eval.c 111 KB
Newer Older
Jim Blandy's avatar
Jim Blandy committed
1
/* Evaluator for GNU Emacs Lisp interpreter.
Glenn Morris's avatar
Glenn Morris committed
2

3 4
Copyright (C) 1985-1987, 1993-1995, 1999-2014 Free Software Foundation,
Inc.
Jim Blandy's avatar
Jim Blandy committed
5 6 7

This file is part of GNU Emacs.

8
GNU Emacs is free software: you can redistribute it and/or modify
Jim Blandy's avatar
Jim Blandy committed
9
it under the terms of the GNU General Public License as published by
10 11
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Jim Blandy's avatar
Jim Blandy committed
12 13 14 15 16 17 18

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
19
along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
Jim Blandy's avatar
Jim Blandy committed
20 21


22
#include <config.h>
23
#include <limits.h>
24
#include <stdio.h>
Jim Blandy's avatar
Jim Blandy committed
25
#include "lisp.h"
26
#include "blockinput.h"
Jim Blandy's avatar
Jim Blandy committed
27
#include "commands.h"
Jim Blandy's avatar
Jim Blandy committed
28
#include "keyboard.h"
29
#include "dispextern.h"
30
#include "buffer.h"
31

32
/* Chain of condition and catch handlers currently in effect.  */
33 34 35

struct handler *handlerlist;

36 37 38 39 40
#ifdef DEBUG_GCPRO
/* Count levels of GCPRO to detect failure to UNGCPRO.  */
int gcpro_level;
#endif

41
Lisp_Object Qautoload, Qmacro, Qexit, Qinteractive, Qcommandp;
42
Lisp_Object Qinhibit_quit;
43 44
Lisp_Object Qand_rest;
static Lisp_Object Qand_optional;
45
static Lisp_Object Qinhibit_debugger;
46
static Lisp_Object Qdeclare;
47 48
Lisp_Object Qinternal_interpreter_environment, Qclosure;

Paul Eggert's avatar
Paul Eggert committed
49
static Lisp_Object Qdebug;
Jim Blandy's avatar
Jim Blandy committed
50

51 52 53
/* This holds either the symbol `run-hooks' or nil.
   It is nil at an early stage of startup, and when Emacs
   is shutting down.  */
54

Jim Blandy's avatar
Jim Blandy committed
55 56 57 58 59
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:
60
   (FUN . ODEF) for a defun, (0 . OFEATURES) for a provide.  */
Jim Blandy's avatar
Jim Blandy committed
61 62 63

Lisp_Object Vautoload_queue;

64 65
/* Current number of specbindings allocated in specpdl, not counting
   the dummy entry specpdl[-1].  */
66

67
ptrdiff_t specpdl_size;
Jim Blandy's avatar
Jim Blandy committed
68

69 70
/* Pointer to beginning of specpdl.  A dummy entry specpdl[-1] exists
   only so that its address can be taken.  */
71

72
union specbinding *specpdl;
Jim Blandy's avatar
Jim Blandy committed
73 74

/* Pointer to first unused element in specpdl.  */
75

76
union specbinding *specpdl_ptr;
Jim Blandy's avatar
Jim Blandy committed
77 78

/* Depth in Lisp evaluations and function calls.  */
79

80
EMACS_INT lisp_eval_depth;
Jim Blandy's avatar
Jim Blandy committed
81

82
/* The value of num_nonmacro_input_events as of the last time we
83
   started to enter the debugger.  If we decide to enter the debugger
84
   again when this is still equal to num_nonmacro_input_events, then we
85 86 87
   know that the debugger itself has an error, and we should just
   signal the error instead of entering an infinite loop of debugger
   invocations.  */
88

89
static EMACS_INT when_entered_debugger;
Jim Blandy's avatar
Jim Blandy committed
90

