sldb-break-at-start implementation, package l. violation

[Ph. Marek]

I saw that sldb-break-at-start wasn't implemented for SBCL, so I did my own. But when I want to look at the arguments via inspect-in-frame I get an error ...

 (defimplementation sldb-break-at-start (fname)
   (trace :break T :function fname))

but then trying to inspect SB-INT:ARG-LIST gives

(:emacs-rex (swank:inspect-in-frame "SB-INT:ARG-LIST" 2) "COMMON-LISP-USER" 3 25)

; in: LAMBDA (#:G940)
; (SYMBOL-MACROLET ((SB-INT:ARG-LIST
; (SB-DI:DEBUG-VAR-VALUE
; '#<SB-DI::COMPILED-DEBUG-VAR SB-INT:ARG-LIST 0
; {10042B45E1}>
; #:G940)))
; SB-INT:ARG-LIST)
;
; caught WARNING:
; Compile-time package lock violation:
; Lock on package SB-INT violated when binding ARG-LIST as a local symbol-macro
; while in package COMMON-LISP-USER.
; See also:
; The SBCL Manual, Node \"Package Locks\"
;
; caught ERROR:
; Lock on package SB-INT violated when binding ARG-LIST as a local symbol-macro
; while in package COMMON-LISP-USER.
; See also:
; The SBCL Manual, Node \"Package Locks\"
;

    (LAMBDA (#:G941))
    SWANK-BACKEND:EVAL-IN-FRAME SB-INT:ARG-LIST 2
    (LAMBDA ())
    SWANK::CALL-WITH-RETRY-RESTART \"Retry SLIME inspection request.\" #<CLOSURE (LAMBDA #)
    (LAMBDA ())
    SWANK-BACKEND:CALL-WITH-SYNTAX-HOOKS #<CLOSURE (LAMBDA #)
    SWANK::CALL-WITH-BUFFER-SYNTAX NIL #<CLOSURE (LAMBDA #)
    SWANK:INSPECT-IN-FRAME \"SB-INT:ARG-LIST\" 2

This is SBCL x86_64 1.0.51.0.debian, quicklisp slime-20111001-cvs.

[Ph. Marek (ph-marek)]

This seems to be the part

(let ((res (coerce `(lambda (,n-frame)
                            (declare (ignorable ,n-frame))
                            (symbol-macrolet ,(specs) ,form))
                         'function)))

in src/code/debug-int.lisp (preprocess-for-eval)

[Anton Kovalenko (anton-sw4me)]

While the reporter's problem is observed in SLIME, there is indeed an underlying issue in SBCL: when SB-DI:PREPROCESS-FOR-EVAL wraps symbols in SYMBOL-MACROLET, it probably should take care on disabling package locks (as it's not the user or his code who violates the lock, it's SBCL debugger itself; signalling package lock violation in this case is confusing and unexpected).

[Ph. Marek (ph-marek)]

On a similar note, there's another problem with swank:inspect - gensyms.
I noticed that for variables in a macro expansion; this example uses the reader instead:

    (defun fn1 ( #. *v* )
      (funcall #. *v* 'a))
    (fn1 #'1+)

Tthen inspect that variable; please note that this is from slimv, perhaps the command is wrong and a different inspect string should be sent?

    (:emacs-rex (swank:inspect-in-frame "#:G1752" 2) "CL-USER" 23 217)

    gives
    (:write-string "
     ; in: LAMBDA (#:G1754)
     ; (SYMBOL-MACROLET ((#:G1752
        ; (SB-DI:DEBUG-VAR-VALUE
         ; '#<SB-DI::COMPILED-DEBUG-VAR #:G1752 0 {1006E36B51}>
         ; #:G1754)))
      ; #:G1752)
     ;
     ; caught WARNING:
     ; undefined variable: #:G1752
     ;
     ; compilation unit finished
     ; Undefined variable:
     ; #:G1752
     ; caught 1 WARNING condition
     ")

[Ph. Marek (ph-marek)]

Fixed via inspect-frame-var in slimv. Thanks to nikodemus on #lisp for the hint, sorry for the noise.

[Nikodemus Siivola (nikodemus)]

This /is/ a valid SBCL bug none the less:

(defpackage :test
  (:use :cl)
  (:lock t))

(in-package :test)

(define-symbol-macro x 0)

(defun foo (x)
  (declare (optimize debug))
  (let ((y (* 2 x)))
    (declare (single-float y))
     y))

(in-package :cl-user)

(test::foo 1)

;; in the debugger
test::x

;; results in
; in: LAMBDA (#:G775)
; (SYMBOL-MACROLET ((TEST::X
; (SB-DI:DEBUG-VAR-VALUE
; '#<SB-DI::COMPILED-DEBUG-VAR TEST::X 0 {10036124B3}>
; #:G775)))
; TEST::X)
;
; caught WARNING:
; Compile-time package lock violation:
; Lock on package TEST violated when binding X as a local symbol-macro while in
; package COMMON-LISP-USER.
; See also:
; The SBCL Manual, Node "Package Locks"
;
; caught ERROR:
; Lock on package TEST violated when binding X as a local symbol-macro while in
; package COMMON-LISP-USER.
; See also:
; The SBCL Manual, Node "Package Locks"
;
; compilation unit finished
; caught 1 ERROR condition
; caught 1 WARNING condition

debugger invoked on a SB-INT:COMPILED-PROGRAM-ERROR:
  Execution of a form compiled with errors.
Form:
  (SYMBOL-MACROLET ((X
                   (DEBUG-VAR-VALUE
                    '#<COMPILED-DEBUG-VAR TEST::X 0 {10036124B3}> G775)))
  X)
Compile-time error:
  Lock on package TEST violated when binding X as a local symbol-macro while in
package COMMON-LISP-USER.
See also:
  The SBCL Manual, Node "Package Locks"

(defun foo (x)
  (