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

Estevo euccastro at gmail.com
Mon Dec 30 12:52:00 EST 2013


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)
>>>
>>
>>
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>
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