std::vector push_back 上的 Segfault/“向量不可解引用”

Posted 2023-02-21

【中文标题】std::vector push_back 上的 Segfault/“向量不可解引用”

【英文标题】：Segfault/ "Vector is not dereferencable" on std::vector push_back

【发布时间】：2013-09-09 20:02:14

【问题描述】：

我有一些处理纸牌游戏的 C++ 代码，它出现了段错误，我不知道为什么。我尝试在 MSVS 2012 中运行它以获得更清晰的错误，但它抛出了“Vector is not dereferencable”。我试着做一些研究，但我不知道错误来自哪里。我猜这个错误不在 push_back 中，而是在其他地方，因为问题线大部分时间都有效。错误发生在 Table::hit() 中。查看代码后，我认为该错误可能存在于 Hand::split() 中，但我不确定，我更不确定如何修复它。谢谢！

class Hand
    
public:
std::vector<Card> hand;
bool active, doubled, isBlackjack, busted;

Hand() : active(true), doubled(false), isBlackjack(false), busted(false)  
Hand(const Hand& _hand);

void removeCard(Card card)  hand.erase( hand.begin() ); 
Card split();
void clear();
int cards() const  return hand.size(); 
int getHandValue() const;
Card at(int pos)  return hand[pos]; 

friend std::ostream& operator<< (std::ostream& out, const Hand& hand);
friend std::ostream& operator<< (std::ostream& out, const std::vector<Hand>& hands);
;

Hand::Hand(const Hand& _hand)
: hand(_hand.hand), active(_hand.active), doubled(_hand.doubled), isBlackjack(_hand.isBlackjack), busted(_hand.busted)
 

Card Hand::split()
 //COULD THE BELOW CODE BE CAUSING ISSUES?
Card card = hand[0];

hand.erase( hand.begin() );

return card;    


void Hand::clear()

active = true;
hand.clear();


int Hand::getHandValue() const

int value(0), aces(0);

for(std::vector<Card>::const_iterator it = hand.cbegin(); it != hand.cend(); ++it)

    value += getCardValue(it->getRank());
    if(it->getRank() == ACE)
        ++aces;


while(aces > 0 && value > 21)

    value -= 10;
    --aces;


return value;


std::ostream& operator<< (std::ostream& out, const Hand& hand)

for(std::vector<Card>::const_iterator it = hand.hand.begin(); it != hand.hand.end(); ++it)

    out << *it << " ";


out << hand.getHandValue();

return out;


std::ostream& operator<< (std::ostream& out, const std::vector<Hand>& hands)

for(std::vector<Hand>::const_iterator it = hands.begin(); it != hands.end(); ++it)

    out << *it << " ";


return out;


class Table

protected:
Shoe shoe;
Strategy strat;
Hand dealer;
std::vector< Hand > player;

double balance, blackjackPayoff;
bool hitSoft17;

void deal();

void hit(int split=0);

void split(int split=0);

double stand();

Action getUserAction();

bool isCurrentGame();

public:
Table(int decks, int _balance);

double bet;

void play();

void print();

void simulate(std::string fileName, int hands);
;

 Table::Table(int decks, int _balance)
: shoe(decks), balance(_balance), blackjackPayoff(1.5), hitSoft17(true), bet(10)


bool Table::isCurrentGame()

for(std::vector<Hand>::iterator it = player.begin(); it != player.end(); ++it)

    if(it->active)
        return true;


return false;


void Table::deal()

dealer.clear();
player.clear();

dealer.addCard( shoe.pullCard(true) );
dealer.addCard( shoe.pullCard() );

player.push_back(Hand());

player[0].addCard( shoe.pullCard() );
player[0].addCard( shoe.pullCard() );

if(player[0].getHandValue() == 21 && dealer.getHandValue() == 21)

    player[0].active = false;

else if(player[0].getHandValue() == 21)

    player[0].active = false;

else if(dealer.getHandValue() == 21)

    player[0].active = false;




void Table::hit(int split)

player[split].hand.push_back( shoe.pullCard() ); //SEGFAULT HERE

if(player[split].getHandValue() > 21)

    player[split].active = false;



void Table::split(int split)
 
player.push_back(Hand());
player[player.size() - 1].hand.push_back( player[split].split() );
player[split].hand.push_back( shoe.pullCard() );
player[player.size() - 1].hand.push_back( shoe.pullCard() );

if(player[split].getHandValue() == 21)

    player[split].active = false;

