Is undefined behavior possible in safe Rust?

user_12816539 0
Viewed 2005

Is there any way to achieve undefined behavior in Rust without using unsafe?

Of course, such behavior can be wrapped by a third-party library in a "safe" function so let's assume we're using only the standard one.

rust standard-library undefined-behavior unsafe
1 Answers

Absolutely, but any such case is a bug with Rust or the standard libary.

My favorite example is LLVM loop optimization can make safe programs crash, which actually occurs due to a poor interaction of Rust and LLVM semantics:

pub fn oops() {
    (|| loop {
        drop(42)
    })()
}

Compiled with optimizations on Rust 1.49.0, this produces the assembly:

playground::oops:
    ud2

such behavior can be wrapped by a third-party library in a "safe" function so let's assume we're using only the standard one

The standard library is a "third-party library", so I don't get the distinction.

user_1554230
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