eval.c 102 KB
Newer Older
Jim Blandy's avatar
Jim Blandy committed
1
/* Evaluator for GNU Emacs Lisp interpreter.
2 3
   Copyright (C) 1985-1987, 1993-1995, 1999-2013 Free Software
   Foundation, Inc.
Jim Blandy's avatar
Jim Blandy committed
4 5 6

This file is part of GNU Emacs.

7
GNU Emacs is free software: you can redistribute it and/or modify
Jim Blandy's avatar
Jim Blandy committed
8
it under the terms of the GNU General Public License as published by
9 10
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Jim Blandy's avatar
Jim Blandy committed
11 12 13 14 15 16 17

GNU Emacs 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
18
along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
Jim Blandy's avatar
Jim Blandy committed
19 20


21
#include <config.h>
22
#include <limits.h>
23
#include <stdio.h>
Jim Blandy's avatar
Jim Blandy committed
24
#include "lisp.h"
25
#include "blockinput.h"
Jim Blandy's avatar
Jim Blandy committed
26
#include "commands.h"
Jim Blandy's avatar
Jim Blandy committed
27
#include "keyboard.h"
28
#include "dispextern.h"
29
#include "frame.h"		/* For XFRAME.  */
Jim Blandy's avatar
Jim Blandy committed
30

31 32 33 34
#if HAVE_X_WINDOWS
#include "xterm.h"
#endif

35 36 37
#if !BYTE_MARK_STACK
static
#endif
Jim Blandy's avatar
Jim Blandy committed
38 39
struct catchtag *catchlist;

40 41 42 43 44 45 46 47 48 49 50
/* Chain of condition handlers currently in effect.
   The elements of this chain are contained in the stack frames
   of Fcondition_case and internal_condition_case.
   When an error is signaled (by calling Fsignal, below),
   this chain is searched for an element that applies.  */

#if !BYTE_MARK_STACK
static
#endif
struct handler *handlerlist;

51 52 53 54 55
#ifdef DEBUG_GCPRO
/* Count levels of GCPRO to detect failure to UNGCPRO.  */
int gcpro_level;
#endif

56
Lisp_Object Qautoload, Qmacro, Qexit, Qinteractive, Qcommandp;
57
Lisp_Object Qinhibit_quit;
58 59
Lisp_Object Qand_rest;
static Lisp_Object Qand_optional;
60
static Lisp_Object Qinhibit_debugger;
61
static Lisp_Object Qdeclare;
62 63
Lisp_Object Qinternal_interpreter_environment, Qclosure;

Paul Eggert's avatar
Paul Eggert committed
64
static Lisp_Object Qdebug;
Jim Blandy's avatar
Jim Blandy committed
65

66 67 68
/* This holds either the symbol `run-hooks' or nil.
   It is nil at an early stage of startup, and when Emacs
   is shutting down.  */
69

Jim Blandy's avatar
Jim Blandy committed
70 71 72 73 74
Lisp_Object Vrun_hooks;

/* Non-nil means record all fset's and provide's, to be undone
   if the file being autoloaded is not fully loaded.
   They are recorded by being consed onto the front of Vautoload_queue:
75
   (FUN . ODEF) for a defun, (0 . OFEATURES) for a provide.  */
Jim Blandy's avatar
Jim Blandy committed
76 77 78

Lisp_Object Vautoload_queue;

79 80
/* Current number of specbindings allocated in specpdl, not counting
   the dummy entry specpdl[-1].  */
81

82
ptrdiff_t specpdl_size;
Jim Blandy's avatar
Jim Blandy committed
83

84 85
/* Pointer to beginning of specpdl.  A dummy entry specpdl[-1] exists
   only so that its address can be taken.  */
86

87
union specbinding *specpdl;
Jim Blandy's avatar
Jim Blandy committed
88 89

/* Pointer to first unused element in specpdl.  */
90

91
union specbinding *specpdl_ptr;
Jim Blandy's avatar
Jim Blandy committed
92 93

/* Depth in Lisp evaluations and function calls.  */
94

95
static EMACS_INT lisp_eval_depth;
Jim Blandy's avatar
Jim Blandy committed
96

97
/* The value of num_nonmacro_input_events as of the last time we
98
   started to enter the debugger.  If we decide to enter the debugger
99
   again when this is still equal to num_nonmacro_input_events, then we
100 101 102
   know that the debugger itself has an error, and we should just
   signal the error instead of entering an infinite loop of debugger
   invocations.  */
103