91 92
/* The function from which the last `signal' was called.  Set in
   Fsignal.  */
93
/* FIXME: We should probably get rid of this!  */
94 95
Lisp_Object Vsignaling_function;

96 97
/* If non-nil, Lisp code must not be run since some part of Emacs is in
   an inconsistent state.  Currently unused.  */
98 99
Lisp_Object inhibit_lisp_code;

100 101 102 103 104 105 106
/* These would ordinarily be static, but they need to be visible to GDB.  */
bool backtrace_p (union specbinding *) EXTERNALLY_VISIBLE;
Lisp_Object *backtrace_args (union specbinding *) EXTERNALLY_VISIBLE;
Lisp_Object backtrace_function (union specbinding *) EXTERNALLY_VISIBLE;
union specbinding *backtrace_next (union specbinding *) EXTERNALLY_VISIBLE;
union specbinding *backtrace_top (void) EXTERNALLY_VISIBLE;

107
static Lisp_Object funcall_lambda (Lisp_Object, ptrdiff_t, Lisp_Object *);
108
static Lisp_Object apply_lambda (Lisp_Object, Lisp_Object, ptrdiff_t);
109

110
static Lisp_Object
111
specpdl_symbol (union specbinding *pdl)
112 113
{
  eassert (pdl->kind >= SPECPDL_LET);
114
  return pdl->let.symbol;
115 116 117
}

static Lisp_Object
118
specpdl_old_value (union specbinding *pdl)
119 120
{
  eassert (pdl->kind >= SPECPDL_LET);
121
  return pdl->let.old_value;
122 123
}

124 125 126 127 128 129 130
static void
set_specpdl_old_value (union specbinding *pdl, Lisp_Object val)
{
  eassert (pdl->kind >= SPECPDL_LET);
  pdl->let.old_value = val;
}

131
static Lisp_Object
132
specpdl_where (union specbinding *pdl)
133 134
{
  eassert (pdl->kind > SPECPDL_LET);
135
  return pdl->let.where;
136 137 138
}

static Lisp_Object
139
specpdl_arg (union specbinding *pdl)
140 141
{
  eassert (pdl->kind == SPECPDL_UNWIND);
142
  return pdl->unwind.arg;
143 144
}

145
Lisp_Object
146
backtrace_function (union specbinding *pdl)
147 148
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
149
  return pdl->bt.function;
150 151 152
}

static ptrdiff_t
153
backtrace_nargs (union specbinding *pdl)
154 155
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
156
  return pdl->bt.nargs;
157 158
}

159
Lisp_Object *
160
backtrace_args (union specbinding *pdl)
161 162
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
163
  return pdl->bt.args;
164 165 166
}

static bool
167
backtrace_debug_on_exit (union specbinding *pdl)
168 169
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
170
  return pdl->bt.debug_on_exit;
171 172
}

173
/* Functions to modify slots of backtrace records.  */
174

175
static void
176
set_backtrace_args (union specbinding *pdl, Lisp_Object *args, ptrdiff_t nargs)
177 178 179
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
  pdl->bt.args = args;
180
  pdl->bt.nargs = nargs;
181
}
182

183
static void
184 185 186 187 188
set_backtrace_debug_on_exit (union specbinding *pdl, bool doe)
{
  eassert (pdl->kind == SPECPDL_BACKTRACE);
  pdl->bt.debug_on_exit = doe;
}
189 190 191

/* Helper functions to scan the backtrace.  */

192 193
bool
backtrace_p (union specbinding *pdl)
194
{ return pdl >= specpdl; }
195

196
union specbinding *
197
backtrace_top (void)
198
{
199
  union specbinding *pdl = specpdl_ptr - 1;
200
  while (backtrace_p (pdl) && pdl->kind != SPECPDL_BACKTRACE)
201 202
    pdl--;
  return pdl;
203
}
204

205 206
union specbinding *
backtrace_next (union specbinding *pdl)
207
{
208 209 210 211
  pdl--;
  while (backtrace_p (pdl) && pdl->kind != SPECPDL_BACKTRACE)
    pdl--;
  return pdl;
212 213
}

