c++ - 究竟什么时候复制返回值

Question

假设我有以下代码:

int bar = 0;

struct Foo {
    ~Foo() { bar = 1; }
};

int main(int argc, char ** argv) {
    Foo f;
    return bar;
}

程序的返回值是多少？ 0 还是 1？

Answer 1

来自 [stmt.return]/3:

The copy-initialization of the returned entity is sequenced before the destruction of temporaries at the end of the full-expression established by the operand of the return statement, which, in turn, is sequenced before the destruction of local variables (6.6) of the block enclosing the return statement.

所以析构函数在返回值初始化后运行，因此在第一次调用函数时返回值为 0。