virtual const char* name() const noexcept = 0;
"generic"
"system"
"iostream"
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// error_category::name #include <iostream> // std::cout #include <system_error> // std::error_code int main() { std::error_code ec; // the default error code is system error 0 std::cout << ec.category().name() << '\n'; return 0; }
system