1 ;;; macroexp.el --- Additional macro-expansion support -*- lexical-binding: t -*-
3 ;; Copyright (C) 2004-2016 Free Software Foundation, Inc.
5 ;; Author: Miles Bader <miles@gnu.org>
6 ;; Keywords: lisp, compiler, macros
8 ;; This file is part of GNU Emacs.
10 ;; GNU Emacs is free software: you can redistribute it and/or modify
11 ;; it under the terms of the GNU General Public License as published by
12 ;; the Free Software Foundation, either version 3 of the License, or
13 ;; (at your option) any later version.
15 ;; GNU Emacs is distributed in the hope that it will be useful,
16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ;; GNU General Public License for more details.
20 ;; You should have received a copy of the GNU General Public License
21 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
25 ;; This file contains macro-expansions functions that are not defined in
26 ;; the Lisp core, namely `macroexpand-all', which expands all macros in
27 ;; a form, not just a top-level one.
31 ;; Bound by the top-level `macroexpand-all', and modified to include any
32 ;; macros defined by `defmacro'.
33 (defvar macroexpand-all-environment nil
)
35 (defun macroexp--cons (car cdr original-cons
)
36 "Return (CAR . CDR), using ORIGINAL-CONS if possible."
37 (if (and (eq car
(car original-cons
)) (eq cdr
(cdr original-cons
)))
41 ;; We use this special macro to iteratively process forms and share list
42 ;; structure of the result with the input. Doing so recursively using
43 ;; `macroexp--cons' results in excessively deep recursion for very long
45 (defmacro macroexp--accumulate
(var+list
&rest body
)
46 "Return a list of the results of evaluating BODY for each element of LIST.
47 Evaluate BODY with VAR bound to each `car' from LIST, in turn.
48 Return a list of the values of the final form in BODY.
49 The list structure of the result will share as much with LIST as
50 possible (for instance, when BODY just returns VAR unchanged, the
51 result will be eq to LIST).
53 \(fn (VAR LIST) BODY...)"
55 (let ((var (car var
+list
))
56 (list (cadr var
+list
))
57 (shared (make-symbol "shared"))
58 (unshared (make-symbol "unshared"))
59 (tail (make-symbol "tail"))
60 (new-el (make-symbol "new-el")))
61 `(let* ((,shared
,list
)
66 (setq ,var
(car ,tail
)
67 ,new-el
(progn ,@body
))
68 (unless (eq ,var
,new-el
)
69 (while (not (eq ,shared
,tail
))
70 (push (pop ,shared
) ,unshared
))
71 (setq ,shared
(cdr ,shared
))
72 (push ,new-el
,unshared
))
73 (setq ,tail
(cdr ,tail
)))
74 (nconc (nreverse ,unshared
) ,shared
))))
76 (defun macroexp--all-forms (forms &optional skip
)
77 "Return FORMS with macros expanded. FORMS is a list of forms.
78 If SKIP is non-nil, then don't expand that many elements at the start of
80 (macroexp--accumulate (form forms
)
81 (if (or (null skip
) (zerop skip
))
82 (macroexp--expand-all form
)
86 (defun macroexp--all-clauses (clauses &optional skip
)
87 "Return CLAUSES with macros expanded.
88 CLAUSES is a list of lists of forms; any clause that's not a list is ignored.
89 If SKIP is non-nil, then don't expand that many elements at the start of
91 (macroexp--accumulate (clause clauses
)
93 (macroexp--all-forms clause skip
)
96 (defun macroexp--compiler-macro (handler form
)
98 (apply handler form
(cdr form
))
100 (message "Compiler-macro error for %S: %S" (car form
) err
)
103 (defun macroexp--funcall-if-compiled (_form)
104 "Pseudo function used internally by macroexp to delay warnings.
105 The purpose is to delay warnings to bytecomp.el, so they can use things
106 like `byte-compile-log-warning' to get better file-and-line-number data
107 and also to avoid outputting the warning during normal execution."
109 (put 'macroexp--funcall-if-compiled
'byte-compile
111 (funcall (eval (cadr form
)))
112 (byte-compile-constant nil
)))
114 (defun macroexp--compiling-p ()
115 "Return non-nil if we're macroexpanding for the compiler."
116 ;; FIXME: ¡¡Major Ugly Hack!! To determine whether the output of this
117 ;; macro-expansion will be processed by the byte-compiler, we check
118 ;; circumstantial evidence.
