Exc access error - c++

Question

Very new to C++ and having problems returning a vector. I put a breakpoint and the array is correct (populated with all the objects I would expect from the query). But when it returns I get an error:
EXC_BAD_ACCESS
on line m_pComponentContainer->removeAll();
from CCNode.cpp
Which is strange since this is a base class (does NOT inherit from any kind of CC object) although I am extensively using the Cocos2dx framework, its not included in this class.
Im fairly sure this is because something is being deallocated. However like I said Im very new to C++ and not really sure where the problem is. I was hoping to get a little further in development before I had to start worrying about memory management.
int numberOfCards = DatabaseHelper::getNumberOfCards();
//cant be zero
assert(numberOfCards);
std::vector<CardSlot> returnArray(numberOfCards);
sqlite3_stmt * statement;
if (sqlite3_open(this->dbpath.c_str(),&this->cardWarsDB) == SQLITE_OK)
{
const char* query_stmt = "select ID, HP, MP, AbilityText from Cards WHERE ID IN (SELECT DISTINCT cardsID FROM Deck WHERE name = 'All')";
if (sqlite3_prepare_v2(this->cardWarsDB, query_stmt, -1, &statement, NULL) == SQLITE_OK)
{
while (sqlite3_step(statement) == SQLITE_ROW)
{
CardSlot *aCard;
const char* cardID = (const char*)sqlite3_column_text(statement, 0);
const char* cardHP = (const char*)sqlite3_column_text(statement, 1);
const char* cardMP = (const char*)sqlite3_column_text(statement, 2);
const char* cardAbility = (const char*)sqlite3_column_text(statement, 3);
if (cardID != NULL) {
std::string imageName = ".png";
imageName = cardID + imageName;
aCard = (CardSlot *)CardSlot::spriteWithFile(imageName.c_str());
}
if (cardID != NULL) {
aCard->cardID = std::string(cardID);
cocos2d::CCLog("DB returned results, cardID: %s",aCard->cardID.c_str());
}
if (cardHP != NULL) {
aCard->cardHP = std::string(cardHP);
cocos2d::CCLog("DB returned results, cardHP: %s",aCard->cardHP.c_str());
}
if (cardMP != NULL) {
aCard->cardMP = std::string(cardMP);
cocos2d::CCLog("DB returned results, cardMP: %s",aCard->cardMP.c_str());
}
if (cardAbility != NULL) {
aCard->cardAbility = std::string(cardAbility);
cocos2d::CCLog("DB returned results, cardAbility: %s",aCard->cardAbility.c_str());
}
numberOfCards--;
returnArray[numberOfCards] = *aCard;
}
sqlite3_finalize(statement);
}
sqlite3_close(this->cardWarsDB);
return returnArray;
}
Here is a screenshot of the stack trace. I was just looking at it, and it seems that it is the CardSlot objects are the culprits.
But still dont know how to "retain" them, but Ill look at some Cocos documentation.
NOTE1

Answer 1

It looks like your CardSlot is not safe to copy. You copy CardSlots in at least two places:
aCard = * CardSlot::spriteWithFile(imageName.c_str()); (also a memory leak assuming spriteWithFile returns CardSlot *; the "temporary" is not destructed)
returnArray[numberOfCards] = aCard;
From what I can tell, you are probably keeping a CCSprite pointer in CardSlot and destroying it (with delete) in your CardSlot destructor. However, this pointer gets destroyed multiple times because of the copies, which causes your crash.
You need to redesign your class so it can either be safely copied, or refactor your code so that you make no copies (e.g. by using a vector<shared_ptr<CardSlot> > to hold pointers to the instances).

Answer 2

I have edited the code to use more pointers rather then passing around and filling my array with objects. However I think a big thing that helped fix it was using cocos2d::CCArray instead of a std::vector. Most of my classes are children of Cocos2d classes (CCSprites, and CCLayers) and so using its own array data type makes sense.
cocos2d::CCArray DatabaseHelper::getAllCards()
{
int numberOfCards = DatabaseHelper::getNumberOfCards();
//cant be zero
assert(numberOfCards);
cocos2d::CCArray returnArray(numberOfCards);
sqlite3_stmt * statement;
if (sqlite3_open(this->dbpath.c_str(),&this->cardWarsDB) == SQLITE_OK)
{
const char* query_stmt = "select ID, HP, MP, AbilityText from Cards WHERE ID IN (SELECT DISTINCT cardsID FROM Deck WHERE name = 'All')";
if (sqlite3_prepare_v2(this->cardWarsDB, query_stmt, -1, &statement, NULL) == SQLITE_OK)
{
while (sqlite3_step(statement) == SQLITE_ROW)
{
CardSlot* aCard;
const char* cardID = (const char*)sqlite3_column_text(statement, 0);
const char* cardHP = (const char*)sqlite3_column_text(statement, 1);
const char* cardMP = (const char*)sqlite3_column_text(statement, 2);
const char* cardAbility = (const char*)sqlite3_column_text(statement, 3);
if (cardID != NULL) {
std::string imageName = ".png";
imageName = cardID + imageName;
aCard = CardSlot::spriteWithFile(imageName.c_str());
}
if (cardID != NULL) {
aCard->cardID = std::string(cardID);
cocos2d::CCLog("DB returned results, cardID: %s",aCard->cardID.c_str());
}
if (cardHP != NULL) {
aCard->cardHP = std::string(cardHP);
cocos2d::CCLog("DB returned results, cardHP: %s",aCard->cardHP.c_str());
}
if (cardMP != NULL) {
aCard->cardMP = std::string(cardMP);
cocos2d::CCLog("DB returned results, cardMP: %s",aCard->cardMP.c_str());
}
if (cardAbility != NULL) {
aCard->cardAbility = std::string(cardAbility);
cocos2d::CCLog("DB returned results, cardAbility: %s",aCard->cardAbility.c_str());
}
numberOfCards--;
returnArray.addObject(aCard);
}
sqlite3_finalize(statement);
}
sqlite3_close(this->cardWarsDB);
return returnArray;
}
//incase sql fails, close db and created a "FAILED" card
sqlite3_close(this->cardWarsDB);
cocos2d::CCLog("DB returned error: cant open char catagories file");
cocos2d::CCArray failedReturnArray(1);
CardSlot * aCard;
aCard->cardID = std::string("FAILED");
aCard->cardHP = std::string("FAILED");
aCard->cardMP = std::string("FAILED");
aCard->cardAbility = std::string("FAILED");
failedReturnArray.addObject(aCard);
return failedReturnArray;
}
Also in case anyone cares here is CardSlot (not much to it, only built the constructor at this time):
CardSlot * CardSlot::spriteWithFile(const char *pszFileName)
{
CCLOG("CardSlot::spriteWithFile");
CardSlot * aCard = new CardSlot();
if (aCard && aCard->initWithFile(pszFileName))
{
aCard->cardID = pszFileName;
aCard->scheduleUpdate();
aCard->autorelease();
return aCard;
}
CC_SAFE_DELETE(aCard);
return NULL;
}
The only thing Im concerned about is that I think my CCArray should be a pointer. But its working now and learning all the memory management "tricks of the trade" will come in time, the more I work with C++
Thanks #nneonneo for all the help Im sure your fix would have worked and I tried but no matter what I did couldnt get the vector to work. I 1up'd you as much as I could but really this is the "Answer" I implemented.

Answer 3

The returnArray is declared local to the function, it will be deallocated when the function returns. You would need to either declare it as static or move the declaration to outside the function.