std::numeric_limits<T>:: traps

The value of std:: numeric_limits < T > :: traps is true for all arithmetic 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

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

#include <iostream>
#include <limits>
 
int main()
{
    std::cout << std::boolalpha
              << "bool:     traps = " << std::numeric_limits<bool>::traps << '\n'
              << "char:     traps = " << std::numeric_limits<char>::traps << '\n'
              << "char16_t: traps = " << std::numeric_limits<char16_t>::traps << '\n'
              << "long:     traps = " << std::numeric_limits<long>::traps << '\n'
              << "float:    traps = " << std::numeric_limits<float>::traps << '\n';
}

// 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 retroactively to previously published C++ standards.

See also