Can someone explain me why these two functions have different outputs?
void remove_index (int s[],int n, int N){
while (n < N - 1) s[n] = s[n+1],n++;
}
void remove_index (int s[],int n, int N){
while (n < N - 1) s[n] = s[++n];
}
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2nd version reads and writes `n` without an intervening sequence point. – pmg Mar 12 '20 at 15:50
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@ikegami No, 2nd version. – Ian Abbott Mar 12 '20 at 15:51
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also consider `while (n++ < N - 1) s[n-1] = s[n];` – pmg Mar 12 '20 at 15:52
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@EugeneSh. I'm wondering about your mind-reading skills! – Ian Abbott Mar 12 '20 at 15:56
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@DiogoVieira If `n` is 5 immediately before `s[n] = s[++n]` runs then, as part of working out what to assign, the right hand side of the expression (`s[++n]`) is evaluated first, what value do you think `n` will have when it is time to evaluate `s[n]`? – Caius Jard Mar 12 '20 at 16:36
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I suspect both `s[n] = ...,n++;` and `s[n] = s[++n];` are UB as the increment of `n` is not sequenced with `s[n]`. – chux - Reinstate Monica Mar 12 '20 at 19:04