c++ - C++ Struct - 错误 1 ​​错误 C2143：语法错误：缺少 ';' 前 '*'

Question

当我尝试编译以下内容时，我收到错误“错误 1 ​​错误 C2143：语法错误：缺少';' 前 '*'”。有谁知道我为什么会收到这个错误？我在这里做错了什么？

struct HE_edge {
HE_vert* vert; // vertex at the end of the half-edge<br>
HE_edge* pair; // oppositely oriented half-edge<br>
HE_face* face; // the incident face<br>
HE_edge* prev; // previous half-edge around the face<br>
HE_edge* next; // next half-edge around the face<br>
};

struct HE_vert {
float x, y, z; // the vertex coordinates<br>
HE_edge* edge; // one of the half-edges emanating from the vertex<br>
};

struct HE_face {
HE_edge* edge; // one of the half-edges bordering the face<br>
};

Answer 1

尝试以正确的顺序声明您的结构：由于 HE_edge 依赖于 HE_vert 和 HE_face，因此请先声明它们。

struct HE_vert;
struct HE_face;

struct HE_edge {
HE_vert* vert; // vertex at the end of the half-edge<br>
HE_edge* pair; // oppositely oriented half-edge<br>
HE_face* face; // the incident face<br>
HE_edge* prev; // previous half-edge around the face<br>
HE_edge* next; // next half-edge around the face<br>
};

struct HE_vert {
float x, y, z; // the vertex coordinates<br>
HE_edge* edge; // one of the half-edges emanating from the vertex<br>
};

struct HE_face {
HE_edge* edge; // one of the half-edges bordering the face<br>
};

Answer 2

您需要在使用它们之前转发声明HE_vert和。HE_faceHE_edge

// fwd declarations. Can use "struct" or "class" interchangeably.
struct HE_vert;
struct HE_face;

struct HE_edge { /* as before */ };

请参阅何时使用前向声明？

Answer 3

在使用它们的类型来创建指针之前，您需要声明所有类：

struct HE_edge;
struct HE_vert;
struct HE_face;

// your code

Answer 4

您必须在使用标识符之前声明它们。对于结构，这只需通过例如

struct HE_vert;

把它放在 的定义之前HE_edge。

Answer 5

第一个声明不知道是什么HE_vert，HE_face你需要告诉编译器它们是什么：

struct HE_face;
struct HE_vert;//tell compiler what are HE_vert and HE_face

struct HE_edge {
HE_vert* vert; // vertex at the end of the half-edge<br>
HE_edge* pair; // oppositely oriented half-edge<br>
HE_face* face; // the incident face<br>
HE_edge* prev; // previous half-edge around the face<br>
HE_edge* next; // next half-edge around the face<br>
};

struct HE_vert {
float x, y, z; // the vertex coordinates<br>
HE_edge* edge; // one of the half-edges emanating from the vertex<br>
};

struct HE_face {
HE_edge* edge; // one of the half-edges bordering the face<br>
};

拉兹万。