c++ på linux - får icke-deskriptivt "floating point exception" i program

alexl@PD70PNP:/mnt/Storage_SSD/C++_Projects/denom_val$ ./denom_val
Floating point exception
alexl@PD70PNP:/mnt/Storage_SSD/C++_Projects/denom_val$

#include "include/functions.h"
#include <iostream>

/*
The fraction 49/98 is a curious fraction, as an inexperienced mathematician in attempting to simplify it may incorrectly believe
that 49/98 = 4/8, which is correct, is obtained by cancelling the 9s.

We shall consider fractions like, 30/50 = 3/5, to be trivial examples.

There are exactly four non-trivial examples of this type of fraction, less than one in value,
and containing two digits in the numerator and denominator.

If the product of these four fractions is given in its lowest common terms, find the value of the denominator.
*/

int main() {
    std::cout << "The answer: " << func::get_answer() << '\n';

    return 0;
}

#include "include/functions.h"
#include <string>
#include <algorithm>
#include <vector>
#include <numeric>

namespace func {
    bool is_curious_fraq(func::frac f) {
        std::string numerator = std::to_string(f.numerator);
        std::string denominator = std::to_string(f.denominator);
        bool shares_digit = false;
        char common_char = ' ';
        bool result = false;

        //Does numerator and denominator share a digit?.
        for (int i = 0; i < static_cast<int>(numerator.length()); i++) {
            char test_char = numerator[i];
            if (denominator.find(test_char) != std::string::npos) {
                shares_digit = true;
                common_char = test_char;
            }
        }

        if (shares_digit) {
            numerator.erase(std::find(numerator.begin(), numerator.end(), common_char));
            denominator.erase(std::find(denominator.begin(), denominator.end(), common_char));

            double cancelled_frac = std::stod(numerator) / std::stod(denominator);
            double original_frac = static_cast<double>(f.numerator) / static_cast<double>(f.denominator);

            result = (cancelled_frac == original_frac);
        } else {
            result = false;
        }

        return result;
    }

    void reduce_frac(func::frac &f) {
        int gcd_res = std::gcd(f.numerator, f.denominator);
        int temp_numerator = f.numerator / gcd_res;
        int temp_denominator = f.denominator / gcd_res;
        f = {.numerator = temp_numerator, .denominator = temp_denominator};
    }

    int get_answer() {
        std::vector<func::frac> fracs;

        //Find the candidate fractions.
        for (int a = 11; a <= 98; a++) {
            if (a % 10 != 0) {
                for (int b = 12; b <= 99; b++) {
                    if (b % 10 != 0) {
                        func::frac f = {.numerator = a, .denominator = b};
                        if (is_curious_fraq(f)) {
                            fracs.push_back(f);
                        }
                    }
                }
            }
        }

        //Multiply candidate fractions together.
        int numerator_product = 1;
        int denominator_product = 1;

        for (func::frac f : fracs) {
            numerator_product = numerator_product * f.numerator;
            denominator_product = denominator_product * f.denominator;
        }

        //Declare and initialize product fraction struct.
        func::frac product_fraq = {.numerator = numerator_product, .denominator = denominator_product};

        //Reducing product fraction and returning denominator.
        reduce_frac(product_fraq);

        return product_fraq.denominator;
    }
}

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

namespace func {
    struct frac {
        int numerator;
        int denominator;
    };

    bool is_curious_fraq(func::frac f);
    void reduce_frac(func::frac &f);
    int get_answer(); 
}

#endif

alexl@PD70PNP:~$ neofetch
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    ,g$$$$$$$$$$$$$$$P.       ------------- 
  ,g$$P"     """Y$$.".        OS: Debian GNU/Linux 12 (bookworm) x86_64 
 ,$$P'              `$$$.     Host: PD5x_7xPNP_PNR_PNN_PNT 
',$$P       ,ggs.     `$$b:   Kernel: 6.1.0-16-amd64 
`d$$'     ,$P"'   .    $$$    Uptime: 12 days, 20 hours, 32 mins 
 $$P      d$'     ,    $$P    Packages: 1893 (dpkg) 
 $$:      $$.   -    ,d$$'    Shell: bash 5.2.15 
 $$;      Y$b._   _,d$P'      Resolution: 1920x1080 
 Y$$.    `.`"Y$$$$P"'         DE: GNOME 43.9 
 `$$b      "-.__              WM: Mutter 
  `Y$$                        WM Theme: Adwaita 
   `Y$$.                      Theme: Adwaita [GTK2/3] 
     `$$b.                    Icons: Adwaita [GTK2/3] 
       `Y$$b.                 Terminal: gnome-terminal 
          `"Y$b._             CPU: 12th Gen Intel i7-12700H (20) @ 4.600GHz 
              `"""            GPU: Intel Alder Lake-P 
                              GPU: NVIDIA GeForce RTX 3060 Mobile / Max-Q 
                              Memory: 3430MiB / 15694MiB

Program received signal SIGFPE, Arithmetic exception.
0x000055555555656f in func::reduce_frac (f=...) at src/functions.cpp:54
54              int64_t temp_numerator = f.numerator / gcd_res;