//common_random.h:

#ifndef COMMON_RANDOM_H
#define COMMON_RANDOM_H
#include <random>

class SingletonGenerator {
  static std::mt19937 mersennetwister;
public:
  static std::mt19937& get_mt();
};

#endif //COMMON_RANDOM_H

———————

//common_random.cpp:

#include "common_random.h"

std::mt19937 SingletonGenerator::mersennetwister;

std::mt19937& SingletonGenerator::get_mt() {
    return mersennetwister;
}

———————

//foreign_file.h

#ifndef FOREIGN_FILE_H
#define FOREIGN_FILE_H

double getu01_sing();

#endif //FOREIGN_FILE_H

———————

//foreign_file.cpp

#include "foreign_file.h"
#include "common_random.h"
#include <random>

double getu01_sing() {
  std::uniform_real_distribution<double> unif_real_01(0.0, 1.0);
  return unif_real_01(SingletonGenerator::get_mt());
}

———————


//main.cpp

#include <iostream>
#include "common_random.h"
#include "foreign_file.h"



int main() {
  SingletonGenerator::get_mt().seed(456);

  for (int i = 0; i < 20; ++i) {
    std::cout << i << " " << SingletonGenerator::get_mt()() << std::endl;
  }

  std::cout << "------" << std::endl;
  SingletonGenerator::get_mt().seed(456);

  for (int i = 0; i < 7; ++i) {
    std::cout << i << " " << getu01_sing() << std::endl;
  }
  return 0;
}

———————

how to build:
g++ -c common_random.cpp -o common_random.o
g++ -c foreign_file.cpp -o foreign_file.o
g++ -c main.cpp -o main.o
g++ common_random.o foreign_file.o main.o -o example