0.6.12.37;

[sbcl.git] / BUGS

REPORTING BUGS

Bugs can be reported on the help mailing list
  sbcl-help@lists.sourceforge.net
or on the development mailing list
  sbcl-devel@lists.sourceforge.net

Please include enough information in a bug report that someone reading
it can reproduce the problem, i.e. don't write
     Subject: apparent bug in PRINT-OBJECT (or *PRINT-LENGTH*?)
     PRINT-OBJECT doesn't seem to work with *PRINT-LENGTH*. Is this a bug?
but instead
     Subject: apparent bug in PRINT-OBJECT (or *PRINT-LENGTH*?)
     In sbcl-1.2.3 running under OpenBSD 4.5 on my Alpha box, when
     I compile and load the file
       (DEFSTRUCT (FOO (:PRINT-OBJECT (LAMBDA (X Y)
                                        (LET ((*PRINT-LENGTH* 4))
                                          (PRINT X Y)))))
         X Y)
     then at the command line type
       (MAKE-FOO)
     the program loops endlessly instead of printing the object.


NOTES:

There is also some information on bugs in the manual page and
in the TODO file. Eventually more such information may move here.

The gaps in the number sequence belong to old bug descriptions which
have gone away (typically because they were fixed, but sometimes for
other reasons, e.g. because they were moved elsewhere).


KNOWN BUGS OF NO SPECIAL CLASS:

2:
  DEFSTRUCT almost certainly should overwrite the old LAYOUT information
  instead of just punting when a contradictory structure definition
  is loaded. As it is, if you redefine DEFSTRUCTs in a way which 
  changes their layout, you probably have to rebuild your entire
  program, even if you know or guess enough about the internals of
  SBCL to wager that this (undefined in ANSI) operation would be safe.

3:
  ANSI specifies that a type mismatch in a structure slot
  initialization value should not cause a warning.
WORKAROUND:
  This one might not be fixed for a while because while we're big
  believers in ANSI compatibility and all, (1) there's no obvious
  simple way to do it (short of disabling all warnings for type
  mismatches everywhere), and (2) there's a good portable
  workaround. ANSI justifies this specification by saying 
    The restriction against issuing a warning for type mismatches
    between a slot-initform and the corresponding slot's :TYPE
    option is necessary because a slot-initform must be specified
    in order to specify slot options; in some cases, no suitable
    default may exist.
  In SBCL, as in CMU CL (or, for that matter, any compiler which
  really understands Common Lisp types) a suitable default does
  exist, in all cases, because the compiler understands the concept
  of functions which never return (i.e. has return type NIL, e.g.
  ERROR). Thus, as a portable workaround, you can use a call to
  some known-never-to-return function as the default. E.g.
    (DEFSTRUCT FOO
      (BAR (ERROR "missing :BAR argument")
           :TYPE SOME-TYPE-TOO-HAIRY-TO-CONSTRUCT-AN-INSTANCE-OF))
  or 
    (DECLAIM (FTYPE () NIL) MISSING-ARG) 
    (DEFUN REQUIRED-ARG () ; workaround for SBCL non-ANSI slot init typing
      (ERROR "missing required argument")) 
    (DEFSTRUCT FOO
      (BAR (REQUIRED-ARG) :TYPE TRICKY-TYPE-OF-SOME-SORT)
      (BLETCH (REQUIRED-ARG) :TYPE TRICKY-TYPE-OF-SOME-SORT)
      (N-REFS-SO-FAR 0 :TYPE (INTEGER 0)))
  Such code will compile without complaint and work correctly either
  on SBCL or on a completely compliant Common Lisp system.

6:
  bogus warnings about undefined functions for magic functions like
  SB!C::%%DEFUN and SB!C::%DEFCONSTANT when cross-compiling files
  like src/code/float.lisp. Fixing this will probably require
  straightening out enough bootstrap consistency issues that
  the cross-compiler can run with *TYPE-SYSTEM-INITIALIZED*.
  Instead, the cross-compiler runs in a slightly flaky state
  which is sane enough to compile SBCL itself, but which is
  also unstable in several ways, including its inability
  to really grok function declarations.

7:
  The "byte compiling top-level form:" output ought to be condensed.
  Perhaps any number of such consecutive lines ought to turn into a
  single "byte compiling top-level forms:" line.

10:
  The way that the compiler munges types with arguments together
  with types with no arguments (in e.g. TYPE-EXPAND) leads to
  weirdness visible to the user:
        (DEFTYPE FOO () 'FIXNUM)
        (TYPEP 11 'FOO) => T
        (TYPEP 11 '(FOO)) => T, which seems weird
        (TYPEP 11 'FIXNUM) => T
        (TYPEP 11 '(FIXNUM)) signals an error, as it should
  The situation is complicated by the presence of Common Lisp types
  like UNSIGNED-BYTE (which can either be used in list form or alone)
  so I'm not 100% sure that the behavior above is actually illegal.
  But I'm 90+% sure, and the following related behavior,
        (TYPEP 11 'AND) => T
  treating the bare symbol AND as equivalent to '(AND), is specifically
  forbidden (by the ANSI specification of the AND type).

11:
  It would be nice if the
        caught ERROR:
          (during macroexpansion)
  said what macroexpansion was at fault, e.g.
        caught ERROR:
          (during macroexpansion of IN-PACKAGE,
          during macroexpansion of DEFFOO)

15:
  (SUBTYPEP '(FUNCTION (T BOOLEAN) NIL)
            '(FUNCTION (FIXNUM FIXNUM) NIL)) => T, T
  (Also, when this is fixed, we can enable the code in PROCLAIM which 
  checks for incompatible FTYPE redeclarations.)