214

Andreas Schwab's avatar
Andreas Schwab committed
215
void
216
init_eval_once (void)
Jim Blandy's avatar
Jim Blandy committed
217
{
218
  enum { size = 50 };
219
  union specbinding *pdlvec = xmalloc ((size + 1) * sizeof *specpdl);
220
  specpdl_size = size;
221
  specpdl = specpdl_ptr = pdlvec + 1;
222
  /* Don't forget to update docs (lispref node "Local Variables").  */
Stefan Monnier's avatar
Stefan Monnier committed
223
  max_specpdl_size = 1300; /* 1000 is not enough for CEDET's c-by.el.  */
224
  max_lisp_eval_depth = 600;
225 226

  Vrun_hooks = Qnil;
Jim Blandy's avatar
Jim Blandy committed
227 228
}

229 230
static struct handler handlerlist_sentinel;

Andreas Schwab's avatar
Andreas Schwab committed
231
void
232
init_eval (void)
Jim Blandy's avatar
Jim Blandy committed
233 234
{
  specpdl_ptr = specpdl;
235 236 237 238 239 240 241 242 243 244
  { /* Put a dummy catcher at top-level so that handlerlist is never NULL.
       This is important since handlerlist->nextfree holds the freelist
       which would otherwise leak every time we unwind back to top-level.   */
    struct handler *c;
    handlerlist = handlerlist_sentinel.nextfree = &handlerlist_sentinel;
    PUSH_HANDLER (c, Qunbound, CATCHER);
    eassert (c == &handlerlist_sentinel);
    handlerlist_sentinel.nextfree = NULL;
    handlerlist_sentinel.next = NULL;
  }
Jim Blandy's avatar
Jim Blandy committed
245 246 247
  Vquit_flag = Qnil;
  debug_on_next_call = 0;
  lisp_eval_depth = 0;
248
#ifdef DEBUG_GCPRO
249
  gcpro_level = 0;
250
#endif
251
  /* This is less than the initial value of num_nonmacro_input_events.  */
252
  when_entered_debugger = -1;
Jim Blandy's avatar
Jim Blandy committed
253 254
}

255
/* Unwind-protect function used by call_debugger.  */
256

257
static void
258
restore_stack_limits (Lisp_Object data)
259 260 261 262 263
{
  max_specpdl_size = XINT (XCAR (data));
  max_lisp_eval_depth = XINT (XCDR (data));
}

264 265
static void grow_specpdl (void);

266 267
/* Call the Lisp debugger, giving it argument ARG.  */

268
Lisp_Object
269
call_debugger (Lisp_Object arg)
Jim Blandy's avatar
Jim Blandy committed
270
{
271
  bool debug_while_redisplaying;
272
  ptrdiff_t count = SPECPDL_INDEX ();
273
  Lisp_Object val;
274 275 276
  EMACS_INT old_depth = max_lisp_eval_depth;
  /* Do not allow max_specpdl_size less than actual depth (Bug#16603).  */
  EMACS_INT old_max = max (max_specpdl_size, count);
277 278 279 280

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

281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296
  /* While debugging Bug#16603, previous value of 100 was found
     too small to avoid specpdl overflow in the debugger itself.  */
  if (max_specpdl_size - 200 < count)
    max_specpdl_size = count + 200;

  if (old_max == count)
    {
      /* We can enter the debugger due to specpdl overflow (Bug#16603).  */
      specpdl_ptr--;
      grow_specpdl ();
    }

  /* Restore limits after leaving the debugger.  */
  record_unwind_protect (restore_stack_limits,
			 Fcons (make_number (old_max),
				make_number (old_depth)));
297

298
#ifdef HAVE_WINDOW_SYSTEM
299 300
  if (display_hourglass_p)
    cancel_hourglass ();
301 302
#endif

