rapidjson erase array and deallocate memory

Question

i try to erase all array elements within a json file and add some new elements cyclically. The problem is, that the memory of the allocator will never be deallocated after erasing so the memory usage increases by every cycle. Here is my actual code:

    void DataExchanger::updateStatusList()
    {        
        /*Remove status entries*/
        removeStatusEntries();

        rapidjson::Document::AllocatorType& allocator = jsonDoc.GetAllocator();

        /*Get actual Statuslist*/
        std::list<st_Status>* stateList = etur_getStatusListe();

        std::list<st_Status>::iterator it_status;

        for (it_status = stateList->begin(); it_status != stateList->end(); ++it_status) {
            if ((it_status->h_status == 0) && (it_status->z_status == 0))
            {
                continue;
            }
            rapidjson::Value objValue;
            objValue.SetObject();
            objValue.AddMember("mainstatus", it_status->h_status, allocator);
            objValue.AddMember("substatus", it_status->z_status, allocator);
            objValue.AddMember("level", it_status->lvl, allocator);
            objValue.AddMember("isFault", (it_status->bits & 0x2) ? true : false, allocator);
            objValue.AddMember("isResetlockTower", (it_status->bits & 0x40) ? true : false, allocator);
            objValue.AddMember("isResetlockNacelle", (it_status->bits & 0x80) ? true : false, allocator);

            
            jsonDoc[FILE_TAG_STATUS.c_str()].PushBack(objValue, allocator);
        }

    }


    void DataExchanger::removeStatusEntries()
    {

        rapidjson::Value::ConstMemberIterator itr = jsonDoc.FindMember(FILE_TAG_STATUS.c_str());
        if (itr != jsonDoc.MemberEnd())
        {
            for (rapidjson::Value::ConstValueIterator it = itr->value.Begin(); it != itr->value.End();)
            {
                const rapidjson::Value& element = (*it);
                if (element.HasMember("mainstatus"))
                {

                    it = jsonDoc[FILE_TAG_STATUS.c_str()].Erase(it);


                }
            }
        }
    }

Except the memeory issue, the code works and does what it should. Here is a snippet of the related json file:

{
    "RM_Bits": 0,
    "serialnumber": 0,
    "statuslist": [
        {
            "mainstatus": 660,
            "substatus": 5199,
            "level": 5000,
            "isFault": false,
            "isResetlockTower": false,
            "isResetlockNacelle": false
        },
        {
            "mainstatus": 660,
            "substatus": 5198,
            "level": 5000,
            "isFault": false,
            "isResetlockTower": false,
            "isResetlockNacelle": false
        },
        {
            "mainstatus": 660,
            "substatus": 5197,
            "level": 5000,
            "isFault": false,
            "isResetlockTower": false,
            "isResetlockNacelle": false
        },
        {
            "mainstatus": 44,
            "substatus": 5203,
            "level": 30000,
            "isFault": true,
            "isResetlockTower": false,
            "isResetlockNacelle": false
        },
        {
            "mainstatus": 44,
            "substatus": 5240,
            "level": 30000,
            "isFault": true,
            "isResetlockTower": false,
            "isResetlockNacelle": false
        }

    ],
    "warnlist": []
}

I am very grateful for any help. Thanks in advance!

EDIT: I prove the memory usage by printing out the allocators capacity against the actual usage in every cycle.

printf("Capacity: %d\t Used: %d", jsonDoc.GetAllocator().Capacity(), jsonDoc.GetAllocator().Size());

Here is an example output from the memory usage, if the array was empty and one element will be pushed back into it.

I:Capacity: 196608       Used: 132584 //Array is empty, usage is constant
I:Capacity: 196608       Used: 132584
I:Capacity: 196608       Used: 132584
I:Capacity: 196608       Used: 132584
I:Capacity: 196608       Used: 132584
I:Capacity: 196608       Used: 132584
I:Capacity: 196608       Used: 132584
I:Capacity: 196608       Used: 133096 //one element pushed back
I:Capacity: 196608       Used: 133608 //usage increasing 
I:Capacity: 196608       Used: 134120
I:Capacity: 196608       Used: 134632
I:Capacity: 196608       Used: 135144
I:Capacity: 196608       Used: 135656
I:Capacity: 196608       Used: 136168
I:Capacity: 196608       Used: 136680
I:Capacity: 196608       Used: 137192
I:Capacity: 196608       Used: 137704
I:Capacity: 196608       Used: 138216
I:Capacity: 196608       Used: 138728
I:Capacity: 196608       Used: 139240
I:Capacity: 196608       Used: 139752
I:Capacity: 196608       Used: 140264
I:Capacity: 196608       Used: 140776
I:Capacity: 196608       Used: 141800
I:Capacity: 196608       Used: 142312
I:Capacity: 196608       Used: 142824
I:Capacity: 196608       Used: 143336
I:Capacity: 196608       Used: 143848
I:Capacity: 196608       Used: 144360
I:Capacity: 196608       Used: 144872
I:Capacity: 196608       Used: 145384
I:Capacity: 196608       Used: 145896 //the added element above was deleted
I:Capacity: 196608       Used: 146408 //usage is constant again
I:Capacity: 196608       Used: 146408 
I:Capacity: 196608       Used: 146408
I:Capacity: 196608       Used: 146408
I:Capacity: 196608       Used: 146408
I:Capacity: 196608       Used: 146408
I:Capacity: 196608       Used: 146408

If the array is a emtpty the usage stay constant, but as soon as i push one new element to it, the usage will be increased in every cycle.

How were you able to prove memory does not get deallocated? Could you share the results? — mfnx, Dec 14 '20 at 23:09
@mfnx: i have edited my question with the information, how i prove it. Thanks for your help in advance. — joen, Dec 15 '20 at 07:06
Where did you write the printf line? Where did you insert it in your code? I would say you are continuously pushing an object... — mfnx, Dec 16 '20 at 18:16
The order is as followed: In every cycle first i remove the whole array, then i push back elements into the array from a list and finally i print out the capacity and usage. So you are right if you say, that i push objects continuously to the array, but before i do that, i try to remove all array elements. And it seems that the remove function apperently doesn't work correctly. All the elements are deleted but the memory will never deallocated. — joen, Dec 17 '20 at 07:18
Ok, you should provide a minimal reproducable example so we can try it out. — mfnx, Dec 17 '20 at 07:41

rapidjson erase array and deallocate memory

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