NSAutoreleasePool.m

/** Implementation of auto release pool for delayed disposal
   Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.

   Written by:  Andrew Kachites McCallum <mccallum@gnu.ai.mit.edu>
   Written by:  Richard Frith-Macdonald <rfm@gnu.org>
   Date: January 1995

   This file is part of the GNUstep Base Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 31 Milk Street #960789 Boston, MA 02196 USA.

   <title>NSAutoreleasePool class reference</title>
   $Date$ $Revision$
   */

#import "common.h"
#define	EXPOSE_NSAutoreleasePool_IVARS	1
#define	EXPOSE_NSThread_IVARS	1
#import "Foundation/NSAutoreleasePool.h"
#import "Foundation/NSException.h"
#import "Foundation/NSThread.h"

#if __has_include(<objc/capabilities.h>)
#  include <objc/capabilities.h>
#  ifdef OBJC_ARC_AUTORELEASE_DEBUG
#    include <objc/objc-arc.h>
#    define ARC_RUNTIME 1
#  endif
#endif




#define	LOG_LIFETIME	0

/* When this is `NO', autoreleased objects are never actually recorded
   in an NSAutoreleasePool, and are not sent a `release' message.
   Thus memory for objects use grows, and grows, and... */
static BOOL autorelease_enabled = YES;

/* When the _released_count of a pool gets over this value, we raise
   an exception.  This can be adjusted with +setPoolCountThreshold */
static unsigned pool_count_warning_threshold = UINT_MAX-1;

/* When the number of pools in a thread gets over this value, we raise
   an exception.  This can be adjusted with +setPoolNumberThreshold */
static unsigned pool_number_warning_threshold = 10000;

/* The size of the first _released array. */
#define BEGINNING_POOL_SIZE 32

/* Easy access to the thread variables belonging to NSAutoreleasePool. */
#define ARP_THREAD_VARS (&((GSCurrentThread())->_autorelease_vars))


@interface NSAutoreleasePool (Private)
+ (unsigned) autoreleaseCountForObject: (id)anObject;
- (void) _reallyDealloc;
@end


/* Functions for managing a per-thread cache of NSAutoreleasedPool's
   already alloc'ed.  The cache is kept in the autorelease_thread_var
   structure, which is an ivar of NSThread. */

static id pop_pool_from_cache(struct autorelease_thread_vars *tv);

static inline void
free_pool_cache(struct autorelease_thread_vars *tv)
{
  while (tv->pool_cache_count)
    {
      NSAutoreleasePool	*pool = pop_pool_from_cache(tv);

      [pool _reallyDealloc];
    }

  if (tv->pool_cache)
    {
      NSZoneFree(NSDefaultMallocZone(), tv->pool_cache);
      tv->pool_cache = 0;
      tv->pool_cache_size = 0;
    }
}

static inline void
init_pool_cache(struct autorelease_thread_vars *tv)
{
  tv->pool_cache_size = 32;
  tv->pool_cache_count = 0;
  tv->pool_cache = (id*)NSZoneMalloc(NSDefaultMallocZone(),
    sizeof(id) * tv->pool_cache_size);
}

static void
push_pool_to_cache(struct autorelease_thread_vars *tv, id p)
{
  if (!tv->pool_cache)
    {
      init_pool_cache(tv);
    }
  else if (tv->pool_cache_count == tv->pool_cache_size)
    {
      tv->pool_cache_size *= 2;
      tv->pool_cache = (id*)NSZoneRealloc(NSDefaultMallocZone(),
	tv->pool_cache, sizeof(id) * tv->pool_cache_size);
    }
  tv->pool_cache[tv->pool_cache_count++] = p;
}

static id
pop_pool_from_cache(struct autorelease_thread_vars *tv)
{
  return tv->pool_cache[--(tv->pool_cache_count)];
}


@implementation NSAutoreleasePool

+ (void) initialize
{
  /* Do nothing here which might interact with ther classes since this
   * is called by [NSObject+initialize] !
   */
  return;
}

+ (id) allocWithZone: (NSZone*)zone
{
  struct autorelease_thread_vars *tv = ARP_THREAD_VARS;
  NSAutoreleasePool	*p;

  if (tv->pool_cache_count)
    {
      p = pop_pool_from_cache(tv);

      /* When we cache a 'deallocated' pool, we set its _released_count to
       * UINT_MAX, so when we rtrieve it fromm the cache we must increment
       * it to start with a count of zero.
       */
      if (++(p->_released_count) != 0)
        {
          [NSException raise: NSInternalInconsistencyException
                      format: @"NSAutoreleasePool corrupted pool in cache"];
        }
      return p;
    }
  p = (NSAutoreleasePool*)NSAllocateObject (self, 0, zone);

