[hudon]

I interpreted his post as saying it's not binary safe/unsafe, but rather a spectrum, with Java safer than C because of particular features that have pros and cons, not because of a magic free safe/unsafe switch. He's advocating for more nuance, not less.

[Ygg2]

Yeah, it's not binary; it's just a step function. /s

No, it's as close to binary as you can get. Is your only source of Undefined Behavior FFI specially marked functions and/or packages? Have you checked data races for violating thread safety invariants? If yes - You're safe.

Allow a bit of unsafety into the system, like Go, and the unsafety can creep into your ecosystem. See https://www.ralfj.de/blog/2025/07/24/memory-safety.html

Is Go in mostly safer than C++? Maybe. But you can never prove that about either of them. So while you may pretend one is safer than the other, it's a bit like picking which boat is taking on more water.

Can you prove Rust code is safe? Well there is the simple way - no unsafe. But what about unsafe blocks? Yes, you can prove it for them as well. If the unsafe code block is it will note safety invariants and why are they preserved by unsafe block. Can this be practically done? Depends on the crate, but with enough effort, yes.

[lossolo]

> Is Go in mostly safer than C++? Maybe

Maybe? You forgot /s there? Asking if Go is mostly safer than C++ is like asking if child proof caps are mostly safer than mason jars for medicine.

> https://www.ralfj.de/blog/2025/07/24/memory-safety.html

Can you show RCE using this? Because, to this day, no one has been able to show me a reasonable program that someone would write and that would result in RCE from "Go memory unsafety" presented in this article. Meanwhile, I can show you thousands of examples and CVEs of how you can easily get RCE using C++.

> Can you prove Rust code is safe? Well there is the simple way - no unsafe. But what about unsafe blocks? Yes, you can prove it for them as well. If the unsafe code block is it will note safety invariants and why are they preserved by unsafe block. Can this be practically done? Depends on the crate, but with enough effort, yes.

You can’t prove Rust code "safe" in the absolute. Safety guarantees apply to safe Rust under the language’s (still evolving) rules, and even then the compiler/backend must uphold them. We still hit unsoundness[1] and miscompiles in safe code (equal pointers comparing unequal... [2]), and the official unsafe code guidelines are not a finalized spec. So documenting invariants in unsafe helps a lot, but it’s not a formal proof, especially across crates and compiler versions.

1. https://github.com/rust-lang/rust/issues/107975

2. https://github.com/rust-lang/rust/labels/I-unsound

On the safety spectrum: C/C++ -> Zig -> Go -> Rust

[Ygg2]

> Maybe? You forgot /s there?

Neither are memory safe, so if you're going by the "safe in practice" definition then it has to be verified experimentally. Hence - maybe.

> Can you show RCE using this?

RCE and Undefined Behavior are two intersecting sets. Not all UB is RCE, but what all UBs are hard to track bugs that happen at most inconvenient times.

> You can’t prove Rust code "safe" in the absolute.

Sure you can't prove that any Turing machine has some property X or not. But Rust Belt (pdf https://hal.science/hal-01633165v2/document) is proof that safety of safe blocks is extensible and can apply to safe interfaces encapsulating unsafe well.

> We still hit unsoundness[1] and miscompiles in safe code (equal pointers comparing unequal... [2])

Your [1] is an LLVM bug.

As for [2] yeah there ARE bugs, wrong flags, bus they are fixing it and triggering most requires stuff like nightly, hitting bugs in specific hardware/LLVM, or very contrived trait constructions.

I mean sure by that token nothing is ever safe, reality is crooked, coins have three sides, and white is black, so traffic crossing are mass hallucinations.

> On the safety spectrum: C/C++ -> Zig -> Go -> Rust

Honestly it goes like this. C -> C++ --> Zig ------> Go --------------------------------------------------------------------------> Rust --> Ada Core

[lossolo]

> Neither are memory safe, so if you're going by the "safe in practice" definition then it has to be verified experimentally. Hence - maybe.

This is a ridiculous claim that it’s only "maybe". It’s so obvious, it’s like saying cars are not safe to drive, but if you use seatbelts and have airbags, then MAYBE they’re safer. I have verified this experimentally, like millions of other people. This argument is totally in bad faith, given the sea of CVEs caused by memory safety issues in C++ versus the almost virtually non-existent problem in safe Go in practice.

> Your [1] is an LLVM bug.

