/* remove.c -- core functions for removing files and directories
   Copyright (C) 88, 90, 91, 1994-2003 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Extracted from rm.c and librarified, then rewritten by Jim Meyering.  */

#ifdef _AIX
 #pragma alloca
#endif

#include <config.h>
#include <stdio.h>
#include <sys/types.h>
#include <assert.h>

#include "save-cwd.h"
#include "system.h"
#include "dirname.h"
#include "error.h"
#include "file-type.h"
#include "hash.h"
#include "hash-pjw.h"
#include "obstack.h"
#include "quote.h"
#include "remove.h"

/* Avoid shadowing warnings because these are functions declared
   in dirname.h as well as locals used below.  */
#define dir_name rm_dir_name
#define dir_len rm_dir_len

#define obstack_chunk_alloc malloc
#define obstack_chunk_free free

/* FIXME: if possible, use autoconf...  */
#ifdef __GLIBC__
# define ROOT_CAN_UNLINK_DIRS 0
#else
# define ROOT_CAN_UNLINK_DIRS 1
#endif

enum Ternary
  {
    T_UNKNOWN = 2,
    T_NO,
    T_YES
  };
typedef enum Ternary Ternary;

/* The prompt function may be called twice a given directory.
   The first time, we ask whether to descend into it, and the
   second time, we ask whether to remove it.  */
enum Prompt_action
  {
    PA_DESCEND_INTO_DIR = 2,
    PA_REMOVE_DIR
  };

/* On systems with an lstat function that accepts the empty string,
   arrange to make lstat calls go through the wrapper function.  */
#if HAVE_LSTAT_EMPTY_STRING_BUG
int rpl_lstat (const char *, struct stat *);
# define lstat(Name, Stat_buf) rpl_lstat(Name, Stat_buf)
#endif

#ifdef D_INO_IN_DIRENT
# define D_INO(dp) ((dp)->d_ino)
# define ENABLE_CYCLE_CHECK
#else
/* Some systems don't have inodes, so fake them to avoid lots of ifdefs.  */
# define D_INO(dp) 1
#endif

/* Initial capacity of per-directory hash table of entries that have
   been processed but not been deleted.  */
#define HT_UNREMOVABLE_INITIAL_CAPACITY 13

/* An entry in the active directory stack.
   Each entry corresponds to an `active' directory.  */
struct AD_ent
{
  /* For a given active directory, this is the set of names of
     entries in that directory that could/should not be removed.
     For example, `.' and `..', as well as files/dirs for which
     unlink/rmdir failed e.g., due to access restrictions.  */
  Hash_table *unremovable;

  /* Record the status for a given active directory; we need to know
     whether an entry was not removed, either because of an error or
     because the user declined.  */
  enum RM_status status;

  union
  {
    /* The directory's dev/ino.  Used to ensure that `chdir some-subdir', then
       `chdir ..' takes us back to the same directory from which we started).
       (valid for all but the bottommost entry on the stack.  */
    struct dev_ino a;

    /* Enough information to restore the initial working directory.
       (valid only for the bottommost entry on the stack)  */
    struct saved_cwd saved_cwd;
  } u;
};

int euidaccess ();
int yesno ();

extern char *program_name;

struct dirstack_state
{
  /* The name of the directory (starting with and relative to a command
     line argument) being processed.  When a subdirectory is entered, a new
     component is appended (pushed).  Remove (pop) the top component
     upon chdir'ing out of a directory.  This is used to form the full
     name of the current directory or a file therein, when necessary.  */
  struct obstack dir_stack;

  /* Stack of lengths of directory names (including trailing slash)
     appended to dir_stack.  We have to have a separate stack of lengths
     (rather than just popping back to previous slash) because the first
     element pushed onto the dir stack may contain slashes.  */
  struct obstack len_stack;

  /* Stack of active directory entries.
     The first `active' directory is the initial working directory.
     Additional active dirs are pushed onto the stack as we `chdir'
     into each directory to be processed.  When finished with the
     hierarchy under a directory, pop the active dir stack.  */
  struct obstack Active_dir;
};
typedef struct dirstack_state DS;

