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 (#-sb-xc :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 we are building the cross-compiler, we could be in a host
  24     ;; lisp which implements CL macros (e.g. CL:AND) as special
  25     ;; operators (while still providing a macroexpansion for
  26     ;; compliance): therefore can't use the host's SPECIAL-OPERATOR-P
  27     ;; as a discriminator, but that's OK because the set of forms the
  28     ;; cross-compiler compiles is tightly controlled.  -- CSR,
  29     ;; 2003-04-20
  30     #-sb-xc-host
  31     (when (special-operator-p name)
  32       (error "The special operator ~S can't be redefined as a macro."
  33              name))
  34     (with-unique-names (whole environment)
  35       (multiple-value-bind (new-body local-decs doc)
  36           (parse-defmacro lambda-list whole body name 'defmacro
  37                           :environment environment)
  38         (let ((def `(lambda (,whole ,environment)
  39                       ,@local-decs
  40                       ,new-body))
  41               ;; If we want to move over to list-style names
  42               ;; [e.g. (DEFMACRO FOO), maybe to support some XREF-like
  43               ;; functionality] here might be a good place to start.
  44               (debug-name (sb!c::debug-name 'macro-function name)))
  45           `(eval-when (:compile-toplevel :load-toplevel :execute)
  46              (sb!c::%defmacro ',name #',def ',lambda-list
  47                               ,doc ',debug-name)))))))
  48
  49 (macrolet
  50     ((def (times set-p)
  51        `(eval-when (,@times)
  52           (defun sb!c::%defmacro (name definition lambda-list doc debug-name)
  53             ;; old note (ca. 1985, maybe:-): "Eventually %%DEFMACRO
  54             ;; should deal with clearing old compiler information for
  55             ;; the functional value."
  56             ,@(unless set-p
  57                 '((declare (ignore lambda-list debug-name))))
  58             (ecase (info :function :kind name)
  59               ((nil))
  60               (:function
  61                ;; (remhash name *free-funs*)
  62                (undefine-fun-name name)
  63                (style-warn
  64                 "~S is being redefined as a macro when it was ~
  65                  previously ~(~A~) to be a function."
  66                 name
  67                 (info :function :where-from name)))
  68               (:macro)
  69               (:special-form
  70                (error "The special form ~S can't be redefined as a macro."
  71                       name)))
  72             (clear-info :function :where-from name)
  73             ;; FIXME: It would be nice to warn about DEFMACRO of an
  74             ;; already-defined macro, but that's slightly hard to do
  75             ;; because in common usage DEFMACRO is defined at compile
  76             ;; time and then redefined at load time. We'd need to make a
  77             ;; distinction between the defined-at-compile-time state and
  78             ;; the defined-at-load-time state to make this work. (Trying
  79             ;; to warn about duplicate DEFTYPEs runs into the same
  80             ;; problem.)
  81             #+nil (when (sb!xc:macro-function name)
  82                     ;; Someday we could check for macro arguments
  83                     ;; being incompatibly redefined. Doing this right
  84                     ;; will involve finding the old macro lambda-list
  85                     ;; and comparing it with the new one.
  86                     (style-warn "redefining ~S in DEFMACRO" name))
  87             (setf (sb!xc:macro-function name) definition
  88                   (fdocumentation name 'function) doc)
  89             ,(when set-p
  90                    `(case (widetag-of definition)
  91                       (#.sb!vm:closure-header-widetag
  92                        (setf (%simple-fun-arglist (%closure-fun definition))
  93                              lambda-list
  94                              (%simple-fun-name (%closure-fun definition))
  95                              debug-name))
  96                       (#.sb!vm:simple-fun-header-widetag
  97                        (setf (%simple-fun-arglist definition) lambda-list
  98                              (%simple-fun-name definition) debug-name))))
  99             name))))
 100   (progn
 101     (def (:load-toplevel :execute) #-sb-xc-host t #+sb-xc-host nil)
 102     (def (#-sb-xc :compile-toplevel) nil)))
 103
 104 ;;; Parse the definition and make an expander function. The actual
 105 ;;; definition is done by %DEFMACRO which we expand into. After the
 106 ;;; compiler has gotten the information it wants out of macro
 107 ;;; definition, it compiles a call to %DEFMACRO which happens at load
 108 ;;; time.
 109 (defmacro sb!xc:defmacro (name lambda-list &rest body)
 110   (%expander-for-defmacro name lambda-list body))
 111
 112 ;;; In the cross-compiler, we not only need to support the definition
 113 ;;; of target macros at cross-compiler-build-time (with SB!XC:DEFMACRO
 114 ;;; running in the cross-compilation host), we also need to support
 115 ;;; the definition of target macros at target compilation time (with
 116 ;;; CL:DEFMACRO processed by the cross-compiler)..
 117 #+sb-xc-host
 118 (sb!xc:defmacro defmacro (name lambda-list &rest body)
 119   (%expander-for-defmacro name lambda-list body))
 120
 121 ;;; DEFMACRO-MUNDANELY is like SB!XC:DEFMACRO, except that it doesn't
 122 ;;; have any EVAL-WHEN or IR1 magic associated with it, so it only
 123 ;;; takes effect in :LOAD-TOPLEVEL or :EXECUTE situations.
 124 (def!macro defmacro-mundanely (name lambda-list &body body)
 125
 126   ;; old way:
 127   ;;(let ((whole (gensym "WHOLE-"))
 128   ;;      (environment (gensym "ENVIRONMENT-")))
 129   ;;  (multiple-value-bind (new-body local-decs doc)
 130   ;;      (parse-defmacro lambda-list whole body name 'defmacro
 131   ;;                      :environment environment)
 132   ;;    `(progn
 133   ;;       (setf (sb!xc:macro-function ',name)
 134   ;;             (lambda (,whole ,environment)
 135   ;;                 ,@local-decs
 136   ;;                 (block ,name
 137   ;;                 ,new-body)))
 138   ;;       (setf (fdocumentation ',name 'macro)
 139   ;;             ,doc)
 140   ;;       ',name)))
 141
 142   `(let ()
 143      (sb!xc:defmacro ,name ,lambda-list ,@body)))