18:
  from DTC on the CMU CL mailing list 25 Feb 2000:
;;; Compiler fails when this file is compiled.
;;;
;;; Problem shows up in delete-block within ir1util.lisp. The assertion
;;; (assert (member (functional-kind lambda) '(:let :mv-let :assignment)))
;;; fails within bind node branch.
;;;
;;; Note that if c::*check-consistency* is enabled then an un-reached
;;; entry is also reported.
;;;
(defun foo (val)
  (declare (values nil))
  nil)
(defun bug (val)
  (multiple-value-call
      #'(lambda (res)
          (block nil
            (tagbody
             loop
               (when res
                 (return nil))
               (go loop))))
    (foo val))
  (catch 'ccc1
    (throw 'ccc1
      (block bbbb
        (tagbody

           (let ((ttt #'(lambda () (go cccc))))
             (declare (special ttt))
             (return-from bbbb nil))

         cccc
           (return-from bbbb nil))))))

19:
  (I *think* this is a bug. It certainly seems like strange behavior. But
  the ANSI spec is scary, dark, and deep..)
    (FORMAT NIL  "~,1G" 1.4) => "1.    "
    (FORMAT NIL "~3,1G" 1.4) => "1.    "

20:
  from Marco Antoniotti on cmucl-imp mailing list 1 Mar 2000:
        (defclass ccc () ())
        (setf (find-class 'ccc1) (find-class 'ccc))
        (defmethod zut ((c ccc1)) 123)
  DTC's recommended workaround from the mailing list 3 Mar 2000:
        (setf (pcl::find-class 'ccc1) (pcl::find-class 'ccc))

22:
  The ANSI spec, in section "22.3.5.2 Tilde Less-Than-Sign: Logical Block",
  says that an error is signalled if ~W, ~_, ~<...~:>, ~I, or ~:T is used
  inside "~<..~>" (without the colon modifier on the closing syntax).
  However, SBCL doesn't do this:
        * (FORMAT T "~<munge~wegnum~>" 12)
        munge12egnum
        NIL

23:
  When too many files are opened, OPEN will fail with an
  uninformative error message 
        error in function OPEN: error opening #P"/tmp/foo.lisp": NIL
  instead of saying that too many files are open.

26:
  reported by Sam Steingold on the cmucl-imp mailing list 12 May 2000:
    Also, there is another bug: `array-displacement' should return an
    array or nil as first value (as per ANSI CL), while CMUCL declares
    it as returning an array as first value always.
  (Actually, I think the old CMU CL version in SBCL never returns NIL,
  i.e. it's not just a declaration problem, but the definition doesn't
  behave ANSIly.)

27:
  Sometimes (SB-EXT:QUIT) fails with 
        Argh! maximum interrupt nesting depth (4096) exceeded, exiting
        Process inferior-lisp exited abnormally with code 1
  I haven't noticed a repeatable case of this yet.

29:
  some sort of bug in inlining and RETURN-FROM in sbcl-0.6.5: Compiling
    (DEFUN BAR? (X)
      (OR (NAR? X)
          (BLOCK USED-BY-SOME-Y?
            (FLET ((FROB (STK)
                     (DOLIST (Y STK)
                       (UNLESS (REJECTED? Y)
                         (RETURN-FROM USED-BY-SOME-Y? T)))))
              (DECLARE (INLINE FROB))
              (FROB (RSTK X))
              (FROB (MRSTK X)))
            NIL)))
  gives
   error in function SB-KERNEL:ASSERT-ERROR:
   The assertion (EQ (SB-C::CONTINUATION-KIND SB-C::CONT) :BLOCK-START) failed.
  This is still present in sbcl-0.6.8.

31:
  In some cases the compiler believes type declarations on array
  elements without checking them, e.g.
        (DECLAIM (OPTIMIZE (SAFETY 3) (SPEED 1) (SPACE 1)))
        (DEFSTRUCT FOO A B)
        (DEFUN BAR (X)
          (DECLARE (TYPE (SIMPLE-ARRAY CONS 1) X))
          (WHEN (CONSP (AREF X 0))
            (PRINT (AREF X 0))))
        (BAR (VECTOR (MAKE-FOO :A 11 :B 12)))
  prints
        #S(FOO :A 11 :B 12) 
  in SBCL 0.6.5 (and also in CMU CL 18b). This does not happen for
  all cases, e.g. the type assumption *is* checked if the array
  elements are declared to be of some structure type instead of CONS.

32:
  The printer doesn't report closures very well. This is true in 
  CMU CL 18b as well:
    (PRINT #'CLASS-NAME)
  gives
    #<Closure Over Function "DEFUN STRUCTURE-SLOT-ACCESSOR" {134D1A1}>
  It would be nice to make closures have a settable name slot,
  and make things like DEFSTRUCT and FLET, which create closures,
  set helpful values into this slot.

33:
  And as long as we're wishing, it would be awfully nice if INSPECT could
  also report on closures, telling about the values of the bound variables.

35:
  The compiler assumes that any time a function of declared FTYPE
  doesn't signal an error, its arguments were of the declared type.
  E.g. compiling and loading
    (DECLAIM (OPTIMIZE (SAFETY 3)))
    (DEFUN FACTORIAL (X) (GAMMA (1+ X)))
    (DECLAIM (FTYPE (FUNCTION (UNSIGNED-BYTE) FACTORIAL)))
    (DEFUN FOO (X)
      (COND ((> (FACTORIAL X) 1.0E6)
             (FORMAT T "too big~%"))
            ((INTEGERP X)
             (FORMAT T "exactly ~S~%" (FACTORIAL X)))
            (T
             (FORMAT T "approximately ~S~%" (FACTORIAL X)))))
  then executing
    (FOO 1.5)
  will cause the INTEGERP case to be selected, giving bogus output a la
    exactly 1.33..
  This violates the "declarations are assertions" principle.
  According to the ANSI spec, in the section "System Class FUNCTION",
  this is a case of "lying to the compiler", but the lying is done
  by the code which calls FACTORIAL with non-UNSIGNED-BYTE arguments,
  not by the unexpectedly general definition of FACTORIAL. In any case,
  "declarations are assertions" means that lying to the compiler should
  cause an error to be signalled, and should not cause a bogus
  result to be returned. Thus, the compiler should not assume
  that arbitrary functions check their argument types. (It might
  make sense to add another flag (CHECKED?) to DEFKNOWN to 
  identify functions which *do* check their argument types.)

38:
  DEFMETHOD doesn't check the syntax of &REST argument lists properly,
  accepting &REST even when it's not followed by an argument name:
        (DEFMETHOD FOO ((X T) &REST) NIL)

41:
  TYPEP of VALUES types is sometimes implemented very inefficiently, e.g. in 
        (DEFTYPE INDEXOID () '(INTEGER 0 1000))
        (DEFUN FOO (X)
          (DECLARE (TYPE INDEXOID X))
          (THE (VALUES INDEXOID)
            (VALUES X)))
  where the implementation of the type check in function FOO 
  includes a full call to %TYPEP. There are also some fundamental problems
  with the interpretation of VALUES types (inherited from CMU CL, and
  from the ANSI CL standard) as discussed on the cmucl-imp@cons.org
  mailing list, e.g. in Robert Maclachlan's post of 21 Jun 2000.

