Analysis of the Causes of Program Failure

Usually the reasons why our program runs out of control are as follows: 
1. memset/ memcpy usage error 
error code 
aucCpyLength=NAME_DATA_LENGTH- ((wucCdTextCmdBufferPara.stTagCmdPara.ucPageNo+1)*TAG_PAGE_LENGTH); 
memset(pucCpyDestAdress + TAG_PAGE_LENGTH,0x00,aucCpyLength) 
where: NAME_DATA_LENGTH is 64 
      TAG_PAGE_LENGTH is 10 

wrong reason  

Since the variable wucCdTextCmdBufferPara.stTagCmdPara.ucPageNo is 6, aucCpyLength=64-70=0xFA. Since the memset function is called later, the contents of the 0xFA addresses starting from the pucCpyDestAdress address are all rewritten to 0, resulting in pointer variable calculation errors during engine control and pointing to illegal areas, eventually causing the program to run away. 

Solution  

1 Before calling the memset function, perform error tolerance on the maximum range of length to avoid other variables being modified due to length exceeding
the range  .
2 Review the variables involved in length calculation to avoid assigning out-of-range values ​​in the program. 
Method example 
if(NAME_DATA_LENGTH>= ((wucCdTextCmdBufferPara.stTagCmdPara.ucPageNo+1)* TAG_PAGE_LENGTH )) 

{          
aucCpyLength=NAME_DATA_LENGTH- ((wucCdTextCmdBufferPara.stTagCmdPara.ucPageNo+1)*TAG_PAGE_LENGTH); 
  memset(pucCpyDestAdress+ TAG_PAGE_LENGTH,0x00,aucCpyLength); 
} 

2 Pointer usage error 
Error code 
INT8U* pucCDMode; 
CDDRV_L1_wvdGetCDMP3Mode(pucCDMode); 
Function prototype void CDDRV_L1_wvdGetCDMP3Mode(INT8U* pucCDMode)  
Error reason Pointer pucCDMode is used without being initialized. 
Solution 

1 Initialize the pointer pucCDMode 

2 Use automatic variables and perform operations through the addresses of automatic variables. 
Method example 
INT8U pucCDMode; 
CDDRV_L1_wvdGetCDMP3Mode(&pucCDMode); 

3 Array control error 
error code 
for(nuiBTDrvUartRcvSvCnt=REC_DATA_CMDID_ADDR1; nuiBTDrvUartRcvSvCnt

{
nucBTDrvReceiveSaveBuffer[nuiBTDrvUartRcvSvCnt] =nucBTUartReceiveBuffer[nuiBTDrvUartRcvRp]; 
nuiBTDrvUartRcvRp++; 
 if(nuiBTDrvUartRcvRp >= RECEIVE_DATA_LENGTH_MAX){ 
  nuiBTDrvUartRcvRp = BT_DRV_NULL; 
 }    
} 
The nucBTDrvReceiveSaveBuffer size is defined as 200 

wrong reason 

When nuiBTDrvOnePacketDataSize is larger than the size of the nucBTDrvReceiveSaveBuffer array, that is, nuiBTDrvOnePacketDataSize>200, the content after the address of nucBTDrvReceiveSaveBuffer+200 will be overwritten, eventually causing the program to run away. 
This situation will only occur when there is an interference signal in BT communication. 
Solution  

When the size of the acquired data exceeds the size range specified by the communication array, the erroneous data is discarded or other corresponding processing is performed. In other words, when assigning values ​​to the array, it is necessary to determine whether it exceeds the range, and if it exceeds the range, corresponding processing is performed. 
Method Example  

Add fault tolerance before the wrong code. 
if(nuiBTDrvOnePacketDataSize >= RECEIVE_DATA_PROC_LENGTH) 
{ 
  nuiBTDrvOnePacketDataSize = RECEIVE_DATA_PROC_LENGTH; 
}