Get current thread name by prctl syscall in Rust

prctl.rs

// Given by Alice: https://users.rust-lang.org/t/cstring-into-string-s-behavior-on-android/44470/3
use std::ffi::CStr;
use std::os::raw::c_char;

const PR_GET_NAME: libc::c_int = 16;

unsafe fn call_prctl(allocation: &mut Vec<u8>) -> &CStr {
    let ptr = allocation.as_mut_ptr() as *mut c_char;
    let ret: libc::c_int = libc::prctl(PR_GET_NAME, ptr);
    if ret != 0 {
        panic!("prctl failed: {}", ret);
    }
    
    CStr::from_ptr(allocation.as_ptr() as *const c_char)
}

fn main() {
    unsafe {
        let mut allocation = Vec::with_capacity(32);
        let c_str_slice = call_prctl(&mut allocation);
        
        match c_str_slice.to_str() {
            Ok(s) => {
                println!("Return: {}, debug print: {:#?}, len: {}.", s, s, s.len());
            },
            Err(_) => println!("into_string failed.!"),
        };
    }
}

prctl_BUG.rs

use std::ffi::CString;

const PR_GET_NAME: libc::c_int = 16;

fn main() {
    unsafe {
        // WRONG WAY!!
        let cs = CString::from_vec_unchecked(Vec::with_capacity(32) as Vec<u8>);
        let ptr = cs.into_raw();
        let ret: libc::c_int = libc::prctl(PR_GET_NAME, ptr);
        if ret != 0 {
            println!("prctl failed: {}", ret);
            return;
        }
        let c_string = CString::from_raw(ptr);
        match c_string.into_string() {
            Ok(s) => {
                println!("Return: {}, debug print: {:#?}, len: {}.", s, s, s.len());
            },
            Err(_) => println!("into_string failed.!"),
        };
    }
}

prctl_bytes.rs

use std::ffi::CString;

const PR_GET_NAME: libc::c_int = 16;

fn main() {
    unsafe {
        let cs = CString::from_vec_unchecked(Vec::with_capacity(32) as Vec<u8>);
        let ptr = cs.into_raw();
        let ret: libc::c_int = libc::prctl(PR_GET_NAME, ptr);
        if ret != 0 {
            println!("prctl failed: {}", ret);
            return;
        }
        let c_string = CString::from_raw(ptr);
        let bytes = c_string.into_bytes_with_nul();
        println!("Bytes: {:#?}", bytes);
        match String::from_utf8(bytes) {
            Ok(s) => {
                // s.retain(|c| c.is_alphabetic());
                println!("Return: {}, debug print: {:#?}, len: {}.", s, s, s.len());
            },
            Err(e) => println!("into_string failed: {}!", e),
        };
    }
}