Weird quirks of C++, written up as I stumble across them.
Substitution Failure
Opting in, and back out again
The ways to manually opt your code into a function through the history of C++, and the black magic required to opt it back out again.
The complement of true is true, except when it's false
Consequences of integral promotion, UB on unscoped enums, and why boolean conversion is surprising.