dll-reverse_true-unreach-call_true-valid-memsafety.i

typedef unsigned int size_t;
typedef int wchar_t;








typedef enum
{
  P_ALL,
  P_PID,
  P_PGID
} idtype_t;
typedef struct
  {
    int quot;
    int rem;
  } div_t;



typedef struct
  {
    long int quot;
    long int rem;
  } ldiv_t;







__extension__ typedef struct
  {
    long long int quot;
    long long int rem;
  } lldiv_t;
extern size_t __ctype_get_mb_cur_max (void) __attribute__ ((__nothrow__ )) ;




extern double atof (const char *__nptr)
     __attribute__ ((__nothrow__ )) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;

extern int atoi (const char *__nptr)
     __attribute__ ((__nothrow__ )) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;

extern long int atol (const char *__nptr)
     __attribute__ ((__nothrow__ )) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;





__extension__ extern long long int atoll (const char *__nptr)
     __attribute__ ((__nothrow__ )) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;





extern double strtod (const char *__restrict __nptr,
        char **__restrict __endptr)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));





extern float strtof (const char *__restrict __nptr,
       char **__restrict __endptr) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));

extern long double strtold (const char *__restrict __nptr,
       char **__restrict __endptr)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));





extern long int strtol (const char *__restrict __nptr,
   char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));

extern unsigned long int strtoul (const char *__restrict __nptr,
      char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));




__extension__
extern long long int strtoq (const char *__restrict __nptr,
        char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));

__extension__
extern unsigned long long int strtouq (const char *__restrict __nptr,
           char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));





__extension__
extern long long int strtoll (const char *__restrict __nptr,
         char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));

__extension__
extern unsigned long long int strtoull (const char *__restrict __nptr,
     char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));
extern char *l64a (long int __n) __attribute__ ((__nothrow__ )) ;


extern long int a64l (const char *__s)
     __attribute__ ((__nothrow__ )) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;







typedef unsigned char __u_char;
typedef unsigned short int __u_short;
typedef unsigned int __u_int;
typedef unsigned long int __u_long;


typedef signed char __int8_t;
typedef unsigned char __uint8_t;
typedef signed short int __int16_t;
typedef unsigned short int __uint16_t;
typedef signed int __int32_t;
typedef unsigned int __uint32_t;




__extension__ typedef signed long long int __int64_t;
__extension__ typedef unsigned long long int __uint64_t;







__extension__ typedef long long int __quad_t;
__extension__ typedef unsigned long long int __u_quad_t;


__extension__ typedef __u_quad_t __dev_t;
__extension__ typedef unsigned int __uid_t;
__extension__ typedef unsigned int __gid_t;
__extension__ typedef unsigned long int __ino_t;
__extension__ typedef __u_quad_t __ino64_t;
__extension__ typedef unsigned int __mode_t;
__extension__ typedef unsigned int __nlink_t;
__extension__ typedef long int __off_t;
__extension__ typedef __quad_t __off64_t;
__extension__ typedef int __pid_t;
__extension__ typedef struct { int __val[2]; } __fsid_t;
__extension__ typedef long int __clock_t;
__extension__ typedef unsigned long int __rlim_t;
__extension__ typedef __u_quad_t __rlim64_t;
__extension__ typedef unsigned int __id_t;
__extension__ typedef long int __time_t;
__extension__ typedef unsigned int __useconds_t;
__extension__ typedef long int __suseconds_t;

__extension__ typedef int __daddr_t;
__extension__ typedef int __key_t;


__extension__ typedef int __clockid_t;


__extension__ typedef void * __timer_t;


__extension__ typedef long int __blksize_t;




__extension__ typedef long int __blkcnt_t;
__extension__ typedef __quad_t __blkcnt64_t;


__extension__ typedef unsigned long int __fsblkcnt_t;
__extension__ typedef __u_quad_t __fsblkcnt64_t;


__extension__ typedef unsigned long int __fsfilcnt_t;
__extension__ typedef __u_quad_t __fsfilcnt64_t;


__extension__ typedef int __fsword_t;

__extension__ typedef int __ssize_t;


__extension__ typedef long int __syscall_slong_t;

__extension__ typedef unsigned long int __syscall_ulong_t;



typedef __off64_t __loff_t;
typedef __quad_t *__qaddr_t;
typedef char *__caddr_t;