#if	LOG_LIFETIME
  fprintf(stderr, "*** %p autorelease pool allocated in %p\n",
    p, GSCurrentThread());
#endif

  return p;
}

+ (id) new
{
  static IMP	allocImp = 0;
  static IMP	initImp = 0;
  id		arp;

  if (0 == allocImp)
    {
      allocImp
	= [NSAutoreleasePool methodForSelector: @selector(allocWithZone:)];
      initImp
	= [NSAutoreleasePool instanceMethodForSelector: @selector(init)];
    }
  arp = (*allocImp)(self, @selector(allocWithZone:), NSDefaultMallocZone());
  return (*initImp)(arp, @selector(init));
}

- (void) _emptyChild
{
  /* If there are NSAutoreleasePool below us in the list of
   * NSAutoreleasePools, then deallocate them also.
   * The (only) way we could get in this situation (in correctly
   * written programs, that don't release NSAutoreleasePools in
   * weird ways), is if an exception threw us up the stack.
   * However, if a program has leaked pools we may be deallocating
   * a pool with LOTS of children. To avoid stack overflow we
   * therefore deallocate children starting with the oldest first.
   */
  if (nil != _child)
    {
      NSAutoreleasePool	*pool = _child;

      /* Find other end of linked list ... oldest child.
       */
      while (nil != pool->_child)
	{
	  pool = pool->_child;
	}
      /* Deallocate the children in the list.
       */
      while (pool != self)
	{
	  pool = pool->_parent;
	  [pool->_child dealloc];
	}
    }
}

#ifdef ARC_RUNTIME

- (id) init
{
  _released = objc_autoreleasePoolPush();
  {
    struct autorelease_thread_vars *tv = ARP_THREAD_VARS;
    unsigned	level = 0;

    _parent = tv->current_pool;
    if (_parent)
      {
	NSAutoreleasePool	*pool = _parent;

	_child = _parent->_child;
	while (nil != pool)
	  {
	    level++;
	    pool = pool->_parent;
	  }
        _parent->_child = self;
      }
    tv->current_pool = self;
    if (level > pool_number_warning_threshold)
      {
	[NSException raise: NSGenericException
	  format: @"Too many (%u) autorelease pools ... leaking them?", level];
      }
  }

  /* Catch the case where the receiver is a pool still in use (wrongly put in 
     the pool cache previously). */
  NSCAssert(_child != self, @"Invalid child pool");
  NSCAssert(_parent != self, @"Invalid parent pool");

  return self;
}

- (unsigned) autoreleaseCountForObject: (id)anObject
{
  return objc_arc_autorelease_count_for_object_np(anObject);
}

+ (unsigned) autoreleaseCountForObject: (id)anObject
{
  return objc_arc_autorelease_count_for_object_np(anObject);
}

- (unsigned) autoreleaseCount
{
  return objc_arc_autorelease_count_np();
}

+ (void) addObject: (id)anObj
{
  if (autorelease_enabled)
    objc_autorelease(anObj);
}

- (void) addObject: (id)anObj
{
  if (autorelease_enabled)
    objc_autorelease(anObj);
}
- (void) emptyPool
{
  struct autorelease_thread_vars *tv = ARP_THREAD_VARS;

  if (nil != _child)
    {
      [self _emptyChild];
    }
  objc_autoreleasePoolPop(_released);
  tv->current_pool = self;
}
/**
 * Indicate to the runtime that we have an ARC-compatible implementation of
 * NSAutoreleasePool and that it doesn't need to bother creating objects for
 * pools.
 */
- (void)_ARCCompatibleAutoreleasePool {}
#else
- (id) init
{
  if (!_released_head)
    {
      _addImp = (void (*)(id, SEL, id))
	[self methodForSelector: @selector(addObject:)];
      /* Allocate the array that will be the new head of the list of arrays. */
      _released = (struct autorelease_array_list*)
	NSZoneMalloc(NSDefaultMallocZone(),
	sizeof(struct autorelease_array_list)
	+ (BEGINNING_POOL_SIZE * sizeof(id)));
      /* Currently no NEXT array in the list, so NEXT == NULL. */
      _released->next = NULL;
      _released->size = BEGINNING_POOL_SIZE;
      _released->count = 0;
      _released_head = _released;
      _released_count = 0;
    }
  else
    /* Already initialized; (it came from autorelease_pool_cache);
       we don't have to allocate new array list memory. */
    {
      _released = _released_head;
    }

  /* Install ourselves as the current pool.
   * The only other place where the parent/child linked list is modified
   * should be in -dealloc
   */
  {
    struct autorelease_thread_vars *tv = ARP_THREAD_VARS;
    unsigned	level = 0;

