You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: riscv.rs
    path of file: ./repos/wasmtime/cranelift/native/src
    
    the code of the file until where you have to start completion: use cranelift_codegen::settings::Configurable;
use std::fs::File;
use std::io::{BufRead, BufReader};

pub fn hwcap_detect(isa_builder: &mut dyn Configurable) -> Result<(), &'static str> {
    let v = unsafe { libc::getauxval(libc::AT_HWCAP) };

    const HWCAP_RISCV_EXT_A: libc::c_ulong = 1 << (b'a' - b'a');
    const HWCAP_
    
fn isa_string_extensions(isa: &str) -> Vec<&str> {
    let mut parts = isa.split('_');
    let mut extensions = Vec::new();
    // The first entry has the form `rv64imafdcvh`, we need to skip the architecture ("rv64").
    // Each of the letters after the cpu architecture is an extension, so return them
    // individually.
    if let Some(letters) = parts.next().unwrap().strip_prefix("rv64") {
        extensions.extend(letters.matches(|_| true));
        extensions.extend(parts);
    }
    extensions
}