codemap_diagnostic/
lock.rs

1// Copyright 2016 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//! Bindings to acquire a global named lock.
12//!
13//! This is intended to be used to synchronize multiple compiler processes to
14//! ensure that we can output complete errors without interleaving on Windows.
15//! Note that this is currently only needed for allowing only one 32-bit MSVC
16//! linker to execute at once on MSVC hosts, so this is only implemented for
17//! `cfg(windows)`. Also note that this may not always be used on Windows,
18//! only when targeting 32-bit MSVC.
19//!
20//! For more information about why this is necessary, see where this is called.
21
22use std::any::Any;
23
24#[cfg(windows)]
25#[allow(bad_style)]
26pub fn acquire_global_lock(name: &str) -> Box<Any> {
27    use std::ffi::CString;
28    use std::io;
29
30    type LPSECURITY_ATTRIBUTES = *mut u8;
31    type BOOL = i32;
32    type LPCSTR = *const u8;
33    type HANDLE = *mut u8;
34    type DWORD = u32;
35
36    const INFINITE: DWORD = !0;
37    const WAIT_OBJECT_0: DWORD = 0;
38    const WAIT_ABANDONED: DWORD = 0x00000080;
39
40    extern "system" {
41        fn CreateMutexA(lpMutexAttributes: LPSECURITY_ATTRIBUTES,
42                        bInitialOwner: BOOL,
43                        lpName: LPCSTR)
44                        -> HANDLE;
45        fn WaitForSingleObject(hHandle: HANDLE, dwMilliseconds: DWORD) -> DWORD;
46        fn ReleaseMutex(hMutex: HANDLE) -> BOOL;
47        fn CloseHandle(hObject: HANDLE) -> BOOL;
48    }
49
50    struct Handle(HANDLE);
51
52    impl Drop for Handle {
53        fn drop(&mut self) {
54            unsafe {
55                CloseHandle(self.0);
56            }
57        }
58    }
59
60    struct Guard(Handle);
61
62    impl Drop for Guard {
63        fn drop(&mut self) {
64            unsafe {
65                ReleaseMutex((self.0).0);
66            }
67        }
68    }
69
70    let cname = CString::new(name).unwrap();
71    unsafe {
72        // Create a named mutex, with no security attributes and also not
73        // acquired when we create it.
74        //
75        // This will silently create one if it doesn't already exist, or it'll
76        // open up a handle to one if it already exists.
77        let mutex = CreateMutexA(0 as *mut _, 0, cname.as_ptr() as *const u8);
78        if mutex.is_null() {
79            panic!("failed to create global mutex named `{}`: {}",
80                   name,
81                   io::Error::last_os_error());
82        }
83        let mutex = Handle(mutex);
84
85        // Acquire the lock through `WaitForSingleObject`.
86        //
87        // A return value of `WAIT_OBJECT_0` means we successfully acquired it.
88        //
89        // A return value of `WAIT_ABANDONED` means that the previous holder of
90        // the thread exited without calling `ReleaseMutex`. This can happen,
91        // for example, when the compiler crashes or is interrupted via ctrl-c
92        // or the like. In this case, however, we are still transferred
93        // ownership of the lock so we continue.
94        //
95        // If an error happens.. well... that's surprising!
96        match WaitForSingleObject(mutex.0, INFINITE) {
97            WAIT_OBJECT_0 | WAIT_ABANDONED => {}
98            code => {
99                panic!("WaitForSingleObject failed on global mutex named \
100                        `{}`: {} (ret={:x})",
101                       name,
102                       io::Error::last_os_error(),
103                       code);
104            }
105        }
106
107        // Return a guard which will call `ReleaseMutex` when dropped.
108        Box::new(Guard(mutex))
109    }
110}
111
112#[cfg(not(windows))]
113pub fn acquire_global_lock(_name: &str) -> Box<Any> {
114    Box::new(())
115}
codemap_diagnostic/lock.rs

codemap_diagnostic/
lock.rs
