sprintf_s problem

Question

I have a funny problem using this function. I use it as follow:

int nSeq = 1;
char cBuf[8];
int j = sprintf_s(cBuf, sizeof(cBuf), "%08d", nSeq);

And every time I get an exception. The exception is buffer to small. When I changed the second field in the function to sizeof(cBuf) + 1.

Why do I need to add one if I only want to copy 8 bytes and I have an array that contains 8 bytes?

Answer 1

Your buffer contains 8 places. Your string contains 8 characters and a null character to close it.

Answer 2

All sprintf functions add a null to terminate a string. So in effect your string is 9 characters long. 8 bytes of text and the ending zero

Answer 3

Your string will require terminating '\0' and 8 bytes of data(00000001) due to %08d. So you have to size as 9.