119 (member '(declare-function . byte-compile-macroexpand-declare-function
)
120 macroexpand-all-environment
))
122 (defvar macroexp--warned
(make-hash-table :test
#'equal
:weakness
'key
))
124 (defun macroexp--warn-and-return (msg form
&optional compile-only
)
125 (let ((when-compiled (lambda () (byte-compile-log-warning msg t
))))
128 ((macroexp--compiling-p)
129 (if (gethash form macroexp--warned
)
130 ;; Already wrapped this exp with a warning: avoid inf-looping
131 ;; where we keep adding the same warning onto `form' because
132 ;; macroexpand-all gets right back to macroexpanding `form'.
134 (puthash form form macroexp--warned
)
136 (macroexp--funcall-if-compiled ',when-compiled
)
140 (message "%s%s" (if (stringp load-file-name
)
141 (concat (file-relative-name load-file-name
) ": ")
146 (defun macroexp--obsolete-warning (fun obsolescence-data type
)
147 (let ((instead (car obsolescence-data
))
148 (asof (nth 2 obsolescence-data
)))
150 "`%s' is an obsolete %s%s%s" fun type
151 (if asof
(concat " (as of " asof
")") "")
152 (cond ((stringp instead
) (concat "; " (substitute-command-keys instead
)))
153 (instead (format-message "; use `%s' instead." instead
))
156 (defun macroexpand-1 (form &optional environment
)
157 "Perform (at most) one step of macroexpansion."
160 (let* ((head (car form
))
161 (env-expander (assq head environment
)))
163 (if (cdr env-expander
)
164 (apply (cdr env-expander
) (cdr form
))
166 (if (not (and (symbolp head
) (fboundp head
)))
168 (let ((def (autoload-do-load (symbol-function head
) head
'macro
)))
170 ;; Follow alias, but only for macros, otherwise we may end up
171 ;; skipping an important compiler-macro (e.g. cl--block-wrapper).
172 ((and (symbolp def
) (macrop def
)) (cons def
(cdr form
)))
173 ((not (consp def
)) form
)
175 (if (eq 'macro
(car def
))
176 (apply (cdr def
) (cdr form
))
180 (defun macroexp-macroexpand (form env
)
181 "Like `macroexpand' but checking obsolescence."
183 (macroexpand form env
)))
184 (if (and (not (eq form new-form
)) ;It was a macro call.
187 (get (car form
) 'byte-obsolete-info
)
188 (or (not (fboundp 'byte-compile-warning-enabled-p
))
189 (byte-compile-warning-enabled-p 'obsolete
)))
190 (let* ((fun (car form
))
191 (obsolete (get fun
'byte-obsolete-info
)))
192 (macroexp--warn-and-return
193 (macroexp--obsolete-warning
195 (if (symbolp (symbol-function fun
))
200 (defun macroexp--expand-all (form)
201 "Expand all macros in FORM.
202 This is an internal version of `macroexpand-all'.
203 Assumes the caller has bound `macroexpand-all-environment'."
204 (if (eq (car-safe form
) 'backquote-list
*)
205 ;; Special-case `backquote-list*', as it is normally a macro that
206 ;; generates exceedingly deep expansions from relatively shallow input
207 ;; forms. We just process it `in reverse' -- first we expand all the
208 ;; arguments, _then_ we expand the top-level definition.
209 (macroexpand (macroexp--all-forms form
1)
210 macroexpand-all-environment
)
211 ;; Normal form; get its expansion, and then expand arguments.
212 (setq form
(macroexp-macroexpand form macroexpand-all-environment
))
215 (macroexp--cons 'cond
(macroexp--all-clauses clauses
) form
))
216 (`(condition-case .
,(or `(,err
,body .
,handlers
) dontcare
))
220 (macroexp--cons (macroexp--expand-all body
)
221 (macroexp--all-clauses handlers
1)
225 (`(,(or `defvar
`defconst
) .
,_
) (macroexp--all-forms form
2))
226 (`(function ,(and f
`(lambda .
,_
)))
227 (macroexp--cons 'function
228 (macroexp--cons (macroexp--all-forms f
2)
232 (`(,(or `function
`quote
) .
,_
) form
)
233 (`(,(and fun
(or `let
`let
*)) .
,(or `(,bindings .
,body
) dontcare
))
235 (macroexp--cons (macroexp--all-clauses bindings
1)
236 (macroexp--all-forms body
)
239 (`(,(and fun
`(lambda .
,_
)) .
,args
)
240 ;; Embedded lambda in function position.
241 (macroexp--cons (macroexp--all-forms fun
2)
242 (macroexp--all-forms args
)
244 ;; The following few cases are for normal function calls that
245 ;; are known to funcall one of their arguments. The byte
246 ;; compiler has traditionally handled these functions specially
247 ;; by treating a lambda expression quoted by `quote' as if it
248 ;; were quoted by `function'. We make the same transformation
249 ;; here, so that any code that cares about the difference will
250 ;; see the same transformation.
