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Deallocate memory to singleton class which access database ?

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  • Q Qt embedded developer

    @jsulm I want to know how to deallocate memory if my class implemented like below :

    /*
 * SqliteManagerBGSync.h
 *
 *  Created on: 16-Jul-2018
 *      Author: ankita.singh
 */

#ifndef TRANSIT_SRC_SQLITEMANAGERBGSYNC_H_
#define TRANSIT_SRC_SQLITEMANAGERBGSYNC_H_

#include <boomer.h>
#include <sqlite/sqlite3.h>
#include <vector>
#include <string>
#include <pthread.h>
#include "Header/AFCSTicket.h"

namespace app {
namespace dbmanager {

class SqliteManagerBGSync {
public:

public :
	static std::map<int,SqliteManagerBGSync *> sqliteManagerMap;
	static	SqliteManagerBGSync* GetDBInstance();
	sqlite3* handle;
	sqlite3_stmt *statement;
	static sqlite3* getDataBaseHandle();

	static SqliteManagerBGSync* GetDBInstanceForBackSync();
	int prepareStatement(const char *query);
	int openDatabase();
	void closeDatabase();
	boomer::transaction::TransactionResult connectToDataBase(std::string fileName, sqlite3* &handle);
	boomer::transaction::TransactionResult disconnectDataBase(sqlite3* &handle);
	void closeDatabaseForDBBackup();

private:
	std::map<int,sqlite3 *> sqliteHandleMap;
	SqliteManagerBGSync();
	cleanup();

};

} /* namespace dbmanager */
} /* namespace app */

#endif /* TRANSIT_SRC_SQLITEMANAGERBGSYNC_H_ */


    #include "SqliteManagerBGSync.h"
#include <stdio.h>
#include <string>


using namespace std;

using namespace boomer::error;

const char* DB_PATH = "TICKET.DB";
pthread_mutex_t databaseLock;


namespace app
{
namespace dbmanager
{
std::map<int,SqliteManagerBGSync *> SqliteManagerBGSync::sqliteManagerMap;
SqliteManagerBGSync::SqliteManagerBGSync()
{
	DBGF_TRACE("AFCS:SqliteManagerBGSync::Constructor Called");
	handle = NULL;
}

SqliteManagerBGSync::cleanup()
{
for (const auto& kv : sqliteManagerMap) {
    delete kv.second;
}
sqliteManagerMap.clear();

}

SqliteManagerBGSync* SqliteManagerBGSync::GetDBInstance()
{
	std::map<int,SqliteManagerBGSync*>::iterator it;
	int threadId = pthread_self();
	DBGF_TRACE("AFCS:SqliteManagerBGSync::thread Id :%d",threadId);

	//sqliteManagerMap.empty() Return 0 If sqliteManagerMap is Not Empty
	//Return 1 If sqliteManagerMap is Empty
	DBGF_TRACE("AFCS:SqliteManagerBGSync::GetDBInstance()::sqliteManagerMap.empty()=%d",sqliteManagerMap.empty());

	if(sqliteManagerMap.empty())
	{
		DBGF_TRACE("AFCS:SqliteManagerBGSync::GetDBInstance()::sqliteManagerMap.empty() IF");
		if(pthread_mutex_init(&databaseLock, NULL) != 0)
		{
			DBGF_TRACE("databaseLock mutex init failed");

		}
		else
		{
			DBGF_TRACE("databaseLock mutex init Success");

		}
	}
//	else
//	{
//		DBGF_TRACE("AFCS:SqliteManagerBGSync::GetDBInstance()::sqliteManagerMap.empty() Else");
//		sqliteManagerMap.insert(std::pair<int,SqliteManagerBGSync*>(threadId,new SqliteManagerBGSync()));
//		it = sqliteManagerMap.find(threadId);
//		DBGF_TRACE("AFCS:SqliteManagerBGSync::sqliteManagerMap success return 1");
//		return it->second;
//	}

	it = sqliteManagerMap.find(threadId);
	if(it == sqliteManagerMap.end())
	{
		DBGF_TRACE("AFCS:SqliteManagerBGSync::GetDBInstance()::threadId Find Success");

		sqliteManagerMap.insert(std::pair<int,SqliteManagerBGSync*>(threadId,new SqliteManagerBGSync()));
		DBGF_TRACE("AFCS:sqliteManagerMap insert called");

		it = sqliteManagerMap.find(threadId);
	}
	DBGF_TRACE("AFCS:SqliteManagerBGSync::sqliteManagerMap success return 2");

