src/code/macros.lisp

   1 ;;;; lots of basic macros for the target SBCL
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 (in-package "SB!IMPL")
  13 \f
  14 ;;;; ASSERT and CHECK-TYPE
  15
  16 ;;; ASSERT is written this way, to call ASSERT-ERROR, because of how
  17 ;;; closures are compiled. RESTART-CASE has forms with closures that
  18 ;;; the compiler causes to be generated at the top of any function
  19 ;;; using RESTART-CASE, regardless of whether they are needed. Thus if
  20 ;;; we just wrapped a RESTART-CASE around the call to ERROR, we'd have
  21 ;;; to do a significant amount of work at runtime allocating and
  22 ;;; deallocating the closures regardless of whether they were ever
  23 ;;; needed.
  24 ;;;
  25 ;;; ASSERT-ERROR isn't defined until a later file because it uses the
  26 ;;; macro RESTART-CASE, which isn't defined until a later file.
  27 (defmacro-mundanely assert (test-form &optional places datum &rest arguments)
  28   #!+sb-doc
  29   "Signals an error if the value of test-form is nil. Continuing from this
  30    error using the CONTINUE restart will allow the user to alter the value of
  31    some locations known to SETF, starting over with test-form. Returns NIL."
  32   `(do () (,test-form)
  33      (assert-error ',test-form ',places ,datum ,@arguments)
  34      ,@(mapcar (lambda (place)
  35                  `(setf ,place (assert-prompt ',place ,place)))
  36                places)))
  37
  38 (defun assert-prompt (name value)
  39   (cond ((y-or-n-p "The old value of ~S is ~S.~
  40                     ~%Do you want to supply a new value? "
  41                    name value)
  42          (format *query-io* "~&Type a form to be evaluated:~%")
  43          (flet ((read-it () (eval (read *query-io*))))
  44            (if (symbolp name) ;help user debug lexical variables
  45                (progv (list name) (list value) (read-it))
  46                (read-it))))
  47         (t value)))
  48
  49 ;;; CHECK-TYPE is written this way, to call CHECK-TYPE-ERROR, because
  50 ;;; of how closures are compiled. RESTART-CASE has forms with closures
  51 ;;; that the compiler causes to be generated at the top of any
  52 ;;; function using RESTART-CASE, regardless of whether they are
  53 ;;; needed. Because it would be nice if CHECK-TYPE were cheap to use,
  54 ;;; and some things (e.g., READ-CHAR) can't afford this excessive
  55 ;;; consing, we bend backwards a little.
  56 ;;;
  57 ;;; CHECK-TYPE-ERROR isn't defined until a later file because it uses
  58 ;;; the macro RESTART-CASE, which isn't defined until a later file.
  59 (defmacro-mundanely check-type (place type &optional type-string
  60                                 &environment env)
  61   #!+sb-doc
  62   "Signal a restartable error of type TYPE-ERROR if the value of PLACE
  63 is not of the specified type. If an error is signalled and the restart
  64 is used to return, this can only return if the STORE-VALUE restart is
  65 invoked. In that case it will store into PLACE and start over."
  66   ;; KLUDGE: We use a simpler form of expansion if PLACE is just a
  67   ;; variable to work around Python's blind spot in type derivation.
  68   ;; For more complex places getting the type derived should not
  69   ;; matter so much anyhow.
  70   (let ((expanded (sb!xc:macroexpand place env)))
  71     (if (symbolp expanded)
  72         `(do ()
  73              ((typep ,place ',type))
  74           (setf ,place (check-type-error ',place ,place ',type ,type-string)))
  75         (let ((value (gensym)))
  76           `(do ((,value ,place ,place))
  77                ((typep ,value ',type))
  78             (setf ,place
  79                   (check-type-error ',place ,value ',type ,type-string)))))))
  80 \f
  81 ;;;; DEFINE-SYMBOL-MACRO
  82
  83 (defmacro-mundanely define-symbol-macro (name expansion)
  84   `(eval-when (:compile-toplevel :load-toplevel :execute)
  85     (sb!c::%define-symbol-macro ',name ',expansion (sb!c:source-location))))
  86
  87 (defun sb!c::%define-symbol-macro (name expansion source-location)
  88   (unless (symbolp name)
  89     (error 'simple-type-error :datum name :expected-type 'symbol
  90            :format-control "Symbol macro name is not a symbol: ~S."
