What does "control reaches end of non-void function" mean?

c warnings compiler-warnings
tekknolagi picture tekknolagi · May 30, 2011 · Viewed 128.2k times · Source

I've been getting strange compiler errors on this binary search algorithm. I get a warning that control reaches end of non-void function. What does this mean?

int binary(int val, int sorted[], int low, int high) {
    int mid = (low+high)/2;

    if(high < low)
        return -1;

    if(val < sorted[mid])
        return binary(val, sorted, low, mid-1);

    else if(val > sorted[mid])
        return binary(val, sorted, mid+1, high);

    else if(val == sorted[mid])
        return mid;
}

Answer

rid picture rid · May 30, 2011

The compiler cannot tell from that code if the function will ever reach the end and still return something. To make that clear, replace the last else if(...) with just else.

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