CHICKEN Scheme

Metadata

Id: b5051f1b787ffa11cf134630057e4edc775eca60
Trac id: 866
Type: defect
Reporter: megane
Owner: felix
Cc:
Status: closed
Component: core libraries
Estimated difficulty:
Resolution: fixed
Priority: major
Milestone: 4.9.0
Version: 4.7.x
Changetime: 2012-09-24 21:47:48 UTC
Created: 2012-06-13 10:46:22 UTC
Keywords:

Attachments

b5051f1b787ffa11cf134630057e4edc775eca60/attachments/0001-Catch-exceptions-in-finalizers-and-added-tests.patch

Description

 ;; It seems like the gc stops working correctly after an exception
 ;; from a faulty finalizer gets caught (and not crash the whole
 ;; program).
 
 (define n 2000000000)
 (define vector-size 100)
 
 (define (make-objects n gc-msg)
   (let loop [(i 0)]
     (let [(o (make-vector vector-size))]
       (print "making " i)
       (set-finalizer! o (lambda (ob) (print gc-msg " " i))) 
       (if (< i n)
 	  (loop (+ 1 i))))))
 
 (set-finalizer! (make-vector 100) (lambda (ob) (+ i 'a)))
 (handle-exceptions
     exn
   (begin
     (print "Caught an exception" exn))
   (make-objects n "gc'ing"))
 
 (print "done")
 
 ;; Result when compiled: 3 cases
 
 ;; Case 1: out of memory, tweak n, vector-size to avoid this
 ;; ...
 ;; [panic] out of memory - cannot allocate heap segment - execution terminated
 
 ;; Case 2:  100% cpu with no apparent progress
 
 ;; Output with -:g
 ;; ...
 ;; [GC] 2 finalized item(s) still pending
 ;; [GC] 2680 finalizer value(s) marked
 ;; [GC] level  1	gcs(minor)  379	gcs(major)  22
 ;; [GC] stack	0xbfef7880	0xbff36a00	0xbff37880
 ;; [GC]  from	0x773d9008	0xb731f744	0xb73d9000	0x3ff4673c
 ;; [GC]    to	0x09123008	0x09123008	0x49123000 
 ;; [GC] 0 locatives (from 32)
 ;; 681
 ;; [GC] 2 finalized item(s) still pending
 ;; [GC] 2681 finalizer value(s) marked
 ;; [GC] level  1	gcs(minor)  0	gcs(major)  23
 ;; [GC] stack	0xbfef7880	0xbff36a00	0xbff37880
 ;; [GC]  from	0x09123008	0x490cb1d8	0x49123000	0x3ffa81d0
 ;; [GC]    to	0x773d9008	0x773d9008	0xb73d9000 
 ;; [GC] 0 locatives (from 32)
 ;; <- stuck here with 100% cpu
 
 ;; Case 3: 100% at the end
 ;; making 1
 ;; making 2
 ;; ...
 ;; ...
 ;; gc'ing 103
 ;; gc'ing 102
 ;; gc'ing 101
 ;; Caught an exception#<condition: (exn type)>
 ;; done
 ;; <- stuck here with 100% cpu

The attached patch adds catching any errors during finalizer execution, but there still seems to be a problem - running the test sometimes crashes (seems to depend on memory layout or something similar).