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new(2, f) T[5] results in a call of operator new[](sizeof(T) * 5 + y, 2, f).

Here, x ... and y are non-negative unspecified values representing array allocation overhead; the result of the new-expression will be offset by this amount from the value returned by operator new[]. This overhead may be applied in all array new-expressions, including those referencing the library function operator new[](std::size_t, void*) and other placement allocation functions. The amount of overhead may vary from one invocation of new to another.

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