42:
  The definitions of SIGCONTEXT-FLOAT-REGISTER and
  %SET-SIGCONTEXT-FLOAT-REGISTER in x86-vm.lisp say they're not
  supported on FreeBSD because the floating point state is not saved,
  but at least as of FreeBSD 4.0, the floating point state *is* saved,
  so they could be supported after all. Very likely 
  SIGCONTEXT-FLOATING-POINT-MODES could now be supported, too.

43:
  (as discussed by Douglas Crosher on the cmucl-imp mailing list ca. 
  Aug. 10, 2000): CMUCL currently interprets 'member as '(member); same
  issue with 'union, 'and, 'or etc. So even though according to the
  ANSI spec, bare 'MEMBER, 'AND, and 'OR are not legal types, CMUCL
  (and now SBCL) interpret them as legal types.

44:
  ANSI specifies DEFINE-SYMBOL-MACRO, but it's not defined in SBCL.
  CMU CL added it ca. Aug 13, 2000, after some discussion on the mailing
  list, and it is probably possible to use substantially the same 
  patches to add it to SBCL.

45:
  a slew of floating-point-related errors reported by Peter Van Eynde
  on July 25, 2000:
        a: (fixed in sbcl-0.6.11.25)
        b: SBCL's value for LEAST-POSITIVE-SHORT-FLOAT is bogus, and 
           should probably be 1.4012985e-45. In SBCL,
           (/ LEAST-POSITIVE-SHORT-FLOAT 2) returns a number smaller
           than LEAST-POSITIVE-SHORT-FLOAT. Similar problems 
           exist for LEAST-NEGATIVE-SHORT-FLOAT, LEAST-POSITIVE-LONG-FLOAT,
           and LEAST-NEGATIVE-LONG-FLOAT.
        c: Many expressions generate floating infinity:
                (/ 1 0.0)
                (/ 1 0.0d0)
                (EXPT 10.0 1000)
                (EXPT 10.0d0 1000)
           PVE's regression tests want them to raise errors. SBCL
           generates the infinities instead, which may or may not be
           conforming behavior.
        d: (in section12.erg) various forms a la 
                (FLOAT 1 DOUBLE-FLOAT-EPSILON)
           don't give the right behavior.

46:
  type safety errors reported by Peter Van Eynde July 25, 2000:
        a: (COERCE (QUOTE (A B C)) (QUOTE (VECTOR * 4)))
           => #(A B C)
           In general lengths of array type specifications aren't
           checked by COERCE, so it fails when the spec is
           (VECTOR 4), (STRING 2), (SIMPLE-BIT-VECTOR 3), or whatever.
        b: CONCATENATE has the same problem of not checking the length
           of specified output array types. MAKE-SEQUENCE and MAP and
           MERGE also have the same problem.
        c: (COERCE 'AND 'FUNCTION) returns something related to
           (MACRO-FUNCTION 'AND), but ANSI says it should raise an error.
        d: ELT signals SIMPLE-ERROR if its index argument
           isn't a valid index for its sequence argument, but should 
           signal TYPE-ERROR instead.
        e: FILE-LENGTH is supposed to signal a type error when its
           argument is not a stream associated with a file, but doesn't.
        f: (FLOAT-RADIX 2/3) should signal an error instead of 
           returning 2.
        g: (LOAD "*.lsp") should signal FILE-ERROR.
        h: (MAKE-CONCATENATED-STREAM (MAKE-STRING-OUTPUT-STREAM))
           should signal TYPE-ERROR.
        i: MAKE-TWO-WAY-STREAM doesn't check that its arguments can
           be used for input and output as needed. It should fail with
           TYPE-ERROR when handed e.g. the results of
           MAKE-STRING-INPUT-STREAM or MAKE-STRING-OUTPUT-STREAM in
           the inappropriate positions, but doesn't.
        j: (PARSE-NAMESTRING (COERCE (LIST #\f #\o #\o (CODE-CHAR 0) #\4 #\8)
                            (QUOTE STRING)))
           should probably signal an error instead of making a pathname with
           a null byte in it.
        k: READ-BYTE is supposed to signal TYPE-ERROR when its argument is 
           not a binary input stream, but instead cheerfully reads from
           character streams, e.g. (MAKE-STRING-INPUT-STREAM "abc").

47:
  DEFCLASS bugs reported by Peter Van Eynde July 25, 2000:
        a: (DEFCLASS FOO () (A B A)) should signal a PROGRAM-ERROR, and
           doesn't.
        b: (DEFCLASS FOO () (A B A) (:DEFAULT-INITARGS X A X B)) should
           signal a PROGRAM-ERROR, and doesn't.
        c: (DEFCLASS FOO07 NIL ((A :ALLOCATION :CLASS :ALLOCATION :CLASS))),
           and other DEFCLASS forms with duplicate specifications in their
           slots, should signal a PROGRAM-ERROR, and doesn't.
        d: (DEFGENERIC IF (X)) should signal a PROGRAM-ERROR, but instead
           causes a COMPILER-ERROR.

48:
  SYMBOL-MACROLET bugs reported by Peter Van Eynde July 25, 2000:
        a: (SYMBOL-MACROLET ((T TRUE)) ..) should probably signal
           PROGRAM-ERROR, but SBCL accepts it instead.
        b: SYMBOL-MACROLET should refuse to bind something which is
           declared as a global variable, signalling PROGRAM-ERROR.
        c: SYMBOL-MACROLET should signal PROGRAM-ERROR if something
           it binds is declared SPECIAL inside.

49:
  LOOP bugs reported by Peter Van Eynde July 25, 2000:
        a: (LOOP WITH (A B) DO (PRINT 1)) is a syntax error according to
           the definition of WITH clauses given in the ANSI spec, but
           compiles and runs happily in SBCL.
        b: a messy one involving package iteration:
interpreted Form: (LET ((PACKAGE (MAKE-PACKAGE "LOOP-TEST"))) (INTERN "blah" PACKAGE) (LET ((BLAH2 (INTERN "blah2" PACKAGE))) (EXPORT BLAH2 PACKAGE)) (LIST (SORT (LOOP FOR SYM BEING EACH PRESENT-SYMBOL OF PACKAGE FOR SYM-NAME = (SYMBOL-NAME SYM) COLLECT SYM-NAME) (FUNCTION STRING<)) (SORT (LOOP FOR SYM BEING EACH EXTERNAL-SYMBOL OF PACKAGE FOR SYM-NAME = (SYMBOL-NAME SYM) COLLECT SYM-NAME) (FUNCTION STRING<))))
Should be: (("blah" "blah2") ("blah2"))
SBCL: (("blah") ("blah2"))
        * (LET ((X 1)) (LOOP FOR I BY (INCF X) FROM X TO 10 COLLECT I))
          doesn't work -- SBCL's LOOP says BY isn't allowed in a FOR clause.

