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/* A toy re-implementation of CPython's object model. */
#include <stddef.h>
#include <string.h>
#include <stdlib.h>
typedef struct base_obj base_obj;
typedef struct type_obj type_obj;
typedef struct string_obj string_obj;
struct base_obj
{
struct type_obj *ob_type;
int ob_refcnt;
};
struct type_obj
{
base_obj tp_base;
};
struct string_obj
{
base_obj str_base;
size_t str_len;
char str_buf[];
};
type_obj type_type = {
{ &type_type, 1},
};
type_obj str_type = {
{ &str_type, 1},
};
base_obj *alloc_obj (type_obj *ob_type, size_t sz)
{
base_obj *obj = (base_obj *)malloc (sz);
if (!obj)
return NULL;
obj->ob_type = ob_type;
obj->ob_refcnt = 1;
return obj;
}
string_obj *new_string_obj (const char *str)
{
//__analyzer_dump ();
size_t len = strlen (str);
#if 1
string_obj *str_obj
= (string_obj *)alloc_obj (&str_type, sizeof (string_obj) + len + 1);
#else
string_obj *str_obj = (string_obj *)malloc (sizeof (string_obj) + len + 1);
if (!str_obj)
return NULL;
str_obj->str_base.ob_type = &str_type;
str_obj->str_base.ob_refcnt = 1;
#endif
str_obj->str_len = len; /* { dg-warning "dereference of NULL 'str_obj'" } */
memcpy (str_obj->str_buf, str, len);
str_obj->str_buf[len] = '\0';
return str_obj;
}
void unref (string_obj *obj)
{
if (--obj->str_base.ob_refcnt == 0)
free (obj);
}
void test_1 (const char *str)
{
string_obj *obj = new_string_obj (str);
if (obj)
unref (obj);
} /* { dg-bogus "leak" "" { xfail *-*-* } } */
/* XFAIL (false leak):
Given that we only know "len" symbolically, this line:
str_obj->str_buf[len] = '\0';
is a symbolic write which could clobber the ob_type or ob_refcnt.
It reports a leak when following the path where the refcount is clobbered
to be a value that leads to the deallocator not being called. */
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