c++ - 指向结构的指针的 Typedef 等价

Question

我得到了这个结构的实现:

struct NodoQ {
  Etype elem;
  NodoQ *sig;
};

下面是这段代码吗，

typedef NodoQ *PtrNodoQ;
PtrNodoQ ppio, fin;

和这个一样吗？

NodoQ* ppio;
NodoQ* fin;

Answer 1

Is this code below,

typedef NodoQ *PtrNodoQ;
PtrNodoQ ppio, fin;

the same as this one?

NodoQ* ppio;
NodoQ* fin;

是的，它导致 ppio 和 fin 的指针类型完全相同。

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至于你的评论

"I didn't try cause I got the second option everywhere in my code, and just didn't want to loose some time... "

你可以很容易地测试它:

void foo(PtrNodoQ p) {
}

void bar(NodoQ* p) {
    foo(p);
}

和

void baz() {
    NodoQ n;
    foo(&n);
    bar(&n);
}

编译一切都很好，没有无效类型转换警告或错误。

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您也可以在 this excellent reference 中快速找到答案(强调我的):

The typedef-names are aliases for existing types, and are not declarations of new types. Typedef cannot be used to change the meaning of an existing type name (including a typedef-name). Once declared, a typedef-name may only be redeclared to refer to the same type again. Typedef names are only in effect in the scope where they are visible: different functions or class declarations may define identically-named types with different meaning.