Class member function as pthread_create function parameter

From:http://www.cnblogs.com/shijingxiang/articles/5389294.html

Recently, the thread pool needs to be encapsulated into a C + + class named ThreadPool. Call Pthread_create in the member function Exec_task of the class to start the thread execution routine thread_rounter. After compiling the error is as follows:

Spfs_threadpool.cpp:In member function ' int threadpool::exec_task (task*) ':

Spfs_threadpool.cpp:174:error:argument of type ' void* (threadpool::) (void*) ' does not match ' void* (*) (void*) '

There is a type mismatch problem. Because pthread_create requires a parameter type of void* (*) (void*), and Thread_rounter is a member function of a class, its type is void* (Threadpool::) (void*) member function pointer. We know that the member functions of a class will become a global function with the this pointer parameter after being processed by the compiler, so the type is doomed to be mismatched. However, if Thread_rounter is declared as a static type, the compiler converts the static form of a function into a global function without the this pointer, so its type can match the type of parameter that Pthread_create requires. However, a static member function of a class cannot access a non-static member of a class, but this can be resolved by passing the this pointer.

In conclusion, my problem can be solved in this way.

Code before the problem:

void *thread_rounter (void *)//thread execution function

{

Direct access to members of a class

}

Called in the Exec_task function:

Pthread_create (&tid,null,thread_rounter,null);//start thread execution routines

The code to fix the problem:

static void *thread_rounter (void *tmp)/thread execution function

{

Threadpool *p= (Threadpool *) tmp;

Indirect access to non-static members of a class through the P pointer

}

Called in the Exec_task function:

Pthread_create (&tid,null,thread_rounter, (void *) this);//start thread execution routines

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Search on the Internet there are other solutions, excerpts from the following, in order to show respect to mark the source of the article, thank the original author.

Scenario Two:

Declare the thread initiation function as a template function.

Excerpt from: HTTP://HI.BAIDU.COM/ANGELEVIL2006/ITEM/E1806EC30574FF11515058D1

Template <typename TYPE,void(TYPE::* _runthread) () >void* _THREAD_T (void* param)//thread start function, declared as a template function{TYPE* this = (type*) param; this-_runthread (); returnNULL; }      classMyClass { Public: MyClass (); void_runthread (); Private: pthread_t tid;      }; voidMyclass::_runthread () { This-dosomething (); } myclass::myclass () {pthread_create (&tid, NULL, _thread_t<myclass, &myclass::_runthread> This); }              //The function template can replace not only the type itself, but also the member functions of the type. //Note: 1, the name can only be _runthread, can not be modified when the template parameters are specified;//2, _runthread can only be public, unless the _thread_t is defined to the internal MyClass. 

Take this scenario into my project:

Code before the problem:

void *thread_rounter (void *)//thread execution function

{

Direct access to members of a class

}

Called in the Exec_task function:

Pthread_create (&tid,null,thread_rounter,null);//start thread execution routines

The code to fix the problem:

To add a public member function:

void Run ()

{

This function replaces the execution code of the above Thread_rounter

}

Thread_rounter Modify to global template function:

Template <typename type, void (type::* Run) () >

void * Thread_rounter (void * param)

{

TYPE *p= (type*) param;

P->run ();

return NULL;

}

Called in the Exec_task function:

Pthread_create (&tid,null,thread_rounter<threadpool,&threadpool::run>, (void *) this);

Summarize:

The key to solving this problem is to find ways to make the start function pointer satisfy the void* (*) (void *) type.

Overwriting a startup function with a static member function is appropriate for situations where the source code of a class can be modified.

And the start function as a template function can also be applied to the absence of the source code of the case, write a class, the public inherit from the original class, add the Startup function as a template function.

Class member function as pthread_create function parameter