NAME
ACE_Object_Manager - Manager for ACE library services and singleton cleanup.
SYNOPSIS
#include <ace/Object_Manager.h>
class ACE_Object_Manager : public ACE_Object_Manager_Base
{
public:
virtual int init (void);
virtual int fini (void);
static int starting_up (void);
static int shutting_down (void);
static int at_exit (ACE_Cleanup *object, void *param = 0);
static int at_exit (
void *object,
ACE_CLEANUP_FUNC cleanup_hook,
void *param
);
static int at_thread_exit (
void *object,
ACE_CLEANUP_FUNC cleanup_hook,
void *param
);
enum Preallocated_Object{ ACE_FILECACHE_LOCK, #if defined (
ACE_HAS_THREADS) ACE_STATIC_OBJECT_LOCK,
#endif #if defined (ACE_MT_SAFE) && (ACE_MT_SAFE != 0) ACE_MT_CORBA_HANDLER_LOCK,
ACE_DUMP_LOCK,
ACE_SIG_HANDLER_LOCK,
ACE_SINGLETON_NULL_LOCK,
ACE_SINGLETON_RECURSIVE_THREAD_LOCK,
ACE_THREAD_EXIT_LOCK,
#if !defined (ACE_LACKS_ACE_TOKEN) ACE_TOKEN_MANAGER_CREATION_LOCK,
ACE_TOKEN_INVARIANTS_CREATION_LOCK,
#endif ACE_PROACTOR_EVENT_LOOP_LOCK,
#endif ACE_APPLICATION_PREALLOCATED_OBJECT_DECLARATIONS ACE_PREALLOCATED_OBJECTS };
enum Preallocated_Array{ ACE_EMPTY_PREALLOCATED_ARRAY,
ACE_APPLICATION_PREALLOCATED_ARRAY_DECLARATIONS ACE_PREALLOCATED_ARRAYS };
static ACE_Sig_Set &default_mask (void);
static int get_singleton_lock (ACE_Null_Mutex *&);
static int get_singleton_lock (ACE_Thread_Mutex *&);
static int get_singleton_lock (ACE_Mutex *&);
static int get_singleton_lock (ACE_Recursive_Thread_Mutex *&);
static int get_singleton_lock (ACE_RW_Thread_Mutex *&);
static ACE_Object_Manager *instance (void);
static void *preallocated_object[ACE_PREALLOCATED_OBJECTS];
static void *preallocated_array[ACE_PREALLOCATED_ARRAYS];
ACE_Object_Manager (void);
~ACE_Object_Manager (void);
private:
ACE_OS_Exit_Info exit_info_;
ACE_Object_Manager_Preallocations *preallocations_;
ACE_Sig_Adapter *ace_service_config_sig_handler_;
int at_exit_i (
void *object,
ACE_CLEANUP_FUNC cleanup_hook,
void *param
);
static ACE_Object_Manager *instance_;
ACE_Recursive_Thread_Mutex *internal_lock_;
ACE_Cleanup_Adapter<ACE_Null_Mutex> *singleton_null_lock_;
ACE_Cleanup_Adapter<ACE_Recursive_Thread_Mutex> *singleton_recursive_lock_;
void *ts_storage_[ACE_TSS_Emulation::ACE_TSS_THREAD_KEYS_MAX];
friend class ACE_Object_Manager_Manager;
ACE_Object_Manager (const ACE_Object_Manager &);
ACE_Object_Manager &operator= (const ACE_Object_Manager &);
};
DESCRIPTION
The ACE_Object_Manager manages cleanup of objects, typically singletons, at program termination. In addition to managing the cleanup of the ACE library, it provides an interface for application to register objects to be cleaned up.
This class also shuts down ACE library services, so that they can reclaim their storage, at program termination. It works by creating a static instance whose destructor gets called along with those of all other static objects. Hooks are provided for application code to register objects and arrays for cleanup, e.g., destruction. The order of such cleanup calls is in the reverse order of registration, i.e., that last object/array to register gets cleaned up first.
The ACE_Object_Manager API includes ACE_Managed_Object. That class is contained in a separate file because it is a template class, and some compilers require that template and non-template class definitions appear in separate files. Please see ace/Managed_Object.h for a description of that part of the API. In summary, ACE_Managed_Object provides two adapters, the ACE_Cleanup_Adapter and ACE_Managed_Object template classes for adapting objects of any type to be easily managed by the ACE_Object_Manager. There are several mechanisms for adapting objects and arrays for cleanup at program termination, in roughly increasing order of ease-of-use:
1) Derive the object's class from ACE_Cleanup. 2) Allow the ACE_Object_Manager to both dynamically allocate
and deallocate the object. 3) Provide an ACE_CLEANUP_FUNC cleanup hook for the object or
array. 4) Allow the ACE_Object_Manager to both preallocate the object
or array, either statically in global data or dynamically on
the heap, when its singleton instance is construction.