    _parent = tv->current_pool;
    if (_parent)
      {
	NSAutoreleasePool	*pool = _parent;

	_child = _parent->_child;
	while (nil != pool)
	  {
	    level++;
	    pool = pool->_parent;
	  }
        _parent->_child = self;
      }
    tv->current_pool = self;
    if (level > pool_number_warning_threshold)
      {
	[NSException raise: NSGenericException
	  format: @"Too many (%u) autorelease pools ... leaking them?", level];
      }
  }

  return self;
}

- (unsigned) autoreleaseCount
{
  unsigned count = 0;
  struct autorelease_array_list *released = _released_head;
  while (released != 0)
    {
      count += released->count;
      released = released->next;
    }
  return count;
}

- (unsigned) autoreleaseCountForObject: (id)anObject
{
  unsigned count = 0;
  struct autorelease_array_list *released = _released_head;
  unsigned int i;

  while (released != 0)
    {
      for (i = 0; i < released->count; i++)
	if (released->objects[i] == anObject)
	  count++;
      released = released->next;
    }
  return count;
}

+ (unsigned) autoreleaseCountForObject: (id)anObject
{
  unsigned count = 0;
  NSAutoreleasePool *pool = ARP_THREAD_VARS->current_pool;

  while (pool)
    {
      count += [pool autoreleaseCountForObject: anObject];
      pool = pool->_parent;
    }
  return count;
}

+ (void) addObject: (id)anObj
{
  NSThread		*t = GSCurrentThread();
  NSAutoreleasePool	*pool;
  NSAssert(nil != t, @"Creating autorelease pool on nonexistent thread!");

  pool = t->_autorelease_vars.current_pool;
  if (pool == nil && t->_active == NO)
    {
      // Don't leak while exiting thread.
      pool = t->_autorelease_vars.current_pool = [self new];
    }
  if (pool != nil)
    {
      (*pool->_addImp)(pool, @selector(addObject:), anObj);
    }
  else
    {
      NSAutoreleasePool	*arp = [NSAutoreleasePool new];

      if (anObj != nil)
	{
	  NSLog(@"autorelease called without pool for object (%p) "
	    @"of class %@ in thread %@", anObj,
	    NSStringFromClass([anObj class]), [NSThread currentThread]);
	}
      else
	{
	  NSLog(@"autorelease called without pool for nil object.");
	}
      [arp drain];
    }
}

- (void) addObject: (id)anObj
{
  /* If the global, static variable AUTORELEASE_ENABLED is not set,
     do nothing, just return. */
  if (!autorelease_enabled)
    return;

  if (_released_count >= pool_count_warning_threshold)
    {
      [NSException raise: NSGenericException
		  format: @"AutoreleasePool count threshold exceeded."];
    }

  /* Get a new array for the list, if the current one is full. */
  while (_released->count == _released->size)
    {
      if (_released->next)
	{
	  /* There is an already-allocated one in the chain; use it. */
	  _released = _released->next;
	}
      else
	{
	  /* We are at the end of the chain, and need to allocate a new one. */
	  struct autorelease_array_list *new_released;
	  unsigned new_size = _released->size * 2;
	
	  new_released = (struct autorelease_array_list*)
	    NSZoneMalloc(NSDefaultMallocZone(),
	    sizeof(struct autorelease_array_list) + (new_size * sizeof(id)));
	  new_released->next = NULL;
	  new_released->size = new_size;
	  new_released->count = 0;
	  _released->next = new_released;
	  _released = new_released;
	}
    }

  /* Put the object at the end of the list. */
  _released->objects[_released->count] = anObj;
  (_released->count)++;

  /* Keep track of the total number of objects autoreleased in this pool */
  _released_count++;
}

- (void) emptyPool
{
  unsigned	i;
  Class		classes[16];
  IMP	 	imps[16];

  for (i = 0; i < 16; i++)
    {
      classes[i] = 0;
      imps[i] = 0;
    }

  /*
   * Loop throught the deallocation code repeatedly ... since we deallocate
   * objects in the receiver while the receiver remains set as the current
   * autorelease pool ... so if any object which is being deallocated adds
   * any object to the current autorelease pool, we may need to release it
   * again.
   */
  while (_child != nil || _released_count > 0)
    {
      volatile struct autorelease_array_list *released;

      if (nil != _child)
	{
	  [self _emptyChild];
	}

      /* Take the object out of the released list just before releasing it,
       * so if we are doing "double_release_check"ing, then
       * autoreleaseCountForObject: won't find the object we are currently
       * releasing. */
      released = _released_head;
      while (released != 0)
	{
	  id	*objects = (id*)(released->objects);

