[gambit-list] Memory leak (?) using `c-define`d functions from foreign release functions.

Estevo euccastro at gmail.com
Mon Dec 30 13:51:32 EST 2013


Well, just with 2 (modified script follows below, again) I get memory
corruption (note that it seems like the value of the car of `ptr-serials`
has become the string "*** after GC", which is only ever passed to println.)

p is #<point* #2 0x28979a0>
q is #<point* #2 0x28979a0>
release-point called on serial 3
found in object table as: #<void* #3 0x28981b0>
release-point called on serial 4
found in object table as: #<void* #4 0x28979a0>

*** after GC:
foreign serial is *** after GC:, corresponding to not-there, a
mem-allocated something else object with reference count == 10008704

Bye.

;----

(c-declare "struct { int x; int y; } point;")

(define no-err ((c-lambda () scheme-object "___result =
___FIX(___NO_ERR);")))

(define ptr-serials '())

(c-define (release-point ptr)
          ((pointer void)) scheme-object "scm_release_point" ""
  (let ((ptr-serial (object->serial-number ptr)))
    (set! ptr-serials (cons ptr-serial ptr-serials))
    (println "release-point called on serial " ptr-serial)
    (println "found in object table as: "
             (table-ref ##serial-number-to-object-table ptr-serial
'not-there)))
  ((c-lambda ((pointer void)) void "___release_rc") ptr)
  no-err)

(c-define-type point (type "point" (point*) "scm_release_point"))

(define p ((c-lambda () point
             "___result_voidstar = ___EXT(___alloc_rc)(sizeof(point));")))

(define q ((c-lambda () point
             "___result_voidstar = ___EXT(___alloc_rc)(sizeof(point));")))

(println "p is " p)
(println "q is " p)

(set! p #f)
(set! q #f)

(##gc)

(newline)
(println "*** after GC:")
(for-each
  (lambda (ptr-serial)
    (print "foreign serial is " ptr-serial)
    (print ", corresponding to "
           (table-ref ##serial-number-to-object-table ptr-serial
'not-there))

    (print ", a "
           (if
             ((c-lambda (scheme-object) bool "___result =
___MEM_ALLOCATED(___arg1);")
              (table-ref ##serial-number-to-object-table ptr-serial
'not-there)) "" "not")
           " mem-allocated")

    (print " "
           ((c-lambda (scheme-object) char-string "___result =
___HD_TYP(___BODY(___arg1)[-1]) == ___STILL ? \"still\" : \"something
else\";")
            (table-ref ##serial-number-to-object-table ptr-serial
'not-there)))

    (println " object with reference count == "
             ((c-lambda (scheme-object) int "___result =
___UNTAG(___arg1)[___BODY_OFS - 6 + 1];")
              (table-ref ##serial-number-to-object-table ptr-serial
'not-there)))
    (newline))
  ptr-serials)

(println "Bye.")




On Mon, Dec 30, 2013 at 6:56 PM, Mikael <mikael.rcv at gmail.com> wrote:

