This file is enable.def, from which is created enable.c.
It implements the builtin "enable" in Bash.

Copyright (C) 1987, 1989, 1991 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash 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 1, or (at your option) any later
version.

Bash 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 Bash; see the file COPYING.  If not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

$PRODUCES enable.c

$BUILTIN enable
$FUNCTION enable_builtin
$SHORT_DOC enable [-pnds] [-a] [-f filename] [name ...]
Enable and disable builtin shell commands.  This allows
you to use a disk command which has the same name as a shell
builtin.  If -n is used, the NAMEs become disabled; otherwise
NAMEs are enabled.  For example, to use the `test' found on your
path instead of the shell builtin version, type `enable -n test'.
On systems supporting dynamic loading, the -f option may be used
to load new builtins from the shared object FILENAME.  The -d
option will delete a builtin previously loaded with -f.  If no
non-option names are given, or the -p option is supplied, a list
of builtins is printed.  The -a option means to print every builtin
with an indication of whether or not it is enabled.  The -s option
restricts the output to the Posix.2 `special' builtins.  The -n
option displays a list of all disabled builtins.
$END

#include <config.h>

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include <stdio.h>
#include "../bashansi.h"
#include "../shell.h"
#include "../builtins.h"
#include "../flags.h"
#include "common.h"
#include "bashgetopt.h"

#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
static int dyn_load_builtin ();
#endif

#if defined (HAVE_DLCLOSE)
static int dyn_unload_builtin ();
#endif

#define ENABLED  1
#define DISABLED 2
#define SPECIAL  4

#define AFLAG	0x01
#define DFLAG	0x02
#define FFLAG	0x04
#define NFLAG	0x08
#define PFLAG	0x10
#define SFLAG	0x20

static int enable_shell_command ();
static void list_some_builtins ();

/* Enable/disable shell commands present in LIST.  If list is not specified,
   then print out a list of shell commands showing which are enabled and
   which are disabled. */
int
enable_builtin (list)
     WORD_LIST *list;
{
  int result, flags;
  int opt, filter;
#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
  char *filename;
#endif

  result = EXECUTION_SUCCESS;
  flags = 0;

  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "adnpsf:")) != -1)
    {
      switch (opt)
	{
	case 'a':
	  flags |= AFLAG;
	  break;
	case 'n':
	  flags |= NFLAG;
	  break;
	case 'p':
	  flags |= PFLAG;
	  break;
	case 's':
	  flags |= SFLAG;
	  break;
	case 'f':
#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
	  flags |= FFLAG;
	  filename = list_optarg;
	  break;
#else
	  builtin_error ("dynamic loading not available");
	  return (EX_USAGE);
#endif
#if defined (HAVE_DLCLOSE)
	case 'd':
	  flags |= DFLAG;
	  break;
#else
	  builtin_error ("dynamic loading not available");
	  return (EX_USAGE);
#endif /* HAVE_DLCLOSE */
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }

  list = loptend;

#if defined (RESTRICTED_SHELL)
  /* Restricted shells cannot load new builtins. */
  if (restricted && (flags & (FFLAG|DFLAG)))
    {
      builtin_error ("restricted");
      return (EXECUTION_FAILURE);
    }
#endif

  if (list == 0 || (flags & PFLAG))
    {
      filter = (flags & AFLAG) ? (ENABLED | DISABLED)
			       : (flags & NFLAG) ? DISABLED : ENABLED;

      if (flags & SFLAG)
	filter |= SPECIAL;

      list_some_builtins (filter);
    }
#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
  else if (flags & FFLAG)
    {
      filter = (flags & NFLAG) ? DISABLED : ENABLED;
      if (flags & SFLAG)
        filter |= SPECIAL;

      result = dyn_load_builtin (list, filter, filename);
    }
#endif
#if defined (HAVE_DLCLOSE)
  else if (flags & DFLAG)
    {
      while (list)
	{
	  opt = dyn_unload_builtin (list->word->word);
	  if (opt == EXECUTION_FAILURE)
	    result = EXECUTION_FAILURE;
	  list = list->next;
	}
    }
#endif
  else
    {
      while (list)
	{
	  opt = enable_shell_command (list->word->word, flags & NFLAG);

	  if (opt == EXECUTION_FAILURE)
	    {
	      builtin_error ("%s: not a shell builtin", list->word->word);
	      result = EXECUTION_FAILURE;
	    }
	  list = list->next;
	}
    }
  return (result);
}

/* List some builtins.
   FILTER is a mask with two slots: ENABLED and DISABLED. */
static void
list_some_builtins (filter)
     int filter;
{
  register int i;

  for (i = 0; i < num_shell_builtins; i++)
    {
      if (shell_builtins[i].function == 0 || (shell_builtins[i].flags & BUILTIN_DELETED))
	continue;

      if ((filter & SPECIAL) &&
	  (shell_builtins[i].flags & SPECIAL_BUILTIN) == 0)
	continue;

      if ((filter & ENABLED) && (shell_builtins[i].flags & BUILTIN_ENABLED))
	printf ("enable %s\n", shell_builtins[i].name);
      else if ((filter & DISABLED) &&
	       ((shell_builtins[i].flags & BUILTIN_ENABLED) == 0))
	printf ("enable -n %s\n", shell_builtins[i].name);
    }
}

