The problem appear when an in/out variable of a function called by std::thread changes the value during the execution...
Function:
static int func(stThread_t *&pStThread)
Parameters
pStThread: It´s a struct that has a pointer to std::thread and other variables (some flags)
typedef struct stThread {
stThread() noexcept {...};
stThread(const stThread &cRigth) noexcept {...};
stThread & operator = (const stThread &cRigth) noexcept {...};
std::thread *pThread;
volatile bool bBegin;
volatile bool bEnd;
} stThread_t;
The function func print the address of the std::thread of the parameter pStThread and the thread id
func before 1785280 this_id 21968
after making an this_thread::sleep for 2 seconds, it print it again
func afer ... this_id 21968
static int func(stThread_t *&pStThread) {
std::thread::id this_id = std::this_thread::get_id();
long long p_begin = (long long)pStThread;
std::cout << "func before " << std::to_string(p_begin) << " this_id " << this_id << "\n";
std::cout.flush();
pStThread->bBegin = true;
std::this_thread::sleep_for(std::chrono::milliseconds(2000));
this_id = std::this_thread::get_id();
long long p_end = (long long)pStThread;
std::cout << "func afer " << std::to_string(p_end) << " this_id " << this_id << "\n";
std::cout.flush();
pStThread->bEnd = true;
return 1;
};
The address of the pointer to std::thread it´s changed (corrutped, deleted..?)
The pStThread is pushing_back of a list of pointer struct stThread_t
std::list<stThread_t*> listOfThreads;
listOfThreads.push_back(pStThread);
I read about std::move, but does not work with pointers
At the end there is a thread "garbage collector" that it is trying to erase all the threads pending of execution.
Full code here
#include <string>
#include <list>
#include <vector>
#include <map>
#include <thread>
#include <mutex>
#include <atomic>
#include <iostream>
typedef struct stThread {
stThread() noexcept {
pThread = NULL;
bBegin = false;
bEnd = false;
};
stThread(const stThread &cRigth) noexcept {
this->pThread = cRigth.pThread;
this->bBegin = (bool)cRigth.bBegin;
this->bEnd = (bool)cRigth.bEnd;
};
stThread & operator = (const stThread &cRigth) noexcept {
this->pThread = cRigth.pThread;
this->bBegin = (bool)cRigth.bBegin;
this->bEnd = (bool)cRigth.bEnd;
return *this;
};
std::thread *pThread;
volatile bool bBegin;
volatile bool bEnd;
} stThread_t;
class CMain
{
public:
typedef std::list<stThread_t*> MyList_threads;
MyList_threads listOfThreads;
public:
CMain() {
std::cout << std::boolalpha << "Ex1 is move-constructible? "
<< std::is_move_constructible<stThread_t>::value << '\n'
<< "Ex1 is trivially move-constructible? "
<< std::is_trivially_move_constructible<stThread_t>::value << '\n'
<< "Ex1 is nothrow move-constructible? "
<< std::is_nothrow_move_constructible<stThread_t>::value << '\n'
<< "Ex2 is trivially move-constructible? "
<< std::is_trivially_move_constructible<stThread_t>::value << '\n'
<< "Ex2 is nothrow move-constructible? "
<< std::is_nothrow_move_constructible<stThread_t>::value << '\n';
};
static int func(stThread_t *&pStThread) {
std::thread::id this_id = std::this_thread::get_id();
long long p_begin = (long long)pStThread;
std::cout << "func before " << std::to_string(p_begin) << " this_id " << this_id << "\n";
std::cout.flush();
pStThread->bBegin = true;
std::this_thread::sleep_for(std::chrono::milliseconds(2000));
this_id = std::this_thread::get_id();
long long p_end = (long long)pStThread;
std::cout << "func afer " << std::to_string(p_end) << " this_id " << this_id << "\n";
std::cout.flush();
pStThread->bEnd = true;
return 1;
};
int _createThreads() {
for (int iIdx = 0; (iIdx < 5); iIdx++) {
stThread_t *pStThread = new stThread_t;
pStThread->pThread = new std::thread(&CMain::func,
std::ref(pStThread));
if (pStThread) {
do {
std::this_thread::sleep_for(std::chrono::milliseconds(100));
} while (!pStThread->bBegin);
listOfThreads.push_back(pStThread);
std::string sLog;
sLog = "\nlistOfThreads.push_back " + std::to_string((long long)pStThread) + "\n";
std::cout << sLog;
std::cout.flush();
}
std::this_thread::sleep_for(std::chrono::milliseconds(1));
}
return 1;
};
int _main() {
_createThreads();
std::thread thread_collector([=]() {
bool bEnd = false;
MyList_threads::iterator it;
it = listOfThreads.end();
do {
stThread_t *pStThread = NULL;
if (it == listOfThreads.end()) {
it = listOfThreads.begin();
if (it == listOfThreads.end()) bEnd = true;
}
else it++;
if (it != listOfThreads.end()) {
if ((*it)->bEnd) {
pStThread = *it;
listOfThreads.erase(it);
it = listOfThreads.begin();
}
}
if (pStThread) {
if (pStThread->pThread) {
if (pStThread->pThread->joinable()) {
pStThread->pThread->join();
std::cout << " element deleted " << std::to_string((long long)pStThread) << "\n";
std::cout.flush();
}
delete pStThread->pThread;
pStThread->pThread = NULL;
}
delete pStThread;
}
pStThread = NULL;
std::this_thread::sleep_for(std::chrono::milliseconds(1));
} while (!bEnd);
});
if (thread_collector.joinable()) {
thread_collector.join();
}
return 1;
};
};
int main()
{
CMain _main;
_main._main();
return 0;
}
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