manage memory which was not dynamically allocated

Question

I am a c++ programmer coming from C# background and still have some confusions about memory management in c++

I have a class with three functions

1st returns a pointer to a local variable

2nd returns a pointer to a list of pointers

3rd returns a pointer to a list of lists of pointers

consider this code:

AugmentedActivePastConjugator.h

class AugmentedActivePastConjugator {


    public:

    AugmentedActivePastVerb* createVerb(AugmentedTrilateralRoot* root, int pronounIndex, int formulaNo);

    vector<AugmentedActivePastVerb*>* createVerbList(AugmentedTrilateralRoot* root, int formulaNo);

    vector<vector<AugmentedActivePastVerb*>*>* createAllVerbList(AugmentedTrilateralRoot* root) ;

};

AugmentedActivePastConjugator.cpp

AugmentedActivePastVerb* AugmentedActivePastConjugator::createVerb(AugmentedTrilateralRoot* root, int pronounIndex, int formulaNo) {
    string lastDpa = PastConjugationDataContainer.getLastDpa(pronounIndex);
    string connectedPronoun = PastConjugationDataContainer.getConnectedPronoun(pronounIndex);
    AugmentedActivePastVerb verb (root,lastDpa,connectedPronoun,formulaNo);
    return &verb ;
}

vector<AugmentedActivePastVerb*>* AugmentedActivePastConjugator::createVerbList(AugmentedTrilateralRoot* root, int formulaNo) {
    vector<AugmentedPastVerb *> result;
    for (int i = 0; i < 13; i++) {
        AugmentedActivePastVerb* verb = createVerb(root, i, formulaNo);
        result.push_back(verb);
    }

    return &result;

}

vector<vector<AugmentedActivePastVerb*>*>* AugmentedActivePastConjugator::createAllVerbList(AugmentedTrilateralRoot* root) {
    vector<vector<AugmentedActivePastVerb*>*> result;
    vector<AugmentationFormula*>::iterator  begin = root->getAugmentationList().begin();
    vector<AugmentationFormula*>::iterator  end = root->getAugmentationList().end();
    while (begin !=end) {
        AugmentationFormula* formula =  *begin;
        vector<AugmentedActivePastVerb*>* formulaVerbList = createVerbList(root, formula->getFormulaNo());
        result.push_back(formulaVerbList);
    }
    return &result;
}

if I want to create a list of verbs returned by this class, for example

// general variable
list<AugmentedActivePastVerb *> verbslist;
AugmentedActivePastConjugator conjugator;

void createverbslist()
{
    for (int i=0; i < 20; i++) {
        AugmentedActivePastVerb* verbs = conjugator.createVerb(someroot, pIndex, fNo);
        verbslist.push_back(verb)
    }

}

what should I do after I have finished using verbslist , should I delete all the pointers inside it or will it free them automatically

I have read an article that says:

don't free memory which was not dynamically allocated

so if I shouldn't free it, what happens to those pointers inside verbslist

Answer 1

AugmentedActivePastVerb verb (root,lastDpa,connectedPronoun,formulaNo);
return &verb ;

Never ever do this. verb is allocated on the stack and gets destroyed as soon as the method call is removed from the stack. And voila, your applications points to a variable that's no longer in its place.