c语言callback

#include <stdio.h>
typedef enum{
    MY_CAHR=1<<0,
    MY_INT=1<<1,
    MY_FLAOT=1<<2,
    MY_DOUBLE=1<<3,
    MY_PTR_OWN=1<<4,
    MY_PTR_NOWN=1<<5,
}DataType;
typedef struct{
    DataType type;
    union{
    char c;
    char *c_ptr;
    int b;
    float f;
    double d;
    void *ptr;
    };
}MyValue;
typedef void (*void_char_cast)(char,void*usr);
typedef void (*void_ptr_cast)(void*,void*usr);
typedef void (*CallbackTemplate)(void);
typedef void (*ClousureTemplate)(CallbackTemplate cb,MyValue value,void *usr);
void my_void_char_clousure(CallbackTemplate cb,MyValue value,void *usr){
    void_char_cast fn=(void_char_cast)(cb);
    fn(value.c,usr);
}
void my_void_ptr_clousure(CallbackTemplate cb,MyValue value,void *usr){
    void_ptr_cast fn=(void_ptr_cast)(cb);
    fn(value.ptr,usr);
}
typedef struct{
    ClousureTemplate tpl;
    CallbackTemplate cb;
    MyValue value;
    void *usr;
}CallbackWrap;
void test_char_fun(char c,void *usr){
    printf("%c\n",c);
}
void test_ptr_fun(void *ptr,void *usr){
    printf("%p\n",ptr);
}
void invoke_fun(CallbackWrap *fun){
    fun->tpl(fun->cb,fun->value,fun->usr);
}
int main(){
    CallbackWrap wrap={
        .tpl=my_void_char_clousure,
        .cb=test_char_fun,
        .value.c='a',
        .usr=0,
    };
    invoke_fun(&wrap);
    int a=1234;
   CallbackWrap wrap1={
        .tpl=my_void_ptr_clousure,
        .cb=test_ptr_fun,
        .value.ptr=(void*)&a,
        .usr=0,
    };
    invoke_fun(&wrap1);
}