macroexp.el 18.5 KB
Newer Older
1
;;; macroexp.el --- Additional macro-expansion support -*- lexical-binding: t; coding: utf-8 -*-
2
;;
3
;; Copyright (C) 2004-2014 Free Software Foundation, Inc.
4 5 6 7 8 9
;;
;; Author: Miles Bader <miles@gnu.org>
;; Keywords: lisp, compiler, macros

;; 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 13
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
14 15 16 17 18 19 20

;; 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
21
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
22 23 24 25 26 27 28 29 30 31 32 33 34 35

;;; Commentary:
;;
;; This file contains macro-expansions functions that are not defined in
;; the Lisp core, namely `macroexpand-all', which expands all macros in
;; a form, not just a top-level one.
;;

;;; Code:

;; Bound by the top-level `macroexpand-all', and modified to include any
;; macros defined by `defmacro'.
(defvar macroexpand-all-environment nil)

36
(defun macroexp--cons (car cdr original-cons)
37 38 39 40 41 42 43
  "Return (CAR . CDR), using ORIGINAL-CONS if possible."
  (if (and (eq car (car original-cons)) (eq cdr (cdr original-cons)))
      original-cons
    (cons car cdr)))

;; We use this special macro to iteratively process forms and share list
;; structure of the result with the input.  Doing so recursively using
44
;; `macroexp--cons' results in excessively deep recursion for very long
45
;; input forms.
46
(defmacro macroexp--accumulate (var+list &rest body)
47 48 49 50 51
  "Return a list of the results of evaluating BODY for each element of LIST.
Evaluate BODY with VAR bound to each `car' from LIST, in turn.
Return a list of the values of the final form in BODY.
The list structure of the result will share as much with LIST as
possible (for instance, when BODY just returns VAR unchanged, the
52 53 54
result will be eq to LIST).

\(fn (VAR LIST) BODY...)"
55
  (declare (indent 1))
56 57
  (let ((var (car var+list))
	(list (cadr var+list))
58 59 60 61 62 63 64 65
	(shared (make-symbol "shared"))
	(unshared (make-symbol "unshared"))
	(tail (make-symbol "tail"))
	(new-el (make-symbol "new-el")))
    `(let* ((,shared ,list)
	    (,unshared nil)
	    (,tail ,shared)
	    ,var ,new-el)
66
       (while (consp ,tail)
67 68 69 70 71 72 73 74 75 76
	 (setq ,var (car ,tail)
	       ,new-el (progn ,@body))
	 (unless (eq ,var ,new-el)
	   (while (not (eq ,shared ,tail))
	     (push (pop ,shared) ,unshared))
	   (setq ,shared (cdr ,shared))
	   (push ,new-el ,unshared))
	 (setq ,tail (cdr ,tail)))
       (nconc (nreverse ,unshared) ,shared))))

77
(defun macroexp--all-forms (forms &optional skip)
78 79 80
  "Return FORMS with macros expanded.  FORMS is a list of forms.
If SKIP is non-nil, then don't expand that many elements at the start of
FORMS."
81
  (macroexp--accumulate (form forms)
82
    (if (or (null skip) (zerop skip))
83
	(macroexp--expand-all form)
84 85 86
      (setq skip (1- skip))
      form)))

87
(defun macroexp--all-clauses (clauses &optional skip)
88 89 90 91
  "Return CLAUSES with macros expanded.
CLAUSES is a list of lists of forms; any clause that's not a list is ignored.
If SKIP is non-nil, then don't expand that many elements at the start of
each clause."
92
  (macroexp--accumulate (clause clauses)
93
    (if (listp clause)
94
	(macroexp--all-forms clause skip)
95 96
      clause)))

97 98 99
(defun macroexp--compiler-macro (handler form)
  (condition-case err
      (apply handler form (cdr form))
100 101 102 103
    (error
     (message "--------------------------------------------------")
     (backtrace)
     (message "Compiler-macro error for %S: %S" (car form) err)
104
           form)))
105

