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

Estevo euccastro at gmail.com
Sun Dec 29 15:06:38 EST 2013


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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