104
static EMACS_INT when_entered_debugger;
Jim Blandy's avatar
Jim Blandy committed
105

106 107
/* The function from which the last `signal' was called.  Set in
   Fsignal.  */
108
/* FIXME: We should probably get rid of this!  */
109 110
Lisp_Object Vsignaling_function;

111 112 113 114 115 116
/* If non-nil, Lisp code must not be run since some part of Emacs is
   in an inconsistent state.  Currently, x-create-frame uses this to
   avoid triggering window-configuration-change-hook while the new
   frame is half-initialized.  */
Lisp_Object inhibit_lisp_code;

117
static Lisp_Object funcall_lambda (Lisp_Object, ptrdiff_t, Lisp_Object *);
118
static Lisp_Object apply_lambda (Lisp_Object fun, Lisp_Object args);
119

120
static Lisp_Object
121
specpdl_symbol (union specbinding *pdl)
122 123
{
  eassert (pdl->kind >= SPECPDL_LET);
124
  return pdl->let.symbol;
125 126 127
}

static Lisp_Object
128
specpdl_old_value (union specbinding *pdl)
129 130
{
  eassert (pdl->kind >= SPECPDL_LET);
131
  return pdl->let.old_value;
132 133 134
}

static Lisp_Object
135
specpdl_where (union specbinding *pdl)
136 137
{
  eassert (pdl->kind > SPECPDL_LET);
138
  return pdl->let.where;
139 140 141
}

static Lisp_Object
142
specpdl_arg (union specbinding *pdl)
143 144
{
  eassert (pdl->kind == SPECPDL_UNWIND);
145
  return pdl->unwind.arg;
146 147 148
}

static specbinding_func
149
specpdl_func (union specbinding *pdl)
150 151
{
  eassert (pdl->kind == SPECPDL_UNWIND);
152
  return pdl->unwind.func;
153 154 155
}

static Lisp_Object
156
backtrace_function (union specbinding *pdl)
157 158
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
159
  return pdl->bt.function;
160 161 162
}

static ptrdiff_t
163
backtrace_nargs (union specbinding *pdl)
164 165
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
166
  return pdl->bt.nargs;
167 168 169
}

static Lisp_Object *
170
backtrace_args (union specbinding *pdl)
171 172
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
173
  return pdl->bt.args;
174 175 176
}

static bool
177
backtrace_debug_on_exit (union specbinding *pdl)
178 179
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
180
  return pdl->bt.debug_on_exit;
181 182
}

183
/* Functions to modify slots of backtrace records.  */
184

185
static void
186 187 188 189 190
set_backtrace_args (union specbinding *pdl, Lisp_Object *args)
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
  pdl->bt.args = args;
}
191

192
static void
193 194 195 196 197
set_backtrace_nargs (union specbinding *pdl, ptrdiff_t n)
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
  pdl->bt.nargs = n;
}
198

199
static void
200 201 202 203 204
set_backtrace_debug_on_exit (union specbinding *pdl, bool doe)
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
  pdl->bt.debug_on_exit = doe;
}
205 206 207

/* Helper functions to scan the backtrace.  */

208 209 210
bool backtrace_p (union specbinding *) EXTERNALLY_VISIBLE;
union specbinding *backtrace_top (void) EXTERNALLY_VISIBLE;
union specbinding *backtrace_next (union specbinding *pdl) EXTERNALLY_VISIBLE;
211

212 213
bool
backtrace_p (union specbinding *pdl)
214
{ return pdl >= specpdl; }
215

216
union specbinding *
217
backtrace_top (void)
218
{
219
  union specbinding *pdl = specpdl_ptr - 1;
220
  while (backtrace_p (pdl) && pdl->kind != SPECPDL_BACKTRACE)
221 222
    pdl--;
  return pdl;
223
}
224

225 226
union specbinding *
backtrace_next (union specbinding *pdl)
227
{
228 229 230 231
  pdl--;
  while (backtrace_p (pdl) && pdl->kind != SPECPDL_BACKTRACE)
    pdl--;
  return pdl;
232 233
}

234

Andreas Schwab's avatar
Andreas Schwab committed
235
void
236
init_eval_once (void)
Jim Blandy's avatar
Jim Blandy committed
237
{
238
  enum { size = 50 };
239
  union specbinding *pdlvec = xmalloc ((size + 1) * sizeof *specpdl);
240
  specpdl_size = size;
241
  specpdl = specpdl_ptr = pdlvec + 1;
242
  /* Don't forget to update docs (lispref node "Local Variables").  */
Stefan Monnier's avatar
Stefan Monnier committed
243
  max_specpdl_size = 1300; /* 1000 is not enough for CEDET's c-by.el.  */
244
  max_lisp_eval_depth = 600;
245 246