	DBGF_TRACE("SqliteManagerBGSync::GetDBInstance _heap_max() = %d",_heap_max());
	DBGF_TRACE("SqliteManagerBGSync::GetDBInstance _heap_current() = %d",_heap_current());

	return it->second;
}

int SqliteManagerBGSync::openDatabase()
{
	DBGF_TRACE("SqliteManagerBGSync::openDatabase::Mutex locking");

	if(app::Header::AFCSTicket::GetAFCSTicketInstance()->getDBClosed()!=0)
	{
		DBGF_TRACE("SqliteManagerBGSync::openDatabase():: If 1");

		pthread_mutex_lock(&databaseLock);
	}
	DBGF_TRACE("SqliteManagerBGSync::openDatabase::Mutex Locked");
	int memused = sqlite3_memory_used();
	DBGF_TRACE("AFCS:SqliteManager::closeDatabase()::memused=%d",memused);

	if(handle != NULL){

		DBGF_TRACE("before SqliteManagerBGSync::openDatabase _heap_max() = %d",_heap_max());
		DBGF_TRACE("before SqliteManagerBGSync::openDatabase _heap_current() = %d",_heap_current());

		int val = sqlite3_db_release_memory(handle);

		memused = sqlite3_memory_used();
		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase()::memused=%d",memused);

		DBGF_TRACE("SqliteManagerBGSync::openDatabase sqlite3_db_cacheflush val = %d",val);

		DBGF_TRACE("AFCS:SqliteManagerBGSync::Handle success");
		DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_max() = %d",_heap_max());
		DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_current() = %d",_heap_current());
		return SUCCESS;
	}

	int res = sqlite3_open(DB_PATH, &handle);
	DBGF_TRACE("AFCS:SqliteManagerBGSync::sqlite3 open = %d",res);


	DBGF_TRACE("AFCS:SqliteManagerBGSync::openDatabase::mutex lock called");
	if(res != SQLITE_OK)
	{
		DBGF_TRACE("SqliteManagerBGSync::openDatabase::Mutex Unlocking");
		if(app::Header::AFCSTicket::GetAFCSTicketInstance()->getDBClosed()!=0)
		{
			DBGF_TRACE("SqliteManagerBGSync::openDatabase():: If 2");
			pthread_mutex_unlock(&databaseLock);
		}
		DBGF_TRACE("SqliteManagerBGSync::openDatabase::Mutex Unlocked");
		DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_max() = %d",_heap_max());
	    DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_current() = %d",_heap_current());
		ERROR_RETURN(-1);
	}else{
		DBGF_TRACE("AFCS:SqliteManagerBGSync::openDatabase::Sqlite ok");

		if(sqlite3_exec(handle, "PRAGMA journal_mode = WAL;PRAGMA  cache_size = 100000;", NULL, 0, NULL) == SQLITE_OK)
		{
			DBGF_TRACE(" SQLITE QUERY SUCCESS: PRAGMA journal_mode = WAL;PRAGMA  cache_size = 100000;");
			DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_max() = %d",_heap_max());
		    DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_current() = %d",_heap_current());
			return SUCCESS;
		}
		else
		{
			DBGF_TRACE(" SQLITE QUERY FAIL : PRAGMA journal_mode = WAL;PRAGMA  cache_size = 100000;");
			DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_max() = %d",_heap_max());
		    DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_current() = %d",_heap_current());
			ERROR_RETURN(0);
		}
		DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_max() = %d",_heap_max());
		DBGF_TRACE("SqliteManagerBGSync::openDatabase() _heap_current() = %d",_heap_current());
		return SUCCESS;
	}

}

int SqliteManagerBGSync::prepareStatement(const char *query)
{
	if(openDatabase() != SUCCESS)
	{
		ERROR_RETURN(-1);
	}

	statement = NULL;
	int res = sqlite3_prepare_v2(handle, query, -1, &statement, 0);

	if(res != SQLITE_OK)
	{
		sqlite3_finalize(statement);
		statement = NULL;
		DBGF_TRACE("Mutex Unlocking");
		pthread_mutex_unlock(&databaseLock);
		DBGF_TRACE("Mutex Unlocked");
		ERROR_RETURN(-1);

	}else{
		return SUCCESS;
	}
}


void SqliteManagerBGSync::closeDatabase()
{
	DBGF_TRACE("AFCS:close database called");
	//SVC_WAIT(1000);

	DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_max() = %d",_heap_max());
	DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_current() = %d",_heap_current());

	if (handle != NULL)
	{
		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase():IF");
		int intReleaseMemoryInBG = 0,intBeforeReleaseInBG=0,intAfterReleaseInBG=0;

		intBeforeReleaseInBG = sqlite3_memory_used();
		intReleaseMemoryInBG = sqlite3_db_release_memory(handle);
		intAfterReleaseInBG = sqlite3_memory_used();