__extension__ typedef int __intptr_t;


__extension__ typedef unsigned int __socklen_t;



typedef __u_char u_char;
typedef __u_short u_short;
typedef __u_int u_int;
typedef __u_long u_long;
typedef __quad_t quad_t;
typedef __u_quad_t u_quad_t;
typedef __fsid_t fsid_t;




typedef __loff_t loff_t;



typedef __ino_t ino_t;
typedef __dev_t dev_t;




typedef __gid_t gid_t;




typedef __mode_t mode_t;




typedef __nlink_t nlink_t;




typedef __uid_t uid_t;





typedef __off_t off_t;
typedef __pid_t pid_t;





typedef __id_t id_t;




typedef __ssize_t ssize_t;





typedef __daddr_t daddr_t;
typedef __caddr_t caddr_t;





typedef __key_t key_t;
typedef __clock_t clock_t;
typedef __time_t time_t;
typedef __clockid_t clockid_t;
typedef __timer_t timer_t;



typedef unsigned long int ulong;
typedef unsigned short int ushort;
typedef unsigned int uint;
typedef int int8_t __attribute__ ((__mode__ (__QI__)));
typedef int int16_t __attribute__ ((__mode__ (__HI__)));
typedef int int32_t __attribute__ ((__mode__ (__SI__)));
typedef int int64_t __attribute__ ((__mode__ (__DI__)));


typedef unsigned int u_int8_t __attribute__ ((__mode__ (__QI__)));
typedef unsigned int u_int16_t __attribute__ ((__mode__ (__HI__)));
typedef unsigned int u_int32_t __attribute__ ((__mode__ (__SI__)));
typedef unsigned int u_int64_t __attribute__ ((__mode__ (__DI__)));

typedef int register_t __attribute__ ((__mode__ (__word__)));










typedef int __sig_atomic_t;




typedef struct
  {
    unsigned long int __val[(1024 / (8 * sizeof (unsigned long int)))];
  } __sigset_t;



typedef __sigset_t sigset_t;








struct timespec
  {
    __time_t tv_sec;
    __syscall_slong_t tv_nsec;
  };

struct timeval
  {
    __time_t tv_sec;
    __suseconds_t tv_usec;
  };


typedef __suseconds_t suseconds_t;





typedef long int __fd_mask;
typedef struct
  {






    __fd_mask __fds_bits[1024 / (8 * (int) sizeof (__fd_mask))];


  } fd_set;






typedef __fd_mask fd_mask;
extern int select (int __nfds, fd_set *__restrict __readfds,
     fd_set *__restrict __writefds,
     fd_set *__restrict __exceptfds,
     struct timeval *__restrict __timeout);
extern int pselect (int __nfds, fd_set *__restrict __readfds,
      fd_set *__restrict __writefds,
      fd_set *__restrict __exceptfds,
      const struct timespec *__restrict __timeout,
      const __sigset_t *__restrict __sigmask);


__extension__
extern unsigned int gnu_dev_major (unsigned long long int __dev)
     __attribute__ ((__nothrow__ )) __attribute__ ((__const__));
__extension__
extern unsigned int gnu_dev_minor (unsigned long long int __dev)
     __attribute__ ((__nothrow__ )) __attribute__ ((__const__));
__extension__
extern unsigned long long int gnu_dev_makedev (unsigned int __major,
            unsigned int __minor)
     __attribute__ ((__nothrow__ )) __attribute__ ((__const__));





typedef __blksize_t blksize_t;






typedef __blkcnt_t blkcnt_t;



typedef __fsblkcnt_t fsblkcnt_t;



typedef __fsfilcnt_t fsfilcnt_t;
typedef unsigned long int pthread_t;


union pthread_attr_t
{
  char __size[36];
  long int __align;
};

typedef union pthread_attr_t pthread_attr_t;
typedef struct __pthread_internal_slist
{
  struct __pthread_internal_slist *__next;
} __pthread_slist_t;





typedef union
{
  struct __pthread_mutex_s
  {
    int __lock;
    unsigned int __count;
    int __owner;





    int __kind;
    unsigned int __nusers;
    __extension__ union
    {
      struct
      {
 short __espins;
 short __elision;