  91            :format-arguments (list name)))
  92   (with-single-package-locked-error
  93       (:symbol name "defining ~A as a symbol-macro"))
  94   (sb!c:with-source-location (source-location)
  95     (setf (info :source-location :symbol-macro name) source-location))
  96   (ecase (info :variable :kind name)
  97     ((:macro :global nil)
  98      (setf (info :variable :kind name) :macro)
  99      (setf (info :variable :macro-expansion name) expansion))
 100     (:special
 101      (error 'simple-program-error
 102             :format-control "Symbol macro name already declared special: ~S."
 103             :format-arguments (list name)))
 104     (:constant
 105      (error 'simple-program-error
 106             :format-control "Symbol macro name already declared constant: ~S."
 107             :format-arguments (list name))))
 108   name)
 109 \f
 110 ;;;; DEFINE-COMPILER-MACRO
 111
 112 (defmacro-mundanely define-compiler-macro (name lambda-list &body body)
 113   #!+sb-doc
 114   "Define a compiler-macro for NAME."
 115   (legal-fun-name-or-type-error name)
 116   (when (and (symbolp name) (special-operator-p name))
 117     (error 'simple-program-error
 118            :format-control "cannot define a compiler-macro for a special operator: ~S"
 119            :format-arguments (list name)))
 120   (with-unique-names (whole environment)
 121     (multiple-value-bind (body local-decs doc)
 122         (parse-defmacro lambda-list whole body name 'define-compiler-macro
 123                         :environment environment)
 124       (let ((def `(lambda (,whole ,environment)
 125                     ,@local-decs
 126                     ,body))
 127             (debug-name (sb!c::debug-name 'compiler-macro-function name)))
 128         `(eval-when (:compile-toplevel :load-toplevel :execute)
 129            (sb!c::%define-compiler-macro ',name
 130                                          #',def
 131                                          ',lambda-list
 132                                          ,doc
 133                                          ',debug-name))))))
 134
 135 ;;; FIXME: This will look remarkably similar to those who have already
 136 ;;; seen the code for %DEFMACRO in src/code/defmacro.lisp.  Various
 137 ;;; bits of logic should be shared (notably arglist setting).
 138 (macrolet
 139     ((def (times set-p)
 140          `(eval-when (,@times)
 141            (defun sb!c::%define-compiler-macro
 142                (name definition lambda-list doc debug-name)
 143              ,@(unless set-p
 144                  '((declare (ignore lambda-list debug-name))))
 145              ;; FIXME: warn about incompatible lambda list with
 146              ;; respect to parent function?
 147              (setf (sb!xc:compiler-macro-function name) definition)
 148              ;; FIXME: Add support for (SETF FDOCUMENTATION) when
 149              ;; object is a list and type is COMPILER-MACRO. (Until
 150              ;; then, we have to discard any compiler macro
 151              ;; documentation for (SETF FOO).)
