传递变量作为Void *然后稍后进行转换的C语法？

问题描述

我正在尝试使用void *指针编写通用的“更新我的结构”。检查一下：

typedef enum{
        aa,bb
}myEnum;

typedef struct myStruct{
        uint8_t         a;
        uint16_t        b;
}myStr;

// - - - - - - - - - - - - - - - - - - - - - - - - - - - -

void updateStr( myStr* thingee,myEnum flag,void* value ){
        switch( flag ){
                case aa:
                        thingee->a = (uint8_t*)value;
                        break;
                case bb:
                        thingee->b = (uint16_t*)value;
                        break;
        }
}

int main(){
        myStr* thingee = (myStr*)malloc( sizeof(myStr) );
        uint8_t  data1 = 123;
        uint16_t data2 = 456;

        updateStr( thingee,aa,data1 );
        updateStr( thingee,bb,data2 );

        free( thingee );
        return 1;
}

编译器 讨厌 这是

# gcc -Wall toy.c
toy.c: In function ‘updateStr’:
toy.c:27:15: warning: assignment makes integer from pointer without a cast [-Wint-conversion]
    thingee->a = (uint8_t*)value;
               ^
toy.c:30:15: warning: assignment makes integer from pointer without a cast [-Wint-conversion]
    thingee->b = (uint16_t*)value;
               ^
toy.c: In function ‘main’:
toy.c:41:26: warning: passing argument 3 of ‘updateStr’ makes pointer from integer without a cast [-Wint-conversion]
  updateStr( thingee,data1 );
                          ^~~~~
toy.c:24:6: note: expected ‘void *’ but argument is of type ‘uint8_t {aka unsigned char}’
 void updateStr( mystr* thingee,void* value ){
      ^~~~~~~~~
toy.c:42:26: warning: passing argument 3 of ‘updateStr’ makes pointer from integer without a cast [-Wint-conversion]
  updateStr( thingee,data2 );
                          ^~~~~
toy.c:24:6: note: expected ‘void *’ but argument is of type ‘uint16_t {aka short unsigned int}’
 void updateStr( myStr* thingee,void* value ){
      ^~~~~~~~~
#

我正在尝试的可能吗？如果是这样，有人可以在语法方面帮助我吗？我真的只需要知道如何调用我的updatestr()函数...

updateStr( thingee,data1 );

...以及updatestr()应该如何将void *转换回我想要的数据类型...

thingee->a = (uint8_t*)value;

感谢任何帮助和/或建议...

解决方法

您忘记了取消引用指针。应该是

void updateStr( myStr* thingee,myEnum flag,void* value ){
        switch( flag ){
                case aa:
                        thingee->a = *(uint8_t*)value;
                        break;
                case bb:
                        thingee->b = *(uint16_t*)value;
                        break;
        }
}

此外，updateStr希望您将其传递给指针，但您不是。您应该这样称呼

updateStr( thingee,aa,&data1 );
updateStr( thingee,bb,&data2 );