Is the data in nested std::arrays guaranteed to be contiguous post c++17?

Asked Mar 27 '20 at 09:18

Active Mar 27 '20 at 09:18

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I am using a nested std::array, and wonder if it is possible to use memcpy on it in order to copy the content of one array to the other as sketched below:

std::array<std::array<int, 5>, 5> arr;
std::array<std::array<int, 5>, 5> arr2;
memcpy(&arr[0], &arr2[0], sizeof(int) * 25);

Since C++17, a C++ array is a ContiguousContainer; however, I think that the question if padding bytes can be placed at the end of an array (which is basically inside the memory chunk in a nested array) are unaffected by this property.

Is the data in std::array<std::array<T,N>, M> guaranteed to be contiguous? Or does the answer to this pre-c++17 question still hold?

asked Mar 27 '20 at 09:18

mutableVoid

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afaik `std::array` was already a contiguous container but the concept `ContiguousContainer` was introduced in C++17, so basically nothing changed – 463035818_is_not_an_ai Mar 27 '20 at 09:32
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note that also `std::vector` is a ContiguousContainer since C++17, but that didnt mean that anything on `std::vector` had to change – 463035818_is_not_an_ai Mar 27 '20 at 09:33
Okay thanks :) I think then I'll close this question as duplicate of the pre-17 question – mutableVoid Mar 27 '20 at 09:33

Is the data in nested std::arrays guaranteed to be contiguous post c++17?

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