Jim Blandy's avatar
Jim Blandy committed
303
  debug_on_next_call = 0;
304
  when_entered_debugger = num_nonmacro_input_events;
305 306 307 308 309

  /* 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;
310 311
  specbind (intern ("debugger-may-continue"),
	    debug_while_redisplaying ? Qnil : Qt);
312
  specbind (Qinhibit_redisplay, Qnil);
313
  specbind (Qinhibit_debugger, Qt);
314 315 316

#if 0 /* Binding this prevents execution of Lisp code during
	 redisplay, which necessarily leads to display problems.  */
317
  specbind (Qinhibit_eval_during_redisplay, Qt);
318
#endif
319

320 321 322 323
  val = apply1 (Vdebugger, arg);

  /* Interrupting redisplay and resuming it later is not safe under
     all circumstances.  So, when the debugger returns, abort the
324
     interrupted redisplay by going back to the top-level.  */
325 326 327
  if (debug_while_redisplaying)
    Ftop_level ();

328
  return unbind_to (count, val);
Jim Blandy's avatar
Jim Blandy committed
329 330
}

331
static void
332
do_debug_on_call (Lisp_Object code, ptrdiff_t count)
Jim Blandy's avatar
Jim Blandy committed
333 334
{
  debug_on_next_call = 0;
335
  set_backtrace_debug_on_exit (specpdl + count, true);
336
  call_debugger (list1 (code));
Jim Blandy's avatar
Jim Blandy committed
337 338 339 340 341 342 343
}

/* 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
344 345 346
       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
347
usage: (or CONDITIONS...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
348
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
349
{
350
  register Lisp_Object val = Qnil;
Jim Blandy's avatar
Jim Blandy committed
351 352
  struct gcpro gcpro1;

353
  GCPRO1 (args);
Jim Blandy's avatar
Jim Blandy committed
354

355
  while (CONSP (args))
Jim Blandy's avatar
Jim Blandy committed
356
    {
357
      val = eval_sub (XCAR (args));
Jim Blandy's avatar
Jim Blandy committed
358
      if (!NILP (val))
Jim Blandy's avatar
Jim Blandy committed
359
	break;
360
      args = XCDR (args);
Jim Blandy's avatar
Jim Blandy committed
361 362 363 364 365 366 367
    }

  UNGCPRO;
  return val;
}

DEFUN ("and", Fand, Sand, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
368
       doc: /* Eval args until one of them yields nil, then return nil.
Pavel Janík's avatar
Pavel Janík committed
369 370
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
371
usage: (and CONDITIONS...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
372
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
373
{
374
  register Lisp_Object val = Qt;
Jim Blandy's avatar
Jim Blandy committed
375 376
  struct gcpro gcpro1;

377
  GCPRO1 (args);
Jim Blandy's avatar
Jim Blandy committed
378

379
  while (CONSP (args))
Jim Blandy's avatar
Jim Blandy committed
380
    {
381
      val = eval_sub (XCAR (args));
Jim Blandy's avatar
Jim Blandy committed
382
      if (NILP (val))
Jim Blandy's avatar
Jim Blandy committed
383
	break;
384
      args = XCDR (args);
Jim Blandy's avatar
Jim Blandy committed
385 386 387 388 389 390 391
    }

  UNGCPRO;
  return val;
}

DEFUN ("if", Fif, Sif, 2, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
392
       doc: /* If COND yields non-nil, do THEN, else do ELSE...
Pavel Janík's avatar
Pavel Janík committed
393 394 395
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.
396
usage: (if COND THEN ELSE...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
397
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
398
{
399
  Lisp_Object cond;
Jim Blandy's avatar
Jim Blandy committed
400 401 402
  struct gcpro gcpro1;

  GCPRO1 (args);
403
  cond = eval_sub (XCAR (args));
Jim Blandy's avatar
Jim Blandy committed
404 405
  UNGCPRO;

