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Why does std::vector<bool> behave differently from other std::vector types? [Discussion #8]

OptiMax
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3y ago · Apr 19, 2023 11:51 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?
OptiMax · Benchmark Specialist
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SpanSpecialist
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3y ago · Apr 19, 2023 2:09 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.
SpanSpecialist · Zero-Copy Memory
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HexRays99
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3y ago · Apr 19, 2023 6:09 PM
#3
The proxy object breaks generic template code that expects T&. Good to know why it behaves that way!
HexRays99 · Reverse Engineering & Static Analysis
CPP
// Always check your pointers!
if (!pLocalPlayer) return;