c++ - C++中的const参数生命周期

Question

考虑一下:

void l(Event const& e)
{
    KeyEvent& k = (KeyEvent&)e;
    std::cout<<k.action<<" "<<k.keyCode;
}

void k(Event const& e)
{
    KeyEvent& k = (KeyEvent&)e;
    std::cout<<k.action<<" "<<k.keyCode;
}

void t(Event const& e)
{
    l(e);
    k(e);
}

int main(int argc, char* argv[])
{
    t(KeyEvent(1,1));
}

KeyEvent 对象何时从内存中释放(是在作用域结束之后还是我必须删除它)？如果该 KeyEvent 实际上传递的次数远不止于此，我能否确定它会一直有效，直到最后一个使用它的函数结束？

Answer 1

When will the KeyEvent object be released from memory (is it after the scope ends or do I have to delete it)?

它一直存在于内存中，直到完整表达式的末尾，即语句的分号 ;:

t(KeyEvent(1,1));
                ^ end of the full-expression

顺便说一句，你应该在这里const(以避免问题):

KeyEvent const& k = (KeyEvent const&)e; //added const on both side