Jim Blandy's avatar
Jim Blandy committed
406
  if (!NILP (cond))
407 408
    return eval_sub (Fcar (XCDR (args)));
  return Fprogn (XCDR (XCDR (args)));
Jim Blandy's avatar
Jim Blandy committed
409 410 411
}

DEFUN ("cond", Fcond, Scond, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
412 413 414 415 416
       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.
Glenn Morris's avatar
Glenn Morris committed
417 418
If a clause has one element, as in (CONDITION), then the cond-form
returns CONDITION's value, if that is non-nil.
Pavel Janík's avatar
Pavel Janík committed
419
If no clause succeeds, cond returns nil.
420
usage: (cond CLAUSES...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
421
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
422
{
423
  Lisp_Object val = args;
Jim Blandy's avatar
Jim Blandy committed
424 425 426
  struct gcpro gcpro1;

  GCPRO1 (args);
427
  while (CONSP (args))
Jim Blandy's avatar
Jim Blandy committed
428
    {
429
      Lisp_Object clause = XCAR (args);
430
      val = eval_sub (Fcar (clause));
Jim Blandy's avatar
Jim Blandy committed
431
      if (!NILP (val))
Jim Blandy's avatar
Jim Blandy committed
432
	{
433
	  if (!NILP (XCDR (clause)))
434
	    val = Fprogn (XCDR (clause));
Jim Blandy's avatar
Jim Blandy committed
435 436
	  break;
	}
437
      args = XCDR (args);
Jim Blandy's avatar
Jim Blandy committed
438 439 440 441 442 443
    }
  UNGCPRO;

  return val;
}

Paul Eggert's avatar
Paul Eggert committed
444
DEFUN ("progn", Fprogn, Sprogn, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
445
       doc: /* Eval BODY forms sequentially and return value of last one.
Juanma Barranquero's avatar
Juanma Barranquero committed
446
usage: (progn BODY...)  */)
447
  (Lisp_Object body)
Jim Blandy's avatar
Jim Blandy committed
448
{
449
  Lisp_Object val = Qnil;
Jim Blandy's avatar
Jim Blandy committed
450 451
  struct gcpro gcpro1;

452
  GCPRO1 (body);
Jim Blandy's avatar
Jim Blandy committed
453

454
  while (CONSP (body))
Jim Blandy's avatar
Jim Blandy committed
455
    {
456 457
      val = eval_sub (XCAR (body));
      body = XCDR (body);
Jim Blandy's avatar
Jim Blandy committed
458 459 460 461 462 463
    }

  UNGCPRO;
  return val;
}

Paul Eggert's avatar
Paul Eggert committed
464
/* Evaluate BODY sequentially, discarding its value.  Suitable for
465 466 467 468 469 470 471 472
   record_unwind_protect.  */

void
unwind_body (Lisp_Object body)
{
  Fprogn (body);
}

Jim Blandy's avatar
Jim Blandy committed
473
DEFUN ("prog1", Fprog1, Sprog1, 1, UNEVALLED, 0,
474
       doc: /* Eval FIRST and BODY sequentially; return value from FIRST.
Pavel Janík's avatar
Pavel Janík committed
475 476
The value of FIRST is saved during the evaluation of the remaining args,
whose values are discarded.
477
usage: (prog1 FIRST BODY...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
478
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
479 480
{
  Lisp_Object val;
481
  Lisp_Object args_left;
Jim Blandy's avatar
Jim Blandy committed
482 483 484
  struct gcpro gcpro1, gcpro2;

  args_left = args;
485
  val = args;
Jim Blandy's avatar
Jim Blandy committed
486 487
  GCPRO2 (args, val);

488 489 490
  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
491 492 493 494 495 496

  UNGCPRO;
  return val;
}

DEFUN ("prog2", Fprog2, Sprog2, 2, UNEVALLED, 0,
497
       doc: /* Eval FORM1, FORM2 and BODY sequentially; return value from FORM2.
498 499 500
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
501
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
502
{
503
  struct gcpro gcpro1;
Jim Blandy's avatar
Jim Blandy committed
504

