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; 
}