		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase()::intReleaseMemoryInBG=%d",intReleaseMemoryInBG);
		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase()::intBeforeReleaseInBG=%d",intBeforeReleaseInBG);
		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase()::intAfterReleaseInBG=%d",intAfterReleaseInBG);

		int res = sqlite3_close(handle);
		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase()::res=%d",res);
		if( res == SQLITE_OK)
		{
			DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase()::Close Database Success: %s", sqlite3_errmsg(handle));
			//SVC_WAIT(1000);
			DBGF_TRACE("SqliteManagerBGSync::closeDatabase()::Mutex Unlocking");
			if(app::Header::AFCSTicket::GetAFCSTicketInstance()->getDBClosed()!=0)
			{
				DBGF_TRACE("SqliteManagerBGSync::closeDatabase():: If 1");
				pthread_mutex_unlock(&databaseLock);
			}
			DBGF_TRACE("SqliteManagerBGSync::closeDatabase()::Mutex Unlocked");
			handle = NULL;
			DBGF_TRACE("SqliteManagerBGSync::closeDatabase():: Set handle To NULL");
			DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_max() = %d",_heap_max());
			DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_current() = %d",_heap_current());
		}
		else
		{
			DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase()::Close Database Fail: %s", sqlite3_errmsg(handle));
			//LOGF_ERROR("AFCS:Close Database Error: %s", sqlite3_errmsg(handle));
			//SVC_WAIT(1000);
			DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_max() = %d",_heap_max());
			DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_current() = %d",_heap_current());
		}
		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase():Complete IF");
	}
	else
	{
		DBGF_TRACE("AFCS:SqliteManagerBGSync::closeDatabase():Else");
		DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_max() = %d",_heap_max());
		DBGF_TRACE("SqliteManagerBGSync::closeDatabase() _heap_current() = %d",_heap_current());
	}
	cleanup();
}

boomer::transaction::TransactionResult SqliteManagerBGSync::connectToDataBase(std::string dbFilename , sqlite3* &handle)
{
	int res = 0;
	res = sqlite3_open(dbFilename.c_str(), &handle);
	if( res != SQLITE_OK )
	{
		ERROR_RETURN(CONFIG_DB_CONNECT_FAILED);
	}

	return boomer::transaction::trOk;
}

boomer::transaction::TransactionResult SqliteManagerBGSync::disconnectDataBase(sqlite3* &handle)
{
	long errCode = 0;
	//Disconnect to DataBase
	int res = sqlite3_close(handle);
	if(res)
	{
		errCode = CONFIG_DB_DISCONNECT_FAILED;
		return res;
	}
	handle = NULL;
	return boomer::transaction::trOk;
}

}

}
    JonBJ Offline
    JonBJ Offline
    JonB
    wrote on last edited by JonB
    #4

    @Qt-embedded-developer
    This is hundreds of lines of code. Nobody else wants to read through all your code, it's not reasonable to ask them to do so. Please produce a minimal example if you have a question.

    Q 1 Reply Last reply
    1
    • JonBJ JonB

      @Qt-embedded-developer
      This is hundreds of lines of code. Nobody else wants to read through all your code, it's not reasonable to ask them to do so. Please produce a minimal example if you have a question.

      Q Offline
      Q Offline
      Qt embedded developer
      wrote on last edited by Qt embedded developer
      #5

      @JonB sorry for write whole code. but can you give example to how to deallocate memory for recent mentioned singleton class ?

      jsulmJ 1 Reply Last reply
      0
      • Q Qt embedded developer

        @JonB sorry for write whole code. but can you give example to how to deallocate memory for recent mentioned singleton class ?

        jsulmJ Offline
        jsulmJ Offline
        jsulm
        Lifetime Qt Champion
        wrote on last edited by
        #6

        @Qt-embedded-developer Can you please explain what the problem is?
        I already gave you an example how to deallocate memory...

        https://forum.qt.io/topic/113070/qt-code-of-conduct

        Q 1 Reply Last reply
        2
        • jsulmJ jsulm

          @Qt-embedded-developer Can you please explain what the problem is?
          I already gave you an example how to deallocate memory...

