panic!

panic! 宏可用于产生一个 panic （恐慌），并开始回退（unwind）它的栈。在回退栈 的同时，运行时将会释放该线程所拥有的所有资源，这是通过调用线程中所有对象的 析构函数完成的。

因为我们正在处理的程序只有一个线程，panic! 将会引发程序报告 panic 消息并退出。

  1. // 整型除法（/）的重新实现
  2. fn division(dividend: i32, divisor: i32) -> i32 {
  3.     if divisor == 0 {
  4.         // 除以 0 会引发 panic
  5.         panic!("division by zero");
  6.     } else {
  7.         dividend / divisor
  8.     }
  9. }
  11. // `main` 任务
  12. fn main() {
  13.     // 堆分配的整数
  14.     let _x = Box::new(0i32);
  16.     // 此操作将会引发一个任务失败
  17.     division(3, 0);
  19.     println!("This point won't be reached!");
  21.     // `_x` 应当会在此处被销毁
  22. }

可以看到，panic! 不会泄露内存：

  1. $ rustc panic.rs && valgrind ./panic
  2. ==4401== Memcheck, a memory error detector
  3. ==4401== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
  4. ==4401== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
  5. ==4401== Command: ./panic
  6. ==4401== 
  7. thread '<main>' panicked at 'division by zero', panic.rs:5
  8. ==4401== 
  9. ==4401== HEAP SUMMARY:
  10. ==4401==     in use at exit: 0 bytes in 0 blocks
  11. ==4401==   total heap usage: 18 allocs, 18 frees, 1,648 bytes allocated
  12. ==4401== 
  13. ==4401== All heap blocks were freed -- no leaks are possible
  14. ==4401== 
  15. ==4401== For counts of detected and suppressed errors, rerun with: -v
  16. ==4401== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)