- (void)viewDidLoad
{
[super viewDidLoad];
NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(test) object:nil];
[thread start];
}
-(void)test
{
MyClass *my = [[[MyClass alloc] init] autorelease];
NSLog(@"%@",[my description]);
}
我没有为自己的线程创建任何自动释放池,但是当线程退出时,对象“我的”只是dealloc.why？@H_403_5@
- (void)viewDidLoad
{
[super viewDidLoad];
NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(test) object:nil];
[thread start];
}
-(void)test
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
MyClass *my = [[[MyClass alloc] init] autorelease];
NSLog(@"%@",[my description]);
}
我创建了自己的autoreleasepool但在线程退出时不会将其耗尽.对象“我的”仍然可以dealloc.为什么？@H_403_5@
我使用Xcode5而不使用ARC@H_403_5@ @H_301_14@
解决方法
Objective-C运行时为open-source,因此您可以阅读源代码以查看正在进行的操作.如果在当前线程上执行没有池的自动释放,则运行时的最新版本(646,OS X 10.10和iOS 8附带)确实会添加池.在NSObject.mm：@H_403_5@
static __attribute__((noinline))
id *autoreleaseNoPage(id obj)
{
// No pool in place.
assert(!hotPage());
if (obj != POOL_SENTINEL && DebugMissingPools) {
// We are pushing an object with no pool in place,// and no-pool debugging was requested by environment.
_objc_inform("MISSING POOLS: Object %p of class %s "
"autoreleased with no pool in place - "
"just leaking - break on "
"objc_autoreleaseNoPool() to debug",(void*)obj,object_getClassName(obj));
objc_autoreleaseNoPool(obj);
return nil;
}
// Install the first page.
AutoreleasePoolPage *page = new AutoreleasePoolPage(nil);
setHotPage(page);
// Push an autorelease pool boundary if it wasn't already requested.
if (obj != POOL_SENTINEL) {
page->add(POOL_SENTINEL);
}
// Push the requested object.
return page->add(obj);
}
当您推送第一个池时(在这种情况下推送的东西是POOL_SENTINEL),或者您在没有池的情况下自动释放,就会调用此函数.当推送第一个池时,它会设置自动释放堆栈.但是从代码中可以看出,只要未设置DebugMissingPools环境变量(默认情况下不设置),当autorelease完成没有池时,它也会设置自动释放堆栈,然后推送池(推送一个池) POOL_SENTINEL).@H_403_5@
类似地,(在没有查看其他代码的情况下有点难以理解,但这是相关部分)当线程被销毁(并且线程局部存储被销毁)时,它会释放自动释放堆栈中的所有内容(这就是pop(0); does)所以它不依赖于用户弹出最后一个池：@H_403_5@
static void tls_dealloc(void *p)
{
// reinstate TLS value while we work
setHotPage((AutoreleasePoolPage *)p);
pop(0);
setHotPage(nil);
}
之前版本的运行时(551.1,OS X 10.9和iOS 7附带)也是这样做的,你可以从NSObject.mm看到：@H_403_5@
static __attribute__((noinline))
id *autoreleaseSlow(id obj)
{
AutoreleasePoolPage *page;
page = hotPage();
// The code below assumes some cases are handled by autoreleaseFast()
assert(!page || page->full());
if (!page) {
// No pool. Silently push one.
assert(obj != POOL_SENTINEL);
if (DebugMissingPools) {
_objc_inform("MISSING POOLS: Object %p of class %s "
"autoreleased with no pool in place - "
"just leaking - break on "
"objc_autoreleaseNoPool() to debug",object_getClassName(obj));
objc_autoreleaseNoPool(obj);
return nil;
}
push();
page = hotPage();
}
do {
if (page->child) page = page->child;
else page = new AutoreleasePoolPage(page);
} while (page->full());
setHotPage(page);
return page->add(obj);
}
但之前的版本(532.2,OS X 10.8和iOS 6附带),does not：@H_403_5@
static __attribute__((noinline))
id *autoreleaseSlow(id obj)
{
AutoreleasePoolPage *page;
page = hotPage();
// The code below assumes some cases are handled by autoreleaseFast()
assert(!page || page->full());
if (!page) {
assert(obj != POOL_SENTINEL);
_objc_inform("Object %p of class %s autoreleased "
"with no pool in place - just leaking - "
"break on objc_autoreleaseNoPool() to debug",obj,object_getClassName(obj));
objc_autoreleaseNoPool(obj);
return NULL;
}
do {
if (page->child) page = page->child;
else page = new AutoreleasePoolPage(page);
} while (page->full());
setHotPage(page);
return page->add(obj);
}
请注意,上述内容适用于任何pthread,而不仅仅适用于NSThreads.@H_403_5@
所以基本上,如果你在OS X 10.9或iOS 7上运行,在没有池的线程上自动释放不应该导致泄漏.这没有记录,并且是内部实现细节,因此请谨慎依赖此,因为Apple可能会在未来的操作系统中对其进行更改.但是,我没有看到任何理由为什么他们会删除此功能,因为它很简单,只有好处而且没有缺点,除非他们完全重写自动释放池的工作方式或其他方式.@H_403_5@ @H_301_14@ @H_301_14@ 原文链接：https://www.f2er.com/iOS/332919.html
