C语言 C 错误：左值需要作为一元“&”操作数
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C error: lvalue required as unary '&' operand
提问by Shan
I have a code error but not sure what's wrong with my casting and reference.
我有一个代码错误，但不确定我的转换和参考有什么问题。
BOOL xMBPortSerialPutByte( CHAR ucByte )
{
CDC_Send_DATA(&((unsigned char)ucByte), 1); // code error here
xMBPortEventPost(EV_FRAME_SENT);
return TRUE;
}
The CDC_Send_DATA is defined as the following:
CDC_Send_DATA 定义如下：
uint32_t CDC_Send_DATA (uint8_t *ptrBuffer, uint8_t Send_length);
Here is the error message:
这是错误消息：
port/portserial.c:139:19: error: lvalue required as unary '&' operand
Hope someone could help. Thanks!
希望有人能帮忙。谢谢！
回答by Carl Norum
The cast operation causes a conversion, yielding an rvalue. An rvalue doesn't have an address, so you can't operate on it with a unary &. You need to take the address and then cast that:
强制转换操作导致转换，产生一个右值。右值没有地址，因此您不能使用一元对其进行操作&。您需要获取地址，然后将其转换为：
CDC_Send_DATA((unsigned char *)&ucByte, 1);
But to be most correct, you should probably match the argument type in the cast:
但最正确的是，您可能应该匹配演员表中的参数类型：
CDC_Send_DATA((uint8_t *)&ucByte, 1);
Checking the return value would probably be a good idea too.
检查返回值也可能是一个好主意。
