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Bugs can be reported on the help mailing list
or on the development mailing list
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
(PRINT X Y)))))
X Y)
then at the command line type
the program loops endlessly instead of printing the object.
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).
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: "type checking of structure slots"
ANSI specifies that a type mismatch in a structure slot
initialization value should not cause a warning.
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, and (3) by their own reasoning, it looks as though
ANSI may have gotten it wrong. 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.
However, 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).
Thus, as a portable workaround, you can use a call to some
known-never-to-return function as the default. E.g.
(BAR (ERROR "missing :BAR argument")
(DEFUN REQUIRED-ARG () ; workaround for SBCL non-ANSI slot init typing
(ERROR "missing required argument"))
Such code should compile without complaint and work correctly either
on SBCL or on any other completely compliant Common Lisp system.
b: &AUX argument in a boa-constructor without a default value means
"do not initilize this slot" and does not cause type error. But
an error may be signalled at read time and it would be good if
SBCL did it.
d: (fixed in
The "compiling top-level form:" output ought to be condensed.
Perhaps any number of such consecutive lines ought to turn into a
single "compiling top-level forms:" line.
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)
(I *think* this is a bug. It certainly seems like strange behavior. But
the ANSI spec is scary, dark, and deep.. -- WHN)
(FORMAT NIL "~,1G" 1.4) => "1. "
(FORMAT NIL "~3,1G" 1.4) => "1. "
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.
The printer doesn't report closures very well. This is true in
CMU CL 18b as well:
#<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.
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.
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
(COND ((> (FACTORIAL X) 1.0E6)
(FORMAT T "too big~%"))
(FORMAT T "exactly ~S~%" (FACTORIAL X)))
(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 2.5
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.)
(Also, verify that the compiler handles declared function
return types as assertions.)
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.
a slew of floating-point-related errors reported by Peter Van Eynde
on July 25, 2000:
c: Many expressions generate floating infinity on x86/Linux:
(/ 1 0.0)
(/ 1 0.0d0)
(EXPT 10.0 1000)
(EXPT 10.0d0 1000)
PVE's regression tests want them to raise errors. sbcl-
on x86/Linux generates the infinities instead. That might or
might not be conforming behavior, but it's also inconsistent,
which is almost certainly wrong. (Inconsistency: (/ 1 0.0)
should give the same result as (/ 1.0 0.0), but instead (/ 1 0.0)
generates SINGLE-FLOAT-POSITIVE-INFINITY and (/ 1.0 0.0)
signals an error.
d: (in section12.erg) various forms a la
don't give the right behavior.
The debugger LIST-LOCATIONS command doesn't work properly.
(How should it work properly?)
Compiling and loading
(FAIL 12)
then requesting a BACKTRACE at the debugger prompt gives no information
about where in the user program the problem occurred.
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.
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.
ANSI says in one place that type declarations can be abbreviated even
when the type name is not a symbol, e.g.
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 on 2001-01-16 and 2001-01-17 from WHN
and Pierre Mai.)
as pointed out by Dan Barlow on sbcl-devel 2000-07-02:
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.
(partially alleviated in sbcl- by a fix by Matthew Danish to
make the temporary filename less easily guessable)
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.
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 wrong 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.)
In fact, the type system is likely to depend on this inequality not
holding... * is not equivalent to T in many cases, such as
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
(As of it's likely that the latter half of this bug is fixed.
The interaction between gencgc and the variables used by
save-lisp-and-die is still nonoptimal, though, so no respite from
big core files yet)
In sbcl- (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.
To exercise the problem, compile and load
(cl:in-package :cl-user)
(defstruct foo
(bar (error "missing") :type bar))
(defvar *foo*)
(defun wastrel1 (x)
(loop (setf (foo-bar *foo*) x)))
(defstruct bar)
(defvar *bar* (make-bar))
(defvar *foo* (make-foo :bar *bar*))
(defvar *setf-foo-bar* #'(setf foo-bar))
(defun wastrel2 (x)
(loop (funcall *setf-foo-bar* x *foo*)))
then run (WASTREL1 *BAR*) or (WASTREL2 *BAR*), hit Ctrl-C, and
use BACKTRACE, to see it's spending all essentially all its time
in %TYPEP and VALUES-SPECIFIER-TYPE and so forth.
One possible solution would be simply to give up on
representing structure slot accessors as functions, and represent
them as macroexpansions instead. This can be inconvenient for users,
but it's not clear that it's worse than trying to help by expanding
into a horribly inefficient implementation.
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-int: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)
;; no problem, can just use the ordinary expansion
`(function (setf ,place-function-name))))
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.