505 506
  GCPRO1 (args);
  eval_sub (XCAR (args));
507 508
  UNGCPRO;
  return Fprog1 (XCDR (args));
Jim Blandy's avatar
Jim Blandy committed
509 510 511
}

DEFUN ("setq", Fsetq, Ssetq, 0, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
512 513 514 515 516 517 518
       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
519
usage: (setq [SYM VAL]...)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
520
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
521
{
522
  Lisp_Object val, sym, lex_binding;
Jim Blandy's avatar
Jim Blandy committed
523

524 525 526 527 528 529
  val = args;
  if (CONSP (args))
    {
      Lisp_Object args_left = args;
      struct gcpro gcpro1;
      GCPRO1 (args);
Jim Blandy's avatar
Jim Blandy committed
530

531 532 533 534 535 536 537 538 539 540 541 542 543 544
      do
	{
	  val = eval_sub (Fcar (XCDR (args_left)));
	  sym = XCAR (args_left);

	  /* Like for eval_sub, we do not check declared_special here since
	     it's been done when let-binding.  */
	  if (!NILP (Vinternal_interpreter_environment) /* Mere optimization!  */
	      && SYMBOLP (sym)
	      && !NILP (lex_binding
			= Fassq (sym, Vinternal_interpreter_environment)))
	    XSETCDR (lex_binding, val); /* SYM is lexically bound.  */
	  else
	    Fset (sym, val);	/* SYM is dynamically bound.  */
Jim Blandy's avatar
Jim Blandy committed
545

546 547 548
	  args_left = Fcdr (XCDR (args_left));
	}
      while (CONSP (args_left));
549

550
      UNGCPRO;
Jim Blandy's avatar
Jim Blandy committed
551 552 553 554
    }

  return val;
}
555

Jim Blandy's avatar
Jim Blandy committed
556
DEFUN ("quote", Fquote, Squote, 1, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
557
       doc: /* Return the argument, without evaluating it.  `(quote x)' yields `x'.
558 559 560 561 562 563 564 565
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
566
usage: (quote ARG)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
567
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
568
{
569
  if (CONSP (XCDR (args)))
570
    xsignal2 (Qwrong_number_of_arguments, Qquote, Flength (args));
571
  return XCAR (args);
Jim Blandy's avatar
Jim Blandy committed
572
}
573

Jim Blandy's avatar
Jim Blandy committed
574
DEFUN ("function", Ffunction, Sfunction, 1, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
575 576 577 578
       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
579
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
580
{
581 582
  Lisp_Object quoted = XCAR (args);

583
  if (CONSP (XCDR (args)))
584
    xsignal2 (Qwrong_number_of_arguments, Qfunction, Flength (args));
585 586 587 588 589 590

  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.  */
591 592
    return Fcons (Qclosure, Fcons (Vinternal_interpreter_environment,
				   XCDR (quoted)));
593 594 595
  else
    /* Simply quote the argument.  */
    return quoted;
Jim Blandy's avatar
Jim Blandy committed
596 597
}

598

599
DEFUN ("defvaralias", Fdefvaralias, Sdefvaralias, 2, 3, 0,
600
       doc: /* Make NEW-ALIAS a variable alias for symbol BASE-VARIABLE.
Richard M. Stallman's avatar
Richard M. Stallman committed
601
Aliased variables always have the same value; setting one sets the other.
602
Third arg DOCSTRING, if non-nil, is documentation for NEW-ALIAS.  If it is
603 604 605 606
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.
607
The return value is BASE-VARIABLE.  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
608
  (Lisp_Object new_alias, Lisp_Object base_variable, Lisp_Object docstring)
Gerd Moellmann's avatar
Gerd Moellmann committed
609 610
{
  struct Lisp_Symbol *sym;
611