  Vrun_hooks = Qnil;
Jim Blandy's avatar
Jim Blandy committed
247 248
}

Andreas Schwab's avatar
Andreas Schwab committed
249
void
250
init_eval (void)
Jim Blandy's avatar
Jim Blandy committed
251 252 253 254 255 256 257
{
  specpdl_ptr = specpdl;
  catchlist = 0;
  handlerlist = 0;
  Vquit_flag = Qnil;
  debug_on_next_call = 0;
  lisp_eval_depth = 0;
258
#ifdef DEBUG_GCPRO
259
  gcpro_level = 0;
260
#endif
261
  /* This is less than the initial value of num_nonmacro_input_events.  */
262
  when_entered_debugger = -1;
Jim Blandy's avatar
Jim Blandy committed
263 264
}

265
/* Unwind-protect function used by call_debugger.  */
266 267

static Lisp_Object
268
restore_stack_limits (Lisp_Object data)
269 270 271
{
  max_specpdl_size = XINT (XCAR (data));
  max_lisp_eval_depth = XINT (XCDR (data));
272
  return Qnil;
273 274 275 276
}

/* Call the Lisp debugger, giving it argument ARG.  */

277
Lisp_Object
278
call_debugger (Lisp_Object arg)
Jim Blandy's avatar
Jim Blandy committed
279
{
280
  bool debug_while_redisplaying;
281
  ptrdiff_t count = SPECPDL_INDEX ();
282
  Lisp_Object val;
283
  EMACS_INT old_max = max_specpdl_size;
284

285 286
  /* Temporarily bump up the stack limits,
     so the debugger won't run out of stack.  */
287

288 289 290 291 292 293 294 295 296
  max_specpdl_size += 1;
  record_unwind_protect (restore_stack_limits,
			 Fcons (make_number (old_max),
				make_number (max_lisp_eval_depth)));
  max_specpdl_size = old_max;

  if (lisp_eval_depth + 40 > max_lisp_eval_depth)
    max_lisp_eval_depth = lisp_eval_depth + 40;

297
  if (max_specpdl_size - 100 < SPECPDL_INDEX ())
298
    max_specpdl_size = SPECPDL_INDEX () + 100;
299

300
#ifdef HAVE_WINDOW_SYSTEM
301 302
  if (display_hourglass_p)
    cancel_hourglass ();
303 304
#endif

Jim Blandy's avatar
Jim Blandy committed
305
  debug_on_next_call = 0;
306
  when_entered_debugger = num_nonmacro_input_events;
307 308 309 310 311

  /* Resetting redisplaying_p to 0 makes sure that debug output is
     displayed if the debugger is invoked during redisplay.  */
  debug_while_redisplaying = redisplaying_p;
  redisplaying_p = 0;
312 313
  specbind (intern ("debugger-may-continue"),
	    debug_while_redisplaying ? Qnil : Qt);
314
  specbind (Qinhibit_redisplay, Qnil);
315
  specbind (Qinhibit_debugger, Qt);
316 317 318

#if 0 /* Binding this prevents execution of Lisp code during
	 redisplay, which necessarily leads to display problems.  */
319
  specbind (Qinhibit_eval_during_redisplay, Qt);
320
#endif
321

322 323 324 325
  val = apply1 (Vdebugger, arg);

  /* Interrupting redisplay and resuming it later is not safe under
     all circumstances.  So, when the debugger returns, abort the
326
     interrupted redisplay by going back to the top-level.  */
327 328 329
  if (debug_while_redisplaying)
    Ftop_level ();

330
  return unbind_to (count, val);
Jim Blandy's avatar
Jim Blandy committed
331 332
}

333
static void
334
do_debug_on_call (Lisp_Object code)
Jim Blandy's avatar
Jim Blandy committed
335 336
{
  debug_on_next_call = 0;
337
  set_backtrace_debug_on_exit (specpdl_ptr - 1, true);
Jim Blandy's avatar
Jim Blandy committed
338 339 340 341 342 343 344 345
  call_debugger (Fcons (code, Qnil));
}

/* NOTE!!! Every function that can call EVAL must protect its args
   and temporaries from garbage collection while it needs them.
   The definition of `For' shows what you have to do.  */

