ZeroTierOne/ext/opentelemetry-cpp-1.21.0/sdk/test/common/random_fork_test.cc

// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

#ifdef __unix__
// Verifies that IDs don't clash after forking the process.
//
// See https://github.com/opentracing-contrib/nginx-opentracing/issues/52
#  include "src/common/random.h"

#  include <stdint.h>
#  include <sys/mman.h>
#  include <sys/wait.h>
#  include <unistd.h>
#  include <cstdlib>
#  include <iostream>

using opentelemetry::sdk::common::Random;

static uint64_t *child_id;

int main()
{
  // Set up shared memory to communicate between parent and child processes.
  //
  // See https://stackoverflow.com/a/13274800/4447365
  child_id = static_cast<uint64_t *>(
      mmap(nullptr, sizeof(*child_id), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0));
  *child_id = 0;
  if (fork() == 0)
  {
    *child_id = Random::GenerateRandom64();
    exit(EXIT_SUCCESS);
  }
  else
  {
    wait(nullptr);
    auto parent_id     = Random::GenerateRandom64();
    auto child_id_copy = *child_id;
    munmap(static_cast<void *>(child_id), sizeof(*child_id));
    if (parent_id == child_id_copy)
    {
      std::cerr << "Child and parent ids are the same value " << parent_id << "\n";
      return -1;
    }
  }
  return 0;
}
#else
int main()
{
  return 0;
}
#endif