(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).
Daniel Barlow doesn't know what fixed this, but observes that it
doesn't seem to be the case in any more. Instead, (ROOM T)
in a fresh SBCL causes
debugger invoked on a SB-INT:BUG in thread 5911:
unless a GC has happened beforehand.
When the compiler inline expands functions, it may be that different
kinds of return values are generated from different code branches.
E.g. an inline expansion of POSITION generates integer results
from one branch, and NIL results from another. When that inline
expansion is used in a context where only one of those results
is acceptable, e.g.
(defun foo (x)
(aref *a1* (position x *a2*)))
and the compiler can't prove that the unacceptable branch is
never taken, then bogus type mismatch warnings can be generated.
If you need to suppress the type mismatch warnings, you can
suppress the inline expansion,
(defun foo (x)
#+sbcl (declare (notinline position)) ; to suppress bug 117 bogowarnings
(aref *a1* (position x *a2*)))
or, sometimes, suppress them by declaring the result to be of an
appropriate type,
(defun foo (x)
(aref *a1* (the integer (position x *a2*))))
This is not a new compiler problem in 0.7.0, but the new compiler
transforms for FIND, POSITION, FIND-IF, and POSITION-IF make it
more conspicuous. If you don't need performance from these functions,
and the bogus warnings are a nuisance for you, you can return to
your pre-0.7.0 state of grace with
#+sbcl (declaim (notinline find position find-if position-if)) ; bug 117..
(see also bug 279)
as reported by Eric Marsden on 2001-08-14:
when of course it should be NIL. (He says it only fails for X86,
not SPARC; dunno about Alpha.)
Also, "the same problem exists for LONG-FLOAT-EPSILON,
for the -negative- the + is replaced by a - in the test)."
Raymond Toy comments that this is tricky on the X86 since its FPU
uses 80-bit precision internally.
As of version 0.pre7.14, SBCL's implementation of MACROLET makes
the entire lexical environment at the point of MACROLET available
in the bodies of the macroexpander functions. In particular, it
allows the function bodies (which run at compile time) to try to
access lexical variables (which are only defined at runtime).
It doesn't even issue a warning, which is bad.
The SBCL behavior arguably conforms to the ANSI spec (since the
spec says that the behavior is undefined, ergo anything conforms).
However, it would be better to issue a compile-time error.
Unfortunately I (WHN) don't see any simple way to detect this
condition in order to issue such an error, so for the meantime
SBCL just does this weird broken "conforming" thing.
The ANSI standard says, in the definition of the special operator
The macro-expansion functions defined by MACROLET are defined
in the lexical environment in which the MACROLET form appears.
Declarations and MACROLET and SYMBOL-MACROLET definitions affect
the local macro definitions in a MACROLET, but the consequences
are undefined if the local macro definitions reference any
local variable or function bindings that are visible in that
lexical environment.
Then it seems to contradict itself by giving the example
(defun foo (x flag)
(macrolet ((fudge (z)
;The parameters x and flag are not accessible
; at this point; a reference to flag would be to
; the global variable of that name.
` (if flag (* ,z ,z) ,z)))
;The parameters x and flag are accessible here.
(+ x
(fudge x)
(fudge (+ x 1)))))
The comment "a reference to flag would be to the global variable
of the same name" sounds like good behavior for the system to have.
but actual specification quoted above says that the actual behavior
is undefined.
(Since macroexpanders are defined in a restricted version
of the lexical environment, containing no lexical variables and
functions, which seems to conform to ANSI and CLtL2, but signalling
a STYLE-WARNING for references to variables similar to locals might
be a good thing.)
(as reported by Gabe Garza on cmucl-help 2001-09-21)
(defvar *tmp* 3)
(defun test-pred (x y)
(eq x y))
(defun test-case ()
(let* ((x *tmp*)
(func (lambda () x)))
(print (eq func func))
(print (test-pred func func))
(delete func (list func))))
Now calling (TEST-CASE) gives output
(#<FUNCTION {500A9EF9}>)
Evidently Python thinks of the lambda as a code transformation so
much that it forgets that it's also an object.
Ideally, uninterning a symbol would allow it, and its associated
FDEFINITION and PROCLAIM data, to be reclaimed by the GC. However,
at least as of sbcl-0.7.0, this isn't the case. Information about
FDEFINITIONs and PROCLAIMed properties is stored in globaldb.lisp
essentially in ordinary (non-weak) hash tables keyed by symbols.
Thus, once a system has an entry in this system, it tends to live
forever, even when it is uninterned and all other references to it
are lost.