          Q Offline
          Q Offline
          Qt embedded developer
          wrote on last edited by
          #7

          @jsulm yes i understood that. but to deallocate memory for below 2 statement i need example.

          std::map<int,sqlite3 *> sqliteHandleMap;

          static std::map<int,SqliteManagerBGSync *> sqliteManagerMap;

          i have tried to implement deallocate memory for them like below function in that class like below :

          SqliteManagerBGSync::cleanup()
{
for (const auto& kv : sqliteManagerMap) {
    delete kv.second;
}
sqliteManagerMap.clear();

}

          but it gives me many errors like below:

                  ^

          "src\SqliteManagerBGSync.h", line 42: Error: #260-D: explicit type is missing ("int" assumed)
          cleanup();
          ^
          "src\SqliteManagerBGSync.cpp", line 25: Error: #260-D: explicit type is missing ("int" assumed)
          SqliteManagerBGSync::cleanup()
          ^
          "src\SqliteManagerBGSync.cpp", line 27: Error: #260-D: explicit type is missing ("int" assumed)
          for (const auto& kv : sqliteManagerMap) {
          ^
          "src\SqliteManagerBGSync.cpp", line 27: Error: #252: reference variable "kv" requires an initializer
          for (const auto& kv : sqliteManagerMap) {
          ^
          "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
          for (const auto& kv : sqliteManagerMap) {
          ^
          "src\SqliteManagerBGSync.cpp", line 27: Error: #29: expected an expression
          for (const auto& kv : sqliteManagerMap) {
          ^
          "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
          for (const auto& kv : sqliteManagerMap) {
          ^
          "src\SqliteManagerBGSync.cpp", line 28: Error: #153: expression must have class type
          delete kv.second;
          ^
          "src\SqliteManagerBGSync.cpp", line 32: Error: #940-D: missing return statement at end of non-void function "app::dbmanager::SqliteManagerBGSync::cleanup"
          }

          jsulmJ 1 Reply Last reply
          0
          • Q Qt embedded developer

            I have seen that my project code is use singleton class to access database.

            I want to free the memory allocated by this class how to do it ? can any body give example for that ?

            #ifndef SQLMANAGER_H_
#define SQLMANAGER_H_

#include <boomer.h>
#include <sqlite/sqlite3.h>
#include <vector>
#include <string>
#include "Header/AFCSTicket.h"
//#include "Error.h"

using namespace std;

namespace app
{
namespace dbmanager
{

class SqliteManager {

public :
	static	SqliteManager* GetDBInstance();
	sqlite3* handle;
	sqlite3_stmt *statement;
	static sqlite3* getDataBaseHandle();

	int prepareStatement(const char *query);
	int openDatabase();
	void closeDatabase();
	boomer::transaction::TransactionResult connectToDataBase(std::string fileName, sqlite3* &handle);
	boomer::transaction::TransactionResult disconnectDataBase(sqlite3* &handle);
	void closeDatabaseForDBBackup();
private:
	SqliteManager();
	static SqliteManager* iSqlInstanceDB;

};
}

}
#endif


            
#include "SqliteManager.h"
#include <stdio.h>
#include <string>


using namespace std;

using namespace boomer::error;

const char* DB_PATH_MAIN = "CONFIG.DB";

namespace app
{
namespace dbmanager
{
SqliteManager* SqliteManager::iSqlInstanceDB = NULL;
SqliteManager::SqliteManager()
{
	handle = NULL;
}

SqliteManager* SqliteManager::GetDBInstance()
{
	DBGF_TRACE("SqliteManager::GetDBInstance _heap_max() = %d",_heap_max());
	DBGF_TRACE("SqliteManager::GetDBInstance _heap_current() = %d",_heap_current());

	if ( iSqlInstanceDB == NULL ) {
		iSqlInstanceDB = new SqliteManager();
		DBGF_TRACE("SqliteManager::GetDBInstance _heap_max() = %d",_heap_max());
	  DBGF_TRACE("SqliteManager::GetDBInstance _heap_current() = %d",_heap_current());
	}
	else
	{
	DBGF_TRACE("SqliteManager::GetDBInstance _heap_max() = %d",_heap_max());
	DBGF_TRACE("SqliteManager::GetDBInstance _heap_current() = %d",_heap_current());
	}
	return iSqlInstanceDB;
}

int SqliteManager::openDatabase()
{
	int memused = sqlite3_memory_used();
    DBGF_TRACE("AFCS:SqliteManager::closeDatabase()::memused=%d",memused);

	if(handle != NULL)
	{
		DBGF_TRACE("before SqliteManager::openDatabase _heap_max() = %d",_heap_max());
		DBGF_TRACE("before SqliteManager::openDatabase _heap_current() = %d",_heap_current());


		int val = sqlite3_db_release_memory(handle);

	    memused = sqlite3_memory_used();
		DBGF_TRACE("AFCS:SqliteManager::closeDatabase()::memused=%d",memused);

		DBGF_TRACE("SqliteManager::openDatabase sqlite3_db_cacheflush val = %d",val);

