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Why does std::vector<bool> behave differently from other std::vector types? [Discussion #7]

LinQ_Lover
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6y ago · Jul 10, 2020 4:42 PM
#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?
LinQ_Lover · C# Developer
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MathMagician
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6y ago · Jul 10, 2020 6:25 PM
#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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JsonSpeedster
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6y ago · Jul 11, 2020 9:25 PM
#3
The proxy object breaks generic template code that expects T&. Good to know why it behaves that way!
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