void * 类型指针变量如何赋值

 

 

struct _MyDataType
{
/* User data header */
UserDataType Type;

OpcUa_UInt16 Number; // 当前变量在该类型变量的序号

/* Protocol information */
void *pValue;
};
typedef struct _MyDataType MyDataType;

              

 pRes->Results[i].Value.Value.Double = (OpcUa_Double)(*(pSensor->pValue)); //*(pSensor->pValue)的意思

编译时提示如下：

 In function ‘xxxxx’:
 warning: dereferencing ‘void *’ pointer
  108 |                 pRes->Results[i].Value.Value.Double = (OpcUa_Double)(*(pSensor->pValue)); //*(pSensor->pValue)的意思
      |                                                                      ^~~~~~~~~~~~~~~~~~
 error: invalid use of void expression
  108 |                 pRes->Results[i].Value.Value.Double = (OpcUa_Double)(*(pSensor->pValue)); //*(pSensor->pValue)的意思
      |                                                       ^
make[2]: *** [output/CMakeFiles/output.dir/build.make:180：output/CMakeFiles/output.dir/u.c.o] 错误 1
make[1]: *** [CMakeFiles/Makefile2:385：output/CMakeFiles/output.dir/all] 错误 2

 

void*类型定义的指针变量只接收对象的地址，没有对象的类型概念。所以该指针变量是不能直接用；“*指针变量”去访问对象的，只能经强制类型转换后才能“间接”访问：*(type*)指针变量，必须给出正确的type！