		DBGF_TRACE("SqliteManager::openDatabase _heap_max() = %d",_heap_max());
		DBGF_TRACE("SqliteManager::openDatabase _heap_current() = %d",_heap_current());
		return SUCCESS;
	}

	int res = sqlite3_open(DB_PATH_MAIN, &handle);
	if(res != SQLITE_OK)
	{
  	DBGF_TRACE("SqliteManager::openDatabase _heap_max() = %d",_heap_max());
		DBGF_TRACE("SqliteManager::openDatabase _heap_current() = %d",_heap_current());
		ERROR_RETURN(0);
	}
	else
	{
		DBGF_TRACE("openDatabase _heap_max() = %d",_heap_max());
	  DBGF_TRACE("openDatabase _heap_current() = %d",_heap_current());

	    if(sqlite3_exec(handle, "PRAGMA journal_mode = WAL;PRAGMA  cache_size = 100000;", NULL, 0, NULL) == SQLITE_OK)
		{
	    DBGF_TRACE("SQLITE QUERY SUCCESS: PRAGMA journal_mode = WAL;PRAGMA  cache_size = 100000;");
			DBGF_TRACE("openDatabase _heap_max() = %d",_heap_max());
		  DBGF_TRACE("openDatabase _heap_current() = %d",_heap_current());
			return SUCCESS;
		}
		else
		{
			DBGF_TRACE("SQLITE QUERY FAIL: PRAGMA journal_mode = WAL;PRAGMA  cache_size = 100000;");
			DBGF_TRACE("openDatabase _heap_max() = %d",_heap_max());
			DBGF_TRACE("openDatabase _heap_current() = %d",_heap_current());

			ERROR_RETURN(0);
		}
		DBGF_TRACE("openDatabase _heap_max() = %d",_heap_max());
		DBGF_TRACE("openDatabase _heap_current() = %d",_heap_current());
		return SUCCESS;
	}

}

int SqliteManager::prepareStatement(const char *query)
{
	if(openDatabase() != SUCCESS)
	{
		ERROR_RETURN(0);
	}

	statement = NULL;
	int res = sqlite3_prepare_v2(handle, query, -1, &statement, 0);

	if(res != SQLITE_OK)
	{
		sqlite3_finalize(statement);
		statement = NULL;

		ERROR_RETURN(0);

	}else{
		return SUCCESS;
	}
}


void SqliteManager::closeDatabase()
{
	DBGF_TRACE("_heap_max() = %d",_heap_max());
    DBGF_TRACE("_heap_current() = %d",_heap_current());
	//	if (handle != NULL)
	//	{
	//		if(sqlite3_close(handle) == SQLITE_OK)
	//		{
	//			DBGF_TRACE("Close Database Success: %s", sqlite3_errmsg(handle));
	//			handle = NULL;
	//		}
	//		else
	//			LOGF_ERROR("Close Database Error: %s", sqlite3_errmsg(handle));
	//	}
}

boomer::transaction::TransactionResult SqliteManager::connectToDataBase(std::string dbFilename , sqlite3* &handle)
{
	int res = 0;
	res = sqlite3_open(dbFilename.c_str(), &handle);
	if( res != SQLITE_OK )
	{
		ERROR_RETURN(CONFIG_DB_CONNECT_FAILED);
	}

	return boomer::transaction::trOk;
}

boomer::transaction::TransactionResult SqliteManager::disconnectDataBase(sqlite3* &handle)
{
	long errCode = 0;
	//Disconnect to DataBase
	int res = sqlite3_close(handle);
	if(res)
	{
		errCode = CONFIG_DB_DISCONNECT_FAILED;
		return res;
	}
	handle = NULL;
	return boomer::transaction::trOk;
}
void SqliteManager::closeDatabaseForDBBackup()
{
	DBGF_TRACE("AFCS:SqliteManager::closeDatabaseForDBBackup()");
	if (handle != NULL)
	{
		if(sqlite3_close(handle) == SQLITE_OK)
		{
			DBGF_TRACE("closeDatabaseForDBBackup::Close Database Success: %s", sqlite3_errmsg(handle));
			handle = NULL;
		}
		else
		{
			//LOGF_ERROR("closeDatabaseForDBBackup::Close Database Error: %s", sqlite3_errmsg(handle));
		}
	}
}

}

}
            J.HilkJ Offline
            J.HilkJ Offline
            J.Hilk
            Moderators
            wrote on last edited by J.Hilk
            #8

            @Qt-embedded-developer deleting a singleton instance is not a trivial matter, you have to follow proper guidelines, or you program may explode.

            I would suggest reading and following
            https://www.interviewsansar.com/singleton-class-delete-design/

            Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct

            Q: What's that?
            A: It's blue light.
            Q: What does it do?
            A: It turns blue.

