support/include/llvm/Support/ManagedStatic.h

//===-- llvm/Support/ManagedStatic.h - Static Global wrapper ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Chris Lattner and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the ManagedStatic class and the llvm_shutdown() function.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_MANAGED_STATIC_H
#define LLVM_SUPPORT_MANAGED_STATIC_H

namespace llvm {

/// object_deleter - Helper method for ManagedStatic.
///
template<class C>
void object_deleter(void *Ptr) {
  delete (C*)Ptr;
}

/// ManagedStaticBase - Common base class for ManagedStatic instances.
class ManagedStaticBase {
protected:
  // This should only be used as a static variable, which guarantees that this
  // will be zero initialized.
  mutable void *Ptr;
  mutable void (*DeleterFn)(void*);
  mutable const ManagedStaticBase *Next;
  
  void RegisterManagedStatic(void *ObjPtr, void (*deleter)(void*)) const;
public:
  /// isConstructed - Return true if this object has not been created yet.  
  bool isConstructed() const { return Ptr != 0; }
  
  void destroy() const;
};

/// ManagedStatic - This transparently changes the behavior of global statics to
/// be lazily constructed on demand (good for reducing startup times of dynamic
/// libraries that link in LLVM components) and for making destruction be
/// explicit through the llvm_shutdown() function call.
///
template<class C>
class ManagedStatic : public ManagedStaticBase {
public:
  
  // Accessors.
  C &operator*() {
    if (!Ptr) LazyInit();
    return *static_cast<C*>(Ptr);
  }
  C *operator->() {
    if (!Ptr) LazyInit();
    return static_cast<C*>(Ptr);
  }
  const C &operator*() const {
    if (!Ptr) LazyInit();
    return *static_cast<C*>(Ptr);
  }
  const C *operator->() const {
    if (!Ptr) LazyInit();
    return static_cast<C*>(Ptr);
  }
  
public:
  void LazyInit() const {
    RegisterManagedStatic(new C(), object_deleter<C>);
  }
};

template<void (*CleanupFn)(void*)>
class ManagedCleanup : public ManagedStaticBase {
public:
  void Register() { RegisterManagedStatic(0, CleanupFn); }
};


/// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
void llvm_shutdown();

  
/// llvm_shutdown_obj - This is a simple helper class that calls
/// llvm_shutdown() when it is destroyed.
struct llvm_shutdown_obj {
  llvm_shutdown_obj() {}
  ~llvm_shutdown_obj() { llvm_shutdown(); }
};
  
}

#endif