[systemd-devel] sd-bus memory check

[David J]

Will,

thank you very much. I spent my Sunday debugging this thing! Using sd_bus_flush_close_unref() eliminated the memory leak!


Appreciate your help!


On April 12, 2020 at 9:20 PM, William Kennington <william at wkennington.com> wrote:


You are probably looking for sd_bus_flush_close_unref() for this usecase.


On Sun, Apr 12, 2020 at 11:00 AM David J <emacsd at icloud.com> wrote:

Hello!



This is in regards to sd-bus function "sd_bus_open_system", where Valgrind reports possible memory leak. See the following code:



mem_test.c:



#include <stdio.h>
#include <stdlib.h>
#include <systemd/sd-bus.h>

int main(int argc, char *argv[]) {
  sd_bus *bus = NULL;

  int r = sd_bus_open_system(&bus);
  if (r < 0) {
    fprintf(stderr, "sd_bus_open_system: %s\n", strerror(-r));
  }
  bus = sd_bus_unref(bus);
}


compile command: gcc mem_test.c -o mem_test `pkg-config --cflags --libs libsystemd`


Valgrind output:



==4452== Memcheck, a memory error detector
==4452== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==4452== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==4452== Command: ./mem_test
==4452==
==4452==
==4452== HEAP SUMMARY:
==4452==     in use at exit: 7,736 bytes in 12 blocks
==4452==   total heap usage: 17 allocs, 5 frees, 8,045 bytes allocated
==4452==
==4452== LEAK SUMMARY:
==4452==    definitely lost: 0 bytes in 0 blocks
==4452==    indirectly lost: 0 bytes in 0 blocks
==4452==      possibly lost: 3,640 bytes in 11 blocks
==4452==    still reachable: 4,096 bytes in 1 blocks
==4452==         suppressed: 0 bytes in 0 blocks



The question is am I doing anything wrong here? Why Valgrind thinks there "might" be memory leak? The interesting part is if I use "sd_bus_open_system", Valgrind is all happy and no warnings at all!



Thank you,

David J.







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