Ticket #17751: test.cpp

#include <iostream>

#include <fcntl.h>
#include <sys/mman.h>

int main()
{
    int fds[2];
    int flags;

    if (pipe(fds) != 0)
    {
        printf("pipe failed: errno is %d (%s)\n", errno, strerror(errno));
        return false;
    }

    flags = fcntl(fds[0], F_GETFL, 0);
    fcntl(fds[0], F_SETFL, flags | O_NONBLOCK);
    
    flags = fcntl(fds[1], F_GETFL, 0);
    fcntl(fds[1], F_SETFL, flags | O_NONBLOCK);
    
    const int size = 4096;
    void* ptr = mmap(nullptr, size, PROT_NONE, MAP_ANON | MAP_PRIVATE, -1, 0);
    // Crashes
    // std::cout << "Pointer value is: " << std::flush << *(int*)ptr << std::endl;
    // Still returns 1, expected -1
    std::cout << write(fds[1], ptr, 1) << std::endl;
    // false, expected true
    std::cout << std::boolalpha << (errno == EFAULT) << std::noboolalpha << std::endl;
    // -1 as expected
    std::cout << write(fds[1], (void*)0xDEADBEEF, 1) << std::endl;
    // true as expected.
    std::cout << std::boolalpha << (errno == EFAULT) << std::noboolalpha << std::endl;
    return 0;
}