141: "pretty printing and backquote"
* '``(FOO ,@',@S)
c. (reported by Paul F. Dietz)
* '`(lambda ,x)
(reported by Jesse Bouwman 2001-10-24 through the unfortunately
prominent SourceForge web/db bug tracking system, which is
unfortunately not a reliable way to get a timely response from
the SBCL maintainers)
In the course of trying to build a test case for an
application error, I encountered this behavior:
If you start up sbcl, and then lay on CTRL-C for a
minute or two, the lisp process will eventually say:
%PRIMITIVE HALT called; the party is over.
and throw you into the monitor. If I start up lisp,
attach to the process with strace, and then do the same
(abusive) thing, I get instead:
access failure in heap page not marked as write-protected
and the monitor again. I don't know enough to have the
faintest idea of what is going on here.
This is with sbcl 6.12, uname -a reports:
Linux prep 2.2.19 #4 SMP Tue Apr 24 13:59:52 CDT 2001 i686 unknown
I (WHN) have verified that the same thing occurs on sbcl-0.pre7.141
under OpenBSD 2.9 on my X86 laptop. Do be patient when you try it:
it took more than two minutes (but less than five) for me.
ANSI allows types `(COMPLEX ,FOO) to use very hairy values for
COMPLEX implementation didn't deal with this, and hasn't been
upgraded to do so. (This doesn't seem to be a high priority
conformance problem, since seems hard to construct useful code
where it matters.)
b. (fixed in
Floating point errors are reported poorly. E.g. on x86 OpenBSD
with sbcl-0.7.1,
* (expt 2.0 12777)
debugger invoked on condition of type SB-KERNEL:FLOATING-POINT-EXCEPTION:
An arithmetic error SB-KERNEL:FLOATING-POINT-EXCEPTION was signalled.
No traps are enabled? How can this be?
It should be possible to be much more specific (overflow, division
by zero, etc.) and of course the "How can this be?" should be fixable.
See also bugs #45.c and #183
(reported by Robert E. Brown 2002-04-16)
When a function is called with too few arguments, causing the
debugger to be entered, the uninitialized slots in the bad call frame
seem to cause GCish problems, being interpreted as tagged data even
though they're not. In particular, executing ROOM in the
debugger at that point causes AVER failures:
* (machine-type)
* (lisp-implementation-version)
* (typep 10)
0] (room)
(Christophe Rhodes reports that this doesn't occur on the SPARC, which
isn't too surprising since there are many differences in stack
implementation and GC conservatism between the X86 and other ports.)
This is probably the same bug as 216
In sbcl-, compiling the (illegal) code
(in-package :cl-user)
(defmethod prove ((uustk uustk))
(zap ((frob () nil))
gives the (not terribly clear) error message
; caught ERROR:
; (during macroexpansion of (DEFMETHOD PROVE ...))
; can't get template for (FROB NIL NIL)
The problem seems to be that the code walker used by the DEFMETHOD
macro is unhappy with the illegal syntax in the method body, and
is giving an unclear error message.
The compiler sometimes tries to constant-fold expressions before
it checks to see whether they can be reached. This can lead to
bogus warnings about errors in the constant folding, e.g. in code
(WRITE-STRING (> X 0) "+" "0"))
compiled in a context where the compiler can prove that X is NIL,
and the compiler complains that (> X 0) causes a type error because
NIL isn't a valid argument to #'>. Until sbcl- or so this
caused a full WARNING, which made the bug really annoying because then
COMPILE and COMPILE-FILE returned FAILURE-P=T for perfectly legal
code. Since then the warning has been downgraded to STYLE-WARNING,
so it's still a bug but at least it's a little less annoying.
183: "IEEE floating point issues"
Even where floating point handling is being dealt with relatively
well (as of sbcl-0.7.5, on sparc/sunos and alpha; see bug #146), the
accrued-exceptions and current-exceptions part of the fp control
word don't seem to bear much relation to reality. E.g. on
* (/ 1.0 0.0)
debugger invoked on condition of type DIVISION-BY-ZERO:
arithmetic error DIVISION-BY-ZERO signalled
0] (sb-vm::get-floating-point-modes)
0] abort
* (sb-vm::get-floating-point-modes)
188: "compiler performance fiasco involving type inference and UNION-TYPE"
(time (compile
'(lambda ()
(declare (optimize (safety 3)))
(declare (optimize (compilation-speed 2)))
(declare (optimize (speed 1) (debug 1) (space 1)))
(let ((start 4))
(declare (type (integer 0) start))
(print (incf start 22))
(print (incf start 26))
(print (incf start 28)))
(let ((start 6))
(declare (type (integer 0) start))
(print (incf start 22))
(print (incf start 26)))
(let ((start 10))
(declare (type (integer 0) start))
(print (incf start 22))
(print (incf start 26))))))
This example could be solved with clever enough constraint
propagation or with SSA, but consider
(let ((x 0))
(loop (incf x 2)))
The careful type of X is {2k} :-(. Is it really important to be
able to work with unions of many intervals?
