From cppreference.com
staticconstbooltraps;(until C++11)staticconstexprbooltraps;(since C++11)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
.
Standard specializations
Tvalue of std::numeric_limits<T>::traps/* non-specialized */falseboolfalsecharusually truesignedcharusually trueunsignedcharusually truewchar_tusually truechar8_t(since C++20)usually truechar16_t(since C++11)usually truechar32_t(since C++11)usually trueshortusually trueunsignedshortusually trueintusually trueunsignedintusually truelongusually trueunsignedlongusually truelonglong(since C++11)usually trueunsignedlonglong(since C++11)usually truefloatusually falsedoubleusually falselongdoubleusually falseNotes
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
program, where it is true if compiled without -ieee.
Example
Run this code
#include<iostream>#include<limits>intmain(){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';}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 retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 it was unclear what is returned if trapping
is enabled or disabled at runtime returns the enable status
at the start of the program See also