            1 Reply Last reply
            3
            • Q Qt embedded developer

              @jsulm yes i understood that. but to deallocate memory for below 2 statement i need example.

              std::map<int,sqlite3 *> sqliteHandleMap;

              static std::map<int,SqliteManagerBGSync *> sqliteManagerMap;

              i have tried to implement deallocate memory for them like below function in that class like below :

              SqliteManagerBGSync::cleanup()
{
for (const auto& kv : sqliteManagerMap) {
    delete kv.second;
}
sqliteManagerMap.clear();

}

              but it gives me many errors like below:

                      ^

              "src\SqliteManagerBGSync.h", line 42: Error: #260-D: explicit type is missing ("int" assumed)
              cleanup();
              ^
              "src\SqliteManagerBGSync.cpp", line 25: Error: #260-D: explicit type is missing ("int" assumed)
              SqliteManagerBGSync::cleanup()
              ^
              "src\SqliteManagerBGSync.cpp", line 27: Error: #260-D: explicit type is missing ("int" assumed)
              for (const auto& kv : sqliteManagerMap) {
              ^
              "src\SqliteManagerBGSync.cpp", line 27: Error: #252: reference variable "kv" requires an initializer
              for (const auto& kv : sqliteManagerMap) {
              ^
              "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
              for (const auto& kv : sqliteManagerMap) {
              ^
              "src\SqliteManagerBGSync.cpp", line 27: Error: #29: expected an expression
              for (const auto& kv : sqliteManagerMap) {
              ^
              "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
              for (const auto& kv : sqliteManagerMap) {
              ^
              "src\SqliteManagerBGSync.cpp", line 28: Error: #153: expression must have class type
              delete kv.second;
              ^
              "src\SqliteManagerBGSync.cpp", line 32: Error: #940-D: missing return statement at end of non-void function "app::dbmanager::SqliteManagerBGSync::cleanup"
              }

              jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by
              #9

              @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

              SqliteManagerBGSync::cleanup()

              C++ basics: return type is missing...

              https://forum.qt.io/topic/113070/qt-code-of-conduct

              Q 1 Reply Last reply
              1
              • jsulmJ jsulm

                @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

                SqliteManagerBGSync::cleanup()

                C++ basics: return type is missing...

                Q Offline
                Q Offline
                Qt embedded developer
                wrote on last edited by
                #10

                @jsulm hi jsulm i am returning nothing. my return type is void.

                jsulmJ 1 Reply Last reply
                0
                • Q Qt embedded developer

                  @jsulm hi jsulm i am returning nothing. my return type is void.

                  jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #11

                  @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

                  my return type is void.

                  Then write void there. Come on this is really basic stuff...

                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                  Q 1 Reply Last reply
                  1
                  • jsulmJ jsulm

                    @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

                    my return type is void.

                    Then write void there. Come on this is really basic stuff...

                    Q Offline
                    Q Offline
                    Qt embedded developer
                    wrote on last edited by
                    #12

                    @jsulm Okay thanks. but still i am getting below errors:

                    "src\SqliteManagerBGSync.cpp", line 27: Error: #260-D: explicit type is missing ("int" assumed)
                    for (const auto& kv : sqliteManagerMap) {
                    ^
                    "src\SqliteManagerBGSync.cpp", line 27: Error: #252: reference variable "kv" requires an initializer
                    for (const auto& kv : sqliteManagerMap) {
                    ^
                    "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                    for (const auto& kv : sqliteManagerMap) {
                    ^
                    "src\SqliteManagerBGSync.cpp", line 27: Error: #29: expected an expression
                    for (const auto& kv : sqliteManagerMap) {
                    ^
                    "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                    for (const auto& kv : sqliteManagerMap) {
                    ^
                    "src\SqliteManagerBGSync.cpp", line 28: Error: #153: expression must have class type
                    delete kv.second;

                    KroMignonK J.HilkJ 2 Replies Last reply
                    0
                    • Q Qt embedded developer

                      @jsulm Okay thanks. but still i am getting below errors:

                      "src\SqliteManagerBGSync.cpp", line 27: Error: #260-D: explicit type is missing ("int" assumed)
                      for (const auto& kv : sqliteManagerMap) {
                      ^
                      "src\SqliteManagerBGSync.cpp", line 27: Error: #252: reference variable "kv" requires an initializer
                      for (const auto& kv : sqliteManagerMap) {
                      ^
                      "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                      for (const auto& kv : sqliteManagerMap) {
                      ^
                      "src\SqliteManagerBGSync.cpp", line 27: Error: #29: expected an expression
                      for (const auto& kv : sqliteManagerMap) {
                      ^
                      "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                      for (const auto& kv : sqliteManagerMap) {
                      ^
                      "src\SqliteManagerBGSync.cpp", line 28: Error: #153: expression must have class type
                      delete kv.second;

                      KroMignonK Offline
                      KroMignonK Offline
                      KroMignon
                      wrote on last edited by KroMignon
                      #13

                      @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

                      Okay thanks. but still i am getting below errors:

                      Do your compiler support C++11 and did you enable C++11 support (eg. add CONFIG += c++11 in your PRO file)?