191: "Miscellaneous PCL deficiencies"
(reported by Alexey Dejneka sbcl-devel 2002-08-04)
a. DEFCLASS does not inform the compiler about generated
functions. Compiling a file with
results in a STYLE-WARNING:
APD's fix for this was checked in to sbcl-, but Pierre
Mai points out that the declamation of functions is in fact
incorrect in some cases (most notably for structure
classes). This means that at present erroneous attempts to use
WITH-SLOTS and the like on classes with metaclass STRUCTURE-CLASS
won't get the corresponding STYLE-WARNING.
c. (fixed in
201: "Incautious type inference from compound types"
a. (reported by APD sbcl-devel 2002-09-17)
(FORMAT NIL "~S IS ~S, Y = ~S"
(FOO ' (1 . 2)) => "NIL IS INTEGER, Y = 1"
* (defun foo (x)
(declare (type (array * (4 4)) x))
(let ((y x))
(setq x (make-array '(4 4)))
(adjust-array y '(3 5))
(= (array-dimension y 0) (eval `(array-dimension ,y 0)))))
* (foo (make-array '(4 4) :adjustable t))
205: "environment issues in cross compiler"
(These bugs have no impact on user code, but should be fixed or
a. Macroexpanders introduced with MACROLET are defined in the null
lexical environment.
b. The body of (EVAL-WHEN (:COMPILE-TOPLEVEL) ...) is evaluated in
the null lexical environment.
c. The cross-compiler cannot inline functions defined in a non-null
lexical environment.
206: ":SB-FLUID feature broken"
(reported by Antonio Martinez-Shotton sbcl-devel 2002-10-07)
Enabling :SB-FLUID in the target-features list in sbcl-0.7.8 breaks
the build.
207: "poorly distributed SXHASH results for compound data"
SBCL's SXHASH could probably try a little harder. ANSI: "the
intent is that an implementation should make a good-faith
effort to produce hash-codes that are well distributed
within the range of non-negative fixnums". But
(let ((hits (make-hash-table)))
(dotimes (i 16)
(dotimes (j 16)
(let* ((ij (cons i j))
(newlist (push ij (gethash (sxhash ij) hits))))
(when (cdr newlist)
(format t "~&collision: ~S~%" newlist))))))
reports lots of collisions in sbcl-0.7.8. A stronger MIX function
would be an obvious way of fix. Maybe it would be acceptably efficient
to redo MIX using a lookup into a 256-entry s-box containing
29-bit pseudorandom numbers?
211: "keywords processing"
a. :ALLOW-OTHER-KEYS T should allow a function to receive an odd
number of keyword arguments.
e. Compiling
(flet ((foo (&key y) (list y)))
(list (foo :y 1 :y 2)))
issues confusing message
; (FOO :Y 1 :Y 2)
; The variable #:G15 is defined but never used.
212: "Sequence functions and circular arguments"
COERCE, MERGE and CONCATENATE go into an infinite loop when given
circular arguments; it would be good for the user if they could be
given an error instead (ANSI 17.1.1 allows this behaviour on the part
of the implementation, as conforming code cannot give non-proper
sequences to these functions. MAP also has this problem (and
solution), though arguably the convenience of being able to do
(MAP 'LIST '+ FOO '#1=(1 . #1#))
might be classed as more important (though signalling an error when
all of the arguments are circular is probably desireable).
213: "Sequence functions and type checking"
a. (fixed in
b. MAP, when given a type argument that is SUBTYPEP LIST, does not
check that it will return a sequence of the given type. Fixing
it along the same lines as the others (cf. work done around
sbcl- is possible, but doing so efficiently didn't look
entirely straightforward.
c. All of these functions will silently accept a type of the form
whether or not the return value is of this type. This is
probably permitted by ANSI (see "Exceptional Situations" under
ANSI MAKE-SEQUENCE), but the DERIVE-TYPE mechanism does not
know about this escape clause, so code of the form
can erroneously return T.