/* Enable the shell command NAME.  If DISABLE_P is non-zero, then
   disable NAME instead. */
static int
enable_shell_command (name, disable_p)
     char *name;
     int disable_p;
{
  struct builtin *b;

  b = builtin_address_internal (name, 1);
  if (b == 0)
    return (EXECUTION_FAILURE);

  if (disable_p)
    b->flags &= ~BUILTIN_ENABLED;
  else
    b->flags |= BUILTIN_ENABLED;

  return (EXECUTION_SUCCESS);
}

#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
#include <dlfcn.h>

static int
dyn_load_builtin (list, flags, filename)
     WORD_LIST *list;
     int flags;
     char *filename;
{
  WORD_LIST *l;
  void *handle;
  
  int total, size, new, replaced;
  char *struct_name, *name;
  struct builtin **new_builtins, *b, *new_shell_builtins, *old_builtin;

  if (list == 0)
    return (EXECUTION_FAILURE);

#ifndef RTLD_LAZY
#define RTLD_LAZY 1
#endif

#if defined (_AIX)
  handle = dlopen (filename, RTLD_NOW|RTLD_GLOBAL);
#else
  handle = dlopen (filename, RTLD_LAZY);
#endif /* !_AIX */

  if (handle == 0)
    {
      builtin_error ("cannot open shared object %s: %s", filename, dlerror ());
      return (EXECUTION_FAILURE);
    }

  for (new = 0, l = list; l; l = l->next, new++)
    ;
  new_builtins = (struct builtin **)xmalloc (new * sizeof (struct builtin *));

  /* For each new builtin in the shared object, find it and its describing
     structure.  If this is overwriting an existing builtin, do so, otherwise
     save the loaded struct for creating the new list of builtins. */
  for (replaced = new = 0; list; list = list->next)
    {
      name = list->word->word;

      size = strlen (name);
      struct_name = xmalloc (size + 8);
      strcpy (struct_name, name);
      strcpy (struct_name + size, "_struct");

      b = (struct builtin *)dlsym (handle, struct_name);
      if (b == 0)
	{
	  builtin_error ("cannot find %s in shared object %s: %s", struct_name,
			  filename, dlerror ());
	  free (struct_name);
	  continue;
	}

      free (struct_name);

      b->flags &= ~STATIC_BUILTIN;
      if (flags & SPECIAL)
	b->flags |= SPECIAL_BUILTIN;
      b->handle = handle;

      if (old_builtin = builtin_address_internal (name, 1))
        {
          replaced++;
	  FASTCOPY ((char *)b, (char *)old_builtin, sizeof (struct builtin));
        }
      else
	  new_builtins[new++] = b;
    }

  if (replaced == 0 && new == 0)
    {
      free (new_builtins);
      dlclose (handle);
      return (EXECUTION_FAILURE);
    }

  if (new)
    {
      total = num_shell_builtins + new;
      size = (total + 1) * sizeof (struct builtin);

      new_shell_builtins = (struct builtin *)xmalloc (size);
      FASTCOPY ((char *)shell_builtins, (char *)new_shell_builtins,
		num_shell_builtins * sizeof (struct builtin));
      for (replaced = 0; replaced < new; replaced++)
	FASTCOPY ((char *)new_builtins[replaced],
		  (char *)&new_shell_builtins[num_shell_builtins + replaced],
		  sizeof (struct builtin));

      new_shell_builtins[total].name = (char *)0;
      new_shell_builtins[total].function = (Function *)0;
      new_shell_builtins[total].flags = 0;

      if (shell_builtins != static_shell_builtins)
	free (shell_builtins);

      shell_builtins = new_shell_builtins;
      num_shell_builtins = total;
      initialize_shell_builtins ();
    }

  free (new_builtins);
  return (EXECUTION_SUCCESS);
}
#endif

#if defined (HAVE_DLCLOSE)
static void
delete_builtin (b)
     struct builtin *b;
{
  int ind, size;
  struct builtin *new_shell_builtins;

  /* XXX - funky pointer arithmetic - XXX */
  ind = ((int)b - (int)shell_builtins) / sizeof (struct builtin);
  size = num_shell_builtins * sizeof (struct builtin);
  new_shell_builtins = (struct builtin *)xmalloc (size);

  /* Copy shell_builtins[0]...shell_builtins[ind - 1] to new_shell_builtins */
  if (ind)
    FASTCOPY ((char *)shell_builtins, (char *)new_shell_builtins,
	      ind * sizeof (struct builtin));
  /* Copy shell_builtins[ind+1]...shell_builtins[num_shell_builtins to
     new_shell_builtins, starting at ind. */
  FASTCOPY ((char *)(&shell_builtins[ind+1]),
  	    (char *)(&new_shell_builtins[ind]),
  	    (num_shell_builtins - ind) * sizeof (struct builtin));

  if (shell_builtins != static_shell_builtins)
    free (shell_builtins);

  /* The result is still sorted. */
  num_shell_builtins--;
  shell_builtins = new_shell_builtins;
}

static int
dyn_unload_builtin (name)
     char *name;
{
  struct builtin *b;
  void *handle;
  int ref, i;

  b = builtin_address_internal (name, 1);
  if (b == 0)
    {
      builtin_error ("%s: not a shell builtin", name);
      return (EXECUTION_FAILURE);
    }
  if (b->flags & STATIC_BUILTIN)
    {
      builtin_error ("%s: not dynamically loaded", name);
      return (EXECUTION_FAILURE);
    }

  handle = (void *)b->handle;
  for (ref = i = 0; i < num_shell_builtins; i++)
    {
      if (shell_builtins[i].handle == b->handle)
	ref++;
    }

  /* Don't remove the shared object unless the reference count of builtins
     using it drops to zero. */
  if (ref == 1 && dlclose (handle) != 0)
    {
      builtin_error ("cannot delete %s: %s", name, dlerror ());
      return (EXECUTION_FAILURE);
    }

  /* Now remove this entry from the builtin table and reinitialize. */
  delete_builtin (b);

  return (EXECUTION_SUCCESS);
}
#endif