DS *
ds_init ()
{
  DS *ds = XMALLOC (struct dirstack_state, 1);
  obstack_init (&(ds->dir_stack));
  obstack_init (&(ds->len_stack));
  obstack_init (&(ds->Active_dir));
  return ds;
}

void
ds_free (DS *ds)
{
  obstack_free (&(ds->dir_stack), NULL);
  obstack_free (&(ds->len_stack), NULL);
  obstack_free (&(ds->Active_dir), NULL);
}

static void
hash_freer (void *x)
{
  free (x);
}

static bool
hash_compare_strings (void const *x, void const *y)
{
  return STREQ (x, y) ? true : false;
}

static inline void
push_dir (DS *ds, const char *dir_name)
{
  size_t len;

  len = strlen (dir_name);

  /* Append the string onto the stack.  */
  obstack_grow (&ds->dir_stack, dir_name, len);

  /* Append a trailing slash.  */
  obstack_1grow (&ds->dir_stack, '/');

  /* Add one for the slash.  */
  ++len;

  /* Push the length (including slash) onto its stack.  */
  obstack_grow (&ds->len_stack, &len, sizeof (len));
}

/* Return the entry name of the directory on the top of the stack
   in malloc'd storage.  */
static inline char *
top_dir (DS const *ds)
{
  int n_lengths = obstack_object_size (&ds->len_stack) / sizeof (size_t);
  size_t *length = (size_t *) obstack_base (&ds->len_stack);
  size_t top_len = length[n_lengths - 1];
  char const *p = obstack_next_free (&ds->dir_stack) - top_len;
  char *q = xmalloc (top_len);
  memcpy (q, p, top_len - 1);
  q[top_len - 1] = 0;
  return q;
}

static inline void
pop_dir (DS *ds)
{
  int n_lengths = obstack_object_size (&ds->len_stack) / sizeof (size_t);
  size_t *length = (size_t *) obstack_base (&ds->len_stack);
  size_t top_len;

  assert (n_lengths > 0);
  top_len = length[n_lengths - 1];
  assert (top_len >= 2);

  /* Pop off the specified length of pathname.  */
  assert (obstack_object_size (&ds->dir_stack) >= top_len);
  obstack_blank (&ds->dir_stack, -top_len);

  /* Pop the length stack, too.  */
  assert (obstack_object_size (&ds->len_stack) >= sizeof (size_t));
  obstack_blank (&ds->len_stack, (int) -(sizeof (size_t)));
}

/* Copy the SRC_LEN bytes of data beginning at SRC into the DST_LEN-byte
   buffer, DST, so that the last source byte is at the end of the destination
   buffer.  If SRC_LEN is longer than DST_LEN, then set *TRUNCATED to non-zero.
   Set *RESULT to point to the beginning of (the portion of) the source data
   in DST.  Return the number of bytes remaining in the destination buffer.  */

static size_t
right_justify (char *dst, size_t dst_len, const char *src, size_t src_len,
	       char **result, int *truncated)
{
  const char *sp;
  char *dp;

  if (src_len <= dst_len)
    {
      sp = src;
      dp = dst + (dst_len - src_len);
      *truncated = 0;
    }
  else
    {
      sp = src + (src_len - dst_len);
      dp = dst;
      src_len = dst_len;
      *truncated = 1;
    }

  *result = memcpy (dp, sp, src_len);
  return dst_len - src_len;
}

/* Using the global directory name obstack, create the full path to FILENAME.
   Return it in sometimes-realloc'd space that should not be freed by the
   caller.  Realloc as necessary.  If realloc fails, use a static buffer
   and put as long a suffix in that buffer as possible.  */

#define full_filename(Filename) full_filename_ (ds, Filename)
static char *
full_filename_ (DS const *ds, const char *filename)
{
  static char *buf = NULL;
  static size_t n_allocated = 0;

  int dir_len = obstack_object_size (&ds->dir_stack);
  char *dir_name = (char *) obstack_base (&ds->dir_stack);
  size_t n_bytes_needed;
  size_t filename_len;

  filename_len = strlen (filename);
  n_bytes_needed = dir_len + filename_len + 1;

  if (n_allocated < n_bytes_needed)
    {
      /* This code requires that realloc accept NULL as the first arg.
         This function must not use xrealloc.  Otherwise, an out-of-memory
	 error involving a file name to be expanded here wouldn't ever
	 be issued.  Use realloc and fall back on using a static buffer
	 if memory allocation fails.  */
      buf = realloc (buf, n_bytes_needed);
      n_allocated = n_bytes_needed;

      if (buf == NULL)
	{
#define SBUF_SIZE 512
#define ELLIPSES_PREFIX "[...]"
	  static char static_buf[SBUF_SIZE];
	  int truncated;
	  size_t len;
	  char *p;

	  len = right_justify (static_buf, SBUF_SIZE, filename,
			       filename_len + 1, &p, &truncated);
	  right_justify (static_buf, len, dir_name, dir_len, &p, &truncated);
	  if (truncated)
	    {
	      memcpy (static_buf, ELLIPSES_PREFIX,
		      sizeof (ELLIPSES_PREFIX) - 1);
	    }
	  return p;
	}
    }