DEFUN ("or", For, Sor, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
346 347 348
       doc: /* Eval args until one of them yields non-nil, then return that value.
The remaining args are not evalled at all.
If all args return nil, return nil.
Juanma Barranquero's avatar
Juanma Barranquero committed
349
usage: (or CONDITIONS...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
350
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
351
{
352
  register Lisp_Object val = Qnil;
Jim Blandy's avatar
Jim Blandy committed
353 354
  struct gcpro gcpro1;

355
  GCPRO1 (args);
Jim Blandy's avatar
Jim Blandy committed
356

357
  while (CONSP (args))
Jim Blandy's avatar
Jim Blandy committed
358
    {
359
      val = eval_sub (XCAR (args));
Jim Blandy's avatar
Jim Blandy committed
360
      if (!NILP (val))
Jim Blandy's avatar
Jim Blandy committed
361
	break;
362
      args = XCDR (args);
Jim Blandy's avatar
Jim Blandy committed
363 364 365 366 367 368 369
    }

  UNGCPRO;
  return val;
}

DEFUN ("and", Fand, Sand, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
370
       doc: /* Eval args until one of them yields nil, then return nil.
Pavel Janík's avatar
Pavel Janík committed
371 372
The remaining args are not evalled at all.
If no arg yields nil, return the last arg's value.
Juanma Barranquero's avatar
Juanma Barranquero committed
373
usage: (and CONDITIONS...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
374
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
375
{
376
  register Lisp_Object val = Qt;
Jim Blandy's avatar
Jim Blandy committed
377 378
  struct gcpro gcpro1;

379
  GCPRO1 (args);
Jim Blandy's avatar
Jim Blandy committed
380

381
  while (CONSP (args))
Jim Blandy's avatar
Jim Blandy committed
382
    {
383
      val = eval_sub (XCAR (args));
Jim Blandy's avatar
Jim Blandy committed
384
      if (NILP (val))
Jim Blandy's avatar
Jim Blandy committed
385
	break;
386
      args = XCDR (args);
Jim Blandy's avatar
Jim Blandy committed
387 388 389 390 391 392 393
    }

  UNGCPRO;
  return val;
}

DEFUN ("if", Fif, Sif, 2, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
394
       doc: /* If COND yields non-nil, do THEN, else do ELSE...
Pavel Janík's avatar
Pavel Janík committed
395 396 397
Returns the value of THEN or the value of the last of the ELSE's.
THEN must be one expression, but ELSE... can be zero or more expressions.
If COND yields nil, and there are no ELSE's, the value is nil.
398
usage: (if COND THEN ELSE...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
399
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
400 401 402 403 404
{
  register Lisp_Object cond;
  struct gcpro gcpro1;

  GCPRO1 (args);
405
  cond = eval_sub (Fcar (args));
Jim Blandy's avatar
Jim Blandy committed
406 407
  UNGCPRO;

Jim Blandy's avatar
Jim Blandy committed
408
  if (!NILP (cond))
409
    return eval_sub (Fcar (Fcdr (args)));
Jim Blandy's avatar
Jim Blandy committed
410 411 412 413
  return Fprogn (Fcdr (Fcdr (args)));
}

DEFUN ("cond", Fcond, Scond, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
414 415 416 417 418 419 420 421
       doc: /* Try each clause until one succeeds.
Each clause looks like (CONDITION BODY...).  CONDITION is evaluated
and, if the value is non-nil, this clause succeeds:
then the expressions in BODY are evaluated and the last one's
value is the value of the cond-form.
If no clause succeeds, cond returns nil.
If a clause has one element, as in (CONDITION),
CONDITION's value if non-nil is returned from the cond-form.
422
usage: (cond CLAUSES...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
423
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
424 425 426 427 428 429
{
  register Lisp_Object clause, val;
  struct gcpro gcpro1;

  val = Qnil;
  GCPRO1 (args);
Jim Blandy's avatar
Jim Blandy committed
430
  while (!NILP (args))
Jim Blandy's avatar
Jim Blandy committed
431 432
    {
      clause = Fcar (args);
433
      val = eval_sub (Fcar (clause));
Jim Blandy's avatar
Jim Blandy committed
434
      if (!NILP (val))
Jim Blandy's avatar
Jim Blandy committed
435
	{
436 437
	  if (!EQ (XCDR (clause), Qnil))
	    val = Fprogn (XCDR (clause));
Jim Blandy's avatar
Jim Blandy committed
438 439
	  break;
	}
440
      args = XCDR (args);
Jim Blandy's avatar
Jim Blandy committed
441 442 443 444 445 446
    }
  UNGCPRO;

  return val;
}

Paul Eggert's avatar
Paul Eggert committed
447
DEFUN ("progn", Fprogn, Sprogn, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
448
       doc: /* Eval BODY forms sequentially and return value of last one.
Juanma Barranquero's avatar
Juanma Barranquero committed
449
usage: (progn BODY...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
450
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
451
{
452
  register Lisp_Object val = Qnil;
Jim Blandy's avatar
Jim Blandy committed
453 454
  struct gcpro gcpro1;