612 613
  CHECK_SYMBOL (new_alias);
  CHECK_SYMBOL (base_variable);
Gerd Moellmann's avatar
Gerd Moellmann committed
614

615
  sym = XSYMBOL (new_alias);
616 617

  if (sym->constant)
Stefan Monnier's avatar
Stefan Monnier committed
618 619
    /* Not sure why, but why not?  */
    error ("Cannot make a constant an alias");
620 621 622 623 624 625 626 627 628

  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");
    }

629
  /* http://lists.gnu.org/archive/html/emacs-devel/2008-04/msg00834.html
630 631 632 633
     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)))
634
    set_internal (base_variable, find_symbol_value (new_alias), Qnil, 1);
635 636

  {
637
    union specbinding *p;
638

Paul Eggert's avatar
Paul Eggert committed
639
    for (p = specpdl_ptr; p > specpdl; )
640 641
      if ((--p)->kind >= SPECPDL_LET
	  && (EQ (new_alias, specpdl_symbol (p))))
642 643 644
	error ("Don't know how to make a let-bound variable an alias");
  }

645
  sym->declared_special = 1;
646
  XSYMBOL (base_variable)->declared_special = 1;
647 648
  sym->redirect = SYMBOL_VARALIAS;
  SET_SYMBOL_ALIAS (sym, XSYMBOL (base_variable));
649 650
  sym->constant = SYMBOL_CONSTANT_P (base_variable);
  LOADHIST_ATTACH (new_alias);
651 652
  /* Even if docstring is nil: remove old docstring.  */
  Fput (new_alias, Qvariable_documentation, docstring);
653

654
  return base_variable;
Gerd Moellmann's avatar
Gerd Moellmann committed
655 656
}

657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701
static union specbinding *
default_toplevel_binding (Lisp_Object symbol)
{
  union specbinding *binding = NULL;
  union specbinding *pdl = specpdl_ptr;
  while (pdl > specpdl)
    {
      switch ((--pdl)->kind)
	{
	case SPECPDL_LET_DEFAULT:
	case SPECPDL_LET:
	  if (EQ (specpdl_symbol (pdl), symbol))
	    binding = pdl;
	  break;
	}
    }
  return binding;
}

DEFUN ("default-toplevel-value", Fdefault_toplevel_value, Sdefault_toplevel_value, 1, 1, 0,
       doc: /* Return SYMBOL's toplevel default value.
"Toplevel" means outside of any let binding.  */)
  (Lisp_Object symbol)
{
  union specbinding *binding = default_toplevel_binding (symbol);
  Lisp_Object value
    = binding ? specpdl_old_value (binding) : Fdefault_value (symbol);
  if (!EQ (value, Qunbound))
    return value;
  xsignal1 (Qvoid_variable, symbol);
}

DEFUN ("set-default-toplevel-value", Fset_default_toplevel_value,
       Sset_default_toplevel_value, 2, 2, 0,
       doc: /* Set SYMBOL's toplevel default value to VALUE.
"Toplevel" means outside of any let binding.  */)
     (Lisp_Object symbol, Lisp_Object value)
{
  union specbinding *binding = default_toplevel_binding (symbol);
  if (binding)
    set_specpdl_old_value (binding, value);
  else
    Fset_default (symbol, value);
  return Qnil;
}
Gerd Moellmann's avatar
Gerd Moellmann committed
702

Jim Blandy's avatar
Jim Blandy committed
703
DEFUN ("defvar", Fdefvar, Sdefvar, 1, UNEVALLED, 0,
Juanma Barranquero's avatar
Juanma Barranquero committed
704
       doc: /* Define SYMBOL as a variable, and return SYMBOL.
705 706 707 708 709 710 711 712 713
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
714
If INITVALUE is missing, SYMBOL's value is not set.
715 716 717 718 719 720 721