  /* Copy directory part, including trailing slash, and then
     append the filename part, including a trailing zero byte.  */
  memcpy (mempcpy (buf, dir_name, dir_len), filename, filename_len + 1);

  assert (strlen (buf) + 1 == n_bytes_needed);

  return buf;
}

static size_t
AD_stack_height (DS const *ds)
{
  return obstack_object_size (&ds->Active_dir) / sizeof (struct AD_ent);
}

static struct AD_ent *
AD_stack_top (DS const *ds)
{
  return (struct AD_ent *)
    ((char *) obstack_next_free (&ds->Active_dir) - sizeof (struct AD_ent));
}

static void
AD_stack_pop (DS *ds)
{
  /* operate on Active_dir.  pop and free top entry */
  struct AD_ent *top = AD_stack_top (ds);
  if (top->unremovable)
    hash_free (top->unremovable);
  obstack_blank (&ds->Active_dir, -sizeof (struct AD_ent));
  pop_dir (ds);
}

/* chdir `up' one level.
   Whenever using chdir '..', verify that the post-chdir
   dev/ino numbers for `.' match the saved ones.
   Return the name (in malloc'd storage) of the
   directory (usually now empty) from which we're coming.  */
static char *
AD_pop_and_chdir (DS *ds)
{
  /* Get the name of the current directory from the top of the stack.  */
  char *dir = top_dir (ds);
  enum RM_status old_status = AD_stack_top(ds)->status;
  struct stat sb;
  struct AD_ent *top;

  AD_stack_pop (ds);

  /* Propagate any failure to parent.  */
  UPDATE_STATUS (AD_stack_top(ds)->status, old_status);

  assert (AD_stack_height (ds));

  top = AD_stack_top (ds);
  if (1 < AD_stack_height (ds))
    {
      /* We can give a better diagnostic here, since the target is relative. */
      if (chdir (".."))
	{
	  error (EXIT_FAILURE, errno,
		 _("cannot chdir from %s to .."),
		 quote (full_filename (".")));
	}
    }
  else
    {
      if (restore_cwd (&top->u.saved_cwd, NULL, NULL))
	exit (EXIT_FAILURE);
    }

  if (lstat (".", &sb))
    error (EXIT_FAILURE, errno,
	   _("cannot lstat `.' in %s"), quote (full_filename (".")));

  if (1 < AD_stack_height (ds))
    {
      /*  Ensure that post-chdir dev/ino match the stored ones.  */
      if ( ! SAME_INODE (sb, top->u.a))
	error (EXIT_FAILURE, 0,
	       _("%s changed dev/ino"), quote (full_filename (".")));
    }

  return dir;
}

/* Initialize *HT if it is NULL.
   Insert FILENAME into HT.  */
static void
AD_mark_helper (Hash_table **ht, char const *filename)
{
  if (*ht == NULL)
    *ht = hash_initialize (HT_UNREMOVABLE_INITIAL_CAPACITY, NULL, hash_pjw,
			   hash_compare_strings, hash_freer);
  if (*ht == NULL)
    xalloc_die ();
  if (! hash_insert (*ht, filename))
    xalloc_die ();
}

/* Mark FILENAME (in current directory) as unremovable.  */
static void
AD_mark_as_unremovable (DS *ds, char const *filename)
{
  AD_mark_helper (&AD_stack_top(ds)->unremovable, xstrdup (filename));
}

/* Mark the current directory as unremovable.  I.e., mark the entry
   in the parent directory corresponding to `.'.
   This happens e.g., when an opendir fails and the only name
   the caller has conveniently at hand is `.'.  */
static void
AD_mark_current_as_unremovable (DS *ds)
{
  struct AD_ent *top = AD_stack_top (ds);
  const char *curr = top_dir (ds);

  assert (1 < AD_stack_height (ds));

  --top;
  AD_mark_helper (&top->unremovable, curr);
}

/* Push the initial cwd info onto the stack.
   This will always be the bottommost entry on the stack.  */
static void
AD_push_initial (DS *ds, struct saved_cwd const *cwd)
{
  struct AD_ent *top;