	  for (i = 0; i < released->count; i++)
	    {
	      id	anObject;
	      Class	c;
	      unsigned	hash;

	      anObject = objects[i];
	      objects[i] = nil;
              if (anObject == nil)
                {
                  fprintf(stderr,
                    "nil object encountered in autorelease pool\n");
                  continue;
                }
	      c = object_getClass(anObject);
              if (c == 0)
                {
                  [NSException raise: NSInternalInconsistencyException
                    format: @"nul class for object in autorelease pool"];
                }
	      hash = (((unsigned)(uintptr_t)c) >> 3) & 0x0f;
	      if (classes[hash] != c)
		{
                  /* If anObject was an instance, c is it's class.
                   * If anObject was a class, c is its metaclass.
                   * Either way, we should get the appropriate pointer.
                   * If anObject is a proxy to something,
                   * the +instanceMethodForSelector: and -methodForSelector:
                   * methods may not exist, but this will return the
                   * address of the forwarding method if necessary.
                   */
		  imps[hash]
		    = class_getMethodImplementation(c, @selector(release));
		  classes[hash] = c;
		}
	      (imps[hash])(anObject, @selector(release));
	    }
	  _released_count -= released->count;
	  released->count = 0;
	  released = released->next;
	}
    }
}

#endif // ARC_RUNTIME

+ (id) currentPool
{
  return ARP_THREAD_VARS->current_pool;
}


- (void) drain
{
  // Don't call -release, make both -release and -drain have the same cost in
  // non-GC mode.
  [self dealloc];
}

- (id) retain
{
  [NSException raise: NSGenericException
	       format: @"Don't call `-retain' on a NSAutoreleasePool"];
  return self;
}

- (oneway void) release
{
  [self dealloc];
}

- (void) dealloc
{
  struct autorelease_thread_vars *tv = ARP_THREAD_VARS;

  if (UINT_MAX == _released_count)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"NSAutoreleasePool -dealloc of deallocated pool"];
    }

  [self emptyPool];
  NSAssert(0 == _released_count, NSInternalInconsistencyException);

  /* Remove self from the linked list of pools in use.
   * We already know that we have deallocated any child (in -emptyPool),
   * but we may have a parent which needs to know we have gone.
   * The only other place where the parent/child linked list is modified
   * should be in -init
   */
  if (tv->current_pool == self)
    {
      tv->current_pool = _parent;
    }
  if (_parent != nil)
    {
      _parent->_child = nil;
      _parent = nil;
    }

  /* Mark pool as cached so that any attempt to add an object to use it
   * or to deallocate it again will raise an exception.
   * We reset to zero when we get i out of the cache as a new allocation.
   */
  _released_count = UINT_MAX;

  /* Don't deallocate ourself, just save us for later use. */
  push_pool_to_cache(tv, self);
  GSNOSUPERDEALLOC;
}

- (void) _reallyDealloc
{
  struct autorelease_array_list *a;

  for (a = _released_head; a;)
    {
      void *n = a->next;
      NSZoneFree(NSDefaultMallocZone(), a);
      a = n;
    }
  _released = _released_head = 0;
#if	LOG_LIFETIME
    fprintf(stderr, "*** %p autorelease pool really dealloc\n", self);
#endif

  [super dealloc];
}

- (id) autorelease
{
  [NSException raise: NSGenericException
	       format: @"Don't call `-autorelease' on a NSAutoreleasePool"];
  return self;
}

+ (void) _endThread: (NSThread*)thread
{
  struct autorelease_thread_vars *tv;
  NSAutoreleasePool *pool;

  tv = &((thread)->_autorelease_vars);

  /* First release any objects in the pool... bearing in mind that
   * releasing any object could cause other objects to be added to
   * the pool.
   */
  pool = tv->current_pool;
  while (pool)
    {
      [pool emptyPool];
      pool = pool->_parent;
    }

  /* Now free the memory (we have finished usingthe pool).
   */
  pool = tv->current_pool;
  tv->current_pool = nil;
  while (pool)
    {
      NSAutoreleasePool *p = pool->_parent;

      [pool _reallyDealloc];
      pool = p;
    }

  free_pool_cache(tv);
}

+ (void) enableRelease: (BOOL)enable
{
  autorelease_enabled = enable;
}

+ (void) freeCache
{
  free_pool_cache(ARP_THREAD_VARS);
}

+ (void) setPoolCountThreshold: (unsigned)c
{
  if (c >= UINT_MAX) c = UINT_MAX - 1;
  pool_count_warning_threshold = c;
}

+ (void) setPoolNumberThreshold: (unsigned)c
{
  pool_number_warning_threshold = c;
}

@end