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Why does std::vector<bool> behave differently from other std::vector types? [Discussion #6]

NeighborSpy
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2y ago · Oct 1, 2023 8:33 AM
#1
I tried passing a reference to an element in std::vector<bool> and got a compiler error. Why is std::vector<bool> specialized differently?
NeighborSpy · Secret Neighbor & Unity Netcode
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DevDan
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2y ago · Oct 1, 2023 11:07 AM
#2
std::vector<bool> is a historical space-optimization specialization that packs 8 booleans into each single byte! Because individual bits cannot have a memory address, operator[] returns a proxy object (std::vector<bool>::reference) instead of bool&. If you need a standard container of booleans with true references, use std::vector<uint8_t> or std::deque<bool> instead.
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KernelGamer
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2y ago · Oct 1, 2023 2:07 PM
#3
The proxy object breaks generic template code that expects T&. Good to know why it behaves that way!
KernelGamer · C++ / Driver Dev
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