Unable to step into function depending on its thread

[Denis Budyak]

; Operating systems and SBCL version ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; Windows 7, sbcl taken from binary release
c:\clcon\sbcl\1.2.16>sbcl --version
SBCL 1.2.16

; Debian
$uname -a
Linux d8 3.16.0-4-686-pae #1 SMP Debian 3.16.7-ckt11-1 (2015-05-24) i686 GNU/Linux
$sbcl --version
SBCL 1.2.7

; Example of dialog for Windows (no difference in Linux) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
c:\clcon\sbcl\1.2.16>sbcl --core c:\clcon\sbcl\1.2.16\sbcl.core --no-userinit
...
* *features*
(:ALIEN-CALLBACKS :ANSI-CL :ASH-RIGHT-VOPS :C-STACK-IS-CONTROL-STACK
 :COMMON-LISP :COMPARE-AND-SWAP-VOPS :CYCLE-COUNTER :FP-AND-PC-STANDARD-SAVE
 :GENCGC :IEEE-FLOATING-POINT :INLINE-CONSTANTS :LINKAGE-TABLE :LITTLE-ENDIAN
 :MEMORY-BARRIER-VOPS :MULTIPLY-HIGH-VOPS :OS-PROVIDES-DLOPEN
 :OS-PROVIDES-DLOPEN :OS-PROVIDES-PUTWC :PACKAGE-LOCAL-NICKNAMES
 :PRECISE-ARG-COUNT-ERROR :RAW-INSTANCE-INIT-VOPS :SB-DYNAMIC-CORE :SB-EVAL
 :SB-FUTEX :SB-LDB :SB-PACKAGE-LOCKS :SB-QSHOW :SB-SAFEPOINT
 :SB-SAFEPOINT-STRICTLY :SB-SOURCE-LOCATIONS :SB-TEST :SB-THREAD :SB-THRUPTION
 :SB-UNICODE :SB-WTIMER :SBCL :STACK-ALLOCATABLE-CLOSURES
 :STACK-ALLOCATABLE-FIXED-OBJECTS :STACK-ALLOCATABLE-LISTS
 :STACK-ALLOCATABLE-VECTORS :STACK-GROWS-DOWNWARD-NOT-UPWARD :SYMBOL-INFO-VOPS
 :UNWIND-TO-FRAME-AND-CALL-VOP :WIN32 :X86)
*
* (load (compile-file "c:/tmp/try-to-kill-stepper.lisp"))
...
* (outer-no-args)

debugger invoked on a SIMPLE-CONDITION in thread
#<THREAD "main thread" RUNNING {23FF20E1}>:
  break
...
0] start
; Evaluating call:
; (+ Y 4)
; With unknown arguments

0] stop

19
*
* (outer-no-args-in-thread)
#<SB-THREAD:THREAD "Thread to fail a stepper" RUNNING {24093B79}>
debugger invoked on a SIMPLE-CONDITION in thread
#<THREAD "Thread to fail a stepper" RUNNING {24093B79}>:
* break
; That's it. Debugger didn't even show up properly
; In SLIME, debugger shows up, but unable to switch to stepping mode.

;;; Contents of c:/tmp/try-to-kill-stepper.lisp ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(in-package :cl-user)
(declaim (optimize (debug 3) (speed 0) (compilation-speed 0) (space 0)))
(proclaim '(optimize (debug 3) (speed 0) (compilation-speed 0) (space 0)))
(defun outer (x)
   (+ (inner x) (+ x x)))
(defun inner (y)
  (break)
  (+ y 4)
  )
(defun outer-no-args ()
  (outer 5))
(defun outer-no-args-in-thread ()
  (sb-thread:make-thread #'outer-no-args :name "Thread to fail a stepper"))
;;EOF

[Denis Budyak (budden73)]

May be relevant to chapter "12.8 Sessions/Debugging" of manual

[Denis Budyak (budden73)]

Hi! I have a workaround. I tested it in bare console and in clcon. All we need is to wrap code into

(defmacro with-necessary-stepper-handler (&body body)
  `(handler-bind ((step-condition 'sb-impl::invoke-stepper))
     ,@body))

What goes to console problems, there are no bugs indeed, but I think more details on sessions and foreground state in manual
would be useful. I prepared an example, but unsure if it is correct.

https://bitbucket.org/budden/clcon/src/636ad85f239defe89951618625512b5fd8e26d03/test/dbgtest.lisp?at=default&fileviewer=file-view-default

[Denis Budyak (budden73)]

P.S. from the reading of initial report, it may seem that problem is in my unawereness of manual, especially in sb-thread::release-background.

But this was only a non-essential part of problem.

Essential part of problem is that stepper indeed does not work in threads without handler-bind installed. I'm sure this should be described in the manual, but there is no single word about it. I suggested a fix for the problem, but it took half a day for me to figure out what was the problem.

Please do not ignore this report.