                      It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                      Q 1 Reply Last reply
                      2
                      • KroMignonK KroMignon

                        @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

                        Okay thanks. but still i am getting below errors:

                        Do your compiler support C++11 and did you enable C++11 support (eg. add CONFIG += c++11 in your PRO file)?

                        Q Offline
                        Q Offline
                        Qt embedded developer
                        wrote on last edited by Qt embedded developer
                        #14

                        @KroMignon Hi i am not using qt . and sorry i can not enable C++ 11 because my compiler not support it. i can access map like std::map .

                        KroMignonK 1 Reply Last reply
                        0
                        • Q Qt embedded developer

                          @jsulm Okay thanks. but still i am getting below errors:

                          "src\SqliteManagerBGSync.cpp", line 27: Error: #260-D: explicit type is missing ("int" assumed)
                          for (const auto& kv : sqliteManagerMap) {
                          ^
                          "src\SqliteManagerBGSync.cpp", line 27: Error: #252: reference variable "kv" requires an initializer
                          for (const auto& kv : sqliteManagerMap) {
                          ^
                          "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                          for (const auto& kv : sqliteManagerMap) {
                          ^
                          "src\SqliteManagerBGSync.cpp", line 27: Error: #29: expected an expression
                          for (const auto& kv : sqliteManagerMap) {
                          ^
                          "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                          for (const auto& kv : sqliteManagerMap) {
                          ^
                          "src\SqliteManagerBGSync.cpp", line 28: Error: #153: expression must have class type
                          delete kv.second;

                          J.HilkJ Offline
                          J.HilkJ Offline
                          J.Hilk
                          Moderators
                          wrote on last edited by
                          #15

                          @Qt-embedded-developer

                          SqliteManagerBGSync();
cleanup();

                          both are missing the return type, and also make sure to fix them in the *.cpp file as well!

                          Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct

                          Q: What's that?
                          A: It's blue light.
                          Q: What does it do?
                          A: It turns blue.

                          Q 1 Reply Last reply
                          0
                          • J.HilkJ J.Hilk

                            @Qt-embedded-developer

                            SqliteManagerBGSync();
cleanup();

                            both are missing the return type, and also make sure to fix them in the *.cpp file as well!

                            Q Offline
                            Q Offline
                            Qt embedded developer
                            wrote on last edited by
                            #16

                            @J-Hilk i have changed it . i have used void, But still i am getting as below mentioned error:

                            "src\SqliteManagerBGSync.cpp", line 27: Error: #260-D: explicit type is missing ("int" assumed)
                            for (const auto& kv : sqliteManagerMap) {
                            ^
                            "src\SqliteManagerBGSync.cpp", line 27: Error: #252: reference variable "kv" requires an initializer
                            for (const auto& kv : sqliteManagerMap) {
                            ^
                            "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                            for (const auto& kv : sqliteManagerMap) {
                            ^
                            "src\SqliteManagerBGSync.cpp", line 27: Error: #29: expected an expression
                            for (const auto& kv : sqliteManagerMap) {
                            ^
                            "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                            for (const auto& kv : sqliteManagerMap) {
                            ^
                            "src\SqliteManagerBGSync.cpp", line 28: Error: #153: expression must have class type
                            delete kv.second;

                            jsulmJ 1 Reply Last reply
                            0
                            • Q Qt embedded developer

                              @J-Hilk i have changed it . i have used void, But still i am getting as below mentioned error:

                              "src\SqliteManagerBGSync.cpp", line 27: Error: #260-D: explicit type is missing ("int" assumed)
                              for (const auto& kv : sqliteManagerMap) {
                              ^
                              "src\SqliteManagerBGSync.cpp", line 27: Error: #252: reference variable "kv" requires an initializer
                              for (const auto& kv : sqliteManagerMap) {
                              ^
                              "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                              for (const auto& kv : sqliteManagerMap) {
                              ^
                              "src\SqliteManagerBGSync.cpp", line 27: Error: #29: expected an expression
                              for (const auto& kv : sqliteManagerMap) {
                              ^
                              "src\SqliteManagerBGSync.cpp", line 27: Error: #65: expected a ";"
                              for (const auto& kv : sqliteManagerMap) {
                              ^
                              "src\SqliteManagerBGSync.cpp", line 28: Error: #153: expression must have class type
                              delete kv.second;

                              jsulmJ Offline
                              jsulmJ Offline
                              jsulm
                              Lifetime Qt Champion
                              wrote on last edited by
                              #17

                              @Qt-embedded-developer As @KroMignon already asked you: do you have a C++11 capable compiler? And is C++11 activated?

