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std::numeric_limits::traps(3) C++ Standard Libarystd::numeric_limits::traps(3) NAME std::numeric_limits::traps - std::numeric_limits::traps Synopsis static const bool traps; (until C++11) static constexpr bool traps; (since C++11) The value of std::numeric_limits<T>::traps is true for all arith- metic types T that have at least one value at the start of the program that, if used as an argument to an arithmetic operation, will generate a trap. Standard specializations T value of std::numeric_lim- its<T>::traps /* non-specialized */ false bool false char usually true signed char usually true unsigned char usually true wchar_t usually true char8_t (since C++20) usually true char16_t (since C++11) usually true char32_t (since C++11) usually true short usually true unsigned short usually true int usually true unsigned int usually true long usually true unsigned long usually true long long (since C++11) usually true unsigned long long (since C++11) usually true float usually false double usually false long double usually false Notes On most platforms integer division by zero always traps, and std::numeric_limits<T>::traps is true for all integer types that support the value 0. The exception is the type bool: even though division by false traps due to integral promotion from bool to int, it is the zero-valued int that traps. Zero is not a value of type bool. On most platforms, floating-point exceptions may be turned on and off at run time (e.g. feenableexcept() on Linux or _controlfp on Windows), in which case the value of std::numeric_limits<T>::traps for floating-point types reflects the state of floating-point trapping facility at the time of program startup, which is false on most modern systems. An exception would be a DEC Alpha program, where it is true if compiled without -ieee. Example // Run this code #include <iostream> #include <limits> int main() { std::cout << std::boolalpha << "bool: traps = " << std::numeric_lim- its<bool>::traps << '\n' << "char: traps = " << std::numeric_lim- its<char>::traps << '\n' << "char16_t: traps = " << std::numeric_lim- its<char16_t>::traps << '\n' << "long: traps = " << std::numeric_lim- its<long>::traps << '\n' << "float: traps = " << std::numeric_lim- its<float>::traps << '\n'; } Possible output: // GCC output: bool: traps = true char: traps = true char16_t: traps = true long: traps = true float: traps = false // Clang output: bool: traps = false char: traps = true char16_t: traps = true long: traps = true float: traps = false Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior it was unclear what is returned if returns the enable status LWG 497 C++98 trapping at the start of the program is enabled or disabled at runtime See also Floating-point environment tinyness_before identifies floating-point types that detect tinyness before rounding [static] (public static member constant) has_denorm_loss identifies the floating-point types that detect loss of precision as [static] denormalization loss rather than inexact result (public static member constant) http://cppreference.com 2024.06.10 std::numeric_limits::traps(3)
NAME | Synopsis | Standard specializations | Notes | Example | Possible output: | See also | Floating-point environment
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