50:
  type system errors reported by Peter Van Eynde July 25, 2000:
        a: (SUBTYPEP 'BIGNUM 'INTEGER) => NIL, NIL
           but should be (VALUES T T) instead.
        b: (SUBTYPEP 'EXTENDED-CHAR 'CHARACTER) => NIL, NIL
           but should be (VALUES T T) instead.
        c: (SUBTYPEP '(INTEGER (0) (0)) 'NIL) dies with nested errors.
        d: In general, the system doesn't like '(INTEGER (0) (0)) -- it
           blows up at the level of SPECIFIER-TYPE with
           "Lower bound (0) is greater than upper bound (0)." Probably
           SPECIFIER-TYPE should return NIL instead.
        e: (TYPEP 0 '(COMPLEX (EQL 0)) fails with
           "Component type for Complex is not numeric: (EQL 0)."
           This might be easy to fix; the type system already knows
           that (SUBTYPEP '(EQL 0) 'NUMBER) is true.
        f: The type system doesn't know about the condition system,
           so that e.g. (TYPEP 'SIMPLE-ERROR 'ERROR)=>NIL.
        g: The type system isn't all that smart about relationships
           between hairy types, as shown in the type.erg test results,
           e.g. (SUBTYPEP 'CONS '(NOT ATOM)) => NIL, NIL.

51:
  miscellaneous errors reported by Peter Van Eynde July 25, 2000:
        a: (PROGN
            (DEFGENERIC FOO02 (X))
            (DEFMETHOD FOO02 ((X NUMBER)) T)
            (LET ((M (FIND-METHOD (FUNCTION FOO02)
                                  NIL
                                  (LIST (FIND-CLASS (QUOTE NUMBER))))))
              (REMOVE-METHOD (FUNCTION FOO02) M)
              (DEFGENERIC FOO03 (X))
              (ADD-METHOD (FUNCTION FOO03) M)))
           should give an error, but SBCL allows it.
        b: READ should probably return READER-ERROR, not the bare 
           arithmetic error, when input a la "1/0" or "1e1000" causes
           an arithmetic error.

52:
  It has been reported (e.g. by Peter Van Eynde) that there are 
  several metaobject protocol "errors". (In order to fix them, we might
  need to document exactly what metaobject protocol specification
  we're following -- the current code is just inherited from PCL.)

53:
  another error from Peter Van Eynde 5 September 2000:
  (FORMAT NIL "~F" "FOO") should work, but instead reports an error.
  PVE submitted a patch to deal with this bug, but it exposes other
  comparably serious bugs, so I didn't apply it. It looks as though
  the FORMAT code needs a fair amount of rewriting in order to comply
  with the various details of the ANSI spec.

54:
  The implementation of #'+ returns its single argument without
  type checking, e.g. (+ "illegal") => "illegal".

55:
  In sbcl-0.6.7, there is no doc string for CL:PUSH, probably 
  because it's defined with the DEFMACRO-MUNDANELY macro and something
  is wrong with doc string setting in that macro.

56:
  Attempting to use COMPILE on something defined by DEFMACRO fails:
        (DEFMACRO FOO (X) (CONS X X))
        (COMPILE 'FOO)
Error in function C::GET-LAMBDA-TO-COMPILE:
   #<Closure Over Function "DEFUN (SETF MACRO-FUNCTION)" {480E21B1}> was defined in a non-null environment.

58:
  (SUBTYPEP '(AND ZILCH INTEGER) 'ZILCH) => NIL, NIL
  Note: I looked into fixing this in 0.6.11.15, but gave up. The
  problem seems to be that there are two relevant type methods for
  the subtypep operation, HAIRY :COMPLEX-SUBTYPEP-ARG2 and
  INTERSECTION :COMPLEX-SUBTYPEP-ARG1, and only the first is
  called. This could be fixed, but type dispatch is messy and
  confusing enough already, I don't want to complicate it further.
  Perhaps someday we can make CLOS cross-compiled (instead of compiled
  after bootstrapping) so that we don't need to have the type system
  available before CLOS, and then we can rewrite the type methods to
  CLOS methods, and then expressing the solutions to stuff like this
  should become much more straightforward. -- WHN 2001-03-14

59:
  CL:*DEFAULT-PATHNAME-DEFAULTS* doesn't behave as ANSI suggests (reflecting
  current working directory). And there's no supported way to update
  or query the current working directory (a la Unix "chdir" and "pwd"),
  which is functionality that ILISP needs (and currently gets with low-level
  hacks).
    When this is fixed, probably the more-or-less-parallel Unix-level
  hacks
        DEFAULT-DIRECTORY
        %SET-DEFAULT-DIRECTORY
        etc.?
  should go away. Also we need to figure out what's the proper way to 
  deal with the interaction of users assigning new values to
  *DEFAULT-PATHNAME-DEFAULTS* and cores being saved and restored.
  (Perhaps just make restoring from a save always overwrite the old
  value with the new Unix-level default directory?)

60:
  The debugger LIST-LOCATIONS command doesn't work properly.

61:
  Compiling and loading
    (DEFUN FAIL (X) (THROW 'FAIL-TAG X))
    (FAIL 12)
  then requesting a BACKTRACE at the debugger prompt gives no information
  about where in the user program the problem occurred.

