Abs, std::abs, cmath, math.h

[ToppDev]

Channel

C++Weekly

Topics

Differences in the behavior of abs and std::abs depending on includes. (Compiler Explorer)

#include <cmath>
auto std_abs(auto val) { return std::abs(val); }
auto abs_cmath(auto val) { return abs(val); }

#include <math.h>
auto abs_math_h(auto val) { return abs(val); }

#include<iostream>

int main ()
{
 std::cout << "std::abs (3.1416) = " << std_abs(3.1416) << '\n';
 std::cout << "abs_cmath (3.1416) = " << abs_cmath(3.1416) << '\n';
 std::cout << "abs_math_h (3.1416) = " << abs_math_h(3.1416) << '\n';
 return 0;
}

Result

std::abs (3.1416) = 3.1416
abs_cmath (3.1416) = 3
abs_math_h (3.1416) = 3.1416

Compiler differences:

• gcc does not warn
• clang throws a warning
• apple clang does not cut the value

Length

5-10 minutes

[lefticus]

Coming in Ep480