215: ":TEST-NOT handling by functions"
a. FIND and POSITION currently signal errors when given non-NIL for
both their :TEST and (deprecated) :TEST-NOT arguments, but by
ANSI 17.2 "the consequences are unspecified", which by ANSI 1.4.2
means that the effect is "unpredictable but harmless". It's not
clear what that actually means; it may preclude conforming
implementations from signalling errors.
b. COUNT, REMOVE and the like give priority to a :TEST-NOT argument
when conflict occurs. As a quality of implementation issue, it
might be preferable to treat :TEST and :TEST-NOT as being in some
sense the same &KEY, and effectively take the first test function in
the argument list.
c. Again, a quality of implementation issue: it would be good to issue a
STYLE-WARNING at compile-time for calls with :TEST-NOT, and a
WARNING for calls with both :TEST and :TEST-NOT; possibly this
latter should be WARNed about at execute-time too.
216: "debugger confused by frames with invalid number of arguments"
In sbcl-, executing e.g. (VECTOR-PUSH-EXTEND T), BACKTRACE, Q
leaves the system confused, enough so that (QUIT) no longer works.
It's as though the process of working with the uninitialized slot in
the bad VECTOR-PUSH-EXTEND frame causes GC problems, though that may
not be the actual problem. (CMU CL 18c doesn't have problems with this.)
This is probably the same bug as 162
217: "Bad type operations with FUNCTION types"
In sbcl.0.7.7:
* (values-type-union (specifier-type '(function (base-char)))
(specifier-type '(function (integer))))
It causes insertion of wrong type assertions into generated
code. E.g.
(defun foo (x s)
(let ((f (etypecase x
(character #'write-char)
(integer #'write-byte))))
(funcall f x s)
(etypecase x
(character (write-char x s))
(integer (write-byte x s)))))
Then (FOO #\1 *STANDARD-OUTPUT*) signals type error.
(In the result type is (FUNCTION * *), so Python does not
produce invalid code, but type checking is not accurate.)
233: bugs in constraint propagation
(declaim (optimize (speed 2) (safety 3)))
(defun foo (x y)
(if (typep (prog1 x (setq x y)) 'double-float)
(+ x 1d0)
(+ x 2)))
(foo 1d0 5) => segmentation violation
235: "type system and inline expansion"
(declaim (ftype (function (cons) number) acc))
(declaim (inline acc))
(defun acc (c)
(the number (car c)))
(defun foo (x y)
(values (locally (declare (optimize (safety 0)))
(acc x))
(locally (declare (optimize (safety 3)))
(acc y))))
(foo '(nil) '(t)) => NIL, T.
237: "Environment arguments to type functions"
UPGRADED-COMPLEX-PART-TYPE now have an optional environment
argument, but they ignore it completely. This is almost
certainly not correct.
b. Also, the compiler's optimizers for TYPEP have not been informed
about the new argument; consequently, they will not transform
calls of the form (TYPEP 1 'INTEGER NIL), even though this is
just as optimizeable as (TYPEP 1 'INTEGER).
238: "REPL compiler overenthusiasm for CLOS code"
From the REPL,
* (defclass foo () ())
* (defmethod bar ((x foo) (foo foo)) (call-next-method))
causes approximately 100 lines of code deletion notes. Some
discussion on this issue happened under the title 'Three "interesting"
bugs in PCL', resulting in a fix for this oververbosity from the
compiler proper; however, the problem persists in the interactor
because the notion of original source is not preserved: for the
compiler, the original source of the above expression is (DEFMETHOD
BAR ((X FOO) (FOO FOO)) (CALL-NEXT-METHOD)), while by the time the
compiler gets its hands on the code needing compilation from the REPL,
it has been macroexpanded several times.
A symptom of the same underlying problem, reported by Tony Martinez:
* (handler-case
(with-input-from-string (*query-io* " no")
(simple-type-error () 'error))
; note: deleting unreachable code
; compilation unit finished
; printed 1 note
241: "DEFCLASS mysteriously remembers uninterned accessor names."
(from tonyms on #lisp IRC 2003-02-25)
In sbcl-, typing
(defclass foo () ((bar :accessor foo-bar)))
(profile foo-bar)
(unintern 'foo-bar)
(defclass foo () ((bar :accessor foo-bar)))
gives the error message
"#:FOO-BAR already names an ordinary function or a macro."
So it's somehow checking the uninterned old accessor name instead
of the new requested accessor name, which seems broken to me (WHN).
242: "WRITE-SEQUENCE suboptimality"
(observed from clx performance)
In sbcl-0.7.13, WRITE-SEQUENCE of a sequence of type
(SIMPLE-ARRAY (UNSIGNED-BYTE 8) (*)) on a stream with element-type
(UNSIGNED-BYTE 8) will write to the stream one byte at a time,
rather than writing the sequence in one go, leading to severe
performance degradation.
