rpath = realloc (rpath, new_size);
new_rpath = (char *) realloc (rpath, new_size); if (new_rpath == NULL) return NULL; rpath = new_rpath;
chroot_canon (const char *chroot, const char *name){  char *rpath, *dest, *extra_buf = NULL, *rpath_root;  const char *start, *end, *rpath_limit;  int num_links = 0;  size_t chroot_len = strlen (chroot);  if (chroot_len < 1)    {      __set_errno (EINVAL);      return NULL;    }  rpath = malloc (chroot_len + PATH_MAX);  rpath_limit = rpath + chroot_len + PATH_MAX;  rpath_root = (char *) mempcpy (rpath, chroot, chroot_len) - 1;  if (*rpath_root != '/')    *++rpath_root = '/';  dest = rpath_root + 1;  for (start = end = name; *start; start = end)    {      struct stat64 st;      int n;      /* Skip sequence of multiple path-separators.  */      while (*start == '/')	++start;      /* Find end of path component.  */      for (end = start; *end && *end != '/'; ++end)	/* Nothing.  */;      if (end - start == 0)	break;      else if (end - start == 1 && start[0] == '.')	/* nothing */;      else if (end - start == 2 && start[0] == '.' && start[1] == '.')	{	  /* Back up to previous component, ignore if at root already.  */	  if (dest > rpath_root + 1)	    while ((--dest)[-1] != '/');	}      else	{	  size_t new_size;	  if (dest[-1] != '/')	    *dest++ = '/';	  if (dest + (end - start) >= rpath_limit)	    {	      ptrdiff_t dest_offset = dest - rpath;	      new_size = rpath_limit - rpath;	      if (end - start + 1 > PATH_MAX)		new_size += end - start + 1;	      else		new_size += PATH_MAX;	      rpath = realloc (rpath, new_size);	      rpath_limit = rpath + new_size;	      if (rpath == NULL)		return NULL;	      dest = rpath + dest_offset;	    }	  dest = mempcpy (dest, start, end - start);	  *dest = '\0';	  if (lstat64 (rpath, &st) < 0)	    {	      if (*end == '\0')		goto done;	      goto error;	    }	  if (S_ISLNK (st.st_mode))	    {	      char *buf = alloca (PATH_MAX);	      size_t len;	      if (++num_links > MAXSYMLINKS)		{		  __set_errno (ELOOP);		  goto error;		}	      n = readlink (rpath, buf, PATH_MAX);	      if (n < 0)		{		  if (*end == '\0')		    goto done;		  goto error;		}	      buf[n] = '\0';	      if (!extra_buf)		extra_buf = alloca (PATH_MAX);	      len = strlen (end);	      if ((long int) (n + len) >= PATH_MAX)		{		  __set_errno (ENAMETOOLONG);		  goto error;		}	      /* Careful here, end may be a pointer into extra_buf... */	      memmove (&extra_buf[n], end, len + 1);	      name = end = memcpy (extra_buf, buf, n);	      if (buf[0] == '/')		dest = rpath_root + 1;	/* It's an absolute symlink */	      else		/* Back up to previous component, ignore if at root already: */		if (dest > rpath_root + 1)		  while ((--dest)[-1] != '/');	    }	}    } done:  if (dest > rpath_root + 1 && dest[-1] == '/')    --dest;  *dest = '\0';  return rpath; error:  free (rpath);  return NULL;}