模拟实现C语言中的内存管理

#import <Foundation/Foundation.h> int cnt = 0;  void fun (charchar * p) {   printf("%c/n",p[0]); }  charchar * retain1(charchar * p) {   //retain(p);   cnt ++;   return p; }  void dealloc1(charchar *p) {   free(p); }  void release(charchar * p) {   cnt--;   if (cnt == 0) {     //free(p);     dealloc1(p);   } }  int main(int argc, const charchar * argv[]) {    @autoreleasepool {     charchar * p = (charchar *)malloc(1000);     p[0] = 'a';     p[1] = 'b';     charchar * q = p;     //提前释放     //free(p);     //printf("%c/n",p[0]);     free(q);     //free(q);        }   return 0; }