243: "STYLE-WARNING overenthusiasm for unused variables"
(observed from clx compilation)
In sbcl-0.7.14, in the presence of the macros
somewhat surprising style warnings are emitted for
; in: LAMBDA (Y)
; (LAMBDA (Y) (FOO Y))
; The variable Y is defined but never used.
245: bugs in disassembler
a. On X86 an immediate operand for IMUL is printed incorrectly.
b. On X86 operand size prefix is not recognized.
(defun foo (&key (a :x))
(declare (fixnum a))
does not cause a warning. (BTW: old SBCL issued a warning, but for a
function, which was never called!)
Compiler does not emit warnings for
a. (lambda () (svref (make-array 8 :adjustable t) 1))
b. (lambda (x)
(list (let ((y (the real x)))
(unless (floatp y) (error ""))
(integer-length x)))
c. (lambda (x)
(declare (optimize (debug 0)))
(declare (type vector x))
(list (fill-pointer x)
(svref x 1)))
Complex array type does not have corresponding type specifier.
This is a problem because the compiler emits optimization notes when
you use a non-simple array, and without a type specifier for hairy
array types, there's no good way to tell it you're doing it
intentionally so that it should shut up and just compile the code.
Another problem is confusing error message "asserted type ARRAY
conflicts with derived type (VALUES SIMPLE-VECTOR &OPTIONAL)" during
compiling (LAMBDA (V) (VALUES (SVREF V 0) (VECTOR-POP V))).
The last problem is that when type assertions are converted to type
checks, types are represented with type specifiers, so we could lose
complex attribute. (Now this is probably not important, because
currently checks for complex arrays seem to be performed by
(compile nil '(lambda () (aref (make-array 0) 0))) compiles without
warning. Analogous cases with the index and length being equal and
greater than 0 are warned for; the problem here seems to be that the
type required for an array reference of this type is (INTEGER 0 (0))
which is canonicalized to NIL.
(let* ((s (gensym))
(t1 (specifier-type s)))
(eval `(defstruct ,s))
(type= t1 (specifier-type s)))
(fixed in
b. The same for CSUBTYPEP.
262: "yet another bug in inline expansion of local functions"
Compiler fails on
(defun foo (x y)
(declare (integer x y))
(+ (block nil
(flet ((xyz (u)
(declare (integer u))
(if (> (1+ (the unsigned-byte u)) 0)
(+ 1 u)
(return (+ 38 (cos (/ u 78)))))))
(declare (inline xyz))
(return-from foo
(* (funcall (eval #'xyz) x)
(if (> x 30)
(funcall (if (> x 5) #'xyz #'identity)
(+ x 13))
(sin (* x y))))
Urgh... It's time to write IR1-copier.
David Lichteblau provided (sbcl-devel 2003-06-01) a patch to fix
behaviour of streams with element-type (SIGNED-BYTE 8). The patch
looks reasonable, if not obviously correct; however, it caused the
PPC/Linux port to segfault during warm-init while loading
src/pcl/std-class.fasl. A workaround patch was made, but it would
be nice to understand why the first patch caused problems, and to
fix the cause if possible.
268: "wrong free declaration scope"
The following code must signal type error:
(locally (declare (optimize (safety 3)))
(flet ((foo (x &optional (y (car x)))
(declare (optimize (safety 0)))
(list x y)))
(funcall (eval #'foo) 1)))
SCALE-FLOAT should accept any integer for its second argument.
In the following function constraint propagator optimizes nothing:
(defun foo (x)
(declare (integer x))
(declare (optimize speed))
(typecase x
(fixnum "hala")
(fixnum "buba")
(bignum "hip")
(t "zuz")))
Compilation of the following two forms causes "X is unbound" error:
(symbol-macrolet ((x pi))
(macrolet ((foo (y) (+ x y)))
(declaim (inline bar))
(defun bar (z)
(* z (foo 4)))))
(defun quux (z)
(bar z))
CLHS says that type declaration of a symbol macro should not affect
its expansion, but in SBCL it does. (If you like magic and want to
fix it, don't forget to change all uses of MACROEXPAND to
The following code (taken from CLOCC) takes a lot of time to compile:
(defun foo (n)
(declare (type (integer 0 #.large-constant) n))
(expt 1/10 n))
(fixed in, but a test case would be good)
(defmethod fee ((x fixnum))
(setq x (/ x 2))
(fee 1) => type error
(taken from CLOCC)
(defun foo ()
(declare (optimize speed))
(loop for i of-type (integer 0) from 0 by 2 below 10
collect i))
uses generic arithmetic.
b. (fixed in
279: type propagation error -- correctly inferred type goes astray?
