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<dynAny> {
114 Box::new(())
115}
116