 152              (unless (listp name)
 153                (setf (fdocumentation name 'compiler-macro) doc))
 154              ,(when set-p
 155                     `(case (widetag-of definition)
 156                       (#.sb!vm:closure-header-widetag
 157                        (setf (%simple-fun-arglist (%closure-fun definition))
 158                              lambda-list
 159                              (%simple-fun-name (%closure-fun definition))
 160                              debug-name))
 161                       (#.sb!vm:simple-fun-header-widetag
 162                        (setf (%simple-fun-arglist definition) lambda-list
 163                              (%simple-fun-name definition) debug-name))))
 164              name))))
 165   (progn
 166     (def (:load-toplevel :execute) #-sb-xc-host t #+sb-xc-host nil)
 167     #-sb-xc (def (:compile-toplevel) nil)))
 168 \f
 169 ;;;; CASE, TYPECASE, and friends
 170
 171 (eval-when (#-sb-xc :compile-toplevel :load-toplevel :execute)
 172
 173 (define-condition duplicate-case-key-warning (style-warning)
 174   ((key :initarg :key
 175         :reader case-warning-key)
 176    (case-kind :initarg :case-kind
 177               :reader case-warning-case-kind)
 178    (occurrences :initarg :occurrences
 179                 :type list
 180                 :reader duplicate-case-key-warning-occurrences))
 181   (:report
 182     (lambda (condition stream)
 183       (format stream
 184         "Duplicate key ~S in ~S form, ~
 185          occurring in~{~#[~; and~]~{ the ~:R clause:~%~<  ~S~:>~}~^,~}."
 186         (case-warning-key condition)
 187         (case-warning-case-kind condition)
 188         (duplicate-case-key-warning-occurrences condition)))))
 189
 190 ;;; CASE-BODY returns code for all the standard "case" macros. NAME is
 191 ;;; the macro name, and KEYFORM is the thing to case on. MULTI-P
 192 ;;; indicates whether a branch may fire off a list of keys; otherwise,
 193 ;;; a key that is a list is interpreted in some way as a single key.
 194 ;;; When MULTI-P, TEST is applied to the value of KEYFORM and each key
 195 ;;; for a given branch; otherwise, TEST is applied to the value of
 196 ;;; KEYFORM and the entire first element, instead of each part, of the
 197 ;;; case branch. When ERRORP, no OTHERWISE-CLAUSEs are recognized,
 198 ;;; and an ERROR form is generated where control falls off the end
 199 ;;; of the ordinary clauses. When PROCEEDP, it is an error to
 200 ;;; omit ERRORP, and the ERROR form generated is executed within a
 201 ;;; RESTART-CASE allowing KEYFORM to be set and retested.
 202 (defun case-body (name keyform cases multi-p test errorp proceedp needcasesp)
 203   (unless (or cases (not needcasesp))
 204     (warn "no clauses in ~S" name))
 205   (let ((keyform-value (gensym))
 206         (clauses ())
 207         (keys ())
 208         (keys-seen (make-hash-table :test #'eql)))
 209     (do* ((cases cases (cdr cases))
 210           (case (car cases) (car cases))
 211           (case-position 1 (1+ case-position)))
 212          ((null cases) nil)
 213       (flet ((check-clause (case-keys)
 214                (loop for k in case-keys
 215                      for existing = (gethash k keys-seen)
 216                      do (when existing
 217                           (let ((sb!c::*current-path*
 218                                  (when (boundp 'sb!c::*source-paths*)
 219                                    (or (sb!c::get-source-path case)
 220                                        sb!c::*current-path*))))
 221                             (warn 'duplicate-case-key-warning
 222                                   :key k
 223                                   :case-kind name
 224                                   :occurrences `(,existing (,case-position (,case)))))))
 225                (let ((record (list case-position (list case))))
 226                  (dolist (k case-keys)
 227                    (setf (gethash k keys-seen) record)))))
 228         (unless (list-of-length-at-least-p case 1)
 229           (error "~S -- bad clause in ~S" case name))
 230         (destructuring-bind (keyoid &rest forms) case
 231           (cond (;; an OTHERWISE-CLAUSE
 232                  ;;
 233                  ;; By the way... The old code here tried gave
 234                  ;; STYLE-WARNINGs for normal-clauses which looked as
 235                  ;; though they might've been intended to be
 236                  ;; otherwise-clauses. As Tony Martinez reported on
 237                  ;; sbcl-devel 2004-11-09 there are sometimes good
 238                  ;; reasons to write clauses like that; and as I noticed
 239                  ;; when trying to understand the old code so I could
