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Asked: 2026-06-10T00:08:49+00:00

The C++ standard seems to be a bit laconic about arrays. Let’s assume that

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The C++ standard seems to be a bit laconic about arrays.

Let’s assume that I have two distinct data types: T1 and T2. I create arrays of each of them, with both arrays being of the same length N; so I have T1[N] and T2[N].

Now, does sizeof(T1[N]) == sizeof(T2[N]) imply that the successive elements of both arrays will have the same offsets?

Or, in a more practical form: if I (handling the alignment issues) cast a char[sizeof(T1[N])] both to T1* and to T2*, is it guaranteed that T1[0] and T2[1] will not overlap, and the other way?

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1 Answer

  1. Editorial Team

    Yes.

    Arrays do not have any padding or alignment on the ends, and thus sizeof(T1[N]) always equals sizeof(T1) * N.

    Knowing this, we know that sizeof(T1[N]) == sizeof(T2[N]) implies sizeof(T1) == sizeof(T2) (cancel the N on both sides). Additionally arrays must be contiguous, there is no alignment or padding inside of the array. Thus the answer to your question is yes.

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