指针C++数组中的错误"Stack around the variable was corrupted"

Question

我有一个类Piece和类Board，它们代表棋子和棋盘。在Board类中，我有一个类型为Piece的8*8指针数组，我希望它包含从索引0到63的指针。

然而，我在下面的代码中得到一个错误:

变量'chess_board'周围的堆栈已损坏

Piece* m_Board[8 * 8];
Board() {
int i = 0;
//Black pawns
std::cout << i << std::endl;
m_Board[i] = new Rook(i++, 1);
m_Board[i] = new Knight(i++, 1);
m_Board[i] = new Bishop(i++, 1);
m_Board[i] = new Queen(i++, 1);
m_Board[i] = new King(i++, 1);
m_Board[i] = new Bishop(i++, 1);
m_Board[i] = new Knight(i++, 1);
m_Board[i] = new Rook(i++, 1);
//Black pieces
for (i; i < 16; i++) {
m_Board[i] = new Pawn(i, 1);
}
//Blank squares
std::cout << i << std::endl;
for (i; i < 48; i++) {
m_Board[i] = nullptr;
}
//White pawns
for (i; i < 56; i++) {
m_Board[i] = new Pawn(i, 0);
}
//White pieces
m_Board[i] = new Rook(i++, 0);
m_Board[i] = new Knight(i++, 0);
m_Board[i] = new Bishop(i++, 0);
m_Board[i] = new Queen(i++, 0);
m_Board[i] = new King(i++, 0);
m_Board[i] = new Bishop(i++, 0);
m_Board[i] = new Knight(i++, 0);
m_Board[i] = new Rook(i++, 0);
}

经过一些测试，我发现错误发生在最后m_Board[i] = new Rook(i++, 0);行，其中变量i从63变为64。如果我把那行改成m_Board[i] = new Rook(i, 0);，错误就消失了。

我想知道i++有什么影响，因为我认为m_Board[i] = new Rook(i++, 0);类似于m_Board[i] = new Rook(i, 0); i++?

我只访问数组的第63个元素，并将变量i传递给Rook对象的构造函数，之后变量i将增加1。

这是如何产生错误的?

Answer 1

m_Board[i] = new Rook(i++, 0);和m_Board[i] = new Rook(i, 0); i++;不一样。这是两个不同的序列点。

引用cpp参考

A序列点是执行序列中所有先前求值产生的副作用的点。完整，后续评估也没有副作用。

也

在每个完整表达式的末尾有一个序列点(通常在分号处)。

a[i] = i++; // undefined behavior (until C++17)

请看以下文章:

• https://en.cppreference.com/w/cpp/language/eval_order(特别序列点规则部分)
• https://en.wikipedia.org/wiki/Sequence_point