 240                  ;; understand his patch, trying to guess which clauses
 241                  ;; don't have good reasons is fundamentally kind of a
 242                  ;; mess. SBCL does issue style warnings rather
 243                  ;; enthusiastically, and I have often justified that by
 244                  ;; arguing that we're doing that to detect issues which
 245                  ;; are tedious for programmers to detect for by
 246                  ;; proofreading (like small typoes in long symbol
 247                  ;; names, or duplicate function definitions in large
 248                  ;; files). This doesn't seem to be an issue like that,
 249                  ;; and I can't think of a comparably good justification
 250                  ;; for giving STYLE-WARNINGs for legal code here, so
 251                  ;; now we just hope the programmer knows what he's
 252                  ;; doing. -- WHN 2004-11-20
 253                  (and (not errorp) ; possible only in CASE or TYPECASE,
 254                                    ; not in [EC]CASE or [EC]TYPECASE
 255                       (memq keyoid '(t otherwise))
 256                       (null (cdr cases)))
 257                  (push `(t nil ,@forms) clauses))
 258                 ((and multi-p (listp keyoid))
 259                  (setf keys (append keyoid keys))
 260                  (check-clause keyoid)
 261                  (push `((or ,@(mapcar (lambda (key)
 262                                          `(,test ,keyform-value ',key))
 263                                        keyoid))
 264                          nil
 265                          ,@forms)
 266                        clauses))
 267                 (t
 268                  (push keyoid keys)
 269                  (check-clause (list keyoid))
 270                  (push `((,test ,keyform-value ',keyoid)
 271                          nil
 272                          ,@forms)
 273                        clauses))))))
 274     (case-body-aux name keyform keyform-value clauses keys errorp proceedp
 275                    `(,(if multi-p 'member 'or) ,@keys))))
 276
 277 ;;; CASE-BODY-AUX provides the expansion once CASE-BODY has groveled
 278 ;;; all the cases. Note: it is not necessary that the resulting code
 279 ;;; signal case-failure conditions, but that's what KMP's prototype
 280 ;;; code did. We call CASE-BODY-ERROR, because of how closures are
 281 ;;; compiled. RESTART-CASE has forms with closures that the compiler
 282 ;;; causes to be generated at the top of any function using the case
 283 ;;; macros, regardless of whether they are needed.
 284 ;;;
 285 ;;; The CASE-BODY-ERROR function is defined later, when the
 286 ;;; RESTART-CASE macro has been defined.
 287 (defun case-body-aux (name keyform keyform-value clauses keys
 288                       errorp proceedp expected-type)
 289   (if proceedp
 290       (let ((block (gensym))
 291             (again (gensym)))
 292         `(let ((,keyform-value ,keyform))
 293            (block ,block
 294              (tagbody
 295               ,again
 296               (return-from
 297                ,block
 298                (cond ,@(nreverse clauses)
 299                      (t
 300                       (setf ,keyform-value
 301                             (setf ,keyform
 302                                   (case-body-error
 303                                    ',name ',keyform ,keyform-value
 304                                    ',expected-type ',keys)))
 305                       (go ,again))))))))
 306       `(let ((,keyform-value ,keyform))
 307          (declare (ignorable ,keyform-value)) ; e.g. (CASE KEY (T))
 308          (cond
 309           ,@(nreverse clauses)
 310           ,@(if errorp
 311                 `((t (error 'case-failure
 312                             :name ',name
 313                             :datum ,keyform-value
 314                             :expected-type ',expected-type
 315                             :possibilities ',keys))))))))
 316 ) ; EVAL-WHEN
 317
 318 (defmacro-mundanely case (keyform &body cases)
 319   #!+sb-doc
 320   "CASE Keyform {({(Key*) | Key} Form*)}*
 321   Evaluates the Forms in the first clause with a Key EQL to the value of
 322   Keyform. If a singleton key is T then the clause is a default clause."
 323   (case-body 'case keyform cases t 'eql nil nil nil))
 324
 325 (defmacro-mundanely ccase (keyform &body cases)
 326   #!+sb-doc
 327   "CCASE Keyform {({(Key*) | Key} Form*)}*
 328   Evaluates the Forms in the first clause with a Key EQL to the value of
 329   Keyform. If none of the keys matches then a correctable error is
 330   signalled."
