src/libstd/sys/common/at_exit_imp.rs

   1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Implementation of running at_exit routines
  12 //!
  13 //! Documentation can be found on the `rt::at_exit` function.
  14
  15 use alloc::boxed::FnBox;
  16 use ptr;
  17 use sys_common::mutex::Mutex;
  18
  19 type Queue = Vec<Box<FnBox()>>;
  20
  21 // NB these are specifically not types from `std::sync` as they currently rely
  22 // on poisoning and this module needs to operate at a lower level than requiring
  23 // the thread infrastructure to be in place (useful on the borders of
  24 // initialization/destruction).
  25 static LOCK: Mutex = Mutex::new();
  26 static mut QUEUE: *mut Queue = ptr::null_mut();
  27
  28 // The maximum number of times the cleanup routines will be run. While running
  29 // the at_exit closures new ones may be registered, and this count is the number
  30 // of times the new closures will be allowed to register successfully. After
  31 // this number of iterations all new registrations will return `false`.
  32 const ITERS: usize = 10;
  33
  34 unsafe fn init() -> bool {
  35     if QUEUE.is_null() {
  36         let state: Box<Queue> = box Vec::new();
  37         QUEUE = Box::into_raw(state);
  38     } else if QUEUE as usize == 1 {
  39         // can't re-init after a cleanup
  40         return false
  41     }
  42
  43     true
  44 }
  45
  46 pub fn cleanup() {
  47     for i in 0..ITERS {
  48         unsafe {
  49             LOCK.lock();
  50             let queue = QUEUE;
  51             QUEUE = if i == ITERS - 1 {1} else {0} as *mut _;
  52             LOCK.unlock();
  53
  54             // make sure we're not recursively cleaning up
  55             assert!(queue as usize != 1);
  56
  57             // If we never called init, not need to cleanup!
  58             if queue as usize != 0 {
  59                 let queue: Box<Queue> = Box::from_raw(queue);
  60                 for to_run in *queue {
  61                     to_run();
  62                 }
  63             }
  64         }
  65     }
  66 }
  67
  68 pub fn push(f: Box<FnBox()>) -> bool {
  69     let mut ret = true;
  70     unsafe {
  71         LOCK.lock();
  72         if init() {
  73             (*QUEUE).push(f);
  74         } else {
  75             ret = false;
  76         }
  77         LOCK.unlock();
  78     }
  79     ret
  80 }