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  1. use std::mem;
  2.  
  3. fn main() {
  4.     const N: usize = 32;
  5.     const BIG: usize = N + 1;
  6.  
  7.     // Local array on the stack
  8.     let big = [0u8; BIG];
  9.  
  10.     // Base address of the large array
  11.     let base = big.as_ptr() as usize;
  12.     println!(
  13.         "base addr: {:#x}, base % align_of::<usize>() = {}",
  14.         base,
  15.         base % mem::align_of::<usize>()
  16.     );
  17.  
  18.     // Take a pointer to big[1] and reinterpret it as &[u8; N]
  19.     let arr_ptr = unsafe { big.as_ptr().add(1) as *const [u8; N] };
  20.     let arr_addr = arr_ptr as usize;
  21.     let aligned = arr_addr % mem::align_of::<usize>() == 0;
  22.  
  23.     println!(
  24.         "arr addr:  {:#x}, aligned_to_usize = {}",
  25.         arr_addr,
  26.         aligned
  27.     );
  28.  
  29.     // Optional: actually create a reference to the array
  30.     let _arr_ref: &[u8; N] = unsafe { &*arr_ptr };
  31.  
  32.     println!("align_of::<[u8; N]>()   = {}", mem::align_of::<[u8; N]>());
  33.     println!("align_of::<usize>()     = {}", mem::align_of::<usize>());
  34. }
  35.  
Success #stdin #stdout 0.01s 5320KB
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stdin
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Standard input is empty
stdout
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base addr: 0x7ffc471dd2f0, base % align_of::<usize>() = 0
arr addr:  0x7ffc471dd2f1, aligned_to_usize = false
align_of::<[u8; N]>()   = 1
align_of::<usize>()     = 8
https://ideone.com/XVAv3a
language:
Rust (rust 1.56)
created:
5 days ago
visibility:
public

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