let v: i32 = 10;
let v1 = &v;
let a: *const i32 = &v;
println!("a={:p}", a);
let b = a as *mut i32;  //无法从&v直接转换成*mut i32，需要从*const i32过度
println!("b={:p}", b);
unsafe {*b+=1;
}
println!("v={}   v1={}", v, v1);

 输出

a=0xa7c8fb4d8
b=0xa7c8fb4d8
v=11   v1=11

    let mut mv: i32 = 10;let mut mv2 = &mut mv;*mv2 = *mv2 + 1;let p1 = mv2 as *const i32 as *mut i32;unsafe {*p1 += 1;}//let p2 = mv2 as *const i32;let mv3 = unsafe {let i: i32 = *p1;i};println!("mv2={}  mv3={}", mv2, mv3);

 mv2=12  mv3=12

    use std::borrow::Cow;use std::os::raw::c_char;use std::ffi::CStr;let C: [u8; 11] = [116, 104, 97, 110, 107, 115, 102, 105, 115, 104, 0];let c_str: Cow<str>;unsafe{let c_ptr = &C as *const u8 as *const c_char;c_str = CStr::from_ptr(c_ptr).to_string_lossy();}println!("c_str is    {}", c_str);

 c_str is    thanksfish

原始指针和unsafe块配合，可以避过引用借用保护，但也失去了rust的优势。rust严谨也足够灵活...，除非必要原始指针慎用，用多了又变成c了...