106
(defun macroexp--funcall-if-compiled (_form)
107 108 109 110 111
  "Pseudo function used internally by macroexp to delay warnings.
The purpose is to delay warnings to bytecomp.el, so they can use things
like `byte-compile-log-warning' to get better file-and-line-number data
and also to avoid outputting the warning during normal execution."
  nil)
112
(put 'macroexp--funcall-if-compiled 'byte-compile
113
     (lambda (form)
114
       (funcall (eval (cadr form)))
115 116
       (byte-compile-constant nil)))

117 118 119 120 121 122 123 124 125
(defun macroexp--compiling-p ()
  "Return non-nil if we're macroexpanding for the compiler."
  ;; FIXME: ¡¡Major Ugly Hack!! To determine whether the output of this
  ;; macro-expansion will be processed by the byte-compiler, we check
  ;; circumstantial evidence.
  (member '(declare-function . byte-compile-macroexpand-declare-function)
          macroexpand-all-environment))


126 127 128 129
(defun macroexp--warn-and-return (msg form)
  (let ((when-compiled (lambda () (byte-compile-log-warning msg t))))
    (cond
     ((null msg) form)
130
     ((macroexp--compiling-p)
131 132
      `(progn
         (macroexp--funcall-if-compiled ',when-compiled)
133 134
         ,form))
     (t
135 136 137 138
      (message "%s%s" (if (stringp load-file-name)
                          (concat (file-relative-name load-file-name) ": ")
                        "")
               msg)
139 140 141 142 143 144 145 146 147 148
      form))))

(defun macroexp--obsolete-warning (fun obsolescence-data type)
  (let ((instead (car obsolescence-data))
        (asof (nth 2 obsolescence-data)))
    (format "`%s' is an obsolete %s%s%s" fun type
            (if asof (concat " (as of " asof ")") "")
            (cond ((stringp instead) (concat "; " instead))
                  (instead (format "; use `%s' instead." instead))
                  (t ".")))))
Glenn Morris's avatar
Glenn Morris committed
149

