fmakunbound fails for macros in SBCL 1.0.49

[Matt Kaufmann]

Quoting the CL Hyperspec on fmakunbound:

     Removes the function or macro definition, if any, of name in the global environment.

This worked in SBCL 1.0.45 but fails in 1.0.49. Here are logs for
64-bit linux.

; 1.0.45 (worked)

  * (defmacro foo (x) x)

  FOO
  * (fmakunbound 'foo)

  FOO
  * (macro-function 'foo)

  NIL
  *

; 1.0.49 (failed)

  * (defmacro foo (x) x)

  FOO
  * (fmakunbound 'foo)

  FOO
  * (macro-function 'foo)

  #<FUNCTION (MACRO-FUNCTION FOO) {AABD50D}>
  *

Other info requested for a bug report:

sloth:~> ~/bin/sbcl --version
SBCL 1.0.49
sloth:~> uname -a
Linux sloth 2.6.32-32-server #62-Ubuntu SMP Wed Apr 20 22:07:43 UTC 2011 x86_64 GNU/Linux
sloth:~> ~/bin/sbcl
This is SBCL 1.0.49, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses. See the CREDITS and COPYING files in the
distribution for more information.
* *features*

(:ANSI-CL :COMMON-LISP :SBCL :SB-DOC :SB-TEST :SB-LDB :SB-PACKAGE-LOCKS
 :SB-UNICODE :SB-EVAL :SB-SOURCE-LOCATIONS :IEEE-FLOATING-POINT :X86 :UNIX :ELF
 :LINUX :SB-THREAD :LARGEFILE :GENCGC :STACK-GROWS-DOWNWARD-NOT-UPWARD
 :C-STACK-IS-CONTROL-STACK :COMPARE-AND-SWAP-VOPS :UNWIND-TO-FRAME-AND-CALL-VOP
 :RAW-INSTANCE-INIT-VOPS :STACK-ALLOCATABLE-CLOSURES :STACK-ALLOCATABLE-VECTORS
 :STACK-ALLOCATABLE-LISTS :STACK-ALLOCATABLE-FIXED-OBJECTS :ALIEN-CALLBACKS
 :CYCLE-COUNTER :INLINE-CONSTANTS :MEMORY-BARRIER-VOPS :LINKAGE-TABLE
 :OS-PROVIDES-DLOPEN :OS-PROVIDES-DLADDR :OS-PROVIDES-PUTWC
 :OS-PROVIDES-BLKSIZE-T :OS-PROVIDES-SUSECONDS-T :OS-PROVIDES-GETPROTOBY-R
 :OS-PROVIDES-POLL)
*

[Nikodemus Siivola (nikodemus)]

commit 39c9c1d494f6d8a42c6f701ef1db4f688fe1b310
Author: Nikodemus Siivola <email address hidden>
Date: Fri Jun 10 23:30:52 2011 +0300

    FMAKUNBOUND removes the MACRO-FUNCTION as well

      Fixes lp#795705.

[Matt Kaufmann (kaufmann)]

Thank you for fixing this so quickly!

Is there a bit of code I can put into my sources that works around this
problem? (Otherwise, I'll need to disallow builds of ACL2 on SBCL
1.0.49.)

[Nikodemus Siivola (nikodemus)]

;;; Untested, but should work

(in-package :sb-c)

(without-package-locks

(defun undefine-fun-name (name)
  (when name
    (macrolet ((frob (type &optional val)
                 `(unless (eq (info :function ,type name) ,val)
                    (setf (info :function ,type name) ,val))))
      (frob :info)
      (frob :type (specifier-type 'function))
      (frob :where-from :assumed)
      (frob :inlinep)
      (frob :kind)
      (frob :macro-function)
      (frob :inline-expansion-designator)
      (frob :source-transform)
      (frob :structure-accessor)
      (frob :assumed-type)))
  (values))

)

[Matt Kaufmann (kaufmann)]

>> ;;; Untested, but should work

Thank you! That does the trick.