问题描述
以下代码可以通过g ++和Visual C ++进行编译。为什么是合法的？它看起来不合理，并可能导致隐藏的错误。
The following code can pass compiling under both g++ and Visual C++. Why is it legal? It looks unreasonable, and may cause hidden bugs.
int main() {
int i = i;
}
推荐答案
/ strong> 语法合法，但如果使用 x ，则会导致未定义的行为。
It's syntactically legal, but results in undefined behavior if you use x.
这是不合法，因为您正在为一个未初始化的变量分配另一个（好，相同）未初始化的变量。只是因为它的编译并不意味着它是合法的。它是有效的C ++语法，是的，但不合法。
It's not legal because you're assigning an uninitialized variable with another (well, the same) uninitialized variable. Just because it compiles doesn't mean it's legal. It's valid C++ syntax, yes, but not legal.
赋值运算符的右边必须在赋值时进行完全求值。在这种情况下，这是 i ，这是没有初始化。
The right hand side of the assignment operator must be fully evaluated at the time of the assignment. In this case, that's i, which isn't initialized.
对Steve Jessop的点数：
Credits to Steve Jessop, who dug up the quote:
到价值转换
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