150
(defun macroexp--expand-all (form)
151 152 153 154 155 156 157 158
  "Expand all macros in FORM.
This is an internal version of `macroexpand-all'.
Assumes the caller has bound `macroexpand-all-environment'."
  (if (and (listp form) (eq (car form) 'backquote-list*))
      ;; Special-case `backquote-list*', as it is normally a macro that
      ;; generates exceedingly deep expansions from relatively shallow input
      ;; forms.  We just process it `in reverse' -- first we expand all the
      ;; arguments, _then_ we expand the top-level definition.
159
      (macroexpand (macroexp--all-forms form 1)
160 161
		   macroexpand-all-environment)
    ;; Normal form; get its expansion, and then expand arguments.
162 163 164 165 166 167
    (let ((new-form
           (macroexpand form macroexpand-all-environment)))
      (setq form
            (if (and (not (eq form new-form)) ;It was a macro call.
                     (car-safe form)
                     (symbolp (car form))
168 169 170
                     (get (car form) 'byte-obsolete-info)
                     (or (not (fboundp 'byte-compile-warning-enabled-p))
                         (byte-compile-warning-enabled-p 'obsolete)))
171 172 173
                (let* ((fun (car form))
                       (obsolete (get fun 'byte-obsolete-info)))
                  (macroexp--warn-and-return
174 175 176 177
                   (macroexp--obsolete-warning
                    fun obsolete
                    (if (symbolp (symbol-function fun))
                        "alias" "macro"))
178
                   new-form))
179
              new-form)))
180 181
    (pcase form
      (`(cond . ,clauses)
182
       (macroexp--cons 'cond (macroexp--all-clauses clauses) form))
183
      (`(condition-case . ,(or `(,err ,body . ,handlers) dontcare))
184
       (macroexp--cons
185
        'condition-case
186 187 188
        (macroexp--cons err
                    (macroexp--cons (macroexp--expand-all body)
                                (macroexp--all-clauses handlers 1)
189 190 191
                                (cddr form))
                    (cdr form))
        form))
192
      (`(,(or `defvar `defconst) . ,_) (macroexp--all-forms form 2))
193
      (`(function ,(and f `(lambda . ,_)))
194 195
       (macroexp--cons 'function
                   (macroexp--cons (macroexp--all-forms f 2)
196 197 198 199 200
                               nil
                               (cdr form))
                   form))
      (`(,(or `function `quote) . ,_) form)
      (`(,(and fun (or `let `let*)) . ,(or `(,bindings . ,body) dontcare))
201 202 203
       (macroexp--cons fun
                   (macroexp--cons (macroexp--all-clauses bindings 1)
                               (macroexp--all-forms body)
204 205 206 207
                               (cdr form))
                   form))
      (`(,(and fun `(lambda . ,_)) . ,args)
       ;; Embedded lambda in function position.
208 209
       (macroexp--cons (macroexp--all-forms fun 2)
                   (macroexp--all-forms args)
210 211 212 213 214 215 216 217 218
                   form))
      ;; The following few cases are for normal function calls that
      ;; are known to funcall one of their arguments.  The byte
      ;; compiler has traditionally handled these functions specially
      ;; by treating a lambda expression quoted by `quote' as if it
      ;; were quoted by `function'.  We make the same transformation
      ;; here, so that any code that cares about the difference will
      ;; see the same transformation.
      ;; First arg is a function:
219
      (`(,(and fun (or `funcall `apply `mapcar `mapatoms `mapconcat `mapc))
Stefan Monnier's avatar
Stefan Monnier committed
220
         ',(and f `(lambda . ,_)) . ,args)
221
       (macroexp--warn-and-return
222 223
        (format "%s quoted with ' rather than with #'"
                (list 'lambda (nth 1 f) '...))
224
        (macroexp--expand-all `(,fun ,f . ,args))))
225
      ;; Second arg is a function:
Stefan Monnier's avatar
Stefan Monnier committed
226
      (`(,(and fun (or `sort)) ,arg1 ',(and f `(lambda . ,_)) . ,args)
227
       (macroexp--warn-and-return
228 229
        (format "%s quoted with ' rather than with #'"
                (list 'lambda (nth 1 f) '...))
230
        (macroexp--expand-all `(,fun ,arg1 ,f . ,args))))
231 232 233 234
      (`(,func . ,_)
       ;; Macro expand compiler macros.  This cannot be delayed to
       ;; byte-optimize-form because the output of the compiler-macro can
       ;; use macros.
235
       (let ((handler (function-get func 'compiler-macro)))
236 237 238 239
         (if (null handler)
             ;; No compiler macro.  We just expand each argument (for
             ;; setq/setq-default this works alright because the variable names
             ;; are symbols).
240
             (macroexp--all-forms form 1)
241 242
           ;; If the handler is not loaded yet, try (auto)loading the
           ;; function itself, which may in turn load the handler.
243
           (unless (functionp handler)
244
             (ignore-errors
245
               (autoload-do-load (indirect-function func) func)))
246
           (let ((newform (macroexp--compiler-macro handler form)))
247 248
             (if (eq form newform)
                 ;; The compiler macro did not find anything to do.
249
                 (if (equal form (setq newform (macroexp--all-forms form 1)))
250 251 252
                     form
                   ;; Maybe after processing the args, some new opportunities
                   ;; appeared, so let's try the compiler macro again.
253
                   (setq form (macroexp--compiler-macro handler newform))
254
                   (if (eq newform form)
255
                       newform
256 257
                     (macroexp--expand-all newform)))
               (macroexp--expand-all newform))))))
258

259
      (t form))))
260 261 262 263 264 265 266 267

;;;###autoload
(defun macroexpand-all (form &optional environment)
  "Return result of expanding macros at all levels in FORM.
If no macros are expanded, FORM is returned unchanged.
The second optional arg ENVIRONMENT specifies an environment of macro
definitions to shadow the loaded ones for use in file byte-compilation."
  (let ((macroexpand-all-environment environment))
268
    (macroexp--expand-all form)))
269

270 271 272 273 274 275
;;; Handy functions to use in macros.

