几行代码看懂函数指针和注册回调

 

定义如下几个文件

knight@weare:~$ touch main.c  test1.c test1.c test2.c test2.h
knight@weare:~$ ls
Makefile  main.c  test1.c  test2.c  test2.h
knight@weare:~$

其中在test1.h中定义如下函数：

#ifndef __TEST1_H__
#define __TEST1_H__

typedef void (*test_handle)(void* param);

typedef struct _test_param_handle
{
 test_handle handle;
 void* param;
}test_param_handle_t;

void test_register(void);

#endif
~

在test1.c中定义如下：

 

#include "stdio.h"
#include "test2.h"
void print_user(int i);
void system_register_handle(test_handle handle,void *dat);

void test_register(void)
{
        system_register_handle((test_hadle)print_user,NULL);
}
void system_register_handle(test_handle handle, void *dat)
{
        table.handle = handle;
        table.param  = dat;
}
void print_user(int i)
{
        printf("This is a C test example num=%d\r\n",i);
}

在test2.h 中定义如下

#ifndef __TEST2_H__
#define __TEST2_H__

#include "test1.h"

test_param_handle_t table;

#endif

在main.c中定义如下：

#include "test2.h"

int main(void)
{
  int i=0;
  test_register();
  for(i=0;i<=10;i++)
  {
          table.handle(i*100);
  }
  return 0;
}

 由于我是在linux下编写的，Makfile 按如下编写：

test: main.o test1.o
        gcc -o test main.o test1.o
main.o: main.c test2.h
        gcc -c main.c
test1.o: test1.c test1.h test2.h
        gcc -c test1.c

 编译运行后结果如下：

knight@weare:~$ make
gcc -c main.c
main.c: In function ‘main’:
main.c:9:17: warning: passing argument 1 of ‘table.handle’ makes pointer from integer without a cast [-Wint-conversion]
    table.handle((int)(i*100));
                 ^
main.c:9:17: note: expected ‘void *’ but argument is of type ‘int’
gcc -c test1.c
gcc -o test main.o test1.o
knight@weare:~$ ./test
This is a C test example num=0
This is a C test example num=100
This is a C test example num=200
This is a C test example num=300
This is a C test example num=400
This is a C test example num=500
This is a C test example num=600
This is a C test example num=700
This is a C test example num=800
This is a C test example num=900
This is a C test example num=1000