62:
  The compiler is supposed to do type inference well enough that 
  the declaration in
    (TYPECASE X
      ((SIMPLE-ARRAY SINGLE-FLOAT)
       (LOCALLY
         (DECLARE (TYPE (SIMPLE-ARRAY SINGLE-FLOAT) X))
         ..))
      ..)
  is redundant. However, as reported by Juan Jose Garcia Ripoll for
  CMU CL, it sometimes doesn't. Adding declarations is a pretty good
  workaround for the problem for now, but can't be done by the TYPECASE
  macros themselves, since it's too hard for the macro to detect
  assignments to the variable within the clause. 
    Note: The compiler *is* smart enough to do the type inference in
  many cases. This case, derived from a couple of MACROEXPAND-1
  calls on Ripoll's original test case,
    (DEFUN NEGMAT (A)
      (DECLARE (OPTIMIZE SPEED (SAFETY 0)))
      (COND ((TYPEP A '(SIMPLE-ARRAY SINGLE-FLOAT)) NIL
             (LET ((LENGTH (ARRAY-TOTAL-SIZE A)))
               (LET ((I 0) (G2554 LENGTH))
                 (DECLARE (TYPE REAL G2554) (TYPE REAL I))
                 (TAGBODY
                  SB-LOOP::NEXT-LOOP
                  (WHEN (>= I G2554) (GO SB-LOOP::END-LOOP))
                  (SETF (ROW-MAJOR-AREF A I) (- (ROW-MAJOR-AREF A I)))
                  (GO SB-LOOP::NEXT-LOOP)
                  SB-LOOP::END-LOOP))))))
  demonstrates the problem; but the problem goes away if the TAGBODY
  and GO forms are removed (leaving the SETF in ordinary, non-looping
  code), or if the TAGBODY and GO forms are retained, but the 
  assigned value becomes 0.0 instead of (- (ROW-MAJOR-AREF A I)).

63:
  Paul Werkowski wrote on cmucl-imp@cons.org 2000-11-15
    I am looking into this problem that showed up on the cmucl-help
    list. It seems to me that the "implementation specific environment
    hacking functions" found in pcl/walker.lisp are completely messed
    up. The good thing is that they appear to be barely used within
    PCL and the munged environment object is passed to cmucl only
    in calls to macroexpand-1, which is probably why this case fails.
  SBCL uses essentially the same code, so if the environment hacking
  is screwed up, it affects us too.

64:
  Using the pretty-printer from the command prompt gives funny
  results, apparently because the pretty-printer doesn't know
  about user's command input, including the user's carriage return
  that the user, and therefore the pretty-printer thinks that
  the new output block should start indented 2 or more characters
  rightward of the correct location.

65:
  (probably related to bug #70)
  As reported by Carl Witty on submit@bugs.debian.org 1999-05-08,
  compiling this file
(in-package "CL-USER")
(defun equal-terms (termx termy)
  (labels
    ((alpha-equal-bound-term-lists (listx listy)
       (or (and (null listx) (null listy))
           (and listx listy
                (let ((bindings-x (bindings-of-bound-term (car listx)))
                      (bindings-y (bindings-of-bound-term (car listy))))
                  (if (and (null bindings-x) (null bindings-y))
                      (alpha-equal-terms (term-of-bound-term (car listx))
                                         (term-of-bound-term (car listy)))
                      (and (= (length bindings-x) (length bindings-y))
                           (prog2
                               (enter-binding-pairs (bindings-of-bound-term (car listx))
                                                    (bindings-of-bound-term (car listy)))
                               (alpha-equal-terms (term-of-bound-term (car listx))
                                                  (term-of-bound-term (car listy)))
                             (exit-binding-pairs (bindings-of-bound-term (car listx))
                                                 (bindings-of-bound-term (car listy)))))))
                (alpha-equal-bound-term-lists (cdr listx) (cdr listy)))))

     (alpha-equal-terms (termx termy)
       (if (and (variable-p termx)
                (variable-p termy))
           (equal-bindings (id-of-variable-term termx)
                           (id-of-variable-term termy))
           (and (equal-operators-p (operator-of-term termx) (operator-of-term termy))
                (alpha-equal-bound-term-lists (bound-terms-of-term termx)
                                              (bound-terms-of-term termy))))))

    (or (eq termx termy)
        (and termx termy
             (with-variable-invocation (alpha-equal-terms termx termy))))))
  causes an assertion failure
    The assertion (EQ (C::LAMBDA-TAIL-SET C::CALLER)
                      (C::LAMBDA-TAIL-SET (C::LAMBDA-HOME C::CALLEE))) failed.

  Bob Rogers reports (1999-07-28 on cmucl-imp@cons.org) a smaller test
  case with the same problem:
(defun parse-fssp-alignment ()
  ;; Given an FSSP alignment file named by the argument . . .
  (labels ((get-fssp-char ()
             (get-fssp-char))
           (read-fssp-char ()
             (get-fssp-char)))
    ;; Stub body, enough to tickle the bug.
    (list (read-fssp-char)
          (read-fssp-char))))

66:
  ANSI specifies that the RESULT-TYPE argument of CONCATENATE must be
  a subtype of SEQUENCE, but CONCATENATE doesn't check this properly:
    (CONCATENATE 'SIMPLE-ARRAY #(1 2) '(3)) => #(1 2 3)
  This also leads to funny behavior when derived type specifiers
  are used, as originally reported by Milan Zamazal for CMU CL (on the
  Debian bugs mailing list (?) 2000-02-27), then reported by Martin
  Atzmueller for SBCL (2000-10-01 on sbcl-devel@lists.sourceforge.net):
    (DEFTYPE FOO () 'SIMPLE-ARRAY)
    (CONCATENATE 'FOO #(1 2) '(3)) 
      => #<ARRAY-TYPE SIMPLE-ARRAY> is a bad type specifier for
           sequence functions.
  The derived type specifier FOO should act the same way as the 
  built-in type SIMPLE-ARRAY here, but it doesn't. That problem
  doesn't seem to exist for sequence types:
    (DEFTYPE BAR () 'SIMPLE-VECTOR)
    (CONCATENATE 'BAR #(1 2) '(3)) => #(1 2 3)

67:
  As reported by Winton Davies on a CMU CL mailing list 2000-01-10,
  and reported for SBCL by Martin Atzmueller 2000-10-20: (TRACE GETHASH)
  crashes SBCL. In general tracing anything which is used in the 
  implementation of TRACE is likely to have the same problem.

68: 
  As reported by Daniel Solaz on cmucl-help@cons.org 2000-11-23,
  SXHASH returns the same value for all non-STRUCTURE-OBJECT instances,
  notably including all PCL instances. There's a limit to how much
  SXHASH can do to return unique values for instances, but at least
  it should probably look at the class name, the way that it does
  for STRUCTURE-OBJECTs.