251 ;; First arg is a function:
252 (`(,(and fun
(or `funcall
`apply
`mapcar
`mapatoms
`mapconcat
`mapc
))
253 ',(and f
`(lambda .
,_
)) .
,args
)
254 (macroexp--warn-and-return
255 (format "%s quoted with ' rather than with #'"
256 (list 'lambda
(nth 1 f
) '...
))
257 (macroexp--expand-all `(,fun
,f .
,args
))))
258 ;; Second arg is a function:
259 (`(,(and fun
(or `sort
)) ,arg1
',(and f
`(lambda .
,_
)) .
,args
)
260 (macroexp--warn-and-return
261 (format "%s quoted with ' rather than with #'"
262 (list 'lambda
(nth 1 f
) '...
))
263 (macroexp--expand-all `(,fun
,arg1
,f .
,args
))))
264 (`(funcall #',(and f
(pred symbolp
)) .
,args
)
265 ;; Rewrite (funcall #'foo bar) to (foo bar), in case `foo'
266 ;; has a compiler-macro.
267 (macroexp--expand-all `(,f .
,args
)))
269 ;; Macro expand compiler macros. This cannot be delayed to
270 ;; byte-optimize-form because the output of the compiler-macro can
272 (let ((handler (function-get func
'compiler-macro
)))
274 ;; No compiler macro. We just expand each argument (for
275 ;; setq/setq-default this works alright because the variable names
277 (macroexp--all-forms form
1)
278 ;; If the handler is not loaded yet, try (auto)loading the
279 ;; function itself, which may in turn load the handler.
280 (unless (functionp handler
)
281 (with-demoted-errors "macroexp--expand-all: %S"
282 (autoload-do-load (indirect-function func
) func
)))
283 (let ((newform (macroexp--compiler-macro handler form
)))
284 (if (eq form newform
)
285 ;; The compiler macro did not find anything to do.
286 (if (equal form
(setq newform
(macroexp--all-forms form
1)))
288 ;; Maybe after processing the args, some new opportunities
289 ;; appeared, so let's try the compiler macro again.
290 (setq form
(macroexp--compiler-macro handler newform
))
291 (if (eq newform form
)
293 (macroexp--expand-all newform
)))
294 (macroexp--expand-all newform
))))))
299 (defun macroexpand-all (form &optional environment
)
300 "Return result of expanding macros at all levels in FORM.
301 If no macros are expanded, FORM is returned unchanged.
302 The second optional arg ENVIRONMENT specifies an environment of macro
303 definitions to shadow the loaded ones for use in file byte-compilation."
304 (let ((macroexpand-all-environment environment
))
305 (macroexp--expand-all form
)))
307 ;;; Handy functions to use in macros.
309 (defun macroexp-parse-body (body)
310 "Parse a function BODY into (DECLARATIONS . EXPS)."
312 (while (and (cdr body
)
313 (let ((e (car body
)))
316 '(:documentation declare interactive cl-declare
)))))
317 (push (pop body
) decls
))
318 (cons (nreverse decls
) body
)))
320 (defun macroexp-progn (exps)
321 "Return an expression equivalent to `(progn ,@EXPS)."
322 (if (cdr exps
) `(progn ,@exps
) (car exps
)))
324 (defun macroexp-unprogn (exp)
325 "Turn EXP into a list of expressions to execute in sequence.
326 Never returns an empty list."
327 (if (eq (car-safe exp
) 'progn
) (or (cdr exp
) '(nil)) (list exp
)))
329 (defun macroexp-let* (bindings exp
)
330 "Return an expression equivalent to `(let* ,bindings ,exp)."
332 ((null bindings
) exp
)
333 ((eq 'let
* (car-safe exp
)) `(let* (,@bindings
,@(cadr exp
)) ,@(cddr exp
)))
334 (t `(let* ,bindings
,exp
))))
336 (defun macroexp-if (test then else
)
337 "Return an expression equivalent to `(if ,TEST ,THEN ,ELSE)."
339 ((eq (car-safe else
) 'if
)
341 ;; Drop this optimization: It's unsafe (it assumes that `test' is
342 ;; pure, or at least idempotent), and it's not used even a single
343 ;; time while compiling Emacs's sources.
344 ;;((equal test (nth 1 else))
345 ;; ;; Doing a test a second time: get rid of the redundancy.
