SBCL bypass debugger and print error for display in other environment?

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I am controlling SBCL through shell commands with the environment MaxMSP.

Typically my commands are : sbcl --core some/path/to/a/.core/file --script my/script/generated/in/max

Everything works wonderfully except when errors happen... In that case I don't get any result but also no way to know what went wrong except evaluating the same command in the Terminal, where the SBCL debugger shows up.

Is there a way to just disable the debugger for this evaluation — typically give up if you meet an error — but then to "echo" the actual content of the error?

Typically to get the actual string that says something like "The value 'TOTO is not of type NUMBER when binding SB-KERNEL::X", so I can see it directly from Max with going to the terminal?

Thanks for your help ! Best,

Julien

I tried adding --non-interactive on top of my command, it helps but it's definitely not what I need.

Seems I should work with debug-io somehow but I'm not sure how to access its content :(

sbcl runtime-error common-lisp error-handling
1 Answers

You could try to use --disable-debugger:

$ echo '(error "Oh no")' > script.lisp 
$ sbcl --disable-debugger --load $PWD/script.lisp 
This is SBCL 1.5.2.33-d415e2949, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses.  See the CREDITS and COPYING files in the
distribution for more information.
While evaluating the form starting at line 1, column 0
  of #P"/tmp/script.lisp":
Unhandled SIMPLE-ERROR in thread #<SB-THREAD:THREAD "main thread" RUNNING
                                    {10005C85B3}>:
  Oh no

Backtrace for: #<SB-THREAD:THREAD "main thread" RUNNING {10005C85B3}>
0: (SB-DEBUG::DEBUGGER-DISABLED-HOOK #<SIMPLE-ERROR "Oh no" {1003643C33}> #<unused argument> :QUIT T)
1: (SB-DEBUG::RUN-HOOK *INVOKE-DEBUGGER-HOOK* #<SIMPLE-ERROR "Oh no" {1003643C33}>)
2: (INVOKE-DEBUGGER #<SIMPLE-ERROR "Oh no" {1003643C33}>)
3: (ERROR "Oh no")
4: (SB-INT:SIMPLE-EVAL-IN-LEXENV (ERROR "Oh no") #<NULL-LEXENV>)
5: (EVAL-TLF (ERROR "Oh no") 0 NIL)
6: ((LABELS SB-FASL::EVAL-FORM :IN SB-INT:LOAD-AS-SOURCE) (ERROR "Oh no") 0)
7: ((LAMBDA (SB-KERNEL:FORM &KEY :CURRENT-INDEX &ALLOW-OTHER-KEYS) :IN SB-INT:LOAD-AS-SOURCE) (ERROR "Oh no") :CURRENT-INDEX 0)
8: (SB-C::%DO-FORMS-FROM-INFO #<CLOSURE (LAMBDA (SB-KERNEL:FORM &KEY :CURRENT-INDEX &ALLOW-OTHER-KEYS) :IN SB-INT:LOAD-AS-SOURCE) {10036436CB}> #<SB-C::SOURCE-INFO {1003643683}> SB-C::INPUT-ERROR-IN-LOAD)
9: (SB-INT:LOAD-AS-SOURCE #<SB-INT:FORM-TRACKING-STREAM for "file /tmp/script.lisp" {1003641C13}> :VERBOSE NIL :PRINT NIL :CONTEXT "loading")
10: ((FLET SB-FASL::THUNK :IN LOAD))
11: (SB-FASL::CALL-WITH-LOAD-BINDINGS #<CLOSURE (FLET SB-FASL::THUNK :IN LOAD) {7F13FE6777EB}> #<SB-INT:FORM-TRACKING-STREAM for "file /tmp/script.lisp" {1003641C13}>)
12: ((FLET SB-FASL::LOAD-STREAM :IN LOAD) #<SB-INT:FORM-TRACKING-STREAM for "file /tmp/script.lisp" {1003641C13}> NIL)
13: (LOAD #P"/tmp/script.lisp" :VERBOSE NIL :PRINT NIL :IF-DOES-NOT-EXIST T :EXTERNAL-FORMAT :DEFAULT)
14: (SB-IMPL::PROCESS-EVAL/LOAD-OPTIONS ((:LOAD . "/tmp/script.lisp")))
15: (SB-IMPL::TOPLEVEL-INIT)
16: ((FLET SB-UNIX::BODY :IN SAVE-LISP-AND-DIE))
17: ((FLET "WITHOUT-INTERRUPTS-BODY-14" :IN SAVE-LISP-AND-DIE))
18: ((LABELS SB-IMPL::RESTART-LISP :IN SAVE-LISP-AND-DIE))

Note that the trace is printed and then program exits.

Alternatively, you could set *DEBUGGER-HOOK* to a custom function that is called when entering the debugger, in which you print the error and call (sb-ext:quit), for example.

For example:

(setf *debugger-hook*
      (lambda (condition old-hook)
        (declare (ignore old-hook))
        (format *error-output*
                 "Caught error: ~a"
                 condition)
        (finish-output *error-output*)
        (sb-ext:quit)))

The code is almost the same if you prefer to use HANDLER-CASE inside your script:

(handler-case (...main...)
  (condition (c) ...log and quit..))
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