455
  GCPRO1 (args);
Jim Blandy's avatar
Jim Blandy committed
456

457
  while (CONSP (args))
Jim Blandy's avatar
Jim Blandy committed
458
    {
459
      val = eval_sub (XCAR (args));
460
      args = XCDR (args);
Jim Blandy's avatar
Jim Blandy committed
461 462 463 464 465 466 467
    }

  UNGCPRO;
  return val;
}

DEFUN ("prog1", Fprog1, Sprog1, 1, UNEVALLED, 0,
468
       doc: /* Eval FIRST and BODY sequentially; return value from FIRST.
Pavel Janík's avatar
Pavel Janík committed
469 470
The value of FIRST is saved during the evaluation of the remaining args,
whose values are discarded.
471
usage: (prog1 FIRST BODY...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
472
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
473 474 475 476 477 478 479 480 481
{
  Lisp_Object val;
  register Lisp_Object args_left;
  struct gcpro gcpro1, gcpro2;

  args_left = args;
  val = Qnil;
  GCPRO2 (args, val);

482 483 484
  val = eval_sub (XCAR (args_left));
  while (CONSP (args_left = XCDR (args_left)))
    eval_sub (XCAR (args_left));
Jim Blandy's avatar
Jim Blandy committed
485 486 487 488 489 490

  UNGCPRO;
  return val;
}

DEFUN ("prog2", Fprog2, Sprog2, 2, UNEVALLED, 0,
491
       doc: /* Eval FORM1, FORM2 and BODY sequentially; return value from FORM2.
492 493 494
The value of FORM2 is saved during the evaluation of the
remaining args, whose values are discarded.
usage: (prog2 FORM1 FORM2 BODY...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
495
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
496
{
497
  struct gcpro gcpro1;
Jim Blandy's avatar
Jim Blandy committed
498

499 500
  GCPRO1 (args);
  eval_sub (XCAR (args));
501 502
  UNGCPRO;
  return Fprog1 (XCDR (args));
Jim Blandy's avatar
Jim Blandy committed
503 504 505
}

DEFUN ("setq", Fsetq, Ssetq, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
506 507 508 509 510 511 512
       doc: /* Set each SYM to the value of its VAL.
The symbols SYM are variables; they are literal (not evaluated).
The values VAL are expressions; they are evaluated.
Thus, (setq x (1+ y)) sets `x' to the value of `(1+ y)'.
The second VAL is not computed until after the first SYM is set, and so on;
each VAL can use the new value of variables set earlier in the `setq'.
The return value of the `setq' form is the value of the last VAL.
Juanma Barranquero's avatar
Juanma Barranquero committed
513
usage: (setq [SYM VAL]...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
514
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
515 516
{
  register Lisp_Object args_left;
517
  register Lisp_Object val, sym, lex_binding;
Jim Blandy's avatar
Jim Blandy committed
518 519
  struct gcpro gcpro1;

520
  if (NILP (args))
Jim Blandy's avatar
Jim Blandy committed
521 522 523 524 525 526 527
    return Qnil;

  args_left = args;
  GCPRO1 (args);

  do
    {
528
      val = eval_sub (Fcar (Fcdr (args_left)));
Jim Blandy's avatar
Jim Blandy committed
529
      sym = Fcar (args_left);
530

531
      /* Like for eval_sub, we do not check declared_special here since
532 533
	 it's been done when let-binding.  */
      if (!NILP (Vinternal_interpreter_environment) /* Mere optimization!  */
534
	  && SYMBOLP (sym)
535 536
	  && !NILP (lex_binding
		    = Fassq (sym, Vinternal_interpreter_environment)))
537 538 539 540
	XSETCDR (lex_binding, val); /* SYM is lexically bound.  */
      else
	Fset (sym, val);	/* SYM is dynamically bound.  */

Jim Blandy's avatar
Jim Blandy committed
541 542
      args_left = Fcdr (Fcdr (args_left));
    }
Juanma Barranquero's avatar
Juanma Barranquero committed
543
  while (!NILP (args_left));
Jim Blandy's avatar
Jim Blandy committed
544 545 546 547