else if(player[player.size() - 1].getHandValue() == 21)

    player[player.size() - 1].active = false;




double Table::stand()

double winnings(0.0);
bool allNats(true);
//dealer.push_back( shoe.pullCard() );
for(std::vector<Hand>::iterator it = player.begin(); it != player.end(); ++it)

    if(it->cards() == 2 && it->getHandValue() == 21)
    
        winnings += bet * blackjackPayoff;
        it->isBlackjack = true;
    
    else
    
        allNats = false;
        if(it->getHandValue() > 21)
            it->busted = true;
    


if(!allNats)

    while(dealer.getHandValue() <= 17)
    
        if(dealer.getHandValue() == 17)
        
            //dealer has 17 and doesnt hit soft 17s so hes not going to draw anymore cards
            if( !hitSoft17 || dealer.cards() != 2 || !(dealer.hand.at(0) == ACE || dealer.hand.at(1) == ACE) )
                break;
        

        dealer.addCard( shoe.pullCard() );
    


for(std::vector<Hand>::iterator it = player.begin(); it != player.end(); ++it)

    if(!it->isBlackjack)
    
        if(it->busted)
        
            if(it->doubled)
                winnings -= 2.0 * bet;
            else
                winnings -= bet;
        
        else if(dealer.getHandValue() > 21 || dealer.getHandValue() < it->getHandValue())
        
            if(it->doubled)
                winnings += 2.0 * bet;
            else
                winnings += bet;
        
        else if(dealer.getHandValue() > it->getHandValue())
        
            if(it->doubled)
                winnings -= 2.0 * bet;
            else
                winnings -= bet;
        
    

//only other scenario is a push which we dont do anythign for

return winnings;


void Table::simulate(std::string fileName, int hands)

int i(0), countHL;
double trueCountHL;
std::ofstream ofs(fileName);

Action action;

while(i < hands)

    deal();
    VisibleCards vc(player[0].at(0), player[0].at(1), dealer.at(0));
    while(isCurrentGame())
    
        int j(0), q(1);
        countHL = shoe.getCountHL();
        trueCountHL = shoe.getTrueCountHL();

        for(int l = 0; l < q; ++l)
        
            while(player[l].active)
            

                if(player[l].cards() == 2)
                    action = getBasicStrategy(player[l].getHandValue(), dealer.at(0).getCardValue(),
                                player[l].at(0).getCardValue(), player[l].at(1).getCardValue());
                else
                    action = getBasicStrategy(player[l].getHandValue(), dealer.at(0).getCardValue());

                switch(action)
                
                case HIT:
                    hit(j);
                    break;
                case DOUBLE:
                    hit(j);
                    if(player[l].cards() == 3)
                    
                        player[l].doubled = true;
                        player[l].active = false;
                    
                    break;
                case SPLIT:
                    if(player.size() <= 4)
                    
                        split(j);
                        ++q;
                    
                    else
                        hit(j);

                    break;
                case STAND:
                    player[l].active = false;
                    break;
                

                ++j;
            
        
    

    double winnings = stand();
    balance += winnings;

    ofs << std::endl << std::fixed << vc << "," << winnings << "," << std::setprecision(2) << trueCountHL
        << "," << balance << "," << std::setprecision(0) << countHL << "," << shoe.getRemainingDecks();
    ofs << std::endl << 1;
    //BlackjackData bjd(winnings, balance, shoe.getTrueCountHL(), shoe.getCountHL(), HIT);      
    //strat.addData(vc, bjd);
    ++i;


strat.print(fileName);

【问题讨论】：

一个完整的程序，其输入可以证明问题是理想的。

【参考方案1】：

看起来您正在尝试使用 hand[0] 和 hand.erase(hand.begin()) 从 hand 获取第一张卡片，而没有先检查是否有第一张卡片。如果hand 为空（就像从构造函数中新创建的Hand 一样），这会导致未定义的行为，这很可能会在以后表现为崩溃。

【讨论】：

这绝对是我需要解决的一个潜在问题，但似乎不是这里的问题，我尝试检查手是否都是空的，但事实并非如此。此外，我在 MSVS 中进行了调试，似乎有一个有效的卡片对象（具有等级和花色）试图在崩溃前被推回向量中。

【参考方案2】：

我盯着这个看了一天，想不通，走出去，意识到我有一个旧变量“j”，当我调用“hit”时，我用它来访问向量而不是“l” "函数....感谢大家的帮助。