(defun macroexp-progn (exps)
  "Return an expression equivalent to `(progn ,@EXPS)."
  (if (cdr exps) `(progn ,@exps) (car exps)))

276 277 278 279
(defun macroexp-unprogn (exp)
  "Turn EXP into a list of expressions to execute in sequence."
  (if (eq (car-safe exp) 'progn) (cdr exp) (list exp)))

280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304
(defun macroexp-let* (bindings exp)
  "Return an expression equivalent to `(let* ,bindings ,exp)."
  (cond
   ((null bindings) exp)
   ((eq 'let* (car-safe exp)) `(let* (,@bindings ,@(cadr exp)) ,@(cddr exp)))
   (t `(let* ,bindings ,exp))))

(defun macroexp-if (test then else)
  "Return an expression equivalent to `(if ,test ,then ,else)."
  (cond
   ((eq (car-safe else) 'if)
    (if (equal test (nth 1 else))
        ;; Doing a test a second time: get rid of the redundancy.
        `(if ,test ,then ,@(nthcdr 3 else))
      `(cond (,test ,then)
             (,(nth 1 else) ,(nth 2 else))
             (t ,@(nthcdr 3 else)))))
   ((eq (car-safe else) 'cond)
    `(cond (,test ,then)
           ;; Doing a test a second time: get rid of the redundancy, as above.
           ,@(remove (assoc test else) (cdr else))))
   ;; Invert the test if that lets us reduce the depth of the tree.
   ((memq (car-safe then) '(if cond)) (macroexp-if `(not ,test) else then))
   (t `(if ,test ,then ,else))))

305
(defmacro macroexp-let2 (test var exp &rest exps)
306 307 308 309 310
  "Bind VAR to a copyable expression that returns the value of EXP.
This is like `(let ((v ,EXP)) ,EXPS) except that `v' is a new generated
symbol which EXPS can find in VAR.
TEST should be the name of a predicate on EXP checking whether the `let' can
be skipped; if nil, as is usual, `macroexp-const-p' is used."
311
  (declare (indent 3) (debug (sexp sexp form body)))
312 313 314
  (let ((bodysym (make-symbol "body"))
        (expsym (make-symbol "exp")))
    `(let* ((,expsym ,exp)
315
            (,var (if (funcall #',(or test #'macroexp-const-p) ,expsym)
Stefan Monnier's avatar
Stefan Monnier committed
316
                      ,expsym (make-symbol ,(symbol-name var))))
317 318 319 320 321
            (,bodysym ,(macroexp-progn exps)))
       (if (eq ,var ,expsym) ,bodysym
         (macroexp-let* (list (list ,var ,expsym))
                        ,bodysym)))))

322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342
(defun macroexp--maxsize (exp size)
  (cond ((< size 0) size)
        ((symbolp exp) (1- size))
        ((stringp exp) (- size (/ (length exp) 16)))
        ((vectorp exp)
         (dotimes (i (length exp))
           (setq size (macroexp--maxsize (aref exp i) size)))
         (1- size))
        ((consp exp)
         ;; We could try to be more clever with quote&function,
         ;; but it is difficult to do so correctly, and it's not obvious that
         ;; it would be worth the effort.
         (dolist (e exp)
           (setq size (macroexp--maxsize e size)))
         (1- size))
        (t -1)))

(defun macroexp-small-p (exp)
  "Return non-nil if EXP can be considered small."
  (> (macroexp--maxsize exp 10) 0))

343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372
(defsubst macroexp--const-symbol-p (symbol &optional any-value)
  "Non-nil if SYMBOL is constant.
If ANY-VALUE is nil, only return non-nil if the value of the symbol is the
symbol itself."
  (or (memq symbol '(nil t))
      (keywordp symbol)
      (if any-value
	  (or (memq symbol byte-compile-const-variables)
	      ;; FIXME: We should provide a less intrusive way to find out
	      ;; if a variable is "constant".
	      (and (boundp symbol)
		   (condition-case nil
		       (progn (set symbol (symbol-value symbol)) nil)
		     (setting-constant t)))))))

(defun macroexp-const-p (exp)
  "Return non-nil if EXP will always evaluate to the same value."
  (cond ((consp exp) (or (eq (car exp) 'quote)
                         (and (eq (car exp) 'function)
                              (symbolp (cadr exp)))))
        ;; It would sometimes make sense to pass `any-value', but it's not
        ;; always safe since a "constant" variable may not actually always have
        ;; the same value.
        ((symbolp exp) (macroexp--const-symbol-p exp))
        (t t)))

(defun macroexp-copyable-p (exp)
  "Return non-nil if EXP can be copied without extra cost."
  (or (symbolp exp) (macroexp-const-p exp)))

373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407
;;; Load-time macro-expansion.

