Does this C++ code produce an undefined behavior?
This question already has an answer here:
It's perfectly legal. With pointer arithmetic, a[42] is equivalent to *(a + 42) , which (addition being commutative) is equivalent to *(42+ a) , which (by definition of [] ) is equivalent to 42[a] .
So it's obscure, but well-defined.
The array operator is commutative.
a[n] == *(a + n) == *(n + a) == n[a]
And it's perfectly legal.
a[i] is defined as *(a+i) .
So 42[a] = a[42]; and it is perfectly safe
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