> What's the behvior if you allocate 1 000 000 instead, is the problem
> amplified proportionally?
>
>
> 2013/12/30 Estevo <euccastro at gmail.com>
>
>> It seems that's not the problem.  Refcount is 0, yet the object is kept
>> alive.
>>
>> Running the modified script below, I get the following:
>>
>> [BEGIN OUTPUT]
>>
>> p is #<point* #2 0x12309a0>
>> release-point called on serial 3
>> found in object table as: #<void* #3 0x12309a0>
>>
>> *** after GC:
>> foreign serial is 3, corresponding to #<void* #3 0x12309a0>, a
>> mem-allocated still object with reference count == 0
>> Bye.
>>
>> [END OUTPUT]
>>
>>
>> ;--------------------------------------------------------------------------------------
>>
>>
>> (c-declare "struct { int x; int y; } point;")
>>
>> (define no-err ((c-lambda () scheme-object "___result =
>> ___FIX(___NO_ERR);")))
>>
>> (define ptr-serial #f)
>>
>>
>> (c-define (release-point ptr)
>>           ((pointer void)) scheme-object "scm_release_point" ""
>>   (set! ptr-serial (object->serial-number ptr))
>>   (println "release-point called on serial " ptr-serial)
>>   (println "found in object table as: "
>>     (table-ref ##serial-number-to-object-table ptr-serial 'not-there))
>>
>>   ((c-lambda ((pointer void)) void "___release_rc") ptr)
>>   no-err)
>>
>> (c-define-type point (type "point" (point*) "scm_release_point"))
>>
>>
>> (define p ((c-lambda () point
>>              "___result_voidstar = ___EXT(___alloc_rc)(sizeof(point));")))
>>
>> (println "p is " p)
>>
>> (set! p #f)
>>
>> (##gc)
>>
>> (newline)
>> (println "*** after GC:")
>> (print "foreign serial is " ptr-serial)
>> (print ", corresponding to "
>>   (table-ref ##serial-number-to-object-table ptr-serial 'not-there))
>>
>> (print ", a "
>>          (if ((c-lambda (scheme-object) bool "___result =
>> ___MEM_ALLOCATED(___arg1);")
>>               (table-ref ##serial-number-to-object-table ptr-serial
>> 'not-there))
>>            ""
>>            "not")
>>          " mem-allocated")
>>
>> (print " "
>>   ((c-lambda (scheme-object) char-string "___result =
>> ___HD_TYP(___BODY(___arg1)[-1]) == ___STILL ? \"still\" : \"something
>> else\";")
>>    (table-ref ##serial-number-to-object-table ptr-serial 'not-there)))
>>
>> (println " object with reference count == "
>>          ((c-lambda (scheme-object) int "___result =
>> ___UNTAG(___arg1)[___BODY_OFS - 6 + 1];")
>>           (table-ref ##serial-number-to-object-table ptr-serial
>> 'not-there)))
>>
>> (println "Bye.")
>>
>>
>>
>>
>> On Mon, Dec 30, 2013 at 10:09 AM, Mikael <mikael.rcv at gmail.com> wrote:
>>
>>> Refcount is 1 by default so you need to decrease it for it to GFC?
>>>
>>> Allocate a zillion points and check the two respective ways.
>>>
>>>
>>> 2013/12/29 Estevo <euccastro at gmail.com>
>>>
>>>>  Here's a more realistic version of what I was trying to do:
>>>>
>>>> (c-declare "struct { int x; int y; } point;")
>>>>
>>>> (define no-err ((c-lambda () scheme-object "___result =
>>>> ___FIX(___NO_ERR);")))
>>>>
>>>> (c-define (release-point ptr)
>>>>           ((pointer void)) scheme-object "scm_release_point" ""
>>>>   (println "release-point called")
>>>>   ((c-lambda ((pointer void)) void "___release_rc") ptr)
>>>>   no-err)
>>>>
>>>> (c-define-type point (pointer "point" (point*) "scm_release_point"))
>>>>
>>>>
>>>> (define p ((c-lambda () point
>>>>              "___result_voidstar =
>>>> ___EXT(___alloc_rc)(sizeof(point));")))
>>>>
>>>> (println "p is " p)
>>>> (set! p #f)
>>>>
>>>> (##gc)
>>>>
>>>> (println "Bye.")
>>>>
>>>> valgrind's complaint is different in this one.  What is leaked here
>>>> (again, unless valgrind is giving me a false positive) seems to be the
>>>> Scheme representation of `ptr`:
>>>>
>>>> ==9631== Memcheck, a memory error detector
>>>> ==9631== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
>>>> ==9631== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright
>>>> info
>>>> ==9631== Command: ./test-c-define
>>>> ==9631==
>>>> p is #<point* #2 0x5c04620>
>>>> release-point called
>>>> Bye.
>>>> ==9631==
>>>> ==9631== HEAP SUMMARY:
>>>> ==9631==     in use at exit: 158 bytes in 2 blocks
>>>> ==9631==   total heap usage: 154 allocs, 152 frees, 4,247,245 bytes
>>>> allocated
>>>> ==9631==
>>>> ==9631== 158 (87 direct, 71 indirect) bytes in 1 blocks are definitely
>>>> lost in loss record 2 of 2
>>>> ==9631==    at 0x4C2B6CD: malloc (in
>>>> /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
>>>> ==9631==    by 0x4C7DC6: ___alloc_mem (os_base.c:185)
>>>> ==9631==    by 0x4B6905: alloc_mem_aligned (mem.c:452)
>>>> ==9631==    by 0x4B77A7: alloc_scmobj_still (mem.c:1245)
>>>> ==9631==    by 0x4B78B1: ___alloc_scmobj (mem.c:1285)
>>>> ==9631==    by 0x4C3DEE: ___POINTER_to_SCMOBJ (c_intf.c:5154)
