source: CIVL/mods/dev.civl.abc/examples/svcomp/sll_to_dll_rev_false-unreach-call.i

extern void __VERIFIER_error() __attribute__ ((__noreturn__));

typedef long unsigned int size_t;
typedef int wchar_t;

union wait
  {
    int w_status;
    struct
      {
 unsigned int __w_termsig:7;
 unsigned int __w_coredump:1;
 unsigned int __w_retcode:8;
 unsigned int:16;
      } __wait_terminated;
    struct
      {
 unsigned int __w_stopval:8;
 unsigned int __w_stopsig:8;
 unsigned int:16;
      } __wait_stopped;
  };
typedef union
  {
    union wait *__uptr;
    int *__iptr;
  } __WAIT_STATUS __attribute__ ((__transparent_union__));

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__ , __leaf__)) ;

extern double atof (__const char *__nptr)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;
extern int atoi (__const char *__nptr)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;
extern long int atol (__const char *__nptr)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__pure__)) __attribute__ ((__nonnull__ (1))) ;


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


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


extern float strtof (__const char *__restrict __nptr,
       char **__restrict __endptr) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;
extern long double strtold (__const char *__restrict __nptr,
       char **__restrict __endptr)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;


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

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

__extension__
extern long long int strtoll (__const char *__restrict __nptr,
         char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;
__extension__
extern unsigned long long int strtoull (__const char *__restrict __nptr,
     char **__restrict __endptr, int __base)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;

extern char *l64a (long int __n) __attribute__ ((__nothrow__ , __leaf__)) ;
extern long int a64l (__const char *__s)
     __attribute__ ((__nothrow__ , __leaf__)) __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;
typedef signed long int __int64_t;
typedef unsigned long int __uint64_t;
typedef long int __quad_t;
typedef unsigned long int __u_quad_t;
typedef unsigned long int __dev_t;
typedef unsigned int __uid_t;
typedef unsigned int __gid_t;
typedef unsigned long int __ino_t;
typedef unsigned long int __ino64_t;
typedef unsigned int __mode_t;
typedef unsigned long int __nlink_t;
typedef long int __off_t;
typedef long int __off64_t;
typedef int __pid_t;
typedef struct { int __val[2]; } __fsid_t;
typedef long int __clock_t;
typedef unsigned long int __rlim_t;
typedef unsigned long int __rlim64_t;
typedef unsigned int __id_t;
typedef long int __time_t;
typedef unsigned int __useconds_t;
typedef long int __suseconds_t;
typedef int __daddr_t;
typedef long int __swblk_t;
typedef int __key_t;
typedef int __clockid_t;
typedef void * __timer_t;
typedef long int __blksize_t;
typedef long int __blkcnt_t;
typedef long int __blkcnt64_t;
typedef unsigned long int __fsblkcnt_t;
typedef unsigned long int __fsblkcnt64_t;
typedef unsigned long int __fsfilcnt_t;
typedef unsigned long int __fsfilcnt64_t;
typedef long int __ssize_t;
typedef __off64_t __loff_t;
typedef __quad_t *__qaddr_t;
typedef char *__caddr_t;
typedef long int __intptr_t;
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;
    long int 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__ , __leaf__)) __attribute__ ((__const__));
__extension__
extern unsigned int gnu_dev_minor (unsigned long long int __dev)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__const__));
__extension__
extern unsigned long long int gnu_dev_makedev (unsigned int __major,
            unsigned int __minor)
     __attribute__ ((__nothrow__ , __leaf__)) __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;
typedef union
{
  char __size[56];
  long int __align;
} pthread_attr_t;
typedef struct __pthread_internal_list
{
  struct __pthread_internal_list *__prev;
  struct __pthread_internal_list *__next;
} __pthread_list_t;
typedef union
{
  struct __pthread_mutex_s
  {
    int __lock;
    unsigned int __count;
    int __owner;
    unsigned int __nusers;
    int __kind;
    int __spins;
    __pthread_list_t __list;
  } __data;
  char __size[40];
  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;
    int __writer;
    int __shared;
    unsigned long int __pad1;
    unsigned long int __pad2;
    unsigned int __flags;
  } __data;
  char __size[56];
  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[32];
  long int __align;
} pthread_barrier_t;
typedef union
{
  char __size[4];
  int __align;
} pthread_barrierattr_t;

extern long int random (void) __attribute__ ((__nothrow__ , __leaf__));
extern void srandom (unsigned int __seed) __attribute__ ((__nothrow__ , __leaf__));
extern char *initstate (unsigned int __seed, char *__statebuf,
   size_t __statelen) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (2)));


extern char *setstate (char *__statebuf) __attribute__ ((__nothrow__ , __leaf__)) __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__ , __leaf__)) __attribute__ ((__nonnull__ (1, 2)));

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

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

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






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

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




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







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


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


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


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


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


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


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


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

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

extern int lcong48_r (unsigned short int __param[7],
        struct drand48_data *__buffer)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1, 2)));









extern void *malloc (size_t __size) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__malloc__)) ;

extern void *calloc (size_t __nmemb, size_t __size)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__malloc__)) ;










extern void *realloc (void *__ptr, size_t __size)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__warn_unused_result__));

