std::is_constant_evaluated (3) - Linux Man Pages
Defined in header <type_traits>
constexpr bool is_constant_evaluated() noexcept; (since C++20)
Detects whether the function call occurs within a constant-evaluated context. Returns true if the evaluation of the call occurs within the evaluation of an expression or conversion that is manifestly constant-evaluated; otherwise returns false.
The following expressions (including conversions to the destination type) are manifestly constant-evaluated:
* Where a constant expression is grammatically required, including:
* conditions of constexpr_if_statements
* constraint expressions in concept definitions, nested_requirements, and requires_clauses
* initializers of variables that are usable in constant expressions, including:
* initializers of static and thread local variables, when all subexpressions of the initializers (including constructor calls and implicit conversions) are constant_expressions (that is, when the initializers are constant_initializers)
To test the last two conditions, compilers may first perform a trial constant evaluation of the initializers. It is not recommended to depend on the result in this case.
true if the evaluation of the call occurs within the evaluation of an expression or conversion that is manifestly constant-evaluated; otherwise false
When directly used as the condition of static_assert_declaration or constexpr_if_statement, std::is_constant_evaluated() always returns true.
This section is incomplete
Reason: no example