69:
  As reported by Martin Atzmueller on the sbcl-devel list 2000-11-22,
  > There remains one issue, that is a bug in SBCL:
  > According to my interpretation of the spec, the ":" and "@" modifiers
  > should appear _after_ the comma-seperated arguments.
  > Well, SBCL (and CMUCL for that matter) accept 
  > (ASSERT (STRING= (FORMAT NIL "~:8D" 1) "   1"))
  > where the correct way (IMHO) should be
  > (ASSERT (STRING= (FORMAT NIL "~8:D" 1) "   1"))
  Probably SBCL should stop accepting the "~:8D"-style format arguments,
  or at least issue a warning.

70:
  (probably related to bug #65)
  The compiler doesn't like &OPTIONAL arguments in LABELS and FLET
  forms. E.g.
    (DEFUN FIND-BEFORE (ITEM SEQUENCE &KEY (TEST #'EQL))
      (LABELS ((FIND-ITEM (OBJ SEQ TEST &OPTIONAL (VAL NIL))
                 (LET ((ITEM (FIRST SEQ)))
                   (COND ((NULL SEQ)
                          (VALUES NIL NIL))
                         ((FUNCALL TEST OBJ ITEM)
                          (VALUES VAL SEQ))
                         (T     
                          (FIND-ITEM OBJ (REST SEQ) TEST (NCONC VAL `(,ITEM))))))))
      (FIND-ITEM ITEM SEQUENCE TEST)))
  from David Young's bug report on cmucl-help@cons.org 30 Nov 2000
  causes sbcl-0.6.9 to fail with
    error in function SB-KERNEL:ASSERT-ERROR:
       The assertion (EQ (SB-C::LAMBDA-TAIL-SET SB-C::CALLER)
                         (SB-C::LAMBDA-TAIL-SET
                          (SB-C::LAMBDA-HOME SB-C::CALLEE))) failed.

71: 
  (DECLAIM (OPTIMIZE ..)) doesn't work. E.g. even after 
  (DECLAIM (OPTIMIZE (SPEED 3))), things are still optimized with
  the previous SPEED policy. This bug will probably get fixed in
  0.6.9.x in a general cleanup of optimization policy.

72:
  (DECLAIM (OPTIMIZE ..)) doesn't work properly inside LOCALLY forms.

74:
  As noted in the ANSI specification for COERCE, (COERCE 3 'COMPLEX)
  gives a result which isn't COMPLEX. The result type optimizer
  for COERCE doesn't know this, perhaps because it was written before
  ANSI threw this curveball: the optimizer thinks that COERCE always
  returns a result of the specified type. Thus while the interpreted
  function
     (DEFUN TRICKY (X) (TYPEP (COERCE X 'COMPLEX) 'COMPLEX))
  returns the correct result,
     (TRICKY 3) => NIL
  the compiled function
     (COMPILE 'TRICKY)
  does not:
     (TRICKY 3) => T

75:
  As reported by Martin Atzmueller on sbcl-devel 26 Dec 2000,
  ANSI says that WITH-OUTPUT-TO-STRING should have a keyword
  :ELEMENT-TYPE, but in sbcl-0.6.9 this is not defined for
  WITH-OUTPUT-TO-STRING.

78:
  ANSI says in one place that type declarations can be abbreviated even
  when the type name is not a symbol, e.g.
    (DECLAIM ((VECTOR T) *FOOVECTOR*))
  SBCL doesn't support this. But ANSI says in another place that this
  isn't allowed. So it's not clear this is a bug after all. (See the
  e-mail on cmucl-help@cons.org on 2001-01-16 and 2001-01-17 from WHN
  and Pierre Mai.)

79:
  as pointed out by Dan Barlow on sbcl-devel 2000-07-02:
  The PICK-TEMPORARY-FILE-NAME utility used by LOAD-FOREIGN uses
  an easily guessable temporary filename in a way which might open
  applications using LOAD-FOREIGN to hijacking by malicious users
  on the same machine. Incantations for doing this safely are
  floating around the net in various "how to write secure programs
  despite Unix" documents, and it would be good to (1) fix this in 
  LOAD-FOREIGN, and (2) hunt for any other code which uses temporary
  files and make it share the same new safe logic.

80:
  (fixed early Feb 2001 by MNA)

81:
  As reported by wbuss@TELDA.NET (Wolfhard Buss) on cmucl-help
  2001-02-14, 
    According to CLHS
         (loop with (a . b) of-type float = '(0.0 . 1.0)
           and (c . d) of-type float = '(2.0 . 3.0)
           return (list a b c d))
    should evaluate to (0.0 1.0 2.0 3.0). cmucl-18c disagrees and
    invokes the debugger: "B is not of type list".
  SBCL does the same thing.

82: 
  Functions are assigned names based on the context in which they're
  defined. This is less than ideal for the functions which are
  used to implement CLOS methods. E.g. the output of 
  (DESCRIBE 'PRINT-OBJECT) lists functions like 
        #<FUNCTION "DEF!STRUCT (TRACE-INFO (:MAKE-LOAD-FORM-FUN SB-KERNEL:JUST-DUMP-IT-NORMALLY) (:PRINT-OBJECT #))" {1020E49}> 
  and
        #<FUNCTION "MACROLET ((FORCE-DELAYED-DEF!METHODS NIL #))" {1242871}>
  It would be better if these functions' names always identified
  them as methods, and identified their generic functions and
  specializers.

83:
  RANDOM-INTEGER-EXTRA-BITS=10 may not be large enough for the RANDOM
  RNG to be high quality near RANDOM-FIXNUM-MAX; it looks as though
  the mean of the distribution can be systematically O(0.1%) wrong.
  Just increasing R-I-E-B is probably not a good solution, since
  it would decrease efficiency more than is probably necessary. Perhaps
  using some sort of accept/reject method would be better.

84:
  (SUBTYPEP '(SATISFIES SOME-UNDEFINED-FUN) NIL)=>NIL,T (should be NIL,NIL)

85:
  Internally the compiler sometimes evaluates
    (sb-kernel:type/= (specifier-type '*) (specifier-type t))
  (I stumbled across this when I added an
    (assert (not (eq type1 *wild-type*)))
  in the NAMED :SIMPLE-= type method.) '* isn't really a type, and
  in a type context should probably be translated to T, and so it's
  probably to ask whether it's equal to the T type and then (using the
  EQ type comparison in the NAMED :SIMPLE-= type method) return NIL.
  (I haven't tried to investigate this bug enough to guess whether
  there might be any user-level symptoms.)