In sbcl-0.8.3 and sbcl-, the warning
The binding of ABS-FOO is a (VALUES (INTEGER 0 0)
&OPTIONAL), not a (INTEGER 1 536870911)
is emitted when compiling this file:
(declaim (ftype (function ((integer 0 #.most-positive-fixnum))
(integer #.most-negative-fixnum 0))
(defun foo (x)
(- x))
(defun bar (x)
(let* (;; Uncomment this for a type mismatch warning indicating
;; that the type of (FOO X) is correctly understood.
#+nil (fs-foo (float-sign (foo x)))
;; Uncomment this for a type mismatch warning
;; indicating that the type of (ABS (FOO X)) is
;; correctly understood.
#+nil (fs-abs-foo (float-sign (abs (foo x))))
;; something wrong with this one though
(abs-foo (abs (foo x))))
(declare (type (integer 1 100) abs-foo))
(print abs-foo)))
(see also bug 117)
280: bogus WARNING about duplicate function definition
In sbcl-0.8.3 and sbcl-, if BS.MIN is defined inline,
e.g. by
(declaim (inline bs.min))
(defun bs.min (bases) nil)
before compiling the file below, the compiler warns
Duplicate definition for BS.MIN found in one static
unit (usually a file).
when compiling
(declaim (special *minus* *plus* *stagnant*))
(defun b.*.min (&optional (x () xp) (y () yp) &rest rest)
(bs.min avec))
(define-compiler-macro b.*.min (&rest rest)
`(bs.min ,@rest))
(defun afish-d-rbd (pd)
(if *stagnant*
(b.*.min (foo-d-rbd *stagnant*))
(multiple-value-bind (reduce-fn initial-value)
(etypecase pd
(list (values #'bs.min 0))
(vector (values #'bs.min *plus*)))
(let ((cv-ks (cv (kpd.ks pd))))
(funcall reduce-fn d-rbds)))))
(defun bfish-d-rbd (pd)
(if *stagnant*
(b.*.min (foo-d-rbd *stagnant*))
(multiple-value-bind (reduce-fn initial-value)
(etypecase pd
(list (values #'bs.min *minus*))
(vector (values #'bs.min 0)))
(let ((cv-ks (cv (kpd.ks pd))))
(funcall reduce-fn d-rbds)))))
281: COMPUTE-EFFECTIVE-METHOD error signalling.
(slightly obscured by a non-0 default value for
It would be natural for COMPUTE-EFFECTIVE-METHOD to signal errors
when it finds a method with invalid qualifiers. However, it
shouldn't signal errors when any such methods are not applicable to
the particular call being evaluated, and certainly it shouldn't when
simply precomputing effective methods that may never be called.
(setf sb-pcl::*max-emf-precompute-methods* 0)
(defgeneric foo (x)
(:method-combination +)
(:method ((x symbol)) 1)
(:method + ((x number)) x))
(foo 1) -> ERROR, but should simply return 1
The issue seems to be that construction of a discriminating function
calls COMPUTE-EFFECTIVE-METHOD with methods that are not all applicable.
283: Thread safety: libc functions
There are places that we call unsafe-for-threading libc functions
that we should find alternatives for, or put locks around. Known or
strongly suspected problems, as of please update this
bug instead of creating new ones
localtime() - called for timezone calculations in code/time.lisp
284: Thread safety: special variables
There are lots of special variables in SBCL, and I feel sure that at
least some of them are indicative of potentially thread-unsafe
parts of the system. See doc/internals/notes/threading-specials
286: "recursive known functions"
Self-call recognition conflicts with known function
recognition. Currently cross compiler and target COMPILE do not
recognize recursion, and in target compiler it can be disabled. We
can always disable it for known functions with RECURSIVE attribute,
but there remains a possibility of a function with a
(tail)-recursive simplification pass and transforms/VOPs for base
287: PPC/Linux miscompilation or corruption in first GC
When the runtime is compiled with -O3 on certain PPC/Linux machines, a
segmentation fault is reported at the point of first triggered GC,
during the compilation of DEFSTRUCT WRAPPER. As a temporary workaround,
the runtime is no longer compiled with -O3 on PPC/Linux, but it is likely
that this merely obscures, not solves, the underlying problem; as and when
underlying problems are fixed, it would be worth trying again to provoke
this problem.
