Deallocate memory to singleton class which access database ?
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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)); } } } } }@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/ -
@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"
}@Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:
SqliteManagerBGSync::cleanup()
C++ basics: return type is missing...
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@Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:
SqliteManagerBGSync::cleanup()
C++ basics: return type is missing...
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@jsulm hi jsulm i am returning nothing. my return type is void.
@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...
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@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...
@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; -
@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;@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++11in your PRO file)? -
@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++11in your PRO file)?@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 .
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@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;SqliteManagerBGSync(); cleanup();both are missing the return type, and also make sure to fix them in the *.cpp file as well!
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SqliteManagerBGSync(); cleanup();both are missing the return type, and also make sure to fix them in the *.cpp file as well!
@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; -
@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;@Qt-embedded-developer As @KroMignon already asked you: do you have a C++11 capable compiler? And is C++11 activated?
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@Qt-embedded-developer As @KroMignon already asked you: do you have a C++11 capable compiler? And is C++11 activated?
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@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 .
@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++11or-std=gnu++11 -
@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(); }@Qt-embedded-developer Then you can't use auto, write the type instead of auto
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@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++11or-std=gnu++11@KroMignon i can not enable it like that because any change like that not allowed in my device.
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@KroMignon i can not enable it like that because any change like that not allowed in my device.
@Qt-embedded-developer than do a normal for(x; x<y; ++x) loop
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@Qt-embedded-developer than do a normal for(x; x<y; ++x) loop
@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-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(); }@Qt-embedded-developer
usingsizeofis almost certainly wrong here.std::map has a size() function, please use that.
https://en.cppreference.com/w/cpp/container/map/size -
@KroMignon i can not enable it like that because any change like that not allowed in my device.
@Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:
i can not enable it like that because any change like that not allowed in my device.
As @jsulm already wrote before, replace
autowith the corresponding type:for(std::map<int,SqliteManagerBGSync*>::iterator it = sqliteManagerMap::begin(); it != sqliteManagerMap::end(); ++it) { ... }It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)
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@Qt-embedded-developer said in Deallocate memory to singleton class which access database ?:
i can not enable it like that because any change like that not allowed in my device.
As @jsulm already wrote before, replace
autowith the corresponding type:for(std::map<int,SqliteManagerBGSync*>::iterator it = sqliteManagerMap::begin(); it != sqliteManagerMap::end(); ++it) { ... }@KroMignon
IIRC range based for loops is a c++11 feature in itself 🤔never mind, I think need a break!
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. -
@KroMignon
IIRC range based for loops is a c++11 feature in itself 🤔never mind, I think need a break!
@J-Hilk said in Deallocate memory to singleton class which access database ?:
IIRC range based for loops is a c++11 feature in itself 🤔
Are you sure? I don't believe that
std::map<>::iteratorsupport is comming with C++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)
