Mismerged functions with GCC transparent unions

[sim642]

In concrat/zmap, which has been merged with Goblint CIL 1.8.2, merging has produced some non-compilable code.
In particular, this happens with a function argument which is a transparent union, some GCC trickery. CIL does some transformations with it, but when merging, some copies of the function are in a non-compilable intermediate state.

I didn't try to reproduce it with a newer Goblint CIL, but we haven't fixed anything related to transparent unions (I wasn't even aware of them), so it's unlikely to have changed.

Correct version

__inline extern ssize_t ( __attribute__((__gnu_inline__, __always_inline__)) recvfrom)(int __fd ,
                                                                                       void * __restrict  __buf ,
                                                                                       size_t __n ,
                                                                                       int __flags ,
                                                                                       struct sockaddr * __restrict  __cil_tmp14 ,
                                                                                       socklen_t * __restrict  __addr_len )
{
  __SOCKADDR_ARG __addr ;
  unsigned long tmp ;
  ssize_t tmp___0 ;
  unsigned long tmp___1 ;
  ssize_t tmp___2 ;
  unsigned long tmp___3 ;
  unsigned long tmp___4 ;
  ssize_t tmp___5 ;

  {
  __addr.__sockaddr__ = __cil_tmp14;
  tmp___4 = __builtin_object_size((void *)__buf, 0);
  if (tmp___4 != 0xffffffffffffffffUL) {
    tmp = __builtin_object_size((void *)__buf, 0);
    tmp___0 = __recvfrom_chk(__fd, __buf, __n, tmp, __flags, __addr.__sockaddr__,
                             __addr_len);
    return (tmp___0);
    tmp___3 = __builtin_object_size((void *)__buf, 0);
    if (__n > tmp___3) {
      tmp___1 = __builtin_object_size((void *)__buf, 0);
      tmp___2 = __recvfrom_chk_warn(__fd, __buf, __n, tmp___1, __flags, __addr.__sockaddr__,
                                    __addr_len);
      return (tmp___2);
    }
  }
  tmp___5 = __recvfrom_alias(__fd, __buf, __n, __flags, __addr.__sockaddr__, __addr_len);
  return (tmp___5);
}
}

Incorrect version

Body uses __addr but argument has already been replaced with __cil_tmp14, yet no local nor assignment has been added to body:

__inline extern ssize_t ( __attribute__((__gnu_inline__, __always_inline__)) recvfrom)(int __fd ,
                                                                                       void * __restrict  __buf ,
                                                                                       size_t __n ,
                                                                                       int __flags ,
                                                                                       struct sockaddr * __restrict  __cil_tmp14 ,
                                                                                       socklen_t * __restrict  __addr_len )
{
  unsigned long tmp ;
  ssize_t tmp___0 ;
  unsigned long tmp___1 ;
  ssize_t tmp___2 ;
  unsigned long tmp___3 ;
  unsigned long tmp___4 ;
  ssize_t tmp___5 ;

  {
  tmp___4 = __builtin_object_size((void *)__buf, 0);
  if (tmp___4 != 0xffffffffffffffffUL) {
    tmp = __builtin_object_size((void *)__buf, 0);
    tmp___0 = __recvfrom_chk(__fd, __buf, __n, tmp, __flags, __addr, __addr_len);
    return (tmp___0);
    tmp___3 = __builtin_object_size((void *)__buf, 0);
    if (__n > tmp___3) {
      tmp___1 = __builtin_object_size((void *)__buf, 0);
      tmp___2 = __recvfrom_chk_warn(__fd, __buf, __n, tmp___1, __flags, __addr, __addr_len);
      return (tmp___2);
    }
  }
  tmp___5 = __recvfrom_alias(__fd, __buf, __n, __flags, __addr, __addr_len);
  return (tmp___5);
}
}