r/w test

#!/usr/bin/env bash

set -o errexit
set -o verbose
set -o xtrace

g++ -x c++ - -std=gnu++1y -Wall -Wextra -Werror -Wconversion <<__EOF && ./a && echo -e "\e[1;31mOK\e[0m" || echo -e "\e[1;31mfailed!\e[0m"
#include <iostream>
#include <thread>
//#include <mutex>
#include <limits>
#include <cstdint>
#include <cstdlib>

using T = std::uintmax_t;
volatile T globalvalue;

template< bool upper >
struct reader
{

    static
    T constexpr value = upper ? 0 : ~static_cast< T >(0);

    void operator () () const
    {
        for (;;) {
            globalvalue = value;
            //std::cout << std::boolalpha << upper << std::endl;
        }
    }

};

int main() // __attribute__((__noreturn__))
{
    static_assert(std::is_unsigned< T >::value, "Type T is erroneously signed!");
    std::thread r0((reader< true >()));
    std::thread r1((reader< false >()));
    for (;;) {
        volatile T copyvalue = globalvalue;
        if ((copyvalue == reader< true >::value) != (copyvalue == reader< false >::value)) {
            //std::cout << std::boolalpha << (copyvalue == reader< true >::value) << std::endl;
        } else {
            std::cerr << "!" << copyvalue << std::endl;
        }
    }
    return EXIT_SUCCESS;
}

__EOF