类型无效的操作数的挥发性uint8_t有*和'uint8_t有（*）

问题描述

我有地址/指针转换的问题

I have problem with address/pointer conversion

我曾跟随code具有开箱即用的recive（uint8_t有* BUF，uint32_t的* LEN）;功能，当数据被中断了recived异步拼命地跑

I had followed code with OOTB recive (uint8_t* Buf, uint32_t *Len); function, that is runned asynchronously when data interrupt is recived

uint8_t UserRxBufferFS[APP_RX_DATA_SIZE]; //static buffer

volatile uint8_t * __usrRxIndex = UserRxBufferFS; //volatile pointer to data end


static int8_t recive (uint8_t* Buf, uint32_t *Len)
{
    uint8_t result = USBD_OK;
    //copy *Len number of data from Buf to UserRxBufferFS
    memcpy(UserRxBufferFS+__usrRxIndex, Buf, *Len);

    if( (uint32_t)( (__usrRxIndex )- UserRxBufferFS) + *Len > 0xff){ //calculate buffer overflow
        __usrRxIndex = UserRxBufferFS; //buffer
    } else {
        __usrRxIndex += *Len;
    }
}

然后我试图捕捉挥发性__usrRxIndex数据结束，即每当数据被捕获时更新。

Then I trying to catch end of data by volatile __usrRxIndex, that is updated every time when data are captured.

但是，当我试图编译这个使用G ++ compilator我得到了错误：

But When I trying to compile this using g++ compilator I got error:

error: invalid operands of types 'volatile uint8_t* {aka volatile unsigned char*}' and 'uint8_t (*)[512] {aka unsigned char (*)[512]}' to binary 'operator-'

我做了一些解决方法，并计算出每个地址号码，然后做减法，但我的问题是，为什么G ++ compilator不要让数组和指针减法？一些简单的方法来没有得到这个错误？

I made some workaround and calculate each address as number and then do substraction but my question is why g++ compilator dont allow arrays and pointer substraction? Is some easy way to not get this error?

推荐答案

在

memcpy(UserRxBufferFS+__usrRxIndex, Buf, *Len);

这除了不应该将其编译并没有什么意义。你可能想：

That addition should not compile and it does not make sense. You probably want:

memcpy(__usrRxIndex, Buf, *Len);

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另一件事是，你发现后的memcpy 缓冲区溢出已经损坏的内存。它需要在的memcpy 来检测缓冲区溢出。

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Another thing is that you detect buffer overflow after memcpy already corrupted memory. It needs to detect the buffer overflow before memcpy.

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