explore sections of design space you're completely ruling out from before you even start.
In some circumstances, static proofs are also possible. IIRC it's still an open problem in zig as to what the possible language features will be while keeping this guarantee, but the goal is to be able to have recursion in some circumstances and still provide the possibility of stack-overflow-safety with a performance tradeoff, and to know when you've stepped out of the bounds where that is possible.
Here's a thread I'm at least a year out of date on https://github.com/ziglang/zig/issues/1006
The general philosophy is to give the programmer tools to know what the consequence of a choice will be as far as that doesn't hamstring them overly. Ie. the compiler can tell you when a stack overflow is possible, and it's up to you to decide what to do about it (or whether it is wrong because you know something it doesn't).