valgrind reports about leak memory

[DrakonST88]

Describe the bug

==13247== Memcheck, a memory error detector
==13247== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==13247== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==13247== Command: ./test_json
==13247== Parent PID: 1132
==13247== 
==13247== 
==13247== HEAP SUMMARY:
==13247==     in use at exit: 40 bytes in 1 blocks
==13247==   total heap usage: 57 allocs, 56 frees, 93,478 bytes allocated
==13247== 
==13247== 40 bytes in 1 blocks are still reachable in loss record 1 of 1
==13247==    at 0x483BE63: operator new(unsigned long) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==13247==    by 0x486B8D1: Json::Value::nullSingleton() (in /usr/lib/x86_64-linux-gnu/libjsoncpp.so.1.7.4)
==13247==    by 0x485F93C: ??? (in /usr/lib/x86_64-linux-gnu/libjsoncpp.so.1.7.4)
==13247==    by 0x4011B99: call_init.part.0 (dl-init.c:72)
==13247==    by 0x4011CA0: call_init (dl-init.c:30)
==13247==    by 0x4011CA0: _dl_init (dl-init.c:119)
==13247==    by 0x4001139: ??? (in /usr/lib/x86_64-linux-gnu/ld-2.31.so)
==13247== 
==13247== LEAK SUMMARY:
==13247==    definitely lost: 0 bytes in 0 blocks
==13247==    indirectly lost: 0 bytes in 0 blocks
==13247==      possibly lost: 0 bytes in 0 blocks
==13247==    still reachable: 40 bytes in 1 blocks
==13247==         suppressed: 0 bytes in 0 blocks
==13247== 
==13247== For lists of detected and suppressed errors, rerun with: -s
==13247== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

To Reproduce
Steps to reproduce the behavior:

1. Compile:
   test_json.cc

include <cstdlib>
#include <fstream>
#include <iostream>
#include <ctime>
#include <fstream>
#include <jsoncpp/json/json.h>

int main(int argc, char *argv[])
{
    Json::Value _json;
    Json::StyledStreamWriter writer_jsonf;
    Json::FastWriter writer_json;
    std::ofstream outFile;

    // Data for json
    std::string name = "MyTest";
    int host = 2;
    int core = 5;

    _json[name]["timestamp"] = Json::Value::UInt64(time(nullptr));
    _json[name]["host"] = Json::Value(host);
    _json[name]["core"] = Json::Value(core);

    std::cout << "=> _json:\n" << _json << std::endl;

    // Write the output to a file
    outFile.open("output.jsonf");
    writer_jsonf.write(outFile, _json);
    outFile.close();

    // Write the output to a file as single line
    outFile.open("output.json");
    outFile << writer_json.write(_json);
    outFile.close();

    return 0;
}

Makefile

CPPFLAGS = -fdiagnostics-color=always -g3 -O0 -Wall -std=c++17
LDFLAGS =
LDLIBS = -ljsoncpp

APP := test_json

.PHONY: all clean

all:
    $(CXX) $(CPPFLAGS) $(LDFLAGS) $(APP).cc $(LDLIBS) -o $(APP)

clean:
    rm -f $(APP) output.json*

2. Run:
   valgrind --leak-check=full --show-leak-kinds=all --show-reachable=yes --log-file=rslt.log ./test_json

Expected behavior
No leak memory

Desktop (please complete the following information):
Linux 5.4.0-42-generic #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

[BillyDonahue]

Looking at the report, there is no leak reported here.

The unfreed allocation for the null singleton is still reachable. If it's reachable it's not leaked.

Theoretically there would be a leak if the jsoncpp DLL is unloaded though.

[BillyDonahue]

nullSingleton hasn't allocated for a long time.

This is a report about 8 year old version v1.7.4.

==13247==    by 0x486B8D1: Json::Value::nullSingleton() (in /usr/lib/x86_64-linux-gnu/libjsoncpp.so.1.7.4)

I think we can say the fix is to upgrade the library at this point.

[DrakonST88]

I have 20.04 amd64 ubuntu. And I can install via apt-get only 1.7.4 version.
I find https://packages.ubuntu.com/en/source/kinetic/libjsoncpp but it's for 22.04.
I can't upgrade ubuntu.
May I get link repository for install a version with fix this problem?

[BillyDonahue]

I have 20.04 amd64 ubuntu. And I can install via apt-get only 1.7.4 version. I find https://packages.ubuntu.com/en/source/kinetic/libjsoncpp but it's for 22.04. I can't upgrade ubuntu. May I get link repository for install a version with fix this problem?

There are several packages of 1.9.4 and 1.9.5 on this list.
I don't know how you would use them though. I do not have the hang of apt-get.
https://packages.ubuntu.com/search?keywords=jsoncpp