Operation on … may be undefined?

Question

I have the following code

FRAME frameArray[5][10]; // Create the array of frames
int trackBufferFull[5] = {0, 0, 0, 0, 0};// Keeps track of how full the buffer f         


        

Answer 1

trackTail[nodeNumber-1] = ++trackTail[nodeNumber-1] % 10;

Yep, that's undefined behavior just as the error message says. You're not allowed to modify the same value twice without a sequence point in between. In this case that means you're not allowed to both increment trackTail[nodeNumber-1] using ++ and reassign it using =.

If you just use + 1 instead of ++, it will work fine.