      } __elision_data;
      __pthread_slist_t __list;
    };

  } __data;
  char __size[24];
  long int __align;
} pthread_mutex_t;

typedef union
{
  char __size[4];
  int __align;
} pthread_mutexattr_t;




typedef union
{
  struct
  {
    int __lock;
    unsigned int __futex;
    __extension__ unsigned long long int __total_seq;
    __extension__ unsigned long long int __wakeup_seq;
    __extension__ unsigned long long int __woken_seq;
    void *__mutex;
    unsigned int __nwaiters;
    unsigned int __broadcast_seq;
  } __data;
  char __size[48];
  __extension__ long long int __align;
} pthread_cond_t;

typedef union
{
  char __size[4];
  int __align;
} pthread_condattr_t;



typedef unsigned int pthread_key_t;



typedef int pthread_once_t;





typedef union
{
  struct
  {
    int __lock;
    unsigned int __nr_readers;
    unsigned int __readers_wakeup;
    unsigned int __writer_wakeup;
    unsigned int __nr_readers_queued;
    unsigned int __nr_writers_queued;


    unsigned char __flags;
    unsigned char __shared;
    signed char __rwelision;

    unsigned char __pad2;
    int __writer;
  } __data;

  char __size[32];
  long int __align;
} pthread_rwlock_t;

typedef union
{
  char __size[8];
  long int __align;
} pthread_rwlockattr_t;





typedef volatile int pthread_spinlock_t;




typedef union
{
  char __size[20];
  long int __align;
} pthread_barrier_t;

typedef union
{
  char __size[4];
  int __align;
} pthread_barrierattr_t;






extern long int random (void) __attribute__ ((__nothrow__ ));


extern void srandom (unsigned int __seed) __attribute__ ((__nothrow__ ));





extern char *initstate (unsigned int __seed, char *__statebuf,
   size_t __statelen) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (2)));



extern char *setstate (char *__statebuf) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));







struct random_data
  {
    int32_t *fptr;
    int32_t *rptr;
    int32_t *state;
    int rand_type;
    int rand_deg;
    int rand_sep;
    int32_t *end_ptr;
  };

extern int random_r (struct random_data *__restrict __buf,
       int32_t *__restrict __result) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));

extern int srandom_r (unsigned int __seed, struct random_data *__buf)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (2)));

extern int initstate_r (unsigned int __seed, char *__restrict __statebuf,
   size_t __statelen,
   struct random_data *__restrict __buf)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (2, 4)));

extern int setstate_r (char *__restrict __statebuf,
         struct random_data *__restrict __buf)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));






extern int rand (void) __attribute__ ((__nothrow__ ));

extern void srand (unsigned int __seed) __attribute__ ((__nothrow__ ));




extern int rand_r (unsigned int *__seed) __attribute__ ((__nothrow__ ));







extern double drand48 (void) __attribute__ ((__nothrow__ ));
extern double erand48 (unsigned short int __xsubi[3]) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));


extern long int lrand48 (void) __attribute__ ((__nothrow__ ));
extern long int nrand48 (unsigned short int __xsubi[3])
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));


extern long int mrand48 (void) __attribute__ ((__nothrow__ ));
extern long int jrand48 (unsigned short int __xsubi[3])
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));


extern void srand48 (long int __seedval) __attribute__ ((__nothrow__ ));
extern unsigned short int *seed48 (unsigned short int __seed16v[3])
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));
extern void lcong48 (unsigned short int __param[7]) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));





struct drand48_data
  {
    unsigned short int __x[3];
    unsigned short int __old_x[3];
    unsigned short int __c;
    unsigned short int __init;
    __extension__ unsigned long long int __a;