90: 
  a latent cross-compilation/bootstrapping bug: The cross-compilation
  host's CL:CHAR-CODE-LIMIT is used in target code in readtable.lisp
  and possibly elsewhere. Instead, we should use the target system's
  CHAR-CODE-LIMIT. This will probably cause problems if we try to 
  bootstrap on a system which uses a different value of CHAR-CODE-LIMIT
  than SBCL does.

91:
  (subtypep '(or (integer -1 1)
                 unsigned-byte)
            '(or (rational -1 7)
                 unsigned-byte
                 (integer -1 1))) => NIL,T
  An analogous problem with SINGLE-FLOAT and REAL types was fixed in 
  sbcl-0.6.11.22, but some peculiarites of the RATIO type make it 
  awkward to generalize the fix to INTEGER and RATIONAL. It's not 
  clear what's the best fix. (See the "bug in type handling" discussion
  on cmucl-imp ca. 2001-03-22 and ca. 2001-02-12.)

93:
  In sbcl-0.6.11.26, (COMPILE 'IN-HOST-COMPILATION-MODE) in
  src/cold/shared.lisp doesn't correctly translate the
  interpreted function
    (defun in-host-compilation-mode (fn)
      (let ((*features* (cons :sb-xc-host *features*))
            ;; the CROSS-FLOAT-INFINITY-KLUDGE, as documented in
            ;; base-target-features.lisp-expr:
            (*shebang-features* (set-difference *shebang-features*
                                                '(:sb-propagate-float-type
                                                  :sb-propagate-fun-type))))
        (with-additional-nickname ("SB-XC" "SB!XC")
          (funcall fn))))
  No error is reported by the compiler, but when the function is executed,
  it causes an error
    TYPE-ERROR in SB-KERNEL::OBJECT-NOT-TYPE-ERROR-HANDLER:
      (:LINUX :X86 :IEEE-FLOATING-POINT :SB-CONSTRAIN-FLOAT-TYPE :SB-TEST
       :SB-INTERPRETER :SB-DOC :UNIX ...) is not of type SYMBOL.

94a: 
  Inconsistencies between derived and declared VALUES return types for
  DEFUN aren't checked very well. E.g. the logic which successfully
  catches problems like
    (declaim (ftype (function (fixnum) float) foo))
    (defun foo (x)
      (declare (type integer x))
      (values x)) ; wrong return type, detected, gives warning, good!
  fails to catch
    (declaim (ftype (function (t) (values t t)) bar))
    (defun bar (x)
      (values x)) ; wrong number of return values, no warning, bad!
  The cause of this is seems to be that (1) the internal function 
  VALUES-TYPES-EQUAL-OR-INTERSECT used to make the check handles its
  arguments symmetrically, and (2) when the type checking code was
  written back when when SBCL's code was still CMU CL, the intent
  was that this case
    (declaim (ftype (function (t) t) bar))
    (defun bar (x)
      (values x x)) ; wrong number of return values; should give warning?
  not be warned for, because a two-valued return value is considered
  to be compatible with callers who expects a single value to be
  returned. That intent is probably not appropriate for modern ANSI
  Common Lisp, but fixing this might be complicated because of other
  divergences between auld-style and new-style handling of
  multiple-VALUES types. (Some issues related to this were discussed
  on cmucl-imp at some length sometime in 2000.)

95:
  The facility for dumping a running Lisp image to disk gets confused
  when run without the PURIFY option, and creates an unnecessarily large
  core file (apparently representing memory usage up to the previous
  high-water mark). Moreover, when the file is loaded, it confuses the
  GC, so that thereafter memory usage can never be reduced below that
  level.

96:
  The TRACE facility can't be used on some kinds of functions.
  (Basically, the breakpoint facility was incompletely implemented
  in the X86 port of CMU CL, and hasn't been fixed in SBCL.)

98:
  In sbcl-0.6.11.41 (and in all earlier SBCL, and in CMU
  CL), out-of-line structure slot setters are horribly inefficient
  whenever the type of the slot is declared, because out-of-line
  structure slot setters are implemented as closures to save space,
  so the compiler doesn't compile the type test into code, but
  instead just saves the type in a lexical closure and interprets it
  at runtime.
    A proper solution involves deciding whether it's really worth
  saving space by implementing structure slot accessors as closures.
  (If it's not worth it, the problem vanishes automatically. If it
  is worth it, there are hacks we could use to force type tests to
  be compiled anyway, and even shared. E.g. we could implement
  an EQUAL hash table mapping from types to compiled type tests, 
  and save the appropriate compiled type test as part of each lexical
  closure; or we could make the lexical closures be placeholders
  which overwrite their old definition as a lexical closure with
  a new compiled definition the first time that they're called.)
    As a workaround for the problem, #'(SETF FOO) expressions can
  be replaced with (EFFICIENT-SETF-FUNCTION FOO), where
(defmacro efficient-setf-function (place-function-name)
  (or #+sbcl (and (sb-impl::info :function :accessor-for place-function-name)
                  ;; a workaround for the problem, encouraging the
                  ;; inline expansion of the structure accessor, so
                  ;; that the compiler can optimize its type test
                  (let ((new-value (gensym "NEW-VALUE-"))
                        (structure-value (gensym "STRUCTURE-VALUE-")))
                    `(lambda (,new-value ,structure-value)
                       (setf (,place-function-name ,structure-value)
                             ,new-value))))
      ;; no problem, can just use the ordinary expansion
      `(function (setf ,place-function-name))))

99:
  DESCRIBE interacts poorly with *PRINT-CIRCLE*, e.g. the output from 
    (let ((*print-circle* t)) (describe (make-hash-table)))
  is weird,
    #<HASH-TABLE :TEST EQL :COUNT 0 {90BBFC5}> is an . (EQL)
    Its SIZE is 16.
    Its REHASH-SIZE is 1.5. Its REHASH-THRESHOLD is . (1.0)
    It holds 0 key/value pairs.
  where the ". (EQL)" and ". (1.0)" substrings are screwups.
  (This is likely a pretty-printer problem which happens to
  be exercised by DESCRIBE, not actually a DESCRIBE problem.)

100:
  There's apparently a bug in CEILING optimization which caused 
  Douglas Crosher to patch the CMU CL version. Martin Atzmueller
  applied the patches to SBCL and they didn't seem to cause problems
  (as reported sbcl-devel 2001-05-04). However, since the patches
  modify nontrivial code which was apparently written incorrectly
  the first time around, until regression tests are written I'm not 
  comfortable merging the patches in the CVS version of SBCL.

