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List:       sbcl-devel
Subject:    Re: [Sbcl-devel] Introspection bug
From:       "Tobias C. Rittweiler" <tcr () freebits ! de>
Date:       2009-10-22 16:11:23
Message-ID: 87ws2ntnmc.fsf () freebits ! de
[Download RAW message or body]

Levente Mészáros <levente.meszaros@gmail.com> writes:

> The following form errors in SBCL 1.0.31.29 x86-64.
>
> (sb-introspect:find-definition-sources-by-name
> 'common-lisp:structure-object :structure)

The error is because

  (sb-kernel::layout-source-location 
    (sb-impl::classoid-layout
      (sb-impl::find-classoid FOO)))

for the following symbols

  FILE-STREAM
  SB-EVAL:INTERPRETED-FUNCTION
  STRUCTURE-OBJECT
  STREAM
  STRING-STREAM
  SEQUENCE
  T
  FUNCTION
  CONDITION

returns 0 rather than NIL.

The reason for that (this insight came from Xof) is that the LAYOUT
classoid is also actually initialized by genesis and in MAKE-COLD-LAYOUT
a

  (cold-set-layout-slot result 'source-location *nil-descriptor*)

is missing.

A comment in code/class.lisp just above the defstruct definition of
LAYOUT says that this initialization should probably be automated, and I
agree. But that's somewhat outside my capabilities now because I'm
drowning in related KLUDGEs and FIXMEs.

For example the FIXME in %INIT-OR-CHECK-LAYOUT (class.lisp) seems also
apropos to be fixed in one go.

All I can provide is a test case which checks that each class/structure
has a non-bogus source-location. This test could be extended to cover
not only class/structures but everything in the infodb.

Say if you want me to do that. I'll decline to provide a patch for the
actual issue, though.

  -T.

PS.

  (dolist (env sb-c::*info-environment*)
    (sb-c::do-info (env :class class :type type :name info-name :value value)
      (when (and (symbolp info-name) 
                 (eql class :type)
                 (eql type :kind))
        (let* ((classoid (sb-kernel:find-classoid info-name nil))
               (layout   (and classoid (sb-kernel:classoid-layout classoid)))
               (srcloc   (and layout (sb-kernel::layout-source-location layout))))
          (when (and layout)
            (assert (or (sb-c::definition-source-location-p srcloc)
                        (null srcloc))))))))


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