switch里面报crosses-initialization

最新推荐文章于 2024-05-13 05:16:19 发布

chadm

最新推荐文章于 2024-05-13 05:16:19 发布

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文章标签： c++ switch

本文链接：https://blog.youkuaiyun.com/weixin_42695485/article/details/130835636

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文章讨论了在C++中遇到的交叉初始化问题，指出在switch语句中直接跳转到局部变量作用域内并使用未初始化的变量会导致编译失败。只有当变量是POD类型并且没有初始值时，这样的跳跃才是允许的。解决方案是确保变量在使用前被正确初始化。

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如下写法会报错crosses initialization of ‘int r’

    switch(i) {
        case 1:
            int r = 1; // Failed to Compile
            cout << r;
            break;
        case 2:
            cout << r;
            break;
    };

正确的写法应该是

switch(i)
{
case 1:
    {
        int r = 1;
        cout << r;
    }
    break;
case 2:
    {
        int r = x - y;
        cout << r;
    }
    break;
};

标准说明如下：

It is possible to transfer into a block, but not in a way that
bypasses declarations with initialization. A program that jumps from a
point where a local variable with automatic storage duration is not in
scope to a point where it is in scope is ill-formed unless the
variable has POD type (3.9) and is declared without an initializer
(8.5).

https://stackoverflow.com/questions/2392655/what-are-the-signs-of-crosses-initialization