  /* Extend the stack.  */
  obstack_blank (&ds->Active_dir, sizeof (struct AD_ent));

  /* Fill in the new values.  */
  top = AD_stack_top (ds);
  top->u.saved_cwd = *cwd;
  top->unremovable = NULL;
}

/* Push info about the current working directory (".") onto the
   active directory stack.  DIR is the ./-relative name through
   which we've just `chdir'd to this directory.  DIR_SB_FROM_PARENT
   is the result of calling lstat on DIR from the parent of DIR.  */
static void
AD_push (DS *ds, char const *dir, struct stat const *dir_sb_from_parent)
{
  struct stat sb;
  struct AD_ent *top;

  push_dir (ds, dir);

  if (lstat (".", &sb))
    error (EXIT_FAILURE, errno,
	   _("cannot lstat `.' in %s"), quote (full_filename (".")));

  if ( ! SAME_INODE (sb, *dir_sb_from_parent))
    error (EXIT_FAILURE, errno,
	   _("%s changed dev/ino"), quote (full_filename (".")));

  /* Extend the stack.  */
  obstack_blank (&ds->Active_dir, sizeof (struct AD_ent));

  /* Fill in the new values.  */
  top = AD_stack_top (ds);
  top->u.a.st_dev = sb.st_dev;
  top->u.a.st_ino = sb.st_ino;
  top->unremovable = NULL;
}

static int
AD_is_removable (DS const *ds, char const *file)
{
  struct AD_ent *top = AD_stack_top (ds);
  return ! (top->unremovable && hash_lookup (top->unremovable, file));
}

static inline bool
is_power_of_two (unsigned int i)
{
  return (i & (i - 1)) == 0;
}

static void
cycle_check (DS const *ds, struct stat const *sb)
{
#ifdef ENABLE_CYCLE_CHECK
  /* If there is a directory cycle, detect it (lazily) and die.  */
  static struct dev_ino dir_cycle_detect_dev_ino;
  static unsigned int chdir_counter;

  /* If the current directory ever happens to be the same
     as the one we last recorded for the cycle detection,
     then it's obviously part of a cycle.  */
  if (chdir_counter && SAME_INODE (*sb, dir_cycle_detect_dev_ino))
    {
      error (0, 0, _("\
WARNING: Circular directory structure.\n\
This almost certainly means that you have a corrupted file system.\n\
NOTIFY YOUR SYSTEM MANAGER.\n\
The following directory is part of the cycle:\n  %s\n"),
	     quote (full_filename (".")));
      exit (EXIT_FAILURE);
    }

  /* If the number of `descending' chdir calls is a power of two,
     record the dev/ino of the current directory.  */
  if (is_power_of_two (++chdir_counter))
    {
      dir_cycle_detect_dev_ino.st_dev = sb->st_dev;
      dir_cycle_detect_dev_ino.st_ino = sb->st_ino;
    }
#endif
}

static bool
is_empty_dir (char const *dir)
{
  DIR *dirp = opendir (dir);
  if (dirp == NULL)
    {
      closedir (dirp);
      return false;
    }

  while (1)
    {
      struct dirent *dp;
      const char *f;

      errno = 0;
      dp = readdir (dirp);
      if (dp == NULL)
	{
	  closedir (dirp);
	  return errno == 0 ? true : false;
	}

      f = dp->d_name;
      if ( ! DOT_OR_DOTDOT (f))
	{
	  closedir (dirp);
	  return false;
	}
    }
}

/* Prompt whether to remove FILENAME, if required via a combination of
   the options specified by X and/or file attributes.  If the file may
   be removed, return RM_OK.  If the user declines to remove the file,
   return RM_USER_DECLINED.  If not ignoring missing files and we
   cannot lstat FILENAME, then return RM_ERROR.