There are also several mechanisms for registering objects and arrays for cleanup. In decreasing order of flexibility and complexity (with the exception of the last mechanism):
1) ACE_Object_Manager::at_exit (void *object,
ACE_CLEANUP_FUNC cleanup_hook,
void *param);
can be used to register any object or array for any
cleanup activity at program termination.
2) ACE_Object_Manager::at_exit (ACE_Cleanup *object,
void *param = 0);
can be used to register an ACE_Cleanup object
for any cleanup activity at program termination.
The final mechanism is not general purpose, but can only
be used to allocate objects and arrays at program startup:
3) ACE_Managed_Object::get_preallocated_object
(ACE_Object_Manager::Preallocated_Object id);
and
ACE_Managed_Object::get_preallocated_array
(ACE_Object_Manager::Preallocated_Array id);
can only be used to allocate objects at program startup,
either in global data or on the heap (selected at compile
time). These are intended to replace static locks, etc.
Instead of creating a static ACE_Object_Manager instance, one can alternatively be created on the stack of the main program thread. It is created just after entry to ::main (int, char *[]), and before any existing code in that function is executed. To enable this alternative, add #define ACE_HAS_NONSTATIC_OBJECT_MANAGER before including the platform specific config-* file in ace/config.h prior to building the ACE library and your applications. This #define is enabled in some config files that are supplied with ACE. To ensure a static object manager is used, #undef ACE_HAS_NONSTATIC_OBJECT_MANAGER *after* including the platform specific config-* file.
Note that the ACE_Object_Manager _must_ be created before any threads are spawned by the program.
If ACE_HAS_NONSTATIC_OBJECT_MANAGER is not #defined, the ACE library creates a static, singleton ACE_Object_Manager instance. The instance is placed in global program data, and constructed via a static object constructor. If ACE_HAS_NONSTATIC_OBJECT_MANAGER is #defined, the ACE_Object_Manager instance is created on the stack of the main program thread, as noted above.
With ACE_HAS_NONSTATIC_OBJECT_MANAGER enabled, the ACE library has no static objects that require destruction. However, there are two drawbacks to using it:
1) main (int, char *[]) must be declared with arguments, even
if they're not used. All of ACE is converted to this, so
just applications have to be concerned with it.
2) If there any static objects that depend on those that are
cleaned up by the Object_Manager, they'll get cleaned up too
late. The ACE tests do not violate this requirement.
However, applications may have trouble with it.
NOTE on the use of ::exit -- ::exit does not destroy static objects. Therefore, if ACE_HAS_NONSTATIC_OBJECT_MANAGER is enabled, the ACE_Object_Manager instance will *not* be destroyed if ::exit is called! However, ACE_OS::exit will properly destroy the ACE_Object_Manager. It is highly recommended that ACE_OS::exit be used instead of ::exit.
However, ::exit and ACE_OS::exit are tricky to use properly, especially in multithread programs. It is much safer to throw an exception (or simulate that effect) that will be caught by main instead of calling exit. Then, main can perform any necessary application-specific cleanup and return the status value. In addition, it's usually best to avoid calling ::exit and ACE_OS::exit from threads other than the main thread. Thanks to Jeff Greif [email protected] for pointing out that ::exit doesn't destroy automatic objects, and for developing the recommendations in this paragraph.
Instead of creating a static ACE_Object_Manager, or letting ACE create it on the stack of main for you, another alternative is to #define ACE_DOESNT_INSTANTIATE_NONSTATIC_OBJECT_MANAGER. With that #define, the application must create the ACE_Object_Manager. The recommended way is to call ACE::init at the start of the program, and call ACE::fini at the end. Alternatively, the application could explicity construct an ACE_Object_Manager.
PUBLIC MEMBERS
virtual int init (void);
Explicitly initialize (construct the singleton instance of) the ACE_Object_Manager. Returns 0 on success, -1 on failure, and 1 if it had already been called.
virtual int fini (void);
Explicitly destroy the singleton instance of the ACE_Object_Manager. Returns 0 on success, -1 on failure, and 1 if it had already been called.
static int starting_up (void);
Returns 1 before the ACE_Object_Manager has been constructed. This flag can be used to determine if the program is constructing static objects. If no static object spawns any threads, the program will be single-threaded when this flag returns 1. (Note that the program still might construct some static objects when this flag returns 0, if ACE_HAS_NONSTATIC_OBJECT_MANAGER is not defined.)
static int shutting_down (void);
Returns 1 after the ACE_Object_Manager has been destroyed. This flag can be used to determine if the program is in the midst of destroying static objects. (Note that the program might destroy some static objects before this flag can return 1, if ACE_HAS_NONSTATIC_OBJECT_MANAGER is not defined.)