  };


extern int drand48_r (struct drand48_data *__restrict __buffer,
        double *__restrict __result) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));
extern int erand48_r (unsigned short int __xsubi[3],
        struct drand48_data *__restrict __buffer,
        double *__restrict __result) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));


extern int lrand48_r (struct drand48_data *__restrict __buffer,
        long int *__restrict __result)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));
extern int nrand48_r (unsigned short int __xsubi[3],
        struct drand48_data *__restrict __buffer,
        long int *__restrict __result)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));


extern int mrand48_r (struct drand48_data *__restrict __buffer,
        long int *__restrict __result)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));
extern int jrand48_r (unsigned short int __xsubi[3],
        struct drand48_data *__restrict __buffer,
        long int *__restrict __result)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));


extern int srand48_r (long int __seedval, struct drand48_data *__buffer)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (2)));

extern int seed48_r (unsigned short int __seed16v[3],
       struct drand48_data *__buffer) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));

extern int lcong48_r (unsigned short int __param[7],
        struct drand48_data *__buffer)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2)));
extern void *malloc (size_t __size) __attribute__ ((__nothrow__ )) __attribute__ ((__malloc__)) ;

extern void *calloc (size_t __nmemb, size_t __size)
     __attribute__ ((__nothrow__ )) __attribute__ ((__malloc__)) ;
extern void *realloc (void *__ptr, size_t __size)
     __attribute__ ((__nothrow__ )) __attribute__ ((__warn_unused_result__));

extern void free (void *__ptr) __attribute__ ((__nothrow__ ));




extern void cfree (void *__ptr) __attribute__ ((__nothrow__ ));











extern void *alloca (size_t __size) __attribute__ ((__nothrow__ ));





extern void *valloc (size_t __size) __attribute__ ((__nothrow__ )) __attribute__ ((__malloc__)) ;




extern int posix_memalign (void **__memptr, size_t __alignment, size_t __size)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1))) ;




extern void *aligned_alloc (size_t __alignment, size_t __size)
     __attribute__ ((__nothrow__ )) __attribute__ ((__malloc__)) ;




extern void abort (void) __attribute__ ((__nothrow__ )) __attribute__ ((__noreturn__));



extern int atexit (void (*__func) (void)) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));







extern int at_quick_exit (void (*__func) (void)) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));







extern int on_exit (void (*__func) (int __status, void *__arg), void *__arg)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));






extern void exit (int __status) __attribute__ ((__nothrow__ )) __attribute__ ((__noreturn__));





extern void quick_exit (int __status) __attribute__ ((__nothrow__ )) __attribute__ ((__noreturn__));







extern void _Exit (int __status) __attribute__ ((__nothrow__ )) __attribute__ ((__noreturn__));






extern char *getenv (const char *__name) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1))) ;
extern int putenv (char *__string) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));





extern int setenv (const char *__name, const char *__value, int __replace)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (2)));


extern int unsetenv (const char *__name) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));






extern int clearenv (void) __attribute__ ((__nothrow__ ));
extern char *mktemp (char *__template) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));
extern int mkstemp (char *__template) __attribute__ ((__nonnull__ (1))) ;
extern int mkstemps (char *__template, int __suffixlen) __attribute__ ((__nonnull__ (1))) ;
extern char *mkdtemp (char *__template) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1))) ;
extern int system (const char *__command) ;
extern char *realpath (const char *__restrict __name,
         char *__restrict __resolved) __attribute__ ((__nothrow__ )) ;






typedef int (*__compar_fn_t) (const void *, const void *);
extern void *bsearch (const void *__key, const void *__base,
        size_t __nmemb, size_t __size, __compar_fn_t __compar)
     __attribute__ ((__nonnull__ (1, 2, 5))) ;







extern void qsort (void *__base, size_t __nmemb, size_t __size,
     __compar_fn_t __compar) __attribute__ ((__nonnull__ (1, 4)));
extern int abs (int __x) __attribute__ ((__nothrow__ )) __attribute__ ((__const__)) ;
extern long int labs (long int __x) __attribute__ ((__nothrow__ )) __attribute__ ((__const__)) ;



__extension__ extern long long int llabs (long long int __x)
     __attribute__ ((__nothrow__ )) __attribute__ ((__const__)) ;







extern div_t div (int __numer, int __denom)
     __attribute__ ((__nothrow__ )) __attribute__ ((__const__)) ;
extern ldiv_t ldiv (long int __numer, long int __denom)
     __attribute__ ((__nothrow__ )) __attribute__ ((__const__)) ;




