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Asked: 2026-06-12T07:33:02+00:00

For writing/reading files, I do some low-level/binary manipulation with tuples and vectors. When I

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For writing/reading files, I do some low-level/binary manipulation with tuples and vectors.
When I do std::vector<bool> v(8) or std::tuple<bool, bool, bool, bool, bool, bool...>, do I have the guarantee that the boolean are not concatenated ? (and consequently the vector and the tuples weights at least n bytes (where n is the number of booleans).

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  1. Editorial Team

    It is implementation-defined whether std::vector<bool> is bit-packed. Its interface doesn’t provide any way to directly access the bool values, thus trying to access the underlying array directly, you will certainly get burnt at some point.

    std::tuple is a generalization of std::pair. Thus std::tuple<bool, bool, bool> is equivalent to struct SomeStruct { bool a, b, c; };, in other words, bool values won’t be bit-packed.

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