;; Because macro-expansion used to be more lazy, eager macro-expansion
;; tends to bump into previously harmless/unnoticeable cyclic-dependencies.
;; So, we have to delay macro-expansion like we used to when we detect
;; such a cycle, and we also want to help coders resolve those cycles (since
;; they can be non-obvious) by providing a usefully trimmed backtrace
;; (hopefully) highlighting the problem.

(defun macroexp--backtrace ()
  "Return the Elisp backtrace, more recent frames first."
  (let ((bt ())
        (i 0))
    (while
        (let ((frame (backtrace-frame i)))
          (when frame
            (push frame bt)
            (setq i (1+ i)))))
    (nreverse bt)))

(defun macroexp--trim-backtrace-frame (frame)
  (pcase frame
    (`(,_ macroexpand (,head . ,_) . ,_) `(macroexpand (,head )))
    (`(,_ internal-macroexpand-for-load (,head ,second . ,_) . ,_)
     (if (or (symbolp second)
             (and (eq 'quote (car-safe second))
                  (symbolp (cadr second))))
         `(macroexpand-all (,head ,second ))
       '(macroexpand-all )))
    (`(,_ load-with-code-conversion ,name . ,_)
     `(load ,(file-name-nondirectory name)))))

(defvar macroexp--pending-eager-loads nil
  "Stack of files currently undergoing eager macro-expansion.")

408
(defun internal-macroexpand-for-load (form full-p)
409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430
  ;; Called from the eager-macroexpansion in readevalloop.
  (cond
   ;; Don't repeat the same warning for every top-level element.
   ((eq 'skip (car macroexp--pending-eager-loads)) form)
   ;; If we detect a cycle, skip macro-expansion for now, and output a warning
   ;; with a trimmed backtrace.
   ((and load-file-name (member load-file-name macroexp--pending-eager-loads))
    (let* ((bt (delq nil
                     (mapcar #'macroexp--trim-backtrace-frame
                             (macroexp--backtrace))))
           (elem `(load ,(file-name-nondirectory load-file-name)))
           (tail (member elem (cdr (member elem bt)))))
      (if tail (setcdr tail (list ')))
      (if (eq (car-safe (car bt)) 'macroexpand-all) (setq bt (cdr bt)))
      (message "Warning: Eager macro-expansion skipped due to cycle:\n  %s"
               (mapconcat #'prin1-to-string (nreverse bt) " => "))
      (push 'skip macroexp--pending-eager-loads)
      form))
   (t
    (condition-case err
        (let ((macroexp--pending-eager-loads
               (cons load-file-name macroexp--pending-eager-loads)))
431 432 433
          (if full-p
              (macroexpand-all form)
            (macroexpand form)))
434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454
      (error
       ;; Hopefully this shouldn't happen thanks to the cycle detection,
       ;; but in case it does happen, let's catch the error and give the
       ;; code a chance to macro-expand later.
       (message "Eager macro-expansion failure: %S" err)
       form)))))

;; ¡¡¡ Big Ugly Hack !!!
;; src/bootstrap-emacs is mostly used to compile .el files, so it needs
;; macroexp, bytecomp, cconv, and byte-opt to be fast.  Generally this is done
;; by compiling those files first, but this only makes a difference if those
;; files are not preloaded.  But macroexp.el is preloaded so we reload it if
;; the current version is interpreted and there's a compiled version available.
(eval-when-compile
  (add-hook 'emacs-startup-hook
            (lambda ()
              (and (not (byte-code-function-p
                         (symbol-function 'macroexpand-all)))
                   (locate-library "macroexp.elc")
                   (load "macroexp.elc")))))

455 456 457
(provide 'macroexp)

;;; macroexp.el ends here