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| //===-- 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 <condition_variable>
#include <cstdio>
#include <thread>
std::condition_variable g_condition_variable;
std::mutex g_mutex;
int g_count;
char *g_char_ptr = nullptr;
void
barrier_wait()
{
std::unique_lock<std::mutex> lock{g_mutex};
if (--g_count > 0)
g_condition_variable.wait(lock);
else
g_condition_variable.notify_all();
}
void
do_bad_thing_with_location(unsigned index, char *char_ptr, char new_val)
{
unsigned what = new_val;
printf("new value written to array(%p) and index(%u) = %u\n", char_ptr, index, what);
char_ptr[index] = new_val;
}
uint32_t
access_pool (bool flag = false)
{
static std::mutex g_access_mutex;
static unsigned idx = 0; // Well-behaving thread only writes into indexs from 0..6.
if (!flag)
g_access_mutex.lock();
// idx valid range is [0, 6].
if (idx > 6)
idx = 0;
if (flag)
{
// Write into a forbidden area.
do_bad_thing_with_location(7, g_char_ptr, 99);
}
unsigned index = idx++;
if (!flag)
g_access_mutex.unlock();
return g_char_ptr[index];
}
void
thread_func (uint32_t thread_index)
{
printf ("%s (thread index = %u) startng...\n", __FUNCTION__, thread_index);
barrier_wait();
uint32_t count = 0;
uint32_t val;
while (count++ < 15)
{
printf ("%s (thread = %u) sleeping for 1 second...\n", __FUNCTION__, thread_index);
std::this_thread::sleep_for(std::chrono::seconds(1));
if (count < 7)
val = access_pool ();
else
val = access_pool (true);
printf ("%s (thread = %u) after sleep 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[])
{
g_count = 4;
std::thread threads[3];
g_char_ptr = new char[10]{};
// Create 3 threads
for (auto &thread : threads)
thread = std::thread{thread_func, std::distance(threads, &thread)};
struct {
int a;
int b;
int c;
} MyAggregateDataType;
printf ("Before turning all three threads loose...\n"); // Set break point at this line.
barrier_wait();
// Join all of our threads
for (auto &thread : threads)
thread.join();
delete[] g_char_ptr;
return 0;
}
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