Feds: Critical Software Must Drop C/C++ by 2026 or Face Risk (thenewstack.io)

submitted 2 weeks ago by arendjr@programming.dev to c/programming@programming.dev

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[-] arendjr@programming.dev 31 points 2 weeks ago* (last edited 2 weeks ago)

Using smart pointers doesn’t eliminate the memory safety issue, it merely addresses one aspect of it. Even with smart pointers, nothing is preventing you from passing references and using them after they’re freed.

[+] refalo@programming.dev -10 points 2 weeks ago

To be fair, it's entirely possible to make the same and very similar mistakes in Rust, too.

[-] GetOffMyLan@programming.dev 7 points 2 weeks ago* (last edited 2 weeks ago)

I'm fairly sure use after free isn't possible unless you explicitly use unsafe code right?

It's compiler enforced is the point.

[-] robinm@programming.dev 1 points 1 week ago

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.

[-] refalo@programming.dev 0 points 1 week ago

I think you could argue the same point with C++

[-] robinm@programming.dev 1 points 6 days ago

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, …)

[-] refalo@programming.dev 1 points 6 days ago* (last edited 6 days ago)

This would be caught by ASan and other tools though, which should be part of any review.

[-] robinm@programming.dev 0 points 3 days ago

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

[-] robinm@programming.dev 1 points 6 days ago

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.

this post was submitted on 01 Nov 2024

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