 331   (case-body 'ccase keyform cases t 'eql t t t))
 332
 333 (defmacro-mundanely ecase (keyform &body cases)
 334   #!+sb-doc
 335   "ECASE Keyform {({(Key*) | Key} Form*)}*
 336   Evaluates the Forms in the first clause with a Key EQL to the value of
 337   Keyform. If none of the keys matches then an error is signalled."
 338   (case-body 'ecase keyform cases t 'eql t nil t))
 339
 340 (defmacro-mundanely typecase (keyform &body cases)
 341   #!+sb-doc
 342   "TYPECASE Keyform {(Type Form*)}*
 343   Evaluates the Forms in the first clause for which TYPEP of Keyform and Type
 344   is true."
 345   (case-body 'typecase keyform cases nil 'typep nil nil nil))
 346
 347 (defmacro-mundanely ctypecase (keyform &body cases)
 348   #!+sb-doc
 349   "CTYPECASE Keyform {(Type Form*)}*
 350   Evaluates the Forms in the first clause for which TYPEP of Keyform and Type
 351   is true. If no form is satisfied then a correctable error is signalled."
 352   (case-body 'ctypecase keyform cases nil 'typep t t t))
 353
 354 (defmacro-mundanely etypecase (keyform &body cases)
 355   #!+sb-doc
 356   "ETYPECASE Keyform {(Type Form*)}*
 357   Evaluates the Forms in the first clause for which TYPEP of Keyform and Type
 358   is true. If no form is satisfied then an error is signalled."
 359   (case-body 'etypecase keyform cases nil 'typep t nil t))
 360 \f
 361 ;;;; WITH-FOO i/o-related macros
 362
 363 (defmacro-mundanely with-open-stream ((var stream) &body forms-decls)
 364   (multiple-value-bind (forms decls)
 365       (parse-body forms-decls :doc-string-allowed nil)
 366     (let ((abortp (gensym)))
 367       `(let ((,var ,stream)
 368              (,abortp t))
 369          ,@decls
 370          (unwind-protect
 371              (multiple-value-prog1
 372               (progn ,@forms)
 373               (setq ,abortp nil))
 374            (when ,var
 375              (close ,var :abort ,abortp)))))))
 376
 377 (defmacro-mundanely with-open-file ((stream filespec &rest options)
 378                                     &body body)
 379   `(with-open-stream (,stream (open ,filespec ,@options))
 380      ,@body))
 381
 382 (defmacro-mundanely with-input-from-string ((var string &key index start end)
 383                                             &body forms-decls)
 384   (multiple-value-bind (forms decls)
 385       (parse-body forms-decls :doc-string-allowed nil)
 386     ;; The ONCE-ONLY inhibits compiler note for unreachable code when
 387     ;; END is true.
 388     (once-only ((string string))
 389       `(let ((,var
 390               ,(cond ((null end)
 391                       `(make-string-input-stream ,string ,(or start 0)))
 392                      ((symbolp end)
 393                       `(if ,end
 394                            (make-string-input-stream ,string
 395                                                      ,(or start 0)
 396                                                      ,end)
 397                            (make-string-input-stream ,string
 398                                                      ,(or start 0))))
 399                      (t
 400                       `(make-string-input-stream ,string
 401                                                  ,(or start 0)
 402                                                  ,end)))))
 403          ,@decls
 404          (multiple-value-prog1
 405              (unwind-protect
 406                   (progn ,@forms)
 407                (close ,var))
 408            ,@(when index
 409                `((setf ,index (string-input-stream-current ,var)))))))))
 410
 411 (defmacro-mundanely with-output-to-string
 412     ((var &optional string &key (element-type ''character))
 413      &body forms-decls)
 414   (multiple-value-bind (forms decls)
 415       (parse-body forms-decls :doc-string-allowed nil)
 416     (if string
 417         (let ((element-type-var (gensym)))
 418           `(let ((,var (make-fill-pointer-output-stream ,string))
 419                  ;; ELEMENT-TYPE isn't currently used for anything
 420                  ;; (see FILL-POINTER-OUTPUT-STREAM FIXME in stream.lisp),
 421                  ;; but it still has to be evaluated for side-effects.