static int at_exit (ACE_Cleanup *object, void *param = 0);
Register an ACE_Cleanup object for cleanup at process termination. The object is deleted via the ace_cleanup_destroyer. If you need more flexiblity, see the other at_exit method below. For OS's that do not have processes, cleanup takes place at the end of main. Returns 0 on success. On failure, returns -1 and sets errno to: EAGAIN if shutting down, ENOMEM if insufficient virtual memory, or EEXIST if the object (or array) had already been registered.
static int at_exit (
void *object,
ACE_CLEANUP_FUNC cleanup_hook,
void *param
);
Register an object (or array) for cleanup at process termination. "cleanup_hook" points to a (global, or static member) function that is called for the object or array when it to be destroyed. It may perform any necessary cleanup specific for that object or its class. "param" is passed as the second parameter to the "cleanup_hook" function; the first parameter is the object (or array) to be destroyed. "cleanup_hook", for example, may delete the object (or array). For OS's that do not have processes, this function is the same as at_thread_exit. Returns 0 on success. On failure, returns -1 and sets errno to: EAGAIN if shutting down, ENOMEM if insufficient virtual memory, or EEXIST if the object (or array) had already been registered.
static int at_thread_exit (
void *object,
ACE_CLEANUP_FUNC cleanup_hook,
void *param
);
Similar to at_exit, except that the cleanup_hook is called when the current thread exits instead of when the program terminates.
static ACE_Sig_Set &default_mask (void);
Accesses a default signal set used, for example, in ACE_Sig_Guard methods. Deprecated: use ACE_Object_Manager::default_mask () instead.
static int get_singleton_lock (ACE_Null_Mutex *&);
Accesses an ACE_Null_Mutex to be used for construction of ACE_Singletons. Returns 0, and the lock in the argument, on success; returns -1 on failure.
static int get_singleton_lock (ACE_Thread_Mutex *&);
Accesses a non-recursive ACE_Thread_Mutex to be used for construction of ACE_Singletons. Returns 0, and the lock in the argument, on success; returns -1 on failure.
static int get_singleton_lock (ACE_Mutex *&);
Accesses a non-recursive ACE_Mutex to be used for construction of ACE_Singletons. Returns 0, and the lock in the argument, on success; returns -1 on failure.
static int get_singleton_lock (ACE_Recursive_Thread_Mutex *&);
Accesses a recursive ACE_Recursive_Thread_Mutex to be used for construction of ACE_Singletons. Returns 0, and the lock in the argument, on success; returns -1 on failure.
static int get_singleton_lock (ACE_RW_Thread_Mutex *&);
Accesses a readers/writer ACE_RW_Thread_Mutex to be used for construction of ACE_Singletons. Returns 0, and the lock in the argument, on success; returns -1 on failure.
static ACE_Object_Manager *instance (void);
Accessor to singleton instance. Because static member functions are provided in the interface, this should not be public. However, it is public so that ACE_Managed_ObjectTYPE can access it.
static void *preallocated_object[ACE_PREALLOCATED_OBJECTS];
Table of preallocated objects.
static void *preallocated_array[ACE_PREALLOCATED_ARRAYS];
Table of preallocated arrays.
ACE_Object_Manager (void);
~ACE_Object_Manager (void);
PRIVATE MEMBERS
ACE_OS_Exit_Info exit_info_;
For at_exit support.
ACE_Object_Manager_Preallocations *preallocations_;
Preallocated objects collection.
ACE_Sig_Adapter *ace_service_config_sig_handler_;
ACE_Service_Config signal handler.
int at_exit_i (
void *object,
ACE_CLEANUP_FUNC cleanup_hook,
void *param
);
Register an object or array for deletion at program termination. See description of static version above for return values.
static ACE_Object_Manager *instance_;
Singleton pointer.
ACE_Recursive_Thread_Mutex *internal_lock_;
Lock that is used to guard internal structures.
ACE_Cleanup_Adapter<ACE_Null_Mutex> *singleton_null_lock_;
Null lock for guarding singleton creation.
ACE_Cleanup_Adapter<ACE_Recursive_Thread_Mutex> *singleton_recursive_lock_;
Lock for guarding singleton creation, when Object_Manager hasn't been started up, or has already been shut down.
void *ts_storage_[ACE_TSS_Emulation::ACE_TSS_THREAD_KEYS_MAX];
friend class ACE_Object_Manager_Manager;
ACE_Object_Manager (const ACE_Object_Manager &);
ACE_Object_Manager &operator= (const ACE_Object_Manager &);
AUTHORS
David L. Levine, Matthias Kerkhoff, and Per Andersson
LIBRARY
ace