  UNGCPRO;
  return val;
}
548

Jim Blandy's avatar
Jim Blandy committed
549
DEFUN ("quote", Fquote, Squote, 1, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
550
       doc: /* Return the argument, without evaluating it.  `(quote x)' yields `x'.
551 552 553 554 555 556 557 558
Warning: `quote' does not construct its return value, but just returns
the value that was pre-constructed by the Lisp reader (see info node
`(elisp)Printed Representation').
This means that '(a . b) is not identical to (cons 'a 'b): the former
does not cons.  Quoting should be reserved for constants that will
never be modified by side-effects, unless you like self-modifying code.
See the common pitfall in info node `(elisp)Rearrangement' for an example
of unexpected results when a quoted object is modified.
Pavel Janík's avatar
Pavel Janík committed
559
usage: (quote ARG)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
560
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
561
{
562 563
  if (!NILP (Fcdr (args)))
    xsignal2 (Qwrong_number_of_arguments, Qquote, Flength (args));
Jim Blandy's avatar
Jim Blandy committed
564 565
  return Fcar (args);
}
566

Jim Blandy's avatar
Jim Blandy committed
567
DEFUN ("function", Ffunction, Sfunction, 1, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
568 569 570 571
       doc: /* Like `quote', but preferred for objects which are functions.
In byte compilation, `function' causes its argument to be compiled.
`quote' cannot do that.
usage: (function ARG)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
572
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
573
{
574 575
  Lisp_Object quoted = XCAR (args);

576 577
  if (!NILP (Fcdr (args)))
    xsignal2 (Qwrong_number_of_arguments, Qfunction, Flength (args));
578 579 580 581 582 583

  if (!NILP (Vinternal_interpreter_environment)
      && CONSP (quoted)
      && EQ (XCAR (quoted), Qlambda))
    /* This is a lambda expression within a lexical environment;
       return an interpreted closure instead of a simple lambda.  */
584 585
    return Fcons (Qclosure, Fcons (Vinternal_interpreter_environment,
				   XCDR (quoted)));
586 587 588
  else
    /* Simply quote the argument.  */
    return quoted;
Jim Blandy's avatar
Jim Blandy committed
589 590
}

591

592
DEFUN ("defvaralias", Fdefvaralias, Sdefvaralias, 2, 3, 0,
593
       doc: /* Make NEW-ALIAS a variable alias for symbol BASE-VARIABLE.
Richard M. Stallman's avatar
Richard M. Stallman committed
594
Aliased variables always have the same value; setting one sets the other.
595
Third arg DOCSTRING, if non-nil, is documentation for NEW-ALIAS.  If it is
596 597 598 599
omitted or nil, NEW-ALIAS gets the documentation string of BASE-VARIABLE,
or of the variable at the end of the chain of aliases, if BASE-VARIABLE is
itself an alias.  If NEW-ALIAS is bound, and BASE-VARIABLE is not,
then the value of BASE-VARIABLE is set to that of NEW-ALIAS.
600
The return value is BASE-VARIABLE.  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
601
  (Lisp_Object new_alias, Lisp_Object base_variable, Lisp_Object docstring)
Gerd Moellmann's avatar
Gerd Moellmann committed
602 603
{
  struct Lisp_Symbol *sym;
604

605 606
  CHECK_SYMBOL (new_alias);
  CHECK_SYMBOL (base_variable);
Gerd Moellmann's avatar
Gerd Moellmann committed
607

608
  sym = XSYMBOL (new_alias);
609 610

  if (sym->constant)
Stefan Monnier's avatar
Stefan Monnier committed
611 612
    /* Not sure why, but why not?  */
    error ("Cannot make a constant an alias");
613 614 615 616 617 618 619 620 621

  switch (sym->redirect)
    {
    case SYMBOL_FORWARDED:
      error ("Cannot make an internal variable an alias");
    case SYMBOL_LOCALIZED:
      error ("Don't know how to make a localized variable an alias");
    }

622
  /* http://lists.gnu.org/archive/html/emacs-devel/2008-04/msg00834.html
623 624 625 626
     If n_a is bound, but b_v is not, set the value of b_v to n_a,
     so that old-code that affects n_a before the aliasing is setup
     still works.  */
  if (NILP (Fboundp (base_variable)))
627
    set_internal (base_variable, find_symbol_value (new_alias), Qnil, 1);
628 629

