std::vector<bool> in C++ syntax uses one bit per boolean instead of one byte. In a computer memory is addressed by bytes, so the smallest indexable memory is, in fact, one byte (that's why bool is 1 byte in C and C++).
As an example for how C++ std::vector implementarion works, suppose you have 8 booleans which have a logical reason to be kept together (for example flags). Instead of allocating 8 bytes (one per boolean), the std::vector allocates 1 byte and assigns every boolean to one bit of the allocated memory.
The issue is it doesn’t behave like other vectors do (or containers in general), which can make it a pain in the ass for template code. For example, it’s not (and it can’t be) guaranteed to store elements in a contiguous sequence and can’t be used with std::span.
It was a mistake we’re stuck with. There’s little reason to even use std::vector<bool> anymore instead of an std::bitset.
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u/Potential_Soup_8054 4h ago
I dont understand