[Sbcl-devel] get-internal-real-time bug?

[karol s. <kar...@gm...>]

Hi guys,
  I am confused from behaviour of this piece of code:

(let ((real-time (get-internal-real-time)))
	  (sleep 0.01)
	  (loop :for new-real-time = (get-internal-real-time)
		:repeat 1000000000
		:do (if (> real-time new-real-time)
			(error "!!!!!!!!!! real-time = ~a, new-real-time = ~a~%" real-time
new-real-time)
			(setf real-time new-real-time))))
		
If I understand correctly, new-real-time should be always greater or
equal than time measured in executing previous iteration of loop.
However, this is not true. I often get error which looks like this :

!!!!!!!!!! real-time = 1276670, new-real-time = 1276669

   [Condition of type SIMPLE-ERROR]

Restarts:
  0: [ABORT-REQUEST] Abort handling SLIME request.
  1: [TERMINATE-THREAD] Terminate this thread (#<THREAD "repl-thread"
{B4B7989}>)

Backtrace:
  0: (NIL)
  1: (SB-INT:EVAL-IN-LEXENV (LET ((REAL-TIME #)) (SLEEP 0.01) (LOOP
:FOR NEW-REAL-TIME = (GET-INTERNAL-REAL-TIME) :REPEAT 1000000000 :DO
(IF # # #))) #<NULL-LEXENV>)
  2: (SWANK::EVAL-REGION "(let ((real-time (get-internal-real-time)))
	  (sleep 0.01)
	  (loop :for new-real-time = (get-internal-real-time)
		:repeat 1000000000
		:do (if (> real-time new-real-time)
			(error \"!!!!!!!!!! real-time = ~a, new-real-time = ~a~%\"
real-time new-real-time)
			(setf real-time new-real-time))))
		
		
" T)

When this errors happens, new-real-time is always real-time -1.

I am using SBCL 0.9.14.

My features are :

(:SPLIT-SEQUENCE :SBCL-USES-SB-ROTATE-BYTE :ASDF :SB-THREAD :ANSI-CL
:COMMON-LISP :SBCL :UNIX :SB-DOC :SB-TEST :SB-LDB :SB-PACKAGE-LOCKS
:SB-SOURCE-LOCATIONS :IEEE-FLOATING-POINT :X86 :ELF :LINUX :GENCGC
:STACK-GROWS-DOWNWARD-NOT-UPWARD :C-STACK-IS-CONTROL-STACK
:STACK-ALLOCATABLE-CLOSURES :ALIEN-CALLBACKS :LINKAGE-TABLE
:OS-PROVIDES-DLOPEN :OS-PROVIDES-DLADDR :OS-PROVIDES-PUTWC)

Cheers,
  Karol Skocik