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.)
722 723 724 725 726

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

To define a user option, use `defcustom' instead of `defvar'.
727
usage: (defvar SYMBOL &optional INITVALUE DOCSTRING)  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
728
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
729
{
730
  Lisp_Object sym, tem, tail;
Jim Blandy's avatar
Jim Blandy committed
731

732 733
  sym = XCAR (args);
  tail = XCDR (args);
734

735
  if (CONSP (tail))
Jim Blandy's avatar
Jim Blandy committed
736
    {
737 738 739 740 741
      if (CONSP (XCDR (tail)) && CONSP (XCDR (XCDR (tail))))
	error ("Too many arguments");

      tem = Fdefault_boundp (sym);

742 743
      /* Do it before evaluating the initial value, for self-references.  */
      XSYMBOL (sym)->declared_special = 1;
744

Jim Blandy's avatar
Jim Blandy committed
745
      if (NILP (tem))
746
	Fset_default (sym, eval_sub (XCAR (tail)));
747 748 749
      else
	{ /* Check if there is really a global binding rather than just a let
	     binding that shadows the global unboundness of the var.  */
750 751
	  union specbinding *binding = default_toplevel_binding (sym);
	  if (binding && EQ (specpdl_old_value (binding), Qunbound))
752
	    {
753
	      set_specpdl_old_value (binding, eval_sub (XCAR (tail)));
754 755
	    }
	}
756
      tail = XCDR (tail);
757 758
      tem = Fcar (tail);
      if (!NILP (tem))
759 760 761 762 763
	{
	  if (!NILP (Vpurify_flag))
	    tem = Fpurecopy (tem);
	  Fput (sym, Qvariable_documentation, tem);
	}
764
      LOADHIST_ATTACH (sym);
Jim Blandy's avatar
Jim Blandy committed
765
    }
766 767 768 769 770
  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).  */
771 772
    Vinternal_interpreter_environment
      = Fcons (sym, Vinternal_interpreter_environment);
773
  else
774 775 776 777 778
    {
      /* 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
779

Jim Blandy's avatar
Jim Blandy committed
780 781 782 783
  return sym;
}

DEFUN ("defconst", Fdefconst, Sdefconst, 2, UNEVALLED, 0,
Pavel Janík's avatar
Pavel Janík committed
784
       doc: /* Define SYMBOL as a constant variable.
785 786 787 788 789 790 791 792 793 794 795 796 797
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.
798
usage: (defconst SYMBOL INITVALUE [DOCSTRING])  */)
Dan Nicolaescu's avatar
Dan Nicolaescu committed
799
  (Lisp_Object args)
Jim Blandy's avatar
Jim Blandy committed
800
{
801
  Lisp_Object sym, tem;
Jim Blandy's avatar
Jim Blandy committed
802

803 804
  sym = XCAR (args);
  if (CONSP (Fcdr (XCDR (XCDR (args)))))
805
    error ("Too many arguments");
806

807
  tem = eval_sub (Fcar (XCDR (args)));
808 809 810
  if (!NILP (Vpurify_flag))
    tem = Fpurecopy (tem);
  Fset_default (sym, tem);
811
  XSYMBOL (sym)->declared_special = 1;
812
  tem = Fcar (XCDR (XCDR (args)));
Jim Blandy's avatar
Jim Blandy committed
813
  if (!NILP (tem))
Jim Blandy's avatar
Jim Blandy committed
814
    {
Jim Blandy's avatar
Jim Blandy committed
815
      if (!NILP (Vpurify_flag))
Jim Blandy's avatar
Jim Blandy committed
816 817 818
	tem = Fpurecopy (tem);
      Fput (sym, Qvariable_documentation, tem);
    }
819
  Fput (sym, Qrisky_local_variable, Qt);
820
  LOADHIST_ATTACH (sym);
Jim Blandy's avatar
Jim Blandy committed
821 822 823
  return sym;
}

824 825 826 827 828 829 830 831 832