  {
630
    union specbinding *p;
631

Paul Eggert's avatar
Paul Eggert committed
632
    for (p = specpdl_ptr; p > specpdl; )
633 634
      if ((--p)->kind >= SPECPDL_LET
	  && (EQ (new_alias, specpdl_symbol (p))))
635 636 637
	error ("Don't know how to make a let-bound variable an alias");
  }

638
  sym->declared_special = 1;
639
  XSYMBOL (base_variable)->declared_special = 1;
640 641
  sym->redirect = SYMBOL_VARALIAS;
  SET_SYMBOL_ALIAS (sym, XSYMBOL (base_variable));
642 643
  sym->constant = SYMBOL_CONSTANT_P (base_variable);
  LOADHIST_ATTACH (new_alias);
644 645
  /* Even if docstring is nil: remove old docstring.  */
  Fput (new_alias, Qvariable_documentation, docstring);
646

647
  return base_variable;
Gerd Moellmann's avatar
Gerd Moellmann committed
648 649 650
}


Jim Blandy's avatar
Jim Blandy committed
651
DEFUN ("defvar", Fdefvar, Sdefvar, 1, UNEVALLED, 0,
Juanma Barranquero's avatar
Juanma Barranquero committed
652
       doc: /* Define SYMBOL as a variable, and return SYMBOL.
653 654 655 656 657 658 659 660 661
You are not required to define a variable in order to use it, but
defining it lets you supply an initial value and documentation, which
can be referred to by the Emacs help facilities and other programming
tools.  The `defvar' form also declares the variable as \"special\",
so that it is always dynamically bound even if `lexical-binding' is t.

The optional argument INITVALUE is evaluated, and used to set SYMBOL,
only if SYMBOL's value is void.  If SYMBOL is buffer-local, its
default value is what is set; buffer-local values are not affected.
Pavel Janík's avatar
Pavel Janík committed
662
If INITVALUE is missing, SYMBOL's value is not set.
663 664 665 666 667 668 669

If SYMBOL has a local binding, then this form affects the local
binding.  This is usually not what you want.  Thus, if you need to
load a file defining variables, with this form or with `defconst' or
`defcustom', you should always load that file _outside_ any bindings
for these variables.  \(`defconst' and `defcustom' behave similarly in
this respect.)
670 671 672 673 674

The optional argument DOCSTRING is a documentation string for the
variable.

To define a user option, use `defcustom' instead of `defvar'.
675
usage: (defvar SYMBOL &optional INITVALUE DOCSTRING)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
676
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
677
{
678
  register Lisp_Object sym, tem, tail;
Jim Blandy's avatar
Jim Blandy committed
679 680

  sym = Fcar (args);
681 682
  tail = Fcdr (args);
  if (!NILP (Fcdr (Fcdr (tail))))
683
    error ("Too many arguments");
684

685
  tem = Fdefault_boundp (sym);
686
  if (!NILP (tail))
Jim Blandy's avatar
Jim Blandy committed
687
    {
688 689
      /* Do it before evaluating the initial value, for self-references.  */
      XSYMBOL (sym)->declared_special = 1;
690

Jim Blandy's avatar
Jim Blandy committed
691
      if (NILP (tem))
692
	Fset_default (sym, eval_sub (Fcar (tail)));
693 694 695
      else
	{ /* Check if there is really a global binding rather than just a let
	     binding that shadows the global unboundness of the var.  */
696
	  union specbinding *pdl = specpdl_ptr;
697
	  while (pdl > specpdl)
698
	    {
699 700 701
	      if ((--pdl)->kind >= SPECPDL_LET
		  && EQ (specpdl_symbol (pdl), sym)
		  && EQ (specpdl_old_value (pdl), Qunbound))
702
		{
703 704 705
		  message_with_string
		    ("Warning: defvar ignored because %s is let-bound",
		     SYMBOL_NAME (sym), 1);
706 707 708 709
		  break;
		}
	    }
	}
710
      tail = Fcdr (tail);
711 712
      tem = Fcar (tail);
      if (!NILP (tem))
713 714 715 716 717
	{
	  if (!NILP (Vpurify_flag))
	    tem = Fpurecopy (tem);
	  Fput (sym, Qvariable_documentation, tem);
	}
718
      LOADHIST_ATTACH (sym);
Jim Blandy's avatar
Jim Blandy committed
719
    }
720 721 722 723 724
  else if (!NILP (Vinternal_interpreter_environment)
	   && !XSYMBOL (sym)->declared_special)
    /* A simple (defvar foo) with lexical scoping does "nothing" except
       declare that var to be dynamically scoped *locally* (i.e. within
       the current file or let-block).  */
725 726
    Vinternal_interpreter_environment
      = Fcons (sym, Vinternal_interpreter_environment);
727
  else
728 729 730 731 732
    {
      /* Simple (defvar <var>) should not count as a definition at all.
	 It could get in the way of other definitions, and unloading this
	 package could try to make the variable unbound.  */
    }
Andreas Schwab's avatar
Andreas Schwab committed
733