346 ;; (message "macroexp-if: sharing 'test' %S" test)
347 ;; `(if ,test ,then ,@(nthcdr 3 else)))
348 ((equal then
(nth 2 else
))
349 ;; (message "macroexp-if: sharing 'then' %S" then)
350 `(if (or ,test
,(nth 1 else
)) ,then
,@(nthcdr 3 else
)))
351 ((equal (macroexp-unprogn then
) (nthcdr 3 else
))
352 ;; (message "macroexp-if: sharing 'then' with not %S" then)
353 `(if (or ,test
(not ,(nth 1 else
)))
354 ,then
,@(macroexp-unprogn (nth 2 else
))))
356 `(cond (,test
,@(macroexp-unprogn then
))
357 (,(nth 1 else
) ,@(macroexp-unprogn (nth 2 else
)))
358 (t ,@(nthcdr 3 else
))))))
359 ((eq (car-safe else
) 'cond
)
360 `(cond (,test
,@(macroexp-unprogn then
)) ,@(cdr else
)))
361 ;; Invert the test if that lets us reduce the depth of the tree.
362 ((memq (car-safe then
) '(if cond
)) (macroexp-if `(not ,test
) else then
))
363 (t `(if ,test
,then
,@(macroexp-unprogn else
)))))
365 (defmacro macroexp-let2
(test sym exp
&rest body
)
366 "Evaluate BODY with SYM bound to an expression for EXP's value.
367 The intended usage is that BODY generates an expression that
368 will refer to EXP's value multiple times, but will evaluate
369 EXP only once. As BODY generates that expression, it should
370 use SYM to stand for the value of EXP.
372 If EXP is a simple, safe expression, then SYM's value is EXP itself.
373 Otherwise, SYM's value is a symbol which holds the value produced by
374 evaluating EXP. The return value incorporates the value of BODY, plus
375 additional code to evaluate EXP once and save the result so SYM can
378 If BODY consists of multiple forms, they are all evaluated
379 but only the last one's value matters.
381 TEST is a predicate to determine whether EXP qualifies as simple and
382 safe; if TEST is nil, only constant expressions qualify.
385 (macroexp-let2 nil foo EXP
387 generates an expression that evaluates EXP once,
388 then returns the square of that value.
389 You could do this with
392 but using `macroexp-let2' produces more efficient code in
393 cases where EXP is a constant."
394 (declare (indent 3) (debug (sexp sexp form body
)))
395 (let ((bodysym (make-symbol "body"))
396 (expsym (make-symbol "exp")))
397 `(let* ((,expsym
,exp
)
398 (,sym
(if (funcall #',(or test
#'macroexp-const-p
) ,expsym
)
399 ,expsym
(make-symbol ,(symbol-name sym
))))
400 (,bodysym
,(macroexp-progn body
)))
401 (if (eq ,sym
,expsym
) ,bodysym
402 (macroexp-let* (list (list ,sym
,expsym
))
405 (defmacro macroexp-let2
* (test bindings
&rest body
)
406 "Bind each binding in BINDINGS as `macroexp-let2' does."
407 (declare (indent 2) (debug (sexp (&rest
(sexp form
)) body
)))
408 (pcase-exhaustive bindings
409 (`nil
(macroexp-progn body
))
410 (`((,var
,exp
) .
,tl
)
411 `(macroexp-let2 ,test
,var
,exp
412 (macroexp-let2* ,test
,tl
,@body
)))))
414 (defun macroexp--maxsize (exp size
)
415 (cond ((< size
0) size
)
416 ((symbolp exp
) (1- size
))
417 ((stringp exp
) (- size
(/ (length exp
) 16)))
419 (dotimes (i (length exp
))
420 (setq size
(macroexp--maxsize (aref exp i
) size
)))
423 ;; We could try to be more clever with quote&function,
424 ;; but it is difficult to do so correctly, and it's not obvious that
425 ;; it would be worth the effort.
427 (setq size
(macroexp--maxsize e size
)))
431 (defun macroexp-small-p (exp)
432 "Return non-nil if EXP can be considered small."
433 (> (macroexp--maxsize exp
10) 0))
435 (defsubst macroexp--const-symbol-p
(symbol &optional any-value
)
436 "Non-nil if SYMBOL is constant.
437 If ANY-VALUE is nil, only return non-nil if the value of the symbol is the
439 (or (memq symbol
'(nil t
))
442 (or (memq symbol byte-compile-const-variables
)
443 ;; FIXME: We should provide a less intrusive way to find out
444 ;; if a variable is "constant".