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




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

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







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




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




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



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

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

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


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


extern char *getenv (__const char *__name) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;

extern char *__secure_getenv (__const char *__name)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;
extern int putenv (char *__string) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1)));
extern int setenv (__const char *__name, __const char *__value, int __replace)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (2)));
extern int unsetenv (__const char *__name) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1)));
extern int clearenv (void) __attribute__ ((__nothrow__ , __leaf__));
extern char *mktemp (char *__template) __attribute__ ((__nothrow__ , __leaf__)) __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__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;

extern int system (__const char *__command) ;

extern char *realpath (__const char *__restrict __name,
         char *__restrict __resolved) __attribute__ ((__nothrow__ , __leaf__)) ;
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__ , __leaf__)) __attribute__ ((__const__)) ;
extern long int labs (long int __x) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__const__)) ;

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

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


__extension__ extern lldiv_t lldiv (long long int __numer,
        long long int __denom)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__const__)) ;

extern char *ecvt (double __value, int __ndigit, int *__restrict __decpt,
     int *__restrict __sign) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (3, 4))) ;
extern char *fcvt (double __value, int __ndigit, int *__restrict __decpt,
     int *__restrict __sign) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (3, 4))) ;
extern char *gcvt (double __value, int __ndigit, char *__buf)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (3))) ;
extern char *qecvt (long double __value, int __ndigit,
      int *__restrict __decpt, int *__restrict __sign)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (3, 4))) ;
extern char *qfcvt (long double __value, int __ndigit,
      int *__restrict __decpt, int *__restrict __sign)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (3, 4))) ;
extern char *qgcvt (long double __value, int __ndigit, char *__buf)
     __attribute__ ((__nothrow__ , __leaf__)) __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__ , __leaf__)) __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__ , __leaf__)) __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__ , __leaf__)) __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__ , __leaf__)) __attribute__ ((__nonnull__ (3, 4, 5)));

extern int mblen (__const char *__s, size_t __n) __attribute__ ((__nothrow__ , __leaf__)) ;
extern int mbtowc (wchar_t *__restrict __pwc,
     __const char *__restrict __s, size_t __n) __attribute__ ((__nothrow__ , __leaf__)) ;
extern int wctomb (char *__s, wchar_t __wchar) __attribute__ ((__nothrow__ , __leaf__)) ;
extern size_t mbstowcs (wchar_t *__restrict __pwcs,
   __const char *__restrict __s, size_t __n) __attribute__ ((__nothrow__ , __leaf__));
extern size_t wcstombs (char *__restrict __s,
   __const wchar_t *__restrict __pwcs, size_t __n)
     __attribute__ ((__nothrow__ , __leaf__));

extern int rpmatch (__const char *__response) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1))) ;
extern int getsubopt (char **__restrict __optionp,
        char *__const *__restrict __tokens,
        char **__restrict __valuep)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1, 2, 3))) ;
extern int getloadavg (double __loadavg[], int __nelem)
     __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1)));

extern int __VERIFIER_nondet_int(void);
static void fail(void) {
ERROR: __VERIFIER_error();
}
struct node {
    struct node *next;
    struct node *prev;
};
static struct node* alloc_node(void)
{
    struct node *ptr = malloc(sizeof *ptr);
    if (!ptr)
        abort();
    ptr->next = ((void *)0);
    ptr->prev = ((void *)0);
    return ptr;
}
static void chain_node(struct node **ppnode)
{
    struct node *node = alloc_node();
    node->next = *ppnode;
    *ppnode = node;
}
static struct node* create_sll(const struct node **pp1, const struct node **pp2)
{
    struct node *list = ((void *)0);
    do
        chain_node(&list);
    while (__VERIFIER_nondet_int());
    *pp2 = list;
    while (__VERIFIER_nondet_int())
        chain_node(&list);
    *pp1 = list;
    do
        chain_node(&list);
    while (__VERIFIER_nondet_int());
    return list;
}
void init_back_link(struct node *list) {
    for (;;) {
        struct node *next = list->next;
        if (!next)
            return;
        next->prev = list;
        list = next;
    }
}
void reverse_dll(struct node *list) {
    while (list) {
        struct node *next = list->next;
        list->next = list->prev;
        list->prev = next;
        list = next;
    }
}
void remove_fw_link(struct node *list) {
    while (list) {
        struct node *next = list->next;
        list->next = ((void *)0);
        list = next;
    }
}
void check_seq_next(const struct node *beg, const struct node *const end) {
    do { if (!(beg)) fail(); } while (0);
    do { if (!(end)) fail(); } while (0);
    for (beg = beg->next; end != beg; beg = beg->next)
        do { if (!(beg)) fail(); } while (0);
}
void check_seq_prev(const struct node *beg, const struct node *const end) {
    do { if (!(beg)) fail(); } while (0);
    do { if (!(end)) fail(); } while (0);
    for (beg = beg->prev; end != beg; beg = beg->prev)
        do { if (!(beg)) fail(); } while (0);
}
int main()
{
    const struct node *p1, *p2;
    struct node *list = create_sll(&p1, &p2);
    do { } while (0);
    check_seq_next(p1, p2);
    do { if (!(!p1->prev)) fail(); } while (0);
    do { if (!(!p2->prev)) fail(); } while (0);
    init_back_link(list);
    do { } while (0);
    check_seq_next(p1, p2);
    check_seq_prev(p2, p1);
    reverse_dll(list);
    do { } while (0);
    check_seq_prev(p1, p2);
    check_seq_next(p2, p1);
    remove_fw_link(list);
    do { } while (0);
    check_seq_prev(p1, p2);
    while (list) {
        struct node *prev = list->prev;
        free(list);
        list = prev;
    }
    return 0;
}