此线程是从here启动的，但是由于缺少一个很好的示例(并且为了避免删除所有问题)，在此处将其重写。
因此，在以下示例中，生成了void cppthread::ThreadedFunc()作为单独的线程执行。相反，我希望执行void ThreadedWrite::ThreadedFunc()。我怎样才能做到这一点？ (代码后有更多详细信息)
cppthread.hpp
#ifndef CPPTHREAD_HPP
#define CPPTHREAD_HPP
#include <pthread.h>
using namespace std;
class cppthread
{
public:
cppthread();
virtual ~cppthread();
virtual void threadedFunc();
///parentObj (ie "this" pte from caller") is
///necessary in order to execute the correct
///threadedFunc() even when the derived class
///wants to spawn a thread.
int spawn(void *parentObj = NULL);
void terminate();
protected:
pthread_mutex_t mtx;
bool exitThread;
private:
/* add your private declarations */
int join();
pthread_t threadId;
};
#endif /* CPPTHREAD_HPP */
cppthread.cpp
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include "cppthread.hpp"
void* threadCallback(void* obj);
cppthread::cppthread()
{
exitThread = false;
pthread_mutex_init(&mtx, NULL);
}
cppthread::~cppthread()
{
if (!exitThread)
terminate();
pthread_mutex_destroy(&mtx);
}
void cppthread::threadedFunc()
{
while ( !exitThread )
{
printf("Hello from cppthread::threadfunc. This should not be run once derived and redefined.\n");
}
if (exitThread)
{
printf("graceful exit from cppthread::threadfunc. This should not be run once derived and redefined.\n");
}
pthread_exit((void*)0);
}
int cppthread::spawn(void* parentObj)
{
int ret;
printf("parentObj = %p\n", parentObj);
if (parentObj == NULL)
{
ret = pthread_create(&threadId, 0, &threadCallback, this);
printf("cppthread_create with \"this\" \n");
}
else
{
ret = pthread_create(&threadId, 0, &threadCallback, parentObj);
printf("cppthread_create with parentObj\n");
}
if (ret != 0)
{
printf("cppthread_create error\n");
exit(EXIT_FAILURE);
}
else
{
//printf("cppthread::threadID= %lu\n",threadId);
}
return ret;
}
void cppthread::terminate()
{
exitThread = true;
join();
}
int cppthread::join()
{
int status , ret;
//printf("cppthread::join_threadID= %lu\n",threadId);
ret = pthread_join(threadId,(void**)&status);
if (ret != 0)
{
printf("cppthread_join error: ");
switch (ret)
{
case EDEADLK: printf("deadlock\n"); break;
case EINVAL: printf("thread not joinable\n"); break;
case ESRCH: printf("threadID not found\n"); break;
default : printf("unknown error\n"); break;
}
}
return status;
}
//----------------------------------------------------------------------
void* threadCallback(void* obj)
{
static_cast<cppthread*>(obj)->threadedFunc();
return(0);
} // callback
threadedwrite.hpp
#ifndef THREADEDWRITE_HPP
#define THREADEDWRITE_HPP
#include "cppthread.hpp"
using namespace std;
class ThreadedWrite : public cppthread
{
public:
ThreadedWrite(ThreadedWrite* mySelf);
virtual ~ThreadedWrite();
void threadedFunc();
void rrdupdate_thread();
///inherited significant members: from cppthread
/// int spawn();
/// void terminate();
///protected
/// pthread_mutex_t mtx;
/// bool exitThread;
private:
ThreadedWrite* instancePtr;
};
#endif /* THREADEDWRITE_HPP */
threadedwrite.cpp
#include <iostream>
#include "threadedwrite.hpp"
ThreadedWrite::ThreadedWrite(ThreadedWrite* mySelf):instancePtr(mySelf)
{
cout << "instancePtr = " << instancePtr << endl;
}
ThreadedWrite::~ThreadedWrite()
{
}
void ThreadedWrite::threadedFunc()
{
if ( !exitThread )
{
cout << "this is the ThreadedWrite::threadedFunc() running!" << endl;
}
else
{
cout << "ThreadedWrite::threadedFunc must exist now" << endl;
}
pthread_exit((void*)0);
}
void ThreadedWrite::rrdupdate_thread()
{
cout << "about to spawn" << endl;
spawn(instancePtr);
}
main.cpp
#include <iostream>
#include "threadedwrite.hpp"
using namespace std;
//-------main body------------------------------------------------------
int main(int argc, char* argv[])
{
ThreadedWrite thrrdupd(&thrrdupd);
cout << "hello from main 1 " << &thrrdupd << endl;
thrrdupd.rrdupdate_thread();
cout << "hello from main 2 " << &thrrdupd << endl;
return 0;
}
上面产生了输出(对我来说):
instancePtr = 0x7fff39d17860
hello from main 1 0x7fff39d17860
about to spawn
parentObj = 0x7fff39d17860
cppthread_create with parentObj
hello from main 2 0x7fff39d17860
graceful exit from cppthread::threadfunc. This should not be run once derived and redefined.
因此，从派生类“ThreadedWrite”内执行上述
cppthread::spawn()调用，实际上提供了指向callback()函数的“this”指针，该指针指向cppthread::ThreadedFunc()而不是ThreadedWrite::ThreadedFunc()。您还可以看到我尝试(通过“instancePtr”基础结构)将指向“ThreadedWrite”实例的指针传递回回调函数。但这也失败了。
另外，最好我想使cppthread类尽可能通用，以便在可能的情况下使用它。
请注意，如果我从threadedwrite.cpp中删除“spawn(instancePtr)”，然后像这样从main.cpp调用该spawn
int main(int argc, char* argv[])
{
ThreadedWrite thrrdupd(&thrrdupd);
cout << "hello from main 1 " << &thrrdupd << endl;
thrrdupd.rrdupdate_thread();
thrrdupd.spawn();
cout << "hello from main 2 " << &thrrdupd << endl;
return 0;
}
我得到的输出是预期的(和想要的)输出，它看起来像这样:
instancePtr = 0x7ffd24b04ed0
hello from main 1 0x7ffd24b04ed0
about to spawn
parentObj = (nil)
cppthread_create with "this"
hello from main 2 0x7ffd24b04ed0
this is the ThreadedWrite::threadedFunc() running!
最佳答案
从main返回之前，您需要等待线程终止，因为这会破坏您的对象。
否则，您将面临比赛条件:
thrrdupd时，main开始被存储。 ~ThreadedWrite运行；此时，对象不再是ThreadedWrite而是cppthread。 ~cppthread运行并等待线程。 cppthread，因此将调用cppthread::threadedFunc。 5.可能会在3.之前发生，在这种情况下，您将获得预期的输出。
如果您确定等待线程完成在步骤3。那么它将正常工作。也许您可以在
terminate中调用~ThreadedWrite？关于c++ - c++，pthread和静态回调。 “this”返回一个指向派生类的基类inctead的指针(第2部分)，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/34440316/