447 (progn (set symbol
(symbol-value symbol
)) nil
)
448 (setting-constant t
)))))))
450 (defun macroexp-const-p (exp)
451 "Return non-nil if EXP will always evaluate to the same value."
452 (cond ((consp exp
) (or (eq (car exp
) 'quote
)
453 (and (eq (car exp
) 'function
)
454 (symbolp (cadr exp
)))))
455 ;; It would sometimes make sense to pass `any-value', but it's not
456 ;; always safe since a "constant" variable may not actually always have
458 ((symbolp exp
) (macroexp--const-symbol-p exp
))
461 (defun macroexp-copyable-p (exp)
462 "Return non-nil if EXP can be copied without extra cost."
463 (or (symbolp exp
) (macroexp-const-p exp
)))
465 (defun macroexp-quote (v)
466 "Return an expression E such that `(eval E)' is V.
468 E is either V or (quote V) depending on whether V evaluates to
470 (if (and (not (consp v
))
477 ;;; Load-time macro-expansion.
479 ;; Because macro-expansion used to be more lazy, eager macro-expansion
480 ;; tends to bump into previously harmless/unnoticeable cyclic-dependencies.
481 ;; So, we have to delay macro-expansion like we used to when we detect
482 ;; such a cycle, and we also want to help coders resolve those cycles (since
483 ;; they can be non-obvious) by providing a usefully trimmed backtrace
484 ;; (hopefully) highlighting the problem.
486 (defun macroexp--backtrace ()
487 "Return the Elisp backtrace, more recent frames first."
491 (let ((frame (backtrace-frame i
)))
497 (defun macroexp--trim-backtrace-frame (frame)
499 (`(,_ macroexpand
(,head .
,_
) .
,_
) `(macroexpand (,head …
)))
500 (`(,_ internal-macroexpand-for-load
(,head
,second .
,_
) .
,_
)
501 (if (or (symbolp second
)
502 (and (eq 'quote
(car-safe second
))
503 (symbolp (cadr second
))))
504 `(macroexpand-all (,head
,second …
))
505 '(macroexpand-all …
)))
506 (`(,_ load-with-code-conversion
,name .
,_
)
507 `(load ,(file-name-nondirectory name
)))))
509 (defvar macroexp--pending-eager-loads nil
510 "Stack of files currently undergoing eager macro-expansion.")
512 (defvar macroexp--debug-eager nil
)
514 (defun internal-macroexpand-for-load (form full-p
)
515 ;; Called from the eager-macroexpansion in readevalloop.
517 ;; Don't repeat the same warning for every top-level element.
518 ((eq 'skip
(car macroexp--pending-eager-loads
)) form
)
519 ;; If we detect a cycle, skip macro-expansion for now, and output a warning
520 ;; with a trimmed backtrace.
521 ((and load-file-name
(member load-file-name macroexp--pending-eager-loads
))
523 (mapcar #'macroexp--trim-backtrace-frame
524 (macroexp--backtrace))))
525 (elem `(load ,(file-name-nondirectory load-file-name
)))
526 (tail (member elem
(cdr (member elem bt
)))))
527 (if tail
(setcdr tail
(list '…
)))
528 (if (eq (car-safe (car bt
)) 'macroexpand-all
) (setq bt
(cdr bt
)))
529 (if macroexp--debug-eager
530 (debug 'eager-macroexp-cycle
)
531 (message "Warning: Eager macro-expansion skipped due to cycle:\n %s"
532 (mapconcat #'prin1-to-string
(nreverse bt
) " => ")))
533 (push 'skip macroexp--pending-eager-loads
)
537 (let ((macroexp--pending-eager-loads
538 (cons load-file-name macroexp--pending-eager-loads
)))
540 (macroexpand-all form
)
543 ;; Hopefully this shouldn't happen thanks to the cycle detection,
544 ;; but in case it does happen, let's catch the error and give the
545 ;; code a chance to macro-expand later.
546 (message "Eager macro-expansion failure: %S" err
)
549 ;; ¡¡¡ Big Ugly Hack !!!
550 ;; src/bootstrap-emacs is mostly used to compile .el files, so it needs
551 ;; macroexp, bytecomp, cconv, and byte-opt to be fast. Generally this is done
552 ;; by compiling those files first, but this only makes a difference if those
553 ;; files are not preloaded. But macroexp.el is preloaded so we reload it if
554 ;; the current version is interpreted and there's a compiled version available.
556 (add-hook 'emacs-startup-hook
558 (and (not (byte-code-function-p
559 (symbol-function 'macroexpand-all
)))
560 (locate-library "macroexp.elc")
561 (load "macroexp.elc")))))
565 ;;; macroexp.el ends here