1  /* A toy re-implementation of CPython's object model.  */
       2  
       3  #include <stddef.h>
       4  #include <string.h>
       5  #include <stdlib.h>
       6  
       7  typedef struct base_obj base_obj;
       8  typedef struct type_obj type_obj;
       9  typedef struct string_obj string_obj;
      10  
      11  struct base_obj
      12  {
      13    struct type_obj *ob_type;
      14    int ob_refcnt;
      15  };
      16  
      17  struct type_obj
      18  {
      19    base_obj tp_base;
      20  };
      21  
      22  struct string_obj
      23  {
      24    base_obj str_base;
      25    size_t str_len;
      26    char str_buf[];
      27  };
      28  
      29  type_obj type_type = {
      30    { &type_type, 1},
      31  };
      32  
      33  type_obj str_type = {
      34    { &str_type, 1},
      35  };
      36  
      37  base_obj *alloc_obj (type_obj *ob_type, size_t sz)
      38  {
      39    base_obj *obj = (base_obj *)malloc (sz);
      40    if (!obj)
      41      return NULL;
      42    obj->ob_type = ob_type;
      43    obj->ob_refcnt = 1;
      44    return obj;
      45  }
      46  
      47  string_obj *new_string_obj (const char *str)
      48  {
      49    //__analyzer_dump ();
      50    size_t len = strlen (str);
      51  #if 1
      52    string_obj *str_obj
      53      = (string_obj *)alloc_obj (&str_type, sizeof (string_obj) + len + 1);
      54  #else
      55    string_obj *str_obj = (string_obj *)malloc (sizeof (string_obj) + len + 1);
      56    if (!str_obj)
      57      return NULL;
      58    str_obj->str_base.ob_type = &str_type;
      59    str_obj->str_base.ob_refcnt = 1;
      60  #endif
      61    str_obj->str_len = len; /* { dg-warning "dereference of NULL 'str_obj'" } */
      62    memcpy (str_obj->str_buf, str, len);
      63    str_obj->str_buf[len] = '\0';
      64    return str_obj;
      65  }
      66  
      67  void unref (string_obj *obj)
      68  {
      69    if (--obj->str_base.ob_refcnt == 0)
      70      free (obj);
      71  }
      72  
      73  void test_1 (const char *str)
      74  {
      75    string_obj *obj = new_string_obj (str);
      76    if (obj)
      77      unref (obj);
      78  } /* { dg-bogus "leak" "" { xfail *-*-* } } */
      79  /* XFAIL (false leak):
      80     Given that we only know "len" symbolically, this line:
      81       str_obj->str_buf[len] = '\0';
      82     is a symbolic write which could clobber the ob_type or ob_refcnt.
      83     It reports a leak when following the path where the refcount is clobbered
      84     to be a value that leads to the deallocator not being called.  */