__extension__ extern lldiv_t lldiv (long long int __numer,
        long long int __denom)
     __attribute__ ((__nothrow__ )) __attribute__ ((__const__)) ;
extern char *ecvt (double __value, int __ndigit, int *__restrict __decpt,
     int *__restrict __sign) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4))) ;




extern char *fcvt (double __value, int __ndigit, int *__restrict __decpt,
     int *__restrict __sign) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4))) ;




extern char *gcvt (double __value, int __ndigit, char *__buf)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3))) ;




extern char *qecvt (long double __value, int __ndigit,
      int *__restrict __decpt, int *__restrict __sign)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4))) ;
extern char *qfcvt (long double __value, int __ndigit,
      int *__restrict __decpt, int *__restrict __sign)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4))) ;
extern char *qgcvt (long double __value, int __ndigit, char *__buf)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3))) ;




extern int ecvt_r (double __value, int __ndigit, int *__restrict __decpt,
     int *__restrict __sign, char *__restrict __buf,
     size_t __len) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4, 5)));
extern int fcvt_r (double __value, int __ndigit, int *__restrict __decpt,
     int *__restrict __sign, char *__restrict __buf,
     size_t __len) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4, 5)));

extern int qecvt_r (long double __value, int __ndigit,
      int *__restrict __decpt, int *__restrict __sign,
      char *__restrict __buf, size_t __len)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4, 5)));
extern int qfcvt_r (long double __value, int __ndigit,
      int *__restrict __decpt, int *__restrict __sign,
      char *__restrict __buf, size_t __len)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (3, 4, 5)));






extern int mblen (const char *__s, size_t __n) __attribute__ ((__nothrow__ ));


extern int mbtowc (wchar_t *__restrict __pwc,
     const char *__restrict __s, size_t __n) __attribute__ ((__nothrow__ ));


extern int wctomb (char *__s, wchar_t __wchar) __attribute__ ((__nothrow__ ));



extern size_t mbstowcs (wchar_t *__restrict __pwcs,
   const char *__restrict __s, size_t __n) __attribute__ ((__nothrow__ ));

extern size_t wcstombs (char *__restrict __s,
   const wchar_t *__restrict __pwcs, size_t __n)
     __attribute__ ((__nothrow__ ));
extern int rpmatch (const char *__response) __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1))) ;
extern int getsubopt (char **__restrict __optionp,
        char *const *__restrict __tokens,
        char **__restrict __valuep)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1, 2, 3))) ;
extern int getloadavg (double __loadavg[], int __nelem)
     __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (1)));
extern int __VERIFIER_nondet_int(void);
extern void __VERIFIER_error() __attribute__ ((__noreturn__));
typedef struct TDLL
{
 struct TDLL* next;
 struct TDLL* prev;
 int data;
} DLL;

int main()
{

 DLL* head = malloc(sizeof(DLL));
 head->next = ((void*)0);
 head->prev = ((void*)0);
 head->data = 0;

 DLL* x = head;


 while (__VERIFIER_nondet_int()) { x->next = malloc(sizeof(DLL)); x->next->prev = x; x = x->next; x->next = ((void*)0); x->data = 0; }


 x = head;
 while (x->next != ((void*)0) && __VERIFIER_nondet_int())
 {
  do { if (!(x != ((void*)0))) __VERIFIER_error();} while (0);
  x = x->next;
 }
 do { if (!(x != ((void*)0))) __VERIFIER_error();} while (0);

 x->data = 1;

 if (x->next == ((void*)0))
 {
  x->next = malloc(sizeof(DLL)); x->next->prev = x; x = x->next; x->next = ((void*)0); x->data = 2;
 }
 else
  x->next->data = 2;


 DLL* prev = ((void*)0);
 x = head;
 while(x != ((void*)0))
 {
  DLL* next = x->next;

  x->next = prev;
  x->prev = next;

  prev = x;

  x = next;

 }
 head = prev;


 x = head;
 while (x != ((void*)0))
 {
  int t1 = x->data;
  int t2 = 0;
  if (t1 == 2)
   t2 = x->next->data;
  do { if (!(t1 != 2 || t2 == 1)) __VERIFIER_error();} while (0);


  if (x->data == 2)
   x = x->next;

  x = x->next;
 }

 x = head;

 while (x != ((void*)0))
 {
  head = x;
  x = x->next;
  free(head);
 }

 return 0;
}