[Sbcl-devel] Useless backtrace for mapcar even with high debug settings.

[Nikolaus D. <de...@in...>]

Hi list,

given the following function

-------------------------------
(defun test (l)
   (declare (optimize (debug 2)))
   (mapcar #'identity l))
-------------------------------

I get the fairly useless backtrace when calling it as such:

-------------------------------
CL-USER> (test '(1 2 . 3))
-------------------------------

namely:

-------------------------------
The value 3 is not of type LIST.
    [Condition of type TYPE-ERROR]

Restarts:
  0: [RETRY] Retry SLIME REPL evaluation request.
  1: [ABORT] Return to SLIME's top level.
  2: [TERMINATE-THREAD] Terminate this thread (#<THREAD "repl-thread"  
RUNNING {1003439561}>)

Backtrace:
   0: (SB-KERNEL::OBJECT-NOT-LIST-ERROR-HANDLER #<unavailable  
argument> #.(SB-SYS:INT-SAP #X09262DA0) #<SB-ALIEN-INTERNALS:ALIEN- 
VALUE :SAP #X00196000 :TYPE (* (STRUCT SB-VM::OS-CONTEXT-T-STRUCT))>  
(85))
   1: (SB-KERNEL:INTERNAL-ERROR #.(SB-SYS:INT-SAP #X00196000)  
#<unavailable argument>)
   2: ("foreign function: call_into_lisp")
   3: ("foreign function: funcall2")
   4: ("foreign function: interrupt_internal_error")
   5: ("foreign function: signal_emulation_wrapper")
   6: ("foreign function: stack_allocation_recover")
-------------------------------

I suspect the mapcar is inlined although debug is set to 2. Maybe the  
source transformation for mapcar isn't obeying the debug policy.

Best regards,
Niko