How (memory) safe is Zig? (2021)

https://www.scattered-thoughts.net/writing/how-safe-is-zig/

22•vortex_ape•3h ago

Comments

90s_dev•2h ago

> But it does not nearly approach the level of systematic prevention of memory unsafety that rust achieves.

Unless I gravely misunderstood Zig when I learned it, the Zig approach to memory safety is to just write a ton of tests fully exercising your functions and let the test allocators find and log all your bugs for you. Not my favorite approach, but your article doesn't seem to take into account this entirely different mechanism.

nine_k•2h ago

I suppose you can even ship the test/logging allocator with your production build, and instruct your users to run your program with some option / env var set to activate it. This would allow to repro a problem right where it happens, hopefully with some info helpful for debugging attached.

Not a great approach for critical software, but may be much better than what C++ normally offers for e.g. game software, where the development speed definitely trumps correctness.

KerrAvon•1h ago

What that means, though, is that you have a choice between defining memory unsafely away completely with Rust or Swift, or trying to catch memory problems by a writing a bunch of additional code in Zig.

TimSchumann•1h ago

I’d argue that ‘a bunch of additional code’ to solve for memory safety is exactly what you’re doing in the ‘defining memory safety away’ example with Rust or Swift.

It’s just code you didn’t write and thus likely don’t understand as well.

This can potentially lead to performance and/or control flow issues that get incredibly difficult to debug.

ajross•1h ago

Weird that Swift is your totem for "managed/collected runtime" and not Java (or C#/.NET, or Go, or even Javascript). I mean, it fits the bill, but it's hardly the best didactic choice.

90s_dev•53m ago

What if -- stay with me now -- what if we solved it by just writing vastly less code, and having actually reusable code, instead of reinventing every type of wheel in every project? Maybe that's the real secret to sound code. Actual code reuse. I know it's a pipedream, but a man can dream, can't he?

nanolith•2h ago

There is a third category of memory and other software safety mechanisms: model checking. While it does involve compiling software to a different target -- typically an SMT solver -- it is not a compile-time mechanism like in Rust.

Kani is a model checker for Rust, and CBMC is a model checker for C. I'm not aware of one (yet!) for Zig, but it would not be difficult to build a port. Both Kani and CBMC compile down to goto-c, which is then converted to formulas in an SMT solver.

DrNosferatu•1h ago

Any good primers on SMT solvers?

dnautics•1h ago

There isn't a real one yet, but to scratch an itch I tried to build one for Zig. It's not complete nor do I have plans to complete it. https://github.com/ityonemo/clr

If zig locks down the AIR (intermediate representation at the function level) it would be ideal for running model checking of various sorts. Just by looking at AIR I found it possible to:

- identify stack pointer leakage

- basic borrow checking

- detect memory leaks

- assign units to variables and track when units are incompatible

pizlonator•1h ago

> it seems impossible to secure c or c++

False. Fil-C secures C and C++. It’s more comprehensively safe than Rust (Fil-C has no escape hatches). And it’s compatible enough with C/C++ that you can think of it as an alternate clang target.

nzeid•1h ago

I love this shameless self-promotion. ;)

Fil-C is in the cards for my next project.

pizlonator•1h ago

Thank you for considering it :-)

Hit me up if you have questions or issues. I’m easy to find

90s_dev•1h ago

One of these days, a project will catch on that's vastly simpler than any memory solution today, yet solves all the same problems, and more robustly too, just like how it took humanity thousands of years to realize how to use levers to build complex machines. The solution is probably sitting right under our noses. I'm not sure it's your project (maybe it is) but I bet this will happen.

pizlonator•1h ago

That’s a really great attitude! And I think you’re right!

I think in addition to possibly being the solution to safety for someone, Fil-C is helping to elucidate what memory safe systems programming could look like and that might lead to someone building something even better

Dwedit•56m ago

If you're filling uninitialized pointers with AAAAAAAA, it might be best to also reserve that memory page and mark it as no-access.

throwawaymaths•54m ago

that only happens in debug-builds.

https://ziglang.org/documentation/master/#undefined

dang•12m ago

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How (memory) safe is Zig? (2021)

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