>>>> ==9631==    by 0x4B1C88: scm_release_point (test-c-define.c:665)
>>>> ==9631==    by 0x4C1027: ___release_foreign (c_intf.c:1713)
>>>> ==9631==    by 0x4BAEA4: free_unmarked_still_objs (mem.c:3271)
>>>> ==9631==    by 0x4BD472: ___garbage_collect (mem.c:4698)
>>>> ==9631==    by 0x4E4357: ___H__20___kernel (_kernel.c:9170)
>>>> ==9631==    by 0x4B49B2: trampoline (setup.c:1618)
>>>> ==9631==
>>>> ==9631== LEAK SUMMARY:
>>>> ==9631==    definitely lost: 87 bytes in 1 blocks
>>>> ==9631==    indirectly lost: 71 bytes in 1 blocks
>>>> ==9631==      possibly lost: 0 bytes in 0 blocks
>>>> ==9631==    still reachable: 0 bytes in 0 blocks
>>>> ==9631==         suppressed: 0 bytes in 0 blocks
>>>> ==9631==
>>>> ==9631== For counts of detected and suppressed errors, rerun with: -v
>>>> ==9631== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from 2)
>>>>
>>>>
>>>>
>>>> On Thu, Dec 26, 2013 at 11:23 PM, Estevo <euccastro at gmail.com> wrote:
>>>>
>>>>> Valgrind reports Gambit is leaking a "sfun stack marker" if I call,
>>>>> from a foreign release function, another function defined with `c-define`.
>>>>> The code below is about the most innocent looking thing I could come up
>>>>> with.
>>>>>
>>>>> Doesn't Gambit like c-define functions called within release
>>>>> functions, or is Valgrind giving me a false positive here (as it is wont to
>>>>> do quite often.)
>>>>>
>>>>> ; ~/gambit-dbg/bin/gsc -exe -cc-options -g test-c-define.scm &&
>>>>> valgrind --leak-check=full ./test-c-define
>>>>>
>>>>> (c-declare #<<c-declare-end
>>>>>
>>>>> typedef struct { int x; int y; } point;
>>>>>
>>>>> void scm_release_point(unsigned long);
>>>>>
>>>>> ___SCMOBJ c_release_point(void *ptr) {
>>>>>     scm_release_point((unsigned long)ptr);
>>>>>     ___EXT(___release_rc)(ptr);
>>>>>     return ___FIX(___NO_ERR);
>>>>> }
>>>>>
>>>>> c-declare-end
>>>>> )
>>>>>
>>>>> (c-define (release-point ptr) (unsigned-long) void "scm_release_point"
>>>>> ""
>>>>>   (println "release-point called"))
>>>>>
>>>>> (c-define-type point (pointer "point" (point*) "c_release_point"))
>>>>>
>>>>> (define p ((c-lambda () point
>>>>>                  "___result_voidstar =
>>>>> ___EXT(___alloc_rc)(sizeof(point));")))
>>>>>
>>>>> (println "p is " p)
>>>>> (set! p #f)
>>>>>
>>>>> (##gc)
>>>>> ; for good measure...
>>>>> (##gc)
>>>>> (##gc)
>>>>>
>>>>> (println "Bye.")
>>>>>
>>>>>
>>>>> valgrind --leak-check=full ./test-c-define
>>>>> ==16301== Memcheck, a memory error detector
>>>>> ==16301== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et
>>>>> al.
>>>>> ==16301== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright
>>>>> info
>>>>> ==16301== Command: ./test-c-define
>>>>> ==16301==
>>>>> p is #<point* #2 0x5c04640>
>>>>> release-point called
>>>>> Bye.
>>>>> ==16301==
>>>>> ==16301== HEAP SUMMARY:
>>>>> ==16301==     in use at exit: 71 bytes in 1 blocks
>>>>> ==16301==   total heap usage: 153 allocs, 152 frees, 4,247,198 bytes
>>>>> allocated
>>>>> ==16301==
>>>>> ==16301== 71 bytes in 1 blocks are definitely lost in loss record 1 of
>>>>> 1
>>>>> ==16301==    at 0x4C2B6CD: malloc (in
>>>>> /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
>>>>> ==16301==    by 0x4C922E: ___alloc_mem (os_base.c:185)
>>>>> ==16301==    by 0x4B7DB5: alloc_mem_aligned (mem.c:452)
>>>>> ==16301==    by 0x4B8C57: alloc_scmobj_still (mem.c:1245)
>>>>> ==16301==    by 0x4B8D61: ___alloc_scmobj (mem.c:1285)
>>>>> ==16301==    by 0x4B8E44: ___make_vector (mem.c:1362)
>>>>> ==16301==    by 0x4C677B: ___make_sfun_stack_marker (c_intf.c:6452)
>>>>> ==16301==    by 0x4B359E: scm_release_point (test-c-define.c:139)
>>>>> ==16301==    by 0x4B354B: c_release_point (test-c-define.c:130)
>>>>> ==16301==    by 0x4C24D7: ___release_foreign (c_intf.c:1713)
>>>>> ==16301==    by 0x4BC354: free_unmarked_still_objs (mem.c:3271)
>>>>> ==16301==    by 0x4BE922: ___garbage_collect (mem.c:4698)
>>>>> ==16301==
>>>>> ==16301== LEAK SUMMARY:
>>>>> ==16301==    definitely lost: 71 bytes in 1 blocks
>>>>> ==16301==    indirectly lost: 0 bytes in 0 blocks
>>>>> ==16301==      possibly lost: 0 bytes in 0 blocks
>>>>> ==16301==    still reachable: 0 bytes in 0 blocks
>>>>> ==16301==         suppressed: 0 bytes in 0 blocks
>>>>> ==16301==
>>>>> ==16301== For counts of detected and suppressed errors, rerun with: -v
>>>>> ==16301== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from
>>>>> 2)
>>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Gambit-list mailing list
>>>> Gambit-list at iro.umontreal.ca
>>>> https://webmail.iro.umontreal.ca/mailman/listinfo/gambit-list
>>>>
>>>>
>>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.iro.umontreal.ca/pipermail/gambit-list/attachments/20131230/31984074/attachment.htm>


More information about the Gambit-list mailing list