builtins/enable.def

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

Copyright (C) 1987-2009 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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.

$PRODUCES enable.c

$BUILTIN enable
$FUNCTION enable_builtin
$SHORT_DOC enable [-a] [-dnps] [-f filename] [name ...]
Enable and disable shell builtins.

Enables and disables builtin shell commands.  Disabling allows you to
execute a disk command which has the same name as a shell builtin
without using a full pathname.

Options:
  -a	print a list of builtins showing whether or not each is enabled
  -n	disable each NAME or display a list of disabled builtins
  -p	print the list of builtins in a reusable format
  -s	print only the names of Posix `special' builtins

Options controlling dynamic loading:
  -f	Load builtin NAME from shared object FILENAME
  -d	Remove a builtin loaded with -f

Without options, each NAME is enabled.

To use the `test' found in $PATH instead of the shell builtin
version, type `enable -n test'.

Exit Status:
Returns success unless NAME is not a shell builtin or an error occurs.
$END

#include <config.h>

#if defined (HAVE_UNISTD_H)
#  ifdef _MINIX
#    include <sys/types.h>
#  endif
#  include <unistd.h>
#endif

#include <stdio.h>
#include "../bashansi.h"
#include "../bashintl.h"

#include "../shell.h"
#include "../builtins.h"
#include "../flags.h"
#include "common.h"
#include "bashgetopt.h"

#if defined (PROGRAMMABLE_COMPLETION)
#  include "../pcomplete.h"
#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

#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
static int dyn_load_builtin __P((WORD_LIST *, int, char *));
#endif

#if defined (HAVE_DLCLOSE)
static int dyn_unload_builtin __P((char *));
static void delete_builtin __P((struct builtin *));
static int local_dlclose __P((void *));
#endif

static void list_some_builtins __P((int));
static int enable_shell_command __P((char *, int));

/* 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)))
    {
      sh_restricted ((char *)NULL);
      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);
#if defined (PROGRAMMABLE_COMPLETION)
      set_itemlist_dirty (&it_builtins);
#endif
    }
#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;
	}
#if defined (PROGRAMMABLE_COMPLETION)
      set_itemlist_dirty (&it_builtins);
#endif
    }
#endif
  else
    {
      while (list)
	{
	  opt = enable_shell_command (list->word->word, flags & NFLAG);

	  if (opt == EXECUTION_FAILURE)
	    {
	      sh_notbuiltin (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;
#if defined (RESTRICTED_SHELL)
  else if (restricted && ((b->flags & BUILTIN_ENABLED) == 0))
    {
      sh_restricted ((char *)NULL);
      return (EXECUTION_FAILURE);
    }
#endif
  else
    b->flags |= BUILTIN_ENABLED;

#if defined (PROGRAMMABLE_COMPLETION)
  set_itemlist_dirty (&it_enabled);
  set_itemlist_dirty (&it_disabled);
#endif

  return (EXECUTION_SUCCESS);
}

#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)

#if defined (HAVE_DLFCN_H)
#  include <dlfcn.h>
#endif

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 = (char *)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 = (sh_builtin_func_t *)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 */
#ifdef __STDC__
  ind = b - shell_builtins;
#else
  ind = ((int)b - (int)shell_builtins) / sizeof (struct builtin);
#endif
  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;
}

/* Tenon's MachTen has a dlclose that doesn't return a value, so we
   finesse it with a local wrapper. */
static int
local_dlclose (handle)
     void *handle;
{
#if !defined (__MACHTEN__)
  return (dlclose (handle));
#else /* __MACHTEN__ */
  dlclose (handle);
  return ((dlerror () != NULL) ? -1 : 0);    
#endif /* __MACHTEN__ */
}

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)
    {
      sh_notbuiltin (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 && local_dlclose (handle) != 0)
    {
      builtin_error (_("%s: cannot delete: %s"), name, dlerror ());
      return (EXECUTION_FAILURE);
    }

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

  return (EXECUTION_SUCCESS);
}
#endif