Deallocate memory to singleton class which access database ?

[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!

[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;

[jsulm]

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

[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();

}

[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

[jsulm]

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

[Qt embedded developer]

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

[J.Hilk]

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

[Qt embedded developer]

@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]

@Qt-embedded-developer
using sizeof is almost certainly wrong here.

std::map has a size() function, please use that.
https://en.cppreference.com/w/cpp/container/map/size

[KroMignon]

@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 auto with the corresponding type:

for(std::map<int,SqliteManagerBGSync*>::iterator it = sqliteManagerMap::begin(); it != sqliteManagerMap::end(); ++it)
{
...
}

[J.Hilk]

@KroMignon IIRC range based for loops is a c++11 feature in itself 🤔

never mind, I think need a break!

[KroMignon]

@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<>::iterator support is comming with C++11.

[jsulm]

@KroMignon I think @J-Hilk misunderstood your code: you are not using range based loop

[Qt embedded developer]

@KroMignon Here inside for loop i need to write

for(std::map<int,SqliteManagerBGSync*>::iterator it = sqliteManagerMap::begin(); it != sqliteManagerMap::end(); ++it)
{
delete it;
}

or what i need to write to deallocate memory ?

[jsulm]

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

delete it;

delete it->second;

of course

[KroMignon]

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

or what i need to write to deallocate ?

Please, take time to read std::map<> documentation.
You are using a map iterator, so it is a container object which gives you access to key and value.

delete it do not make sense!

You want to delete the pointer hold in the value part: delete it->second

[Qt embedded developer]

This post is deleted!

[Qt embedded developer]

@KroMignon Hi when i put sqliteManagerMap::begin() and sqliteManagerMap::end() i am getting error .

like below :

for(std::map<int,SqliteManagerBGSync *>::iterator it = sqliteManagerMap::begin(); it != sqliteManagerMap::end(); ++it)

but when i put sqliteManagerMap.begin() then i am getting no error.

[jsulm]

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

sqliteManagerMap::begin() and sqliteManagerMap::end()

As already explained in your other thread: begin() and end() are non-static methods, so you call them with . not :: !
Please learn C++ and read documentation!