288: fundamental cross-compilation issues (from old UGLINESS file)
Using host floating point numbers to represent target floating point
numbers, or host characters to represent target characters, is
theoretically shaky. (The characters are OK as long as the characters
are in the ANSI-guaranteed character set, though, so they aren't a
real problem as long as the sources don't need anything but that;
the floats are a real problem.)
289: "type checking and source-transforms"
(block nil (let () (funcall #'+ (eval 'nil) (eval '1) (return :good))))
signals type error.
Our policy is to check argument types at the moment of a call. It
disagrees with ANSI, which says that type assertions are put
immediately onto argument expressions, but is easier to implement in
IR1 and is more compatible to type inference, inline expansion,
etc. IR1-transforms automatically keep this policy, but source
transforms for associative functions (such as +), being applied
during IR1-convertion, do not. It may be tolerable for direct calls
(+ x y z), but for (FUNCALL #'+ x y z) it is non-conformant.
b. Another aspect of this problem is efficiency. [x y + z +]
requires less registers than [x y z + +]. This transformation is
currently performed with source transforms, but it would be good to
also perform it in IR1 optimization phase.
290: Alpha floating point and denormalized traps
In SBCL on the alpha, we work around what appears to be a
hardware or kernel deficiency: the status of the enable/disable
denormalized-float traps bit seems to be ambiguous; by the time we
get to os_restore_fp_control after a trap, denormalized traps seem
to be enabled. Since we don't want a trap every time someone uses a
denormalized float, in general, we mask out that bit when we restore
the control word; however, this clobbers any change the user might
have made.
(reported by Adam Warner, sbcl-devel 2003-09-23)
The --load toplevel argument does not perform any sanitization of its
argument. As a result, files with Lisp pathname pattern characters
(#\* or #\?, for instance) or quotation marks can cause the system
to perform arbitrary behaviour.
LOOP with non-constant arithmetic step clauses suffers from overzealous
type constraint: code of the form
(loop for d of-type double-float from 0d0 to 10d0 by x collect d)
compiles to a type restriction on X of (AND DOUBLE-FLOAT (REAL
(0))). However, an integral value of X should be legal, because
successive adds of integers to double-floats produces double-floats,
so none of the type restrictions in the code is violated.
298: (aka PFD MISC.183)
Compiler fails on
(defun foo ()
(multiple-value-call #'bar
(catch 'tag (return-from foo (int)))))
This program violates "unknown values LVAR stack discipline": if INT
returns, values returned by (EXT) must be removed from under that of
300: (reported by Peter Graves) Function PEEK-CHAR checks PEEK-TYPE
argument type only after having read a character. This is caused
with EXPLICIT-CHECK attribute in DEFKNOWN. The similar problem
exists with =, /=, <, >, <=, >=. They were fixed, but it is probably
less error prone to have EXPLICIT-CHECK be a local declaration,
being put into the definition, instead of an attribute being kept in
a separate file; maybe also put it into SB-EXT?
301: ARRAY-SIMPLE-=-TYPE-METHOD breaks on corner cases which can arise
In sbcl-, compiling the file
(defun foo (x y)
(declare (type integer x))
(declare (type (vector (or hash-table bit)) y))
(bletch 2 y))
(defun bar (x y)
(declare (type integer x))
(declare (type (simple-array base (2)) y))
(bletch 1 y))
gives the error
302: Undefined type messes up DATA-VECTOR-REF expansion.
Compiling this file
(defun dis (s ei x y)
(declare (type (simple-array function (2)) s) (type ei ei))
(funcall (aref s ei) x y))
on sbcl- causes a BUG to be signalled:
303: "nonlinear LVARs" (aka MISC.293)
(defun buu (x)
(multiple-value-call #'list
(block foo
(eval '(values :a :b :c))
(catch 'bar
(if (> x 0)
(return-from foo
(eval `(if (> ,x 1)
(throw 'bar (values 3 4)))))))))))
(BUU 1) returns garbage.
The problem is that both EVALs sequentially write to the same LVAR.
(Reported by Dave Roberts.)
Local INLINE/NOTINLINE declaration removes local FTYPE declaration:
(defun quux (x)
(declare (ftype (function () (integer 0 10)) fee)
(inline fee))
(1+ (fee)))
uses generic arithmetic with INLINE and fixnum without.
306: "Imprecise unions of array types"
a.(defun foo (x)
(declare (optimize speed)
(type (or (array cons) (array vector)) x))
(elt (aref x 0) 0))
(foo #((0))) => TYPE-ERROR
,@(loop for x across sb-vm:*specialized-array-element-type-properties*
collect `(array ,(sb-vm:saetp-specifier x)))))
=> NIL, T (when it should be T, T)
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