robinm

I think you have a hard time understanding the différence between "not possible" and "much harder".

In Rust, the code does not compile.

In C++ the code compile, but

• if you have a test case
• this test case triggers the bug (it is not guarateed to properly reproduce you production environment since it depends on the parameters of the allocator of your vector)
• you use ubsan

... then the bug will be caught.

Yes it is possible, noone says the opposite. But you can't deny it's harder. And because its harder, more bugs get past review, most notably security bugs as demonstrated again and again in many studies. The

That's why I did not said it was impossible, just order of magnitude harder to catch in C++ compared to Rust.

To have asan finding the bug, you need to have a valid unit test, that has a similar enough workload. Otherwise you may not see the bug with asan if the vector doesn't grow (and thus ref would still be valid, not triggering UB), leading to a production-only bug.

Asan is a wonderfull tool, but you can't deny it's much harder to use and much less reliable than just running your compiler.

void foo() {
    std::vector v = {0, 1, 2, 4};
    const auto& ref = v[1];
    add_missing_values(v);
    std::cout << ref << "\n";
}

void add_missing_values(std::vector<int>& v) {
    // ...
    v.push_back(3);
}

Neither foo(), nor add_missing_values() looks suspicious. Nonetheless, if v.push_back(3) requires v to grow, then ref becomes an invalid reference and std::cout << ref becomes UB (use after free). In Rust this would not compiles.

It is order of magnitudes easier to have lifetime errors in C++ than in Rust (use after free, double free, data races, use before initialisation, …)

Is it possible to do in Rust?

Yes

Is possible to do in Rust, by mistake, and not easily caught by a review?

Definitively not.

DRY and YAGNI are awesome iif you also practice YNIRN (You Need It Right Now)! Otherwise you just get boilerplate of spaghetti

You got me in the first 3 quarters, not gonna lie!

There are cases where instead of origin/master..HEAD you may want to use @{upstream}..HEAD instead to compare with the upstream of your current branch. It's unfortunately quite unknown.

The fact that rustc has bugs (which is what cve-rs exploit) doesn't invalidate that rust the language is memory safe.

This post from 2022 was very interesting:

There are approximately 1.5 million total lines of Rust code in AOSP across new functionality and components [...] These are low-level components that require a systems language which otherwise would have been implemented in C++.

To date, there have been zero memory safety vulnerabilities discovered in Android’s Rust code.

https://security.googleblog.com/2022/12/memory-safe-languages-in-android-13.html

The quote (and the associated discussion) is such an important part of Rust and why I love this language so much. Anything that can be automated should at one point be automated reliably, and the sooner the better.

I absolutely agree that method extraction can be abused. One should not forget that locality is important. Functionnal idioms do help to minimise the layer of intermediate functions. Lamda/closure helps too by having the function much closer to its use site. And local variables can sometime be a better choice than having a function that return just an expression.

Good advice, clear, simple and to the point.

Stated otherwise: "whenever you need to add comments to an expression, try to use named intermediate variables, method or free function".