math_signaling_nan/signaling_nan_test2.cpp - SNAN/signaling nan playground
Posted by Anonymous on Mon 12th Jun 2023 16:21
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/*
 * math_signaling_nan/signaling_nan_test2.cpp - SNAN/signaling nan playground
 *
 *
 * Compile with:
 * $ g++ -fsignaling-nans -g -Wall signaling_nan_test2.cpp -lm #
 *
 */

#include <cfenv>
#include <iostream>
#include <limits>
#include <stdlib.h>


static
int show_fe_exceptions(void)
{
        int numexcept = 0;

        int n = std::fetestexcept(FE_ALL_EXCEPT);

        if (n & FE_INVALID) {
                std::cout << "FE_INVALID is raised";
                numexcept++;
        }
        else if (n == 0)
                std::cout << "no exceptions are raised";
        else {
                numexcept++;
                std::cout << "unexpected exceptions " << n << " are raised";
        }

        (void)std::feclearexcept(FE_ALL_EXCEPT);

        return numexcept;
}

static
void show_fe_exceptions_and_expectations(bool exceptions_expected)
{
        int e;

        e = show_fe_exceptions();

        if (((e>0)?true:false) == exceptions_expected)
                std::cout << " (as expected)." << std::endl;
        else
                std::cout << " (not as expected; ERROR)." << std::endl;
}


int main(int ac, char *av[])
{
        double snan = std::numeric_limits<double>::signaling_NaN();
        std::cout << "After sNaN was obtained, ";
        show_fe_exceptions_and_expectations(false);

        double qnan = snan * 2.0;
        std::cout << "After sNaN was multiplied by 2, ";
        show_fe_exceptions_and_expectations(true);

        double qnan2 = qnan * 2.0;
        std::cout << "After the quieted NaN was multiplied by 2, ";
        show_fe_exceptions_and_expectations(false);

        std::cout << "The result is |" << qnan2 << "|" << std::endl;

        return EXIT_SUCCESS;
}