- (id)kscrash_objectAtIndex:(NSUInteger)index {    if (index < self.count) {       return [[self kscrash_objectAtIndex:index] autorelease];     } else {       return nil;   }}

    id *add(id obj)    {        assert(!full());        unprotect();        id *ret = next;  // faster than `return next-1` because of aliasing        *next++ = obj;        protect();        return ret;    }

int main(int argc, const char * argv[]) {    {        void * atautoreleasepoolobj = objc_autoreleasePoolPush();
        // do whatever you want
        objc_autoreleasePoolPop(atautoreleasepoolobj);    }    return 0;}

#define POOL_SENTINEL nil
    static inline void *push() {        id *dest;        {            dest = autoreleaseFast(POOL_SENTINEL);        }        assert(*dest == POOL_SENTINEL);        return dest;    }

    static inline id *autoreleaseFast(id obj)    {        AutoreleasePoolPage *page = hotPage();        if (page && !page->full()) {            return page->add(obj);        } else if (page) {            return autoreleaseFullPage(obj, page);        } else {            return autoreleaseNoPage(obj);        }    }

    static __attribute__((noinline))    id *autoreleaseFullPage(id obj, AutoreleasePoolPage *page)    {        // The hot page is full.         // Step to the next non-full page, adding a new page if necessary.        // Then add the object to that page.        assert(page == hotPage());        assert(page->full()  ||  DebugPoolAllocation);
        do {            if (page->child) page = page->child;            else page = new AutoreleasePoolPage(page);        } while (page->full());
        setHotPage(page);        return page->add(obj);    }

    static inline void pop(void *token)  // nil    {        AutoreleasePoolPage *page;        id *stop;
        page = pageForPointer(token);        // this        stop = (id *)token;
        if (PrintPoolHiwat) printHiwat();
        // 遍历清空自己的值        page->releaseUntil(nil);

        if (page->child) {            // hysteresis: keep one empty child if page is more than half full            if (page->lessThanHalfFull()) {                page->child->kill();            }            // 删掉孙子节点            else if (page->child->child) {                page->child->child->kill();            }        }    }

void releaseUntil(id *stop)     {        // Not recursive: we don't want to blow out the stack         // if a thread accumulates a stupendous amount of garbage
        while (this->next != stop) {            // Restart from hotPage() every time, in case -release             // autoreleased more objects            AutoreleasePoolPage *page = hotPage();
            // fixme I think this `while` can be `if`, but I can't prove it            while (page->empty()) {                page = page->parent;                setHotPage(page);            }
            page->unprotect();            id obj = *--page->next;            memset((void*)page->next, SCRIBBLE, sizeof(*page->next));            page->protect();
            if (obj != POOL_BOUNDARY) {                objc_release(obj);            }        }        setHotPage(this);    }

"<CFRunLoopObserver {valid = Yes, activities = 0x1, repeats = Yes, order = -2147483647, callout = _wrapRunLoopWithAutoreleasePoolHandler , context = {type = mutable-small, count = 0, values = ()}}",    "<CFRunLoopObserver {valid = Yes, activities = 0xa0, repeats = Yes, order = 2147483647, callout = _wrapRunLoopWithAutoreleasePoolHandler , context = {type = mutable-small, count = 0, values = ()}}"