Why is std::vector 's operator[] return type problematic in generic code?

It returns a corrupted bit value, masking the wrong bit when packing bools

It cannot be iterated at all, failing the forward iterator requirements

It returns a proxy reference, not bool&, breaking code needing a real reference

It returns a dangling pointer into a temporary bitfield destroyed on return

Multiple ChoiceIntermediate 45s

vector bool proxy iterator pitfalls

Why is std::vector<bool>'s operator[] return type problematic in generic code?

Options

1It returns a corrupted bit value, masking the wrong bit when packing bools
2It cannot be iterated at all, failing the forward iterator requirements
3It returns a proxy reference, not bool&, breaking code needing a real reference
4It returns a dangling pointer into a temporary bitfield destroyed on return

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