Yes, unfixed for two years. I don’t have this bug in Go, for example, so why, as a Rust user, should I care whose fault it is? If you buy a car and the engine doesn’t work as it should in some cases, do you accept the manufacturer saying, "Well, that’s the engine manufacturer’s issue, so all is OK"?

> As for [2] yeah there ARE bugs, wrong flags, bus they are fixing it and triggering most requires stuff like nightly, hitting bugs in specific hardware/LLVM, or very contrived trait constructions.

That went fast from "proven to be safe" to "yeah there are bugs".

> Honestly it goes like this. C -> C++ --> Zig ------> Go --------------------------------------------------------------------------> Rust --> Ada Core

And how did you arrive at these numbers of "—"? Did you "verify them experimentally"? Because I claim otherwise:

C --> C++ ----> Zig --------------> Go ----> Rust --> Ada Core

can you prove me wrong or prove you are right? You can't. It seems we can only agree on the ranking of the languages.

[Ygg2]

> This is a ridiculous claim that it’s only "maybe". It’s so obvious.

Given enough effort, you can banish all UB and their related CVEs from a codebase. So it becomes a contest of which library had more scrutiny. I.e. you can compare a battle-tested library like cURL to stuff like baby's first XML parser. Plus, seeing how something is safe in practice is much different than just being memory safe.

> That went fast from "proven to be safe" to "yeah there are bugs".

Modulo compiler/hardware bugs goes without saying. Nothing really can exist in vacuum. You could prove your program is proven to work correctly, but if you put it on a platform where carry can randomly flip, and your perfect proof falls flat.

> Yes, unfixed for two years. I don’t have this bug in Go, for example, so why, as a Rust user, should I care whose fault it is?

Because it will be eventually fixed, unlike Go's design (that said they could change their tune and fix it, and I'll respectfully correct my statements). Then again, it's not like it is in scope for Rust. It's a bug in LLVM.

Plus, `unsound` bugs get extra scrutiny. Hell they had to write a new trait solver, Polonius, to solve problems some traits presented to the safety system.

> And how did you arrive at these numbers of "—"?

How many UBs do you leave open? How many errors other errors can your program prevent (e.g. do you allow `null`/`nil`)? And was this an error extremely obvious at time of writing (billion dollar mistake)?

[lossolo]

> Given enough effort, you can banish all UB and their related CVEs from a codebase.

Sure. With infinite energy, anything’s possible - we can prevent all bugs. The problem is, we don’t have infinite energy.

> So it becomes a contest of which library had more scrutiny. I.e. you can compare a battle-tested library like cURL to stuff like baby's first XML parser.

I agree that software varies in quality, and that different people and teams can produce very different levels of quality. The issue is that we’re talking about languages used by many different people with varying capabilities and levels of scrutiny.

What really annoys me is that my phone can get hit with an RCE just from someone sending me a message. That’s exactly the kind of vulnerability that happens because languages like C or C++ are so easy to misuse, due to their complexity and lack of safety. You just can’t compare that to Go or Rust, they’re in a completely different galaxy.

> How many UBs do you leave open? How many errors other errors can your program prevent (e.g. do you allow `null`/`nil`)? And was this an error extremely obvious at time of writing (billion dollar mistake)?

Everything is a trade off. I find Go to be a middle ground where I can offload much of the memory management complexity to the garbage collector, yet still have control over the aspects I care about, with acceptable performance for multi-threaded networking code.

I make extensive use of atomics and mutexes and I don’t need "fearless concurrency," because I can only recall one serious concurrency bug I’ve ever had (a data race) which took some debugging time to track down, but it wasn’t in Go. YMMV.

As for the “billion dollar mistake”, I understand the argument in the context of C or C++, but not in the context of Go. Once every few months, I get a nil pointer dereference notification from the monitoring stack. The middle network layer will report the error to the user, I fix it, and move on, a $0 mistake.

I used Rust in many other projects, where I would never use C++ or C. Rust has a higher cognitive load, more language complexity, and refactoring is painful but it’s a trade off.

Under Go’s memory model, there’s really only one form of undefined behavior: a program with a data race has no defined semantics. That’s pretty much it. Compare that to C or C++, it’s like I said, a different galaxy. I find the whole discussion around Go’s safety exaggerated, and more theoretical than what actually comes up in practice.

[hitekker]

^ This comment demonstrates what I meant by "thick lattice of ideology"