在C中转发结构的声明？

Question

#include <stdio.h>

struct context;

struct funcptrs{
  void (*func0)(context *ctx);
  void (*func1)(void);
};

struct context{
    funcptrs fps;
}; 

void func1 (void) { printf( "1\n" ); }
void func0 (context *ctx) { printf( "0\n" ); }

void getContext(context *con){
    con=?; // please fill this with a dummy example so that I can get this working. Thanks.
}

int main(int argc, char *argv[]){
 funcptrs funcs = { func0, func1 };
   context *c;
   getContext(c);
   c->fps.func0(c);
   getchar();
   return 0;
}

我在这里遗漏了一些东西.请帮我解决这个问题.谢谢.

Answer 1

试试这个

#include <stdio.h>

struct context;

struct funcptrs{
  void (*func0)(struct context *ctx);
  void (*func1)(void);
};

struct context{
    struct funcptrs fps;
}; 

void func1 (void) { printf( "1\n" ); }
void func0 (struct context *ctx) { printf( "0\n" ); }

void getContext(struct context *con){
    con->fps.func0 = func0;  
    con->fps.func1 = func1;  
}

int main(int argc, char *argv[]){
 struct context c;
   c.fps.func0 = func0;
   c.fps.func1 = func1;
   getContext(&c);
   c.fps.func0(&c);
   getchar();
   return 0;
}

Answer 2

结构(没有typedef)在使用时通常需要(或应该)使用关键字struct.

struct A;                      // forward declaration
void function( struct A *a );  // using the 'incomplete' type only as pointer

如果你输入你的结构,你可以省略struct关键字.

typedef struct A A;          // forward declaration *and* typedef
void function( A *a );

请注意,重用结构名称是合法的

尝试在代码中将前向声明更改为:

typedef struct context context;

添加后缀以指示结构名称和类型名称可能更具可读性:

typedef struct context_s context_t;