101:
  The error message for calls to structure accessors with the
  wrong number of arguments is confusing and of the wrong
  condition class (TYPE-ERROR instead of PROGRAM-ERROR):
    * (defstruct foo x y)
    * (foo-x)
    debugger invoked on condition of type SIMPLE-TYPE-ERROR:
    Structure for accessor FOO-X is not a FOO:
    301988783

102:
  As reported by Arthur Lemmens sbcl-devel 2001-05-05, ANSI
  requires that SYMBOL-MACROLET refuse to rebind special variables,
  but SBCL doesn't do this. (Also as reported by AL in the same
  message, SBCL depended on this nonconforming behavior to build
  itself, because of the way that **CURRENT-SEGMENT** was implemented.
  As of sbcl-0.6.12.x, this dependence on the nonconforming behavior
  has been fixed, but the nonconforming behavior remains.)

103:
  As reported by Arthur Lemmens sbcl-devel 2001-05-05, ANSI's
  definition of (LOOP .. DO ..) requires that the terms following
  DO all be compound forms. SBCL's implementation of LOOP allows
  non-compound forms (like the bare symbol COUNT, in his example)
  here.

104:
  (DESCRIBE 'SB-ALIEN:DEF-ALIEN-TYPE) reports the macro argument list
  incorrectly:
        DEF-ALIEN-TYPE is
          an external symbol
          in #<PACKAGE "SB-ALIEN">.
        Macro-function: #<FUNCTION "DEF!MACRO DEF-ALIEN-TYPE" {19F4A39}>
          Macro arguments:  (#:whole-470 #:environment-471)
          On Sat, May 26, 2001 09:45:57 AM CDT it was compiled from:
          /usr/stuff/sbcl/src/code/host-alieneval.lisp
            Created: Monday, March 12, 2001 07:47:43 AM CST

105:
  (DESCRIBE 'STREAM-READ-BYTE)

106:
  (reported by Eric Marsden on cmucl-imp 2001-06-15)
  Executing 
    (TYPEP 0 '(COMPLEX (EQL 0)))
  signals an error in sbcl-0.6.12.34, 
    The component type for COMPLEX is not numeric: (EQL 0)
  This is funny since sbcl-0.6.12.34 knows
    (SUBTYPEP '(EQL 0) 'NUMBER) => T

107:
  (reported as a CMU CL bug by Erik Naggum on comp.lang.lisp
  2001-06-11:)
    * (write #*101 :radix t :base 36)
    #*#36r1#36r0#36r1
    #*101
    * 
  
108:
  (TIME (ROOM T)) reports more than 200 Mbytes consed even for
  a clean, just-started SBCL system. And it seems to be right:
  (ROOM T) can bring a small computer to its knees for a *long*
  time trying to GC afterwards. Surely there's some more economical
  way to implement (ROOM T).

KNOWN BUGS RELATED TO THE IR1 INTERPRETER

(Note: At some point, the pure interpreter (actually a semi-pure
interpreter aka "the IR1 interpreter") will probably go away, replaced
by constructs like
  (DEFUN EVAL (X) (FUNCALL (COMPILE NIL (LAMBDA ..)))))
and at that time these bugs should either go away automatically or
become more tractable to fix. Until then, they'll probably remain,
since some of them aren't considered urgent, and the rest are too hard
to fix as long as so many special cases remain. After the IR1
interpreter goes away is also the preferred time to start
systematically exterminating cases where debugging functionality
(backtrace, breakpoint, etc.) breaks down, since getting rid of the
IR1 interpreter will reduce the number of special cases we need to
support.)

IR1-1:
  The FUNCTION special operator doesn't check properly whether its
  argument is a function name. E.g. (FUNCTION (X Y)) returns a value
  instead of failing with an error. (Later attempting to funcall the
  value does cause an error.) 

IR1-2:
  COMPILED-FUNCTION-P bogusly reports T for interpreted functions:
        * (DEFUN FOO (X) (- 12 X))
        FOO
        * (COMPILED-FUNCTION-P #'FOO)
        T

IR1-3:
  Executing 
    (DEFVAR *SUPPRESS-P* T)
    (EVAL '(UNLESS *SUPPRESS-P*
             (EVAL-WHEN (:COMPILE-TOPLEVEL :LOAD-TOPLEVEL :EXECUTE)
               (FORMAT T "surprise!"))))
  prints "surprise!". Probably the entire EVAL-WHEN mechanism ought to be
  rewritten from scratch to conform to the ANSI definition, abandoning
  the *ALREADY-EVALED-THIS* hack which is used in sbcl-0.6.8.9 (and
  in the original CMU CL source, too). This should be easier to do --
  though still nontrivial -- once the various IR1 interpreter special
  cases are gone.

IR1-3a:
  EVAL-WHEN's idea of what's a toplevel form is even more screwed up 
  than the example in IR1-3 would suggest, since COMPILE-FILE and
  COMPILE both print both "right now!" messages when compiling the
  following code,
    (LAMBDA (X)
      (COND (X
             (EVAL-WHEN (:COMPILE-TOPLEVEL :LOAD-TOPLEVEL :EXECUTE)
               (PRINT "yes! right now!"))
             "yes!")
            (T
             (EVAL-WHEN (:COMPILE-TOPLEVEL :LOAD-TOPLEVEL :EXECUTE)
               (PRINT "no! right now!"))
             "no!")))
  and while EVAL doesn't print the "right now!" messages, the first
  FUNCALL on the value returned by EVAL causes both of them to be printed.

IR1-4:
  The system accepts DECLAIM in most places where DECLARE would be 
  accepted, without even issuing a warning. ANSI allows this, but since
  it's fairly easy to mistype DECLAIM instead of DECLARE, and the
  meaning is rather different, and it's unlikely that the user
  has a good reason for doing DECLAIM not at top level, it would be 
  good to issue a STYLE-WARNING when this happens. A possible
  fix would be to issue STYLE-WARNINGs for DECLAIMs not at top level,
  or perhaps to issue STYLE-WARNINGs for any EVAL-WHEN not at top level.
  [This is considered an IR1-interpreter-related bug because until
  EVAL-WHEN is rewritten, which won't happen until after the IR1
  interpreter is gone, the system's notion of what's a top-level form
  and what's not will remain too confused to fix this problem.]