Jim Blandy's avatar
Jim Blandy committed
734 735 736 737
  return sym;
}

DEFUN ("defconst", Fdefconst, Sdefconst, 2, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
738
       doc: /* Define SYMBOL as a constant variable.
739 740 741 742 743 744 745 746 747 748 749 750 751
This declares that neither programs nor users should ever change the
value.  This constancy is not actually enforced by Emacs Lisp, but
SYMBOL is marked as a special variable so that it is never lexically
bound.

The `defconst' form always sets the value of SYMBOL to the result of
evalling INITVALUE.  If SYMBOL is buffer-local, its default value is
what is set; buffer-local values are not affected.  If SYMBOL has a
local binding, then this form sets the local binding's value.
However, you should normally not make local bindings for variables
defined with this form.

The optional DOCSTRING specifies the variable's documentation string.
752
usage: (defconst SYMBOL INITVALUE [DOCSTRING])  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
753
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
754 755 756 757
{
  register Lisp_Object sym, tem;

  sym = Fcar (args);
758
  if (!NILP (Fcdr (Fcdr (Fcdr (args)))))
759
    error ("Too many arguments");
760

761
  tem = eval_sub (Fcar (Fcdr (args)));
762 763 764
  if (!NILP (Vpurify_flag))
    tem = Fpurecopy (tem);
  Fset_default (sym, tem);
765
  XSYMBOL (sym)->declared_special = 1;
Jim Blandy's avatar
Jim Blandy committed
766
  tem = Fcar (Fcdr (Fcdr (args)));
Jim Blandy's avatar
Jim Blandy committed
767
  if (!NILP (tem))
Jim Blandy's avatar
Jim Blandy committed
768
    {
Jim Blandy's avatar
Jim Blandy committed
769
      if (!NILP (Vpurify_flag))
Jim Blandy's avatar
Jim Blandy committed
770 771 772
	tem = Fpurecopy (tem);
      Fput (sym, Qvariable_documentation, tem);
    }
773
  Fput (sym, Qrisky_local_variable, Qt);
774
  LOADHIST_ATTACH (sym);
Jim Blandy's avatar
Jim Blandy committed
775 776 777
  return sym;
}

778 779 780 781 782 783 784 785 786 787 788
/* Make SYMBOL lexically scoped.  */
DEFUN ("internal-make-var-non-special", Fmake_var_non_special,
       Smake_var_non_special, 1, 1, 0,
       doc: /* Internal function.  */)
     (Lisp_Object symbol)
{
  CHECK_SYMBOL (symbol);
  XSYMBOL (symbol)->declared_special = 0;
  return Qnil;
}

Jim Blandy's avatar
Jim Blandy committed
789 790

DEFUN ("let*", FletX, SletX, 1, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
791 792 793 794 795
       doc: /* Bind variables according to VARLIST then eval BODY.
The value of the last form in BODY is returned.
Each element of VARLIST is a symbol (which is bound to nil)
or a list (SYMBOL VALUEFORM) (which binds SYMBOL to the value of VALUEFORM).
Each VALUEFORM can refer to the symbols already bound by this VARLIST.
796
usage: (let* VARLIST BODY...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
797
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
798
{
799
  Lisp_Object varlist, var, val, elt, lexenv;
800
  ptrdiff_t count = SPECPDL_INDEX ();
Jim Blandy's avatar
Jim Blandy committed
801 802 803 804
  struct gcpro gcpro1, gcpro2, gcpro3;

  GCPRO3 (args, elt, varlist);

805 806
  lexenv = Vinternal_interpreter_environment;

Jim Blandy's avatar
Jim Blandy committed
807
  varlist = Fcar (args);
808
  while (CONSP (varlist))
Jim Blandy's avatar
Jim Blandy committed
809 810
    {
      QUIT;
811 812

      elt = XCAR (varlist);
813
      if (SYMBOLP (elt))
814 815 816 817
	{
	  var = elt;
	  val = Qnil;
	}
Jim Blandy's avatar
Jim Blandy committed
818
      else if (! NILP (Fcdr (Fcdr (elt))))