                              https://forum.qt.io/topic/113070/qt-code-of-conduct

                              Q 1 Reply Last reply
                              1
                              • jsulmJ jsulm

                                @Qt-embedded-developer As @KroMignon already asked you: do you have a C++11 capable compiler? And is C++11 activated?

                                Q Offline
                                Q Offline
                                Qt embedded developer
                                wrote on last edited by Qt embedded developer
                                #18

                                @jsulm no i have not. So what i have to change in below function:

                                SqliteManagerBGSync::cleanup()
{
for (const auto& kv : sqliteManagerMap) {
    delete kv.second;
}
sqliteManagerMap.clear();

}
                                jsulmJ 1 Reply Last reply
                                0
                                • Q Qt embedded developer

                                  @KroMignon Hi i am not using qt . and sorry i can not enable C++ 11 because my compiler not support it. i can access map like std::map .

                                  KroMignonK Offline
                                  KroMignonK Offline
                                  KroMignon
                                  wrote on last edited by KroMignon
                                  #19

                                  @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

                                  Hi i am not using qt . and sorry i can not enable C++ 11. i can access map like std::map .

                                  The problem is not std::map<>() but the way you iterate through the map: for (const auto& kv : sqliteManagerMap) requires at least C++11 support enabled! (cf. https://en.cppreference.com/w/cpp/container/map)

                                  I don't know which kind of C++ compiler you are using, for GCC for example enabling C++11 is done with -std=c++11 or -std=gnu++11

                                  It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                                  Q 1 Reply Last reply
                                  3
                                  • Q Qt embedded developer

                                    @jsulm no i have not. So what i have to change in below function:

                                    SqliteManagerBGSync::cleanup()
{
for (const auto& kv : sqliteManagerMap) {
    delete kv.second;
}
sqliteManagerMap.clear();

}
                                    jsulmJ Offline
                                    jsulmJ Offline
                                    jsulm
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #20

                                    @Qt-embedded-developer Then you can't use auto, write the type instead of auto

                                    https://forum.qt.io/topic/113070/qt-code-of-conduct

                                    1 Reply Last reply
                                    1
                                    • KroMignonK KroMignon

                                      @Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:

                                      Hi i am not using qt . and sorry i can not enable C++ 11. i can access map like std::map .

                                      The problem is not std::map<>() but the way you iterate through the map: for (const auto& kv : sqliteManagerMap) requires at least C++11 support enabled! (cf. https://en.cppreference.com/w/cpp/container/map)

                                      I don't know which kind of C++ compiler you are using, for GCC for example enabling C++11 is done with -std=c++11 or -std=gnu++11

                                      Q Offline
                                      Q Offline
                                      Qt embedded developer
                                      wrote on last edited by
                                      #21

                                      @KroMignon i can not enable it like that because any change like that not allowed in my device.

                                      J.HilkJ KroMignonK 2 Replies Last reply
                                      0
                                      • Q Qt embedded developer

                                        @KroMignon i can not enable it like that because any change like that not allowed in my device.

                                        J.HilkJ Offline
                                        J.HilkJ Offline
                                        J.Hilk
                                        Moderators
                                        wrote on last edited by
                                        #22

                                        @Qt-embedded-developer than do a normal for(x; x<y; ++x) loop

                                        Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct

                                        Q: What's that?
                                        A: It's blue light.
                                        Q: What does it do?
                                        A: It turns blue.

                                        Q 1 Reply Last reply
                                        1
                                        • J.HilkJ J.Hilk

                                          @Qt-embedded-developer than do a normal for(x; x<y; ++x) loop

                                          Q Offline
                                          Q Offline
                                          Qt embedded developer
                                          wrote on last edited by
                                          #23

                                          @J-Hilk ,@jsulm ,@jsulm ,@KroMignon Thanks for enormous support.

                                          i have written like it below and now its not show any error:

                                          void SqliteManagerBGSync::cleanup()
{
for (short int i =0 ; i<sizeof(sqliteManagerMap);i++)
{
    delete sqliteManagerMap[i];
}
sqliteManagerMap.clear();

}
                                          J.HilkJ 1 Reply Last reply
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