1 //===-- ManagedStatic.cpp - Static Global wrapper -------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the ManagedStatic class and llvm_shutdown().
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/Support/ManagedStatic.h"
14 #include "llvm/Config/config.h"
15 #include "llvm/Support/Threading.h"
16 #include <cassert>
17 #include <mutex>
18 using namespace llvm;
19 
20 static const ManagedStaticBase *StaticList = nullptr;
21 static std::recursive_mutex *ManagedStaticMutex = nullptr;
22 static llvm::once_flag mutex_init_flag;
23 
initializeMutex()24 static void initializeMutex() {
25   ManagedStaticMutex = new std::recursive_mutex();
26 }
27 
getManagedStaticMutex()28 static std::recursive_mutex *getManagedStaticMutex() {
29   llvm::call_once(mutex_init_flag, initializeMutex);
30   return ManagedStaticMutex;
31 }
32 
RegisterManagedStatic(void * (* Creator)(),void (* Deleter)(void *)) const33 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
34                                               void (*Deleter)(void*)) const {
35   assert(Creator);
36   if (llvm_is_multithreaded()) {
37     std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
38 
39     if (!Ptr.load(std::memory_order_relaxed)) {
40       void *Tmp = Creator();
41 
42       Ptr.store(Tmp, std::memory_order_release);
43       DeleterFn = Deleter;
44 
45       // Add to list of managed statics.
46       Next = StaticList;
47       StaticList = this;
48     }
49   } else {
50     assert(!Ptr && !DeleterFn && !Next &&
51            "Partially initialized ManagedStatic!?");
52     Ptr = Creator();
53     DeleterFn = Deleter;
54 
55     // Add to list of managed statics.
56     Next = StaticList;
57     StaticList = this;
58   }
59 }
60 
destroy() const61 void ManagedStaticBase::destroy() const {
62   assert(DeleterFn && "ManagedStatic not initialized correctly!");
63   assert(StaticList == this &&
64          "Not destroyed in reverse order of construction?");
65   // Unlink from list.
66   StaticList = Next;
67   Next = nullptr;
68 
69   // Destroy memory.
70   DeleterFn(Ptr);
71 
72   // Cleanup.
73   Ptr = nullptr;
74   DeleterFn = nullptr;
75 }
76 
77 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
llvm_shutdown()78 void llvm::llvm_shutdown() {
79   std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
80 
81   while (StaticList)
82     StaticList->destroy();
83 }
84