 422                  (,element-type-var ,element-type))
 423             (declare (ignore ,element-type-var))
 424             ,@decls
 425             (unwind-protect
 426                  (progn ,@forms)
 427               (close ,var))))
 428       `(let ((,var (make-string-output-stream :element-type ,element-type)))
 429          ,@decls
 430          (unwind-protect
 431              (progn ,@forms)
 432            (close ,var))
 433          (get-output-stream-string ,var)))))
 434 \f
 435 ;;;; miscellaneous macros
 436
 437 (defmacro-mundanely nth-value (n form)
 438   #!+sb-doc
 439   "Evaluate FORM and return the Nth value (zero based). This involves no
 440   consing when N is a trivial constant integer."
 441   ;; FIXME: The above is true, if slightly misleading.  The
 442   ;; MULTIPLE-VALUE-BIND idiom [ as opposed to MULTIPLE-VALUE-CALL
 443   ;; (LAMBDA (&REST VALUES) (NTH N VALUES)) ] does indeed not cons at
 444   ;; runtime.  However, for large N (say N = 200), COMPILE on such a
 445   ;; form will take longer than can be described as adequate, as the
 446   ;; optional dispatch mechanism for the M-V-B gets increasingly
 447   ;; hairy.
 448   (if (integerp n)
 449       (let ((dummy-list nil)
 450             (keeper (gensym "KEEPER-")))
 451         ;; We build DUMMY-LIST, a list of variables to bind to useless
 452         ;; values, then we explicitly IGNORE those bindings and return
 453         ;; KEEPER, the only thing we're really interested in right now.
 454         (dotimes (i n)
 455           (push (gensym "IGNORE-") dummy-list))
 456         `(multiple-value-bind (,@dummy-list ,keeper) ,form
 457            (declare (ignore ,@dummy-list))
 458            ,keeper))
 459       (once-only ((n n))
 460         `(case (the fixnum ,n)
 461            (0 (nth-value 0 ,form))
 462            (1 (nth-value 1 ,form))
 463            (2 (nth-value 2 ,form))
 464            (t (nth (the fixnum ,n) (multiple-value-list ,form)))))))
 465
 466 (defmacro-mundanely declaim (&rest specs)
 467   #!+sb-doc
 468   "DECLAIM Declaration*
 469   Do a declaration or declarations for the global environment."
 470   `(eval-when (:compile-toplevel :load-toplevel :execute)
 471      ,@(mapcar (lambda (spec) `(sb!xc:proclaim ',spec))
 472                specs)))
 473
 474 (defmacro-mundanely print-unreadable-object ((object stream &key type identity)
 475                                              &body body)
 476   "Output OBJECT to STREAM with \"#<\" prefix, \">\" suffix, optionally
 477   with object-type prefix and object-identity suffix, and executing the
 478   code in BODY to provide possible further output."
 479   `(%print-unreadable-object ,object ,stream ,type ,identity
 480                              ,(if body
 481                                   `(lambda () ,@body)
 482                                   nil)))
 483
 484 (defmacro-mundanely ignore-errors (&rest forms)
 485   #!+sb-doc
 486   "Execute FORMS handling ERROR conditions, returning the result of the last
 487   form, or (VALUES NIL the-ERROR-that-was-caught) if an ERROR was handled."
 488   `(handler-case (progn ,@forms)
 489      (error (condition) (values nil condition))))