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

Estevo euccastro at gmail.com
Mon Dec 30 13:54:28 EST 2013


(Ignore the "q is ..." printout.  As you see in the script, I just printed
p again there instead, by mistake.)


On Mon, Dec 30, 2013 at 7:51 PM, Estevo <euccastro at gmail.com> wrote:

> 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
>>>>>
>>>>>
>>>>
>>>
>>
>
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