src/code/defmacro.lisp

   1 ;;;; DEFMACRO machinery
   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
  14 ;;; the guts of the DEFMACRO macro, pulled out into a separate
  15 ;;; function in order to make it easier to express the common
  16 ;;; bootstrap idiom
  17 ;;;   CL:DEFMACRO SB!XC:DEFMACRO
  18 ;;;   SB!XC:DEFMACRO CL:DEFMACRO
  19 (eval-when (:compile-toplevel :load-toplevel :execute)
  20   (defun %expander-for-defmacro (name lambda-list body)
  21     (unless (symbolp name)
  22       (error "The macro name ~S is not a symbol." name))
  23     (when (special-operator-p name)
  24       (error "The special operator ~S can't be redefined as a macro."
  25              name))
  26     (let ((whole (gensym "WHOLE-"))
  27           (environment (gensym "ENV-")))
  28       (multiple-value-bind (new-body local-decs doc)
  29           (parse-defmacro lambda-list whole body name 'defmacro
  30                           :environment environment)
  31         (let ((def `(lambda (,whole ,environment)
  32                       ,@local-decs
  33                       (block ,name
  34                         ,new-body)))
  35               ;; if we want to move over to list-style names
  36               ;; [e.g. (DEFMACRO FOO), maybe to support some XREF-like
  37               ;; functionality] here might be a good place to start.
  38               (debug-name (debug-namify "DEFMACRO ~S" name)))
  39           `(eval-when (:compile-toplevel :load-toplevel :execute)
  40              (sb!c::%defmacro ',name #',def ',lambda-list ,doc ,debug-name)))))))
  41
  42 (macrolet
  43     ((def (times set-p)
  44        `(eval-when (,@times)
  45           (defun sb!c::%defmacro (name definition lambda-list doc debug-name)
  46             ;; old note (ca. 1985, maybe:-): "Eventually %%DEFMACRO
  47             ;; should deal with clearing old compiler information for
  48             ;; the functional value."
  49             ,@(unless set-p
  50                 '((declare (ignore lambda-list debug-name))))
  51             (ecase (info :function :kind name)
  52               ((nil))
  53               (:function
  54                ;; (remhash name *free-funs*)
  55                (undefine-fun-name name)
  56                (style-warn
  57                 "~S is being redefined as a macro when it was ~
  58                  previously ~(~A~) to be a function."
  59                 name
  60                 (info :function :where-from name)))
  61               (:macro)
  62               (:special-form
  63                (error "The special form ~S can't be redefined as a macro."
  64                       name)))
  65             (clear-info :function :where-from name)
  66             ;; FIXME: It would be nice to warn about DEFMACRO of an
  67             ;; already-defined macro, but that's slightly hard to do
  68             ;; because in common usage DEFMACRO is defined at compile
  69             ;; time and then redefined at load time. We'd need to make a
  70             ;; distinction between the defined-at-compile-time state and
  71             ;; the defined-at-load-time state to make this work. (Trying
  72             ;; to warn about duplicate DEFTYPEs runs into the same
  73             ;; problem.)
  74             #+nil (when (sb!xc:macro-function name)
  75                     ;; Someday we could check for macro arguments
  76                     ;; being incompatibly redefined. Doing this right
  77                     ;; will involve finding the old macro lambda-list
  78                     ;; and comparing it with the new one.
  79                     (style-warn "redefining ~S in DEFMACRO" name))
  80             (setf (sb!xc:macro-function name) definition
  81                   (fdocumentation name 'function) doc)
  82             ,(when set-p
  83                    `(case (widetag-of definition)
  84                       (#.sb!vm:closure-header-widetag
  85                        (setf (%simple-fun-arglist (%closure-fun definition))
  86                              lambda-list
  87                              (%simple-fun-name (%closure-fun definition))
  88                              debug-name))
  89                       ((#.sb!vm:simple-fun-header-widetag
  90                         #.sb!vm:closure-fun-header-widetag)
  91                        (setf (%simple-fun-arglist definition) lambda-list
  92                              (%simple-fun-name definition) debug-name))))
  93             name))))
  94   (progn
  95     (def (:load-toplevel :execute) #-sb-xc-host t #+sb-xc-host nil)
  96     (def (:compile-toplevel) nil)))
  97
  98 ;;; Parse the definition and make an expander function. The actual
  99 ;;; definition is done by %DEFMACRO which we expand into. After the
 100 ;;; compiler has gotten the information it wants out of macro
 101 ;;; definition, it compiles a call to %DEFMACRO which happens at load
 102 ;;; time.
 103 (defmacro sb!xc:defmacro (name lambda-list &rest body)
 104   (%expander-for-defmacro name lambda-list body))
 105
 106 ;;; In the cross-compiler, we not only need to support the definition
 107 ;;; of target macros at cross-compiler-build-time (with SB!XC:DEFMACRO
 108 ;;; running in the cross-compilation host), we also need to support
 109 ;;; the definition of target macros at target compilation time (with
 110 ;;; CL:DEFMACRO processed by the cross-compiler)..
 111 #+sb-xc-host
 112 (sb!xc:defmacro defmacro (name lambda-list &rest body)
 113   (%expander-for-defmacro name lambda-list body))
 114
 115 ;;; DEFMACRO-MUNDANELY is like SB!XC:DEFMACRO, except that it doesn't
 116 ;;; have any EVAL-WHEN or IR1 magic associated with it, so it only
 117 ;;; takes effect in :LOAD-TOPLEVEL or :EXECUTE situations.
 118 (def!macro defmacro-mundanely (name lambda-list &body body)
 119
 120   ;; old way:
 121   ;;(let ((whole (gensym "WHOLE-"))
 122   ;;      (environment (gensym "ENVIRONMENT-")))
 123   ;;  (multiple-value-bind (new-body local-decs doc)
 124   ;;      (parse-defmacro lambda-list whole body name 'defmacro
 125   ;;                      :environment environment)
 126   ;;    `(progn
 127   ;;       (setf (sb!xc:macro-function ',name)
 128   ;;             (lambda (,whole ,environment)
 129   ;;                 ,@local-decs
 130   ;;                 (block ,name
 131   ;;                 ,new-body)))
 132   ;;       (setf (fdocumentation ',name 'macro)
 133   ;;             ,doc)
 134   ;;       ',name)))
 135
 136   `(let ()
 137      (sb!xc:defmacro ,name ,lambda-list ,@body)))