   Depending on MODE, ask whether to `descend into' or to `remove' the
   directory FILENAME.  MODE is ignored when FILENAME is not a directory.
   Set *IS_EMPTY to T_YES if FILENAME is an empty directory, and it is
   appropriate to try to remove it with rmdir (e.g. recursive mode).
   Don't even try to set *IS_EMPTY when MODE == PA_REMOVE_DIR.
   Set *IS_DIR to T_YES or T_NO if we happen to determine whether
   FILENAME is a directory.  */
static enum RM_status
prompt (DS const *ds, char const *filename, struct rm_options const *x,
	enum Prompt_action mode, Ternary *is_dir, Ternary *is_empty)
{
  int write_protected = 0;
  *is_empty = T_UNKNOWN;
  *is_dir = T_UNKNOWN;

  if ((!x->ignore_missing_files && (x->interactive || x->stdin_tty)
       && (write_protected = (euidaccess (filename, W_OK) && errno == EACCES)))
      || x->interactive)
    {
      struct stat sbuf;
      if (lstat (filename, &sbuf))
	{
	  /* lstat failed.  This happens e.g., with `rm '''.  */
	  error (0, errno, _("cannot lstat %s"),
		 quote (full_filename (filename)));
	  return RM_ERROR;
	}

      /* Using permissions doesn't make sense for symlinks.  */
      if (S_ISLNK (sbuf.st_mode))
	{
	  if ( ! x->interactive)
	    return RM_OK;
	  write_protected = 0;
	}

      /* Issue the prompt.  */
      {
	char const *quoted_name = quote (full_filename (filename));

	*is_dir = (S_ISDIR (sbuf.st_mode) ? T_YES : T_NO);

	/* FIXME: use a variant of error (instead of fprintf) that doesn't
	   append a newline.  Then we won't have to declare program_name in
	   this file.  */
	if (S_ISDIR (sbuf.st_mode)
	    && x->recursive
	    && mode == PA_DESCEND_INTO_DIR
	    && ((*is_empty = (is_empty_dir (filename) ? T_YES : T_NO))
		== T_NO))
	  fprintf (stderr,
		   (write_protected
		    ? _("%s: descend into write-protected directory %s? ")
		    : _("%s: descend into directory %s? ")),
		   program_name, quoted_name);
	else
	  {
	    /* TRANSLATORS: You may find it more convenient to translate
	       the equivalent of _("%s: remove %s (write-protected) %s? ").
	       It should avoid grammatical problems with the output
	       of file_type.  */
	    fprintf (stderr,
		     (write_protected
		      ? _("%s: remove write-protected %s %s? ")
		      : _("%s: remove %s %s? ")),
		     program_name, file_type (&sbuf), quoted_name);
	  }

	if (!yesno ())
	  return RM_USER_DECLINED;
      }
    }
  return RM_OK;
}

#if HAVE_STRUCT_DIRENT_D_TYPE
# define DT_IS_DIR(D) ((D)->d_type == DT_DIR)
#else
/* Use this only if the member exists -- i.e., don't return 0.  */
# define DT_IS_DIR(D) do_not_use_this_macro
#endif

#define DO_UNLINK(Filename, X)						\
  do									\
    {									\
      if (unlink (Filename) == 0)					\
	{								\
	  if ((X)->verbose)						\
	    printf (_("removed %s\n"), quote (full_filename (Filename))); \
	  return RM_OK;							\
	}								\
									\
      if (errno == ENOENT && (X)->ignore_missing_files)			\
	return RM_OK;							\
    }									\
  while (0)

#define DO_RMDIR(Filename, X)				\
  do							\
    {							\
      if (rmdir (Filename) == 0)			\
	{						\
	  if ((X)->verbose)				\
	    printf (_("removed directory: %s\n"),	\
		    quote (full_filename (Filename)));	\
	  return RM_OK;					\
	}						\
							\
      if (errno == ENOENT && (X)->ignore_missing_files)	\
	return RM_OK;					\
							\
      if (errno == ENOTEMPTY || errno == EEXIST)	\
	return RM_NONEMPTY_DIR;				\
    }							\
  while (0)

/* Remove the file or directory specified by FILENAME.
   Return RM_OK if it is removed, and RM_ERROR or RM_USER_DECLINED if not.
   But if FILENAME specifies a non-empty directory, return RM_NONEMPTY_DIR. */

static enum RM_status
remove_entry (DS const *ds, char const *filename, struct rm_options const *x,
	      struct dirent const *dp)
{
  Ternary is_dir;
  Ternary is_empty_directory;
  enum RM_status s = prompt (ds, filename, x, PA_DESCEND_INTO_DIR,
			     &is_dir, &is_empty_directory);

  if (s != RM_OK)
    return s;

  /* Why bother with the following #if/#else block?  Because on systems with
     an unlink function that *can* unlink directories, we must determine the
     type of each entry before removing it.  Otherwise, we'd risk unlinking an
     entire directory tree simply by unlinking a single directory;  then all
     the storage associated with that hierarchy would not be freed until the
     next reboot.  Not nice.  To avoid that, on such slightly losing systems, we
     need to call lstat to determine the type of each entry, and that represents
     extra overhead that -- it turns out -- we can avoid on GNU-libc-based
     systems, since there, unlink will never remove a directory.  */

#if ROOT_CAN_UNLINK_DIRS

  /* If we don't already know whether FILENAME is a directory, find out now.
     Then, if it's a non-directory, we can use unlink on it.  */
  if (is_dir == T_UNKNOWN)
    {
# if HAVE_STRUCT_DIRENT_D_TYPE
      if (dp)
	is_dir = DT_IS_DIR (dp) ? T_YES : T_NO;
      else
# endif
	{
	  struct stat sbuf;
	  if (lstat (filename, &sbuf))
	    {
	      if (errno == ENOENT && x->ignore_missing_files)
		return RM_OK;

	      error (0, errno,
		     _("cannot lstat %s"), quote (full_filename (filename)));
	      return RM_ERROR;
	    }

	  is_dir = S_ISDIR (sbuf.st_mode) ? T_YES : T_NO;
	}
    }

  if (is_dir == T_NO)
    {
      /* At this point, barring race conditions, FILENAME is known
	 to be a non-directory, so it's ok to try to unlink it.  */
      DO_UNLINK (filename, x);

      /* unlink failed with some other error code.  report it.  */
      error (0, errno, _("cannot remove %s"),
	     quote (full_filename (filename)));
      return RM_ERROR;
    }

  if (! x->recursive)
    {
      error (0, EISDIR, _("cannot remove directory %s"),
	     quote (full_filename (filename)));
      return RM_ERROR;
    }

  if (is_empty_directory == T_YES)
    {
      DO_RMDIR (filename, x);
      /* Don't diagnose any failure here.
	 It'll be detected when the caller tries another way.  */
    }


#else

  if (is_dir == T_YES && ! x->recursive)
    {
      error (0, EISDIR, _("cannot remove directory %s"),
	     quote (full_filename (filename)));
      return RM_ERROR;
    }

  /* is_empty_directory is set iff it's ok to use rmdir.
     Note that it's set only in interactive mode -- in which case it's
     an optimization that arranges so that the user is asked just
     once whether to remove the directory.  */
  if (is_empty_directory == T_YES)
    DO_RMDIR (filename, x);

  /* If we happen to know that FILENAME is a directory, return now
     and let the caller remove it -- this saves the overhead of a failed
     unlink call.  If FILENAME is a command-line argument, then dp is NULL,
     so we'll first try to unlink it.  Using unlink here is ok, because it
     cannot remove a directory.  */
  if ((dp && DT_IS_DIR (dp)) || is_dir == T_YES)
    return RM_NONEMPTY_DIR;

  DO_UNLINK (filename, x);

  /* Accept either EISDIR or EPERM as an indication that FILENAME may be
     a directory.  POSIX says that unlink must set errno to EPERM when it
     fails to remove a directory, while Linux-2.4.18 sets it to EISDIR.  */
  if ((errno != EISDIR && errno != EPERM) || ! x->recursive)
    {
      /* some other error code.  Report it and fail.
	 Likewise, if we're trying to remove a directory without
	 the --recursive option.  */
      error (0, errno, _("cannot remove %s"),
	     quote (full_filename (filename)));
      return RM_ERROR;
    }
#endif

  return RM_NONEMPTY_DIR;
}

/* Remove entries in `.', the current working directory (cwd).
   Upon finding a directory that is both non-empty and that can be chdir'd
   into, return RM_OK and set *SUBDIR and fill in SUBDIR_SB, where
   SUBDIR is the malloc'd name of the subdirectory if the chdir succeeded,
   NULL otherwise (e.g., if opendir failed or if there was no subdirectory).
   Likewise, SUBDIR_SB is the result of calling lstat on SUBDIR.
   Return RM_OK if all entries are removed.  Return RM_ERROR if any
   entry cannot be removed.  Otherwise, return RM_USER_DECLINED if
   the user declines to remove at least one entry.  Remove as much as
   possible, continuing even if we fail to remove some entries.  */
static enum RM_status
remove_cwd_entries (DS *ds, char **subdir, struct stat *subdir_sb,
		    struct rm_options const *x)
{
  DIR *dirp = opendir (".");
  struct AD_ent *top = AD_stack_top (ds);
  enum RM_status status = top->status;

  assert (VALID_STATUS (status));
  *subdir = NULL;

  if (dirp == NULL)
    {
      if (errno != ENOENT || !x->ignore_missing_files)
	{
	  error (0, errno, _("cannot open directory %s"),
		 quote (full_filename (".")));
	  return RM_ERROR;
	}
    }

  while (1)
    {
      struct dirent *dp;
      enum RM_status tmp_status;
      const char *f;

      /* Set errno to zero so we can distinguish between a readdir failure
	 and when readdir simply finds that there are no more entries.  */
      errno = 0;
      if ((dp = readdir (dirp)) == NULL)
	{
	  if (errno)
	    {
	      /* Save/restore errno across closedir call.  */
	      int e = errno;
	      closedir (dirp);
	      errno = e;

	      /* Arrange to give a diagnostic after exiting this loop.  */
	      dirp = NULL;
	    }
	  break;
	}

      f = dp->d_name;
      if (DOT_OR_DOTDOT (f))
	continue;

      /* Skip files we've already tried/failed to remove.  */
      if ( ! AD_is_removable (ds, f))
	continue;

      /* Pass dp->d_type info to remove_entry so the non-glibc
	 case can decide whether to use unlink or chdir.
	 Systems without the d_type member will have to endure
	 the performance hit of first calling lstat F. */
      tmp_status = remove_entry (ds, f, x, dp);
      switch (tmp_status)
	{
	case RM_OK:
	  /* do nothing */
	  break;

	case RM_ERROR:
	case RM_USER_DECLINED:
	  AD_mark_as_unremovable (ds, f);
	  UPDATE_STATUS (status, tmp_status);
	  break;

	case RM_NONEMPTY_DIR:
	  /* Record dev/ino of F so that we can compare
	     that with dev/ino of `.' after the chdir.
	     This dev/ino pair is also used in cycle detection.  */
	  if (lstat (f, subdir_sb))
	    error (EXIT_FAILURE, errno, _("cannot lstat %s"),
		   quote (full_filename (f)));

	  if (chdir (f))
	    {
	      error (0, errno, _("cannot chdir from %s to %s"),
		     quote_n (0, full_filename (".")), quote_n (1, f));
	      AD_mark_as_unremovable (ds, f);
	      status = RM_ERROR;
	      break;
	    }
	  cycle_check (ds, subdir_sb);

	  *subdir = xstrdup (f);
	  break;
	}

      /* Record status for this directory.  */
      UPDATE_STATUS (top->status, status);

      if (*subdir)
	break;
    }

  if (dirp == NULL || CLOSEDIR (dirp) != 0)
    {
      /* Note that this diagnostic serves for both readdir
	 and closedir failures.  */
      error (0, errno, _("reading directory %s"), quote (full_filename (".")));
      status = RM_ERROR;
    }

  return status;
}

/* Do this after each call to AD_push or AD_push_initial.
   Because the status = RM_OK bit is too remove-specific to
   go into the general-purpose AD_* package.  */
#define AD_INIT_OTHER_MEMBERS()			\
  do						\
    {						\
      AD_stack_top(ds)->status = RM_OK;		\
    }						\
  while (0)

/*  Remove the hierarchy rooted at DIR.
    Do that by changing into DIR, then removing its contents, then
    returning to the original working directory and removing DIR itself.
    Don't use recursion.  Be careful when using chdir ".." that we
    return to the same directory from which we came, if necessary.
    Return 1 for success, 0 if some file cannot be removed or if
    a chdir fails.
    If the working directory cannot be restored, exit immediately.  */

static enum RM_status
remove_dir (DS *ds, char const *dir, struct saved_cwd **cwd_state,
	    struct rm_options const *x)
{
  enum RM_status status;
  struct stat dir_sb;

  /* Save any errno (from caller's failed remove_entry call), in case DIR
     is not a directory, so that we can give a reasonable diagnostic.  */
  int saved_errno = errno;

  if (*cwd_state == NULL)
    {
      *cwd_state = XMALLOC (struct saved_cwd, 1);
      if (save_cwd (*cwd_state))
	return RM_ERROR;
      AD_push_initial (ds, *cwd_state);
      AD_INIT_OTHER_MEMBERS ();
    }

  /* There is a race condition in that an attacker could replace the nonempty
     directory, DIR, with a symlink between the preceding call to rmdir
     (in our caller) and the chdir below.  However, the following lstat,
     along with the `stat (".",...' and dev/ino comparison in AD_push
     ensure that we detect it and fail.  */

  if (lstat (dir, &dir_sb))
    {
      error (0, errno,
	     _("cannot lstat %s"), quote (full_filename (dir)));
      return RM_ERROR;
    }

  if (chdir (dir))
    {
      if (! S_ISDIR (dir_sb.st_mode))
	{
	  /* This happens on Linux-2.4.18 when a non-privileged user tries
	     to delete a file that is owned by another user in a directory
	     like /tmp that has the S_ISVTX flag set.  */
	  assert (saved_errno == EPERM);
	  error (0, saved_errno,
		 _("cannot remove %s"), quote (full_filename (dir)));
	}
      else
	{
	  error (0, errno,
		 _("cannot chdir from %s to %s"),
		 quote_n (0, full_filename (".")), quote_n (1, dir));
	}
      return RM_ERROR;
    }

  AD_push (ds, dir, &dir_sb);
  AD_INIT_OTHER_MEMBERS ();

  status = RM_OK;

  while (1)
    {
      char *subdir = NULL;
      struct stat subdir_sb;
      enum RM_status tmp_status = remove_cwd_entries (ds,
						      &subdir, &subdir_sb, x);
      if (tmp_status != RM_OK)
	{
	  UPDATE_STATUS (status, tmp_status);
	  AD_mark_current_as_unremovable (ds);
	}
      if (subdir)
	{
	  AD_push (ds, subdir, &subdir_sb);
	  AD_INIT_OTHER_MEMBERS ();

	  free (subdir);
	  continue;
	}

      /* Execution reaches this point when we've removed the last
	 removable entry from the current directory.  */
      {
	char *d = AD_pop_and_chdir (ds);

	/* Try to remove D only if remove_cwd_entries succeeded.  */
	if (tmp_status == RM_OK)
	  {
	    /* This does a little more work than necessary when it actually
	       prompts the user.  E.g., we already know that D is a directory
	       and that it's almost certainly empty, yet we lstat it.
	       But that's no big deal since we're interactive.  */
	    Ternary is_dir;
	    Ternary is_empty;
	    enum RM_status s = prompt (ds, d, x, PA_REMOVE_DIR,
				       &is_dir, &is_empty);

	    if (s != RM_OK)
	      {
		free (d);
		return s;
	      }

	    if (rmdir (d) == 0)
	      {
		if (x->verbose)
		  printf (_("removed directory: %s\n"),
			  quote (full_filename (d)));
	      }
	    else
	      {
		error (0, errno, _("cannot remove directory %s"),
		       quote (full_filename (d)));
		AD_mark_as_unremovable (ds, d);
		status = RM_ERROR;
		UPDATE_STATUS (AD_stack_top(ds)->status, status);
	      }
	  }

	free (d);

	if (AD_stack_height (ds) == 1)
	  break;
      }
    }

  return status;
}

/* Remove the file or directory specified by FILENAME.
   Return RM_OK if it is removed, and RM_ERROR or RM_USER_DECLINED if not.
   On input, the first time this function is called, CWD_STATE should be
   the address of a NULL pointer.  Do not modify it for any subsequent calls.
   On output, it is either that same NULL pointer or the address of
   a malloc'd `struct saved_cwd' that may be freed.  */

static enum RM_status
rm_1 (DS *ds, char const *filename,
      struct rm_options const *x, struct saved_cwd **cwd_state)
{
  char *base = base_name (filename);
  enum RM_status status;

  if (DOT_OR_DOTDOT (base))
    {
      error (0, 0, _("cannot remove `.' or `..'"));
      return RM_ERROR;
    }

  status = remove_entry (ds, filename, x, NULL);
  if (status != RM_NONEMPTY_DIR)
    return status;

  return remove_dir (ds, filename, cwd_state, x);
}

/* Remove all files and/or directories specified by N_FILES and FILE.
   Apply the options in X.  */
enum RM_status
rm (size_t n_files, char const *const *file, struct rm_options const *x)
{
  struct saved_cwd *cwd_state = NULL;
  enum RM_status status = RM_OK;
  size_t i;
  DS *ds;

  ds = ds_init ();

  for (i = 0; i < n_files; i++)
    {
      enum RM_status s = rm_1 (ds, file[i], x, &cwd_state);
      assert (VALID_STATUS (s));
      UPDATE_STATUS (status, s);
    }

  ds_free (ds);

  XFREE (cwd_state);

  return status;
}