What is the general confusion surrounding constexpr?

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The general confusion surrounding constexpr is related to its exact definition and usage. While constexpr is intended to enable the evaluation of expressions at compile time, there are certain limitations and complex rules that determine when an expression can be evaluated at compile time. Additionally, the exact requirements for a function or variable to be declared as constexpr can be unclear, and different compilers may interpret constexpr differently. As a result, developers may be uncertain about how and when to use constexpr, which can lead to errors or suboptimal performance in their code.