stop-hook-threads.cpp

//===-- main.cpp ------------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include <chrono>
#include <cstdio>
#include <mutex>
#include <random>
#include <thread>

std::default_random_engine g_random_engine{std::random_device{}()};
std::uniform_int_distribution<> g_distribution{0, 3000};

uint32_t g_val = 0;
uint32_t lldb_val = 0;

uint32_t
access_pool (bool flag = false)
{
    static std::mutex g_access_mutex;
    if (!flag)
        g_access_mutex.lock();

    uint32_t old_val = g_val;
    if (flag)
        g_val = old_val + 1;

    if (!flag)
        g_access_mutex.unlock();
    return g_val;
}

void
thread_func (uint32_t thread_index)
{
    // Break here to test that the stop-hook mechanism works for multiple threads.
    printf ("%s (thread index = %u) startng...\n", __FUNCTION__, thread_index);

    uint32_t count = 0;
    uint32_t val;
    while (count++ < 4)
    {
        // random micro second sleep from zero to .3 seconds
        int usec = g_distribution(g_random_engine);
        printf ("%s (thread = %u) doing a usleep (%d)...\n", __FUNCTION__, thread_index, usec);
        std::this_thread::sleep_for(std::chrono::microseconds{usec}); // Set break point at this line

        if (count < 2)
            val = access_pool ();
        else
            val = access_pool (true);

        printf ("%s (thread = %u) after usleep access_pool returns %d (count=%d)...\n", __FUNCTION__, thread_index, val, count);
    }
    printf ("%s (thread index = %u) exiting...\n", __FUNCTION__, thread_index);
}


int main (int argc, char const *argv[])
{
    std::thread threads[3];
    // Break here to set up the stop hook
    printf("Stop hooks engaged.\n");
    // Create 3 threads
    for (auto &thread : threads)
        thread = std::thread{thread_func, std::distance(threads, &thread)};

    // Join all of our threads
    for (auto &thread : threads)
        thread.join();

    // print lldb_val so we can check it here.
    printf ("lldb_val was set to: %d.\n", lldb_val);
    return 0;
}