Understanding Rust Error E0093 - Unknown Intrinsic Function

Introduction to Rust Error E0093

Rust Error E0093 occurs when an unrecognized or unknown intrinsic function is declared in the code, which means the Rust compiler couldn't find the declared intrinsic function in its source code. Intrinsic functions are special functions that are not visible at the source level but can be accessed through the 'extern' keyword.

The error often results from a typo or a mistake in the function's name. In this article, we will delve deeper into the details of Rust Error E009 the context and provide examples to explain the issue.

Example: Erroneous Code

#![feature(intrinsics)]

extern "rust-intrinsic" {
    fn foo(); // error: unrecognized intrinsic function: `foo`
}

fn main() {
    unsafe {
        foo();
    }
}

In the above code snippet, the function 'foo()' is declared as an intrinsic function, but it isn't a valid intrinsic function in the Rust source code.

Finding Intrinsic Functions

In Rust, all intrinsic functions are defined in two files -- compiler/rustc_codegen_llvm/src/intrinsic.rs and library/core/src/intrinsics.rs. To resolve Rust Error E0093, you should check these two files to find a valid name for the intrinsic function. Furthermore, you should make sure to avoid typos when typing the name of the function.

Example: Corrected Code

#![feature(intrinsics)]

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

fn main() {
    unsafe {
        atomic_fence_seqcst();
    }
}

In this corrected code snippet, we replaced the invalid 'foo()' function with a valid intrinsic function 'atomic_fence_seqcst()'. Now, the code will compile and run without any errors.

Conclusion

To fix Rust Error E0093, you should first ensure that you have typed the intrinsic function's name correctly, and that it exists in the Rust source code. By referring to the list of available intrinsic functions in the Rust compiler files and using them accurately in your code, you can successfully resolve this error and proceed with your project.