Understanding Rust Error E0092

Rust Error E0092: Undefined Atomic Operation Function

The Rust error E0092 is encountered when a function is declared within an extern "rust-intrinsic" block, but the function does not correlate with a valid atomic operation function in the Rust compiler.

Let's examine the erroneous code example from the official Rust documentation:

#![allow(unused)]
#![feature(intrinsics)]

fn main() {
extern "rust-intrinsic" {
    fn atomic_foo(); // error: unrecognized atomic operation
                     //        function
}
}

The atomic_foo() function is declared within the extern "rust-intrinsic" block, but it does not correspond to a valid function related to atomic operations. As a result, the Rust compiler raises error E0092.

Fixing Rust Error E0092

To fix error E0092, make sure to reference a valid intrinsic function that exists in the Rust source code. You can find and verify the valid atomic operation functions in library/core/src/intrinsics.rs and compiler/rustc_codegen_llvm/src/intrinsic.rs in the Rust source code.

The corrected code will resemble the following example:

#![allow(unused)]
#![feature(intrinsics)]

fn main() {
extern "rust-intrinsic" {
    fn atomic_fence_seqcst(); // ok!
}
}

In the corrected example, the atomic_fence_seqcst() function replaces atomic_foo() and is recognized as a valid atomic operation function. This code will compile without error.

Additional Tips

When working with the extern "rust-intrinsic" block, be mindful of the following:

1. Verify the function name: Ensure that the function name exactly matches the corresponding function in the Rust source code.

2. Check spelling and formatting: A simple typo can result in error E0092. Ensure that all characters are correctly formatted.

3. Keep up-to-date with the Rust source code: Functions may be added or removed, so verify the library/core/src/intrinsics.